Hard exam questions Flashcards
1
Q
Why do geological time periods shown in cladograms differ in duration?
A
Because the time periods reflect the diversity of fossils and mass extinction events.
2
Q
Explain how an antigen-antibody complex provides protection against pathogens?
A
- Causes agglutination, that is the clumping together of antigens, thus immobilizing the antigen.
- Allows for easier detection by macrophages, leading to the engulfment of the antigen.
3
Q
With reference to the father’s possible phenotypes and genotypes, explain how a Rh- mother could be pregnant with a Rh+ fetus.
A
The father would need to have a genotype of either DD (Rh+) or Dd (Rh+), meaning that the child would be heterozygous for the trait of rhesus factor (Dd), as the child would receive one allele each from both parents.
4
Q
Explain an advantage that genetic variation brings to a species?
A
Genetic variation in a species increases the chance that at least some individuals have favorable alleles and have a greater chance of survival, should the environment change or the species encounter a disease.
5
Q
One particular length of nucleic acid coded for the production of a polymer that was 90 monomers long. How many nucleotide bases on the nucleic acid were involved in the coding for this polymer.
A
273 nucleotide bases. As three nucleotide bases code for one amino acid (3*9=270), and an additional three bases coding for “stop”.
6
Q
Describe in full detail, the process of PCR.
A
- Denaturation
Heating the DNA sample (at 94 for two minutes) to separate the double-stranded DNA. - Annealing
Adding primers (short, single-strands of DNA) to both ends of the DNA strands at 55 for two minutes. - ???
Taq polymerase adds complementary nucleotides to the DNA strands at 72 for one minute. - The process is repeated many times.
7
Q
Describe two effects of bipedalism in hominin behavior.
A
- Hominins could carry tools used for hunting on their hands (making catching prey easier).
- Hominins were more likely to catch sight of predators from afar as they were walking upright.
8
Q
Name the two types of macro-molecules that would be found in the structures in the karyotype.
A
- Protein
- Nucleic Acid
9
Q
Explain how the facilitated diffusion of glucose occurs.
A
The facilitated diffusion of glucose involves the passive movement (non-energy requiring) of glucose molecules from a region of high glucose concentration to a region of low glucose concentration along the concentration gradient through the help of a protein channel embedded in the membrane.
10
Q
Define pathogen.
A
Pathogens are causative agents of disease, such as virus (non-cellular) and pathogenic bacteria (cellular).
11
Q
Which organelle would be present in large numbers in heart muscle cells to supply energy? Explain your response.
A
The mitochondria.
Mitochondria is the site of aerobic respiration, and the product of aerobic respiration is a large amount of ATP/energy (more specifically 38 ATP in heart muscle cells).
12
Q
Explain by referring to the immune response, why the fetus in a second pregnancy is at a far greater risk of HDN (hemolytic disease of the newborn), than the first Rh+ fetus.
A
The fetus in the second pregnancy is at a greater risk as the Rh- mother has already produced B memory cells during the first pregnancy and a larger, more rapid response with more antibodies that are specific to the Rh+ antigen being produced occurs during the second pregnancy.
13
Q
What type of immunity is the treatment of receiving injections of antibodies? Explain your response.
A
A passive form. As the injection of the antibodies only provides a short-term immune response that consist of no memory cells produced by the individual, and that the individual does not produce her own antibodies.
14
Q
Describe in full detail the process of translation, including where it occurs.
A
-
15
Q
What would findings of a study on identical twins reveal?
A
The findings would reveal that these two individuals would have identical traits, as they are genetically identical, but these traits could be modified by the environment.
16
Q
Define karyotype.
A
-
17
Q
Distinguish between convergent and divergent evolution.
A
-
18
Q
Define antigen.
A
-
19
Q
Explain how amino acid differences in a protein can indicate evolutionary relationships.
A
- Over a period of time, mutations can accumulate that may change the sequence of amino acids.
- The more differences in the amino acid sequence, the less related the two species are.
20
Q
Define selection pressure.
A
Selection pressures refer to any factor in an organism’s environment that can result in those that have the more suitable phenotype to continue to survive and pass their traits to the next generation.
21
Q
Explain how the M species probably arose from the M species ancestor.
A
Speciation, that is the process of the creation of a new species. Within the original species, there was existing genetic variation. Through natural selection and a change in environmental selection pressures, individuals with the suitable phenotype survived and pass on their traits to the next generation. This group developed, and over time evolved into a new species.
22
Q
Explain how hydrophilic hormones stimulate a metabolic process inside a cell. Name an example of a hydrophilic hormone.
A
Glucagon is a hydrophilic hormone, meaning that it is water soluble or polar. This means that it is unable to diffuse across the cell membrane and needs to bind to an extracellular receptor located on the surface of the cell membrane. This hormone-receptor complex then activates a secondary messenger within the cell, and this stimulates a cascade of events leading to the desired cellular response.
23
Q
True or False.
As a response to infection, a fever could be initiated by macrophages.
A
True.
Could be initiated through interleukin-1.
24
Q
What would the terminal bud of a neuron contain?
A
Calcium ions.
25
True or False.
| Both mitochondrial DNA and nuclear DNA are able to be used to form mRNA.
True.
26
True or False.
| Hybrid species show characteristics of both species.
True.
27
Explain the importance of secondary messengers in the regulation of the cell by signalling molecules.
The response can be changed or amplified by secondary messengers.
28
Define autoimmune disorder.
-
29
Describe the allergic response in full detail.
-
30
Describe the process of transcription in full detail.
-
31
Define allopatric speciation.
-
32
Describe how the stability of a protein is achieved through its tertiary structure.
The tertiary structure of a protein determines its overall 3D shape and function. This stability is achieved by the formation of bonds to hold the protein chain in its 3D shape. This is also determined by the order of amino acids in its primary structure.
33
Explain in full detail, how a message is passed from the terminal bud of one neuron to a receiving neuron.
- The neurotransmitters are packaged into vesicles at the axon terminal of the pre-synaptic neuron.
- The neurotransmitter is released from the vesicles via exocytosis into the synaptic gap.
- The neurotransmitter diffuses across the gap and binds to receptors located on the post-synaptic membrane.
34
Describe how a vaccine could be created.
A dead or attenuated form of the pathogen is created by radiating a live pathogen, then injected to illicit an immune response.
35
Describe the immune response of memory cells when foreign antigens are recognized.
The B memory cells will undergo clonal expansion and differentiate into plasma cells to produce more antibodies that are specific to the foreign antigen.
36
How would scientists know that two organisms are part of a separate species?
If the two organisms are unable to interbreed to produce viable, fertile offspring, then they are a separate species.
37
What is relative dating?
-
38
What is absolute dating?
-
39
State the ideal conditions for fossilization.
- Rapid burial
| - ???
40
Define cultural evolution.
-
41
How does the discovery of new fossils affect our understanding of human evolution?
As new hominin fossils are discovered, our ideas regarding human evolution and ancestry also have to change to accommodate these new findings.
42
Why is it much more difficult to use progressively older cells for cloning?
As the cells age, they become more specialized and the potency of the cell decreases.
43
Explain why the donor cell had to be a somatic cell rather than a gamete?
The donor cell had to be a somatic cell rather than a gamete because the cloned individual needed to be diploid, and not haploid.
44
Define osmosis.
Osmosis involves the passive movement (non-energy requiring) of water molecules from a region of high water concentration to a region of low water concentration, along a concentration gradient.
45
Name the three main polysaccharide and state their functions.
1. Glycogen - energy storage in animals.
2. Starch - energy storage in plants.
3. Cellulose - composition of the cell wall in plants.
46
Define apoptosis.
Programmed cell death.
47
Why do immunization programs require children to have booster injections for a range of diseases? How does this lead to long-term immunity?
The purpose of carrying out booster shots is to cause individuals to produce additional B memory cells. The presence of these B memory cells increases the ability of individuals to produce higher level of antibodies at a greater rate if the antigen is encountered in the future.
48
Provide an example of artificial passive immunity.
Receiving injections of antibody serums, maybe during a snake bite or something.
49
Provide an example of natural passive immunity.
Receiving antibodies (IgM???) from mother via the placenta.
50
Provide an example of natural active immunity.
Being infected by the disease itself and developing memory cells.
51
Provide an example of artificial active immunity.
Vaccinations.
52
True or False.
| Water is transported by the lymphatic system.
True.
53
Define negative feedback.
-
54
List three ways in which animal cells may differ from plant cells.
- The absence of chloroplast.
- The absence of cell wall.
- Smaller vacuole (try not to mention).
55
What is active transport?
Involves the active movement (energy requiring) of substances from a region of low concentration to a region of high concentration, against a concentration gradient.
56
Provide examples of something that would have a non-self antigen.
- Pathogens, such as bacteria and fungi.
| - Foreign cells, such as transplanted tissues.
57
What is a self-antigen, and why is it important for a body to be able to recognize self- and non-self antigens?
Self-antigen is a marker on the cell membrane that allows other cells to recognize it. It is important as it determines whether which cells belong and which need to be destroyed.
58
What is the role of a neuron?
Transmits and receive nerve impulses.
59
Name four types of mutations.
- Silent mutation
- Nonsense mutation
- Missense mutation
- Frameshift mutation
60
Compared the action of the hormonal system vs. the nervous system.
-
61
What is the difference between an essential amino acid and non-essential amino acid?
Essential amino acids must be included in the diet because they cannot be synthesized by the body, whereas non-essential amino acids can be synthesized by the body and so do not need to be included in diet.
62
Explain why two different amino acids that act as signalling molecules can have such vastly different effects on the body.
Both amino acids have a different overall 3D shape (tertiary structure), and thus bind to different receptors on different target cells within the body.
63
Why do cancer cells not activate the immune system in the same fashion as a pathogenic disease-causing organism?
Because cancer cells are somatic cells from the body, and contain "self" antigens, whereas pathogens contain "non-self" antigens.
64
Describe two events that occur during interphase that prepare a cell for division.
- During G1 phase, the cell grows as a result of protein synthesis, which gets the cell to a sufficient size to replicate.
- During S phase, the DNA replicates so the new cells can carry the same genetic information.
- During G2 phase, the DNA coils with protein to form chromosomes.
- There are a series of checkpoints during interphase as safeguards against errors occurring during the process.
65
Describe how a natural killer (NK) cell can play a role in programmed cell death.
The NK cell binds to receptors located on the cancerous cell and secrete perforins that stimulate the cell to undergo apoptosis.
66
Why is it better for genes to be regulated at the transcriptional level?
???
67
Discuss the importance in the removal of introns prior to the production of mRNA.
Introns are known as "junk DNA", and thus contain no useful genetic information. After the removal of introns, the exons bind to form the final mRNA product which carries the correct order of nucleotides for the protein to be formed.
68
Define hormone.
-
69
Define the term "hominin".
Refers to modern day humans and their ancestors, that are characterized by bipedal movement.
70
True or False.
| Condensation reactions involving amino acids sub units occur at the rough endoplasmic reticulum.
True.
71
What organelle would specialized cells that are able to produce large amounts of glucose contain?
Chloroplasts.
72
Name examples of cultural evolution in hominins.
Mummification, burial rituals, use of language, paintings on stone walls, etc.
73
Name the organelle present in mast cells needed to package the substance into granules.
Golgi complex.
74
What is herd immunity, and how does it improve the health of people living in the same city?
-
75
How would variation FIRST come about in a population?
Genetic mutations.
76
Give a reason why certain gene have been conserved for a long time and show no accumulated mutations.
This gene would serve an important role and mutations to this gene could cause a faulty protein and have a delirious effect on the organism.
77
Define genetic drift.
-
78
What is the product of anaerobic respiration in a human skin cell?
Lactic acid/lactate only.
79
How can the speed of conduction along an axon be increased?
Increasing the diameter of the axon and a thicker layer of insulation.
80
What ions are responsible for the transmission of an action potential along an axon?
Sodium and potassium ions.
81
Which region of the antibody is responsible for binding to an antigen?
The variable region.
82
Give examples of the first line of defense of the immune system.
- Natural flora
- Natural secretions
- Intact skin
- Mucus membranes
83
Give examples of the second line of defense of the immune system.
Complement proteins, interferon, phagocytes, fever, the inflammatory response.
84
Describe the inflammatory response in full detail.
-
85
Distinguish between prokaryotic and eukaryotic chromosomes.
-
86
Name the process of cell division in prokaryotic cells.
Binary fission.
87
What is the earliest to occur during gene expression?
mRNA is read by a ribosome.
88
Define aneuploid.
-
89
Define polyploid.
-
90
Name the most abundant compound in our body.
Water.
91
State the monomers and polymers of the four bio-macromolecules.
Monosaccharide - Polysaccharide/carbohydrate
Amino acids - Protein/poly-peptide
Nucleotides - Nucleic acids
Fatty acids/triglyceride - Fats, lipids, membrane
92
How are polymers formed?
Condensation polymerization reaction.
93
True or False.
| Carbohydrates are insoluble in water.
False.
94
Name the general formula of carbohydrates.
C n H 2n O n
95
What is the product of a condensation reaction?
Water + polymer.
96
Name examples of monosaccharides.
Glucose, fructose (five-ringed), mannose.
97
Name examples of disaccharides.
Sucrose, lactose, maltose.
98
Name the main polysaccharides and their functions.
Glycogen - form of energy storage in plants. Can be stored in the liver or muscle tissue.
Starch - form of energy storage in animals.
Cellulose - component of cell wall in plants.
99
What is the most abundant of biological molecules.
Cellulose.
100
State the elements that protein contains.
Carbohydrates, hydrogen, oxygen, sulfur, phosphorus.
101
Describe the primary structure of protein.
The specific linear sequence of amino acids.
102
Describe the secondary structure of protein.
The coiling and folding of some portion of the amino acid chain due to hydrogen bonding. For example, alpha helix, beta-pleated sheets, and random coiling.
103
Describe the tertiary structure of protein.
The overall 3D shape/structure of the protein.
104
Describe the quaternary structure of protein.
The structure of protein containing a number of polypeptide chains, such as hemoglobin.
105
What is an amino acid composed of?
CH group, carboxyl group, amino group and R (variable) group.
106
What are lipids composed of?
Carbon, hydrogen and oxygen.
107
Describe the phospholipid molecule in detail.
Composed of one glycerol head and two fatty acid tails. The head is hydrophilic and the tails are hydrophobic.
108
What are triglycerides composed of?
One glycerol head and three fatty acid tails.
109
Name the two kinds of nucleic acids?
DNA and RNA.
110
What are the differences between DNA and RNA?
- DNA has deoxyribose sugar, whereas RNA has ribose sugar.
- DNA is double-stranded, RNA is single-stranded.
- RNA contains the base uracil, whereas DNA contains the base thymine.
111
What are nucleotides composed of?
Deoxyribose sugar, nitrogenous base and phosphate group.
112
Name the purines.
Adenine, guanine (double-ringed).
113
Name the pyrimidines.
Cytosine, Uracil and Thymine (single-ringed).
114
How many hydrogen bonds are between adenine and thymine?
Two.
115
How many hydrogen bonds are between cytosine and guanine.
Three.
116
True or False.
| Apoptosis is an essential feature of development.
True.
117
Name the two main pathways that stimulate apoptosis.
- The mitochondrial pathway
Signals from the inside of the cell, such as when the cell is infected by a virus.
- The death receptor pathway
Signals from outside the cell.
118
Name an example of apoptosis.
During embryonic development, the webbing between fingers undergoes apoptosis so that the fingers are separated.
119
What is the main difference between eukaryotic and prokaryotic organisms?
Prokaryotic organisms contain no membrane-bounded organelles.
120
True or False.
| A healthy state relies on a balance between cell production and cell loss in an organism.
True.
121
Define cytoskeleton.
A network of fine protein filaments that hold organelles in place.
122
State the function of the plasma membrane.
Regulates the movement of substances into and out of the cell.
123
True or False.
| The plasma membrane can be seen through an electron microscope.
True.
124
What is the composition of the plasma membrane.
The phospholipid bilayer.
125
True or False.
| The plasma membrane is said to be partially permeable.
True.
126
Define diffusion.
The passive process (non-energy requiring) that involves the movement of substances from a region of high concentration to a region of low concentration, along the concentration gradient.
127
True or False.
| Diffusion never stops.
False.
| Diffusion stops when the two sides are at equilibrium.
128
How can diffusion be facilitated?
- Channel mediated, that is through the help of protein channels embedded on the plasma membrane.
- Carrier mediated, in which a carrier protein is needed to move the substance trough the protein channel.
129
Name and describe the main types of active transport.
- Endocytosis, the transport of substances into the cell.
- Exocytosis, the transport f substances out of the cell
- Phagocytosis, the transport of solid material.
- Pinocytosis, the transport of liquid material.
130
What organisms have a cell wall?
Plants, fungi and bacteria.
131
What is the primary cell wall made out of? What is the secondary cell wall made out of, and what is its function.
Primary cell wall is made out of cellulose. In some flowering plants, lignin combines with the primary cell wall and forms the secondary cell wall, which provides elastic strength and support.
132
State the function of the mitochondria.
The site of energy production in the form of ATP.
133
Do prokaryotic organisms have mitochondria?
No.
134
State the function of ribosomes.
The site of protein synthesis.
135
What are ribosomes composed of?
Protein and rRNA.
136
Do prokaryotic organisms have ribosomes?
YES.
137
True or False.
| Mitochondria and chloroplasts also contain ribosomes.
True.
138
State the function of rough endoplasmic reticulum.
Transport of substances within the cell.
139
State the function of the golgi complex.
Packages protein into secretory vesicles for export out of the cell through exocytosis.
140
State the function of lysosomes.
In animal cells, lysosomes are filled with fluid containing dissolved digestive enzymes that are used to destroy unwanted parts from within or outside the cell.
141
State the function of chloroplasts.
The site of photosynthesis, and production of glucose. Only found in plant cells.
142
Define heterotrophic and autotrophic organisms.
Heterotrophic organisms either ingest or absorb material from either living or dead organisms or their products. Autotrophic organisms use an external energy source to create organic compounds from simple inorganic compounds.
143
True or False.
| In every reaction, some of the energy is always lost as heat energy.
True.
144
Contrast between exergonic and endergonic reactions.
Exergonic/catabolic - releases energy, involves the breakdown of substances into simple molecules.
Endergonic/anabolic - requires the input of energy, involves the synthesis of more complex substances.
145
Name examples of exergonic reactions.
Oxidation reactions, such as respiration, hydrolysis, digestion, etc.
146
Name examples of endergonic reactions.
Reduction reactions, such as photosynthesis condensation reaction, etc.
147
Define enzymes.
Enzymes are molecules that act as biological catalysts to increase the rate of reactions that occur in living organisms. They are not consumed during the biological reaction.
148
True or False.
| All enzymes are proteins.
True.
149
True or False.
| Enzymes can be used for both catabolic and anabolic reactions.
True.
150
What type of protein is an enzyme, according to its structure?
Tertiary level.
151
Why are enzymes important for chemical reactions to occur in living organisms?
Enzymes are organic catalysts, they speed up the rate of biological reactions in the body. Without enzymes, the metabolic reactions would occur too slowly, and the temperature and pH of the body life cannot be sustained.
152
True or False.
Each enzyme has a specific amino acid sequence, and therefore a specific 3D shape, and an active site that has a specific 3D shape.
True.
153
True or False.
| All the metabolic reactions in living organisms are controlled by enzymes.
True.
154
Explain how temperature can affect the rate of reaction of an enzyme catalyzed reaction.
Enzyme activity increases with temperature, until the temperature is too high for the enzyme to function, and enzyme denaturation occurs.
155
Explain how pH can affect the rate of reaction of an enzyme catalyzed reaction.
Enzymes are found in very diverse pH conditions, and any extremes of pH away from the enzyme optimum for that specific enzyme can result in enzyme denaturation.
156
Explain how substrate concentration can affect the rate of reaction of an enzyme catalyzed reaction.
The rate of reaction increases and then plateaus with increasing substrate concentration, provided that there are a fixed amount of enzymes (as the active sites of the enzymes are being occupied).
157
Explain how enzyme concentration can affect the rate of reaction of an enzyme catalyzed reaction.
The rate of reaction increases with increasing enzyme concentration, providing there are an unlimited amount of substrate and co-factors.
158
Explain how inhibitors can affect the rate of reaction of an enzyme catalyzed reaction.
The rate of reaction will decrease with an increase in inhibitors.
159
Define co-factors.
Co-factors are the non-protein component of the enzyme. They can be organic (co-enzymes) or inorganic ions, such as calcium and zinc.
160
Define co-enzymes.
Co-enzymes are the organic non-protein component of the enzyme, such as vitamins.
161
True or False.
| All enzymes require co-factors to be active.
False.
162
What are permanently attached co-factors called?
Prosthetic groups.
163
True or False.
| Co-factors are always permanently attached to the enzyme.
False.
164
Explain what happens to an enzyme in high temperatures and in low temperatures.
At high temperatures, enzymes are no longer able to function and enzyme denaturation occurs.
At low temperatures, enzymes have little activity.
165
Explain what happened to a denatured enzyme.
A denatured enzyme is no longer able to function as the active site has completely changed due to the extremes in temperature and pH. The enzyme will also not be able to regain its function when the temperature does decrease.
166
Name and define the two types of enzyme inhibitors.
-Reversible inhibitor
Are used to control enzyme activity. There is often an interaction between the substrate or end product and the enzymes controlling the reaction.
-Irreversible inhibitor
Bind tightly and permanently to the enzymes, destroying their catalytic activity. They usually covalently modify an enzyme.
167
Describe competitive and non-competitive inhibition
Competitive inhibitor blocks the active site of the enzyme, resulting in the substrate being unable to bind to the active site.
Non-competitive inhibitors works either to slow down the rate of reaction, by binding to a site other than the active site, or by blocking the active site altogether and prevent its functioning (allosteric inhibition).
168
Describe the lock and key model.
This model proposes that the substrate is simply drawn into a closely matching cleft on the enzyme.
169
Describe the induced fit model.
This model proposes that the the enzyme changes its shape, forcing the substrate molecule to combine. The resulting product is released and the enzyme returns to its normal shape.
170
State the process and organelles involved in the synthesis and secretion of proteins.
-
171
True or False.
| The internal environment of an organism remains relatively stable.
True.
172
Define signal transduction.
Signal transduction involves getting the signal from a target cell's exterior to the cell's interior, during which the cell converts one kind of signal to another, by a series of relay molecules and other proteins. Within a cell, signal transduction amplifies the signal that the original hormone molecule produced.
173
Define gametes.
Refers to both egg and sperm cells.
174
Define germ-line cells.
Refers to gametes and the cells that give rise to them.
175
Define genotype and phenotype.
Genotype refers to the collection of alleles of an individual at a particular gene locus. The genetic makeup of an individual.
Phenotype refers to the expression of the genotype as a result of the expression of the particular alleles present, and modified by the influence of the environment.
176
Why are the resulting phenotypic ratios slightly different to the expected ratios? How to overcome?
Due to the chance combination of gametes. Increasing the sample size will usually result in experimental ratios closer in value to the expected ratios.
177
Write the possible alleles for all the blood types.
Blood A - Ia Ia, Ia , i
Blood B - Ib Ib, Ib i
Blood AB - Ia Ib
Blood O - i i
178
Where is the site of meiosis?
The gonads, that is the ovaries of females and testes of males.
179
True or False.
| Gametes are the only cells that can naturally cross the generation gap.
True. All other cells that make up the multi-cellular organism, that is somatic cells, die.
180
Define genes.
Genes are specific segments of DNA carrying instructions encoded in its base sequence for a specific protein product. It is located on chromosomes.
181
True or False.
| Each species has a characteristic number of chromosomes present in its somatic cells.
True.
182
How many number of chromosomes are present in the nucleus of human somatic cells?
46 chromosomes.
183
How many number of chromosomes are present in the nucleus of human sex cells, or gametes?
23 chromosomes.
184
Define diploid and haploid.
Diploid (2n) refers to an organism or cell having two copies of each specific chromosome, that is having a paired set of chromosomes. Haploid (n) refers to an organism or cell having one copy of each specific chromosome, that is having unpaired chromosomes.
185
What is the largest and smallest human chromosome?
Chromosome-1, chromosome-21.
186
Define karyotype.
A karyotype is the specific complement of chromosomes present in a cell or an individual arranged in an organized manner according to an agreed convention.
187
Name the male and female sex chromosomes.
Male XY
| Female XX
188
Define autosomes.
Autosomes refer to the pair of chromosomes that are identical in appearance in males and females of a species (number 1-22).
189
How are autosomes distinguished?
- Their relative size.
- Patterns of light and dark bands that result from special staining techniques.
- Position of the centromere, which appears as a constriction along the chromosome. True
190
What is the 23rd pair of chromosomes?
Sex chromosomes.
191
True or False.
| The larger the chromosome, the more DNA it contains and usually the greater the number of genes it carries.
True.
192
True or False.
| Chromosome number 5 and 14 are homologous chromosomes.
False.
193
Define kinetochore.
Kinetochore refers to a structure that is made of protein that surrounds the centromere and forms the attachment point for the spindle fibers that are necessary for the orderly movement of chromosomes.
194
True or False.
| Humans have 22 pairs of autosomes, and one pair of sex chromosomes.
True.
195
Define telomeres.
Telomeres refer to chromosomal ends, that prevent chromosomes from sticking together and enable complete replication of chromosomes to occur.
196
Name examples of aneuploidy.
The presence of an abnormal number of chromosomes. For example, trisomy and monosomy.
197
What is translocation? Name an example.
Translocation refers to a type of chromosomal change that occurs when a segment of one chromosome becomes physically attached to another non-homologous chromosome. For example, in a special case of Down Syndrome, the number-21 chromosome becomes physically attached to the number-14 chromosome, but the individuals karyotype still shows as 46 chromosomes.
198
Name an example of environmental sex determination.
For reptiles, hatchlings will be male if they are incubated at higher temperatures, regardless of their sex chromosomes.
199
True or False.
| In females, the process of meiosis only produces one functional egg cell.
True. The rest are known as polar bodies.
200
True or False.
| In gametes, there are 22 non-homologous autosomes and one sex chromosome.
True.
201
How does meiosis produce genetic variability on offspring?
- Crossing over between homologous chromosomes during prophase 1 of meiosis.
- Independent disjunction of chromosomes during meiosis, results in the independent assortment of the genes that they carry. This is known as recombination.
- Genetic mutation in gametes.
202
Contrast between mitosis and meiosis.
Mitosis
- Produces two identical daughter cells.
Meiosis
- Produces four non-identical daughter cells.
203
True or False.
| The human genetic material consist of an estimated 21,000 different genes.
True.
204
Define gene loci.
The position occupied by a gene on a chromosome.
205
True or False.
| Mitochondria contain a small number of genes.
True.
206
Define disjunction.
In meiosis, the separation of homologous chromosomes, or chromatids on a replicated chromosome to opposite ends.
207
Define alleles.
Different forms of the same gene.
208
Define heterozygous and homozygous.
Heterozygous (Bb) refers to having different alleles for a trait, whereas homozygous (BB, bb) refers to having the same alleles for a trait.
209
True or False.
| When a gene is located on a sex chromosome, the traits controlled by its alleles do not appear equally in both sexes.
True.
210
Define hemizygous.
In a male mammal, describes the genotype with respect to any gene carried on either the X or Y chromosome, which comprises just a single allele for each gene.
211
Are there any genes located on the Y chromosome in males?
Yes, the SRY gene, which controls testes production in male embryos.
212
Define carrier.
A heterozygous individual that does not show the particular trait, but is able to pass to its offspring alleles responsible for that trait.
213
Define complete dominance.
Where the heterozygous individual only has the dominant allele expressed in its phenotype.
214
Define co-dominance.
The relationship between two alleles of a gene such that a heterozygous individual shows the expression of both alleles in its phenotype.
215
Define incomplete dominance.
A mixture of the two alleles. Think flower example.
216
Why is a test cross performed?
- To determine is an individual displaying the dominant phenotype is heterozygous or homozygous dominant.
- To determine if the genes are linked on the same chromosome.
217
How is a test cross performed?
By crossing the individual with a homozygous recessive individual.
218
True or False.
| Linked genes have unequal ratio of phenotypes in offspring.
True.
219
Define genome.
The total set of genes carried by an individual or cell.
220
Define comparative genomics.
Sequencing the genome of different animals and comparing the base sequences to see similarities and differences.
221
Define mutations.
Changes in the genetic material that can occur during mitosis or meiosis.
222
Name examples of mutagenic agents.
Chemicals, UV rays, high temperatures and radiation.
223
Define silent mutation.
DNA mutation that does not result in change in the amino acid sequence.
224
Define nonsense mutation.
A base mutation that results in the stop codon put in the polypeptide.
225
Define missense mutation.
A single base substitution results in a different amino acid put in the polypeptide.
226
Define population.
A population is a collection of individuals from the same species who are able to breed with one another, and live in the same geographical location at the same time.
227
Name the different types of variation.
Structural, biochemical, physiological, behavioral, developmental and geographic.
228
Define cline.
The gradual change in a trait in members of a population across its geographic range.
229
Describe monomorphic and polymorphic.
Monomorphic is when members of a population are uniform and show no variation with regards to a trait. Polymorphic population show two or more variations with regard to a trait.
230
Where is rRNA stored n the cell?
Nucleolus.
231
Describe continuous and discontinuous variation.
When members of a population vary across a continuum for a trait, the trait is said to show continuous variation, such as adult male height. When members of a population can be organized into a few discrete, non-overlapping classes with regards to a trait, the trait is said to show discontinuous variation, such as flower color.
232
True or False.
| Variation in a trait is only due to genetic factors.
False. Can be due to environmental factors.
233
Describe monogenic and polygenic traits.
Monogenic refers to traits that are due to the action of a single gene, such as blood type. Polygenic refers to traits that are due to the action of many genes, or polygenes, such as human height.
234
Which type of trait usually shows continuous variation?
Polygenic traits.
235
What is the source of new alleles for a population?
Mutations.
236
Define gene pool.
The genetic information present in a population of organisms.
237
What is allele frequency? What is phenotype frequency?
Allele frequencies refer to the incidence of particular alleles in a population, whereas phenotype frequencies refer to the incidence of particular phenotypes in a population.
238
State the Hardy-Weinberg principle.
The principal states the allele frequencies in a population remain constant, generation after generation, provided a particular set of conditions are applied.
- Random mating
- No migration into or out of the population
- The population must be large
- All matings are equally fertile.
239
True or False.
| Allele frequencies can only have a value between zero and one.
True.
240
When is the Hardy-Weinberg equilibrium disrupted?
When an agent of change acts on the population.
241
State the main agents of change in populations.
Selection (either natural or artificial), gene flow (migration) and genetic drift (chance).
242
Define gene flow.
Movement of genes into or out of the population owing to migration, that can result in changes in allele frequencies in a population.
243
Define natural selection.
Natural selection is the process in nature where a range of selection pressure exists that result in only those individuals that are well suited to their environment are able to survive and pass on their favorable traits to the next generation.
244
Define artificial selection.
Artificial selection is where people intervenes in the selection process by controlling which individuals will mate and pass on the traits that are beneficial to the people, but not necessarily of advantage to the individual animal or plant.
245
Compare complete and partial selection.
Complete selection against a phenotype occurs when any organism with that given phenotype cannot reproduce because of death before reproductive age is reached. Partial selection against a phenotype occurs when matings involving that phenotype produce on average fewer viable and fertile offspring relative to other matings.
246
Name examples of genetic drift.
The founder effect and the bottleneck effect.
247
What is the founder effect?
Chance effects on the allele frequencies in a population that is formed from a small unrepresentative sample of a larger population.
248
What is the bottleneck effect?
Chance effects on the allele frequencies in a population as a result of a major reduction in population size.
249
True or False.
| The smaller the population size, the greater the potential impact of genetic drift.
True.
250
Define frameshift mutation.
A type of mutation in which due to insertion or deletion, all codons from that point are affected.
251
State the features that distinguish homos and primates.
Bipedal movement, flattened face, S-shaped spine, foramen magnum located in the central of the skull, larger brain capacity.
252
State the features of a primate.
- Large forward facing eyes
- Larger brain relative to body size
- Five-fingers that can curl around objects, and thumbs or big toes that are opposable.
- Short noses
- Bicuspid teeth
- Long gestation periods
- Social animals, that live in groups
- Protective bone located at the outer side of the eye socket
253
State the key differences between humans and chimps.
Foramen magnum - Central in humans, back of the skull in chimps.
Pelvis - Long and narrow in chimps, short and wide in humans.
Spine - C-shaped in chimps, S-shaped in humans.
Femur - Femur and tibia join in a straight line in chimps, at an angle in humans.
Foot shape - Big toe diverges in chimps, aligned in humans.
Dental arch - U-shaped and diastema gap present in chimps.
Canines - Large in chimps, small in humans.
Chin - small in chimps, large in humans.
Brain size - Larger in humans.
Brow ridges - Profound in chimps, less profound in humans.
Face shape - Flat in humans, sloping face in chimps.
254
What features enable bipedal movement in humans?
- Foramen magnum in central of skull
- S-shaped spine
- Pelvis short and wide.
- Big toe is not opposable on foot
- Femur and tibia at an angle
255
Why is nakedness a selection advantage?
Thermo-regulation, retention of head hair and parasite control.
256
Why is bipedal movement a selection advantage?
Efficient locomotion, carrying food, offspring, weapons and tools, thermo-regulation, and seeing over grass to spot predators.
257
True or False.
| Australopithecus Afarensis displayed bipedal movement.
True.
258
What family did the Australopithecus Afarensis belong to?
Hominid.
259
Who are the first tool makers?
Homo habilis.
260
Who are the first tool makers?
Homo erectus.
261
Define cultural evolution, and state examples.
Cultural evolution refers to changes in human societies over time where those changes are socially transmitted and not genetically inherited, such as development of language, skills, customs, burial rituals, art, etc.
262
Define technological evolution, and state examples.
Refers to changes in technology over time that give humans increased control over their environment, such as development of tools, weapons, etc.
263
Define biological evolution.
The process of change in members of a species under the influence of natural selection and requiring much longer time periods than cultural evolution.
264
What is the out-of-Africa hypothesis?
| OR replacement, Eve hypothesis.
Proposes that modern human populations originated from modern humans who evolved in Africa and migrated from there to the rest of the world.
265
What is the multi-regional hypothesis?
| OR regional continuity hypothesis.
Proposes that modern humans in various regions of the world originated from more primitive human ancestors who were living in those regions.
266
Name the technologies n selective breeding.
- Artificial insemination
- Embryo transfer
- Sex selection through sperm sorting
- Oestrus synchronization
267
Explain artificial insemination.
Involves collecting semen from a male species and then introducing this semen into the reproductive tract of females of the same species by artificial means. This increases the number of offsprings that an animal could produce.
268
State the advantages and disadvantages of artificial insemination.
Advantages
- Sperm van be obtained from a bull anywhere in the world.
- Timing of calving can be better synchronized, which could benefit the farmer as he would know precisely when the calves would be due.
- The farmer can quickly inseminate all his cows with sperm from a bull that has the qualities the farmer wishes to pass on to the next generation.
Disadvantages
- The population would all be very genetically similar. If a disease infects the population, all the individuals in the population would be equally affected.
269
Define artificial pollination.
Artificial pollination involves the cross pollination in which pollen collected from one plant is manually transferred to the stigma of a second plant.
270
How can an infertile plant due to artificial pollination of two closely related species be overcome?
By doubling the number of chromosomes in the plant cell, so that the cell contains two sets of each chromosome.
271
What is cloning?
Cloning is the process of making genetically identical copies of an organism, gene or cell.
272
True or False.
| Cloning involves asexual reproduction.
True.
273
True or False.
| Cloning results in a decrease in genetic variation.
True.
274
Name the two methods of cloning.
- Cloning by embryo splitting
| - Cloning by somatic cell nuclear transfer
275
Describe cloning by embryo splitting.
Embryo splitting occurs when the early cells of an embryo are artificially separated. Each single cell is then implanted in the uterus of a surrogate female, and embryonic development continues. Organisms produced through the splitting of one embryo are identical.
276
Describe cloning by somatic cell nuclear transfer.
This involves removing the nucleus from an egg cell, and this cell is referred to as enucleated. A somatic cell is fused with this enucleated egg cell to form an early embryo. The resulting embryo is implanted in a surrogate female parent and embryonic development continues. The genetic information in the cloned animal comes from the nucleus of the adult somatic cell, and thus the genotype of the cloned animal is determined by the donor nucleus, and not by the egg cell into which the nucleus is transferred.
277
Define transgenic/transformed organism.
Any organism that has a foreign gene or segment of foreign DNA in their genome as a result of human experimentation.
278
True or False.
| If the cells concerned are prokaryotic cells, such as bacterial cells, they are said to be transformed.
True.
279
What are the techniques for gene transfer?
- Micro-injection of the DNA of the gene into the cell
- Use of electric pulse
- Use of vectors such as attenuated virus
280
What is gene therapy?
Gene therapy is a process by which the function of a faulty allele in an organism is replaced by addition of a normally functioning allele of the gene concerned. It is a technique that aims to treat inherited disorders by directly targeting the genotype, and has the potential to change natural evolutionary processes.
281
Name the two types of gene therapy.
In-vivo, in which gene therapy is given directly to the patient.
Ex-vivo, in which a patient's cells are manipulated outside the body and then returned to the individual.
282
What agents can be used for gene therapy?
Attenuated viruses, liposome.
283
What can go wrong in gene therapy?
The attenuated virus could revert or change back to its active state and cause disease. The virus could trigger an allergic response and organs could be damaged, or the person could go into shock. An essential gene in the person's cell could be disrupted, causing other problems.
284
Define stem cells.
Stem cells are undifferentiated or precursor cells that have the ability to differentiate into many different and specialized cell types.
285
Name and state the potency of the different stem cells.
Totipotent - can give rise to all cell types, such as fertilized egg or cell from a 2,4 or 8 cell embryo.
Pluripotent - can give rise to most cell types, such as the inner cell mass of an early embryo (blastocysts).
Multipotent - can give rise to certain cell types, such as adult somatic cells, such as bone marrow cells.
286
Define genetic screening.
Genetic screening is a procedure in which a DNA sample is analyzed to detect the presence of one or more alleles associated with an inherited disorder.
287
What is therapeutic cloning?
Therapeutic cloning is to produce stem cells for use in treatment. Therapeutic cloning involves the creation, through the nuclear transfer technique, of an embryo for the purpose of obtaining stem cells from that embryo. The cell that provides the nucleus in therapeutic cloning is a healthy cell from the patient who is to receive treatment. As a result, the embryo that is created is a genetic match to the patient and these cells do not cause an immune response.
288
What is the purpose of reproductive cloning?
To produce a new organism.
289
Describe the process of transcription. -
1. An enzyme known as RNA polymerase attaches to a specific promoter sequence at the 3 end of the DNA in the upstream region of the DNA template strand. The double-stranded DNA unwinds and exposes the bases of the template strand.
2. The base sequence of the template strand guides the building of a complementary copy of the mRNA. The RNA polymerase moves along the DNA template in a 3' to 5' direction. As it moves, complementary nucleotides are brought into place and are joined together to form the mRNA.
3. After transcription stops, the mRNA is released and this forms the pre-mRNA.
290
Describe the process of post-transcription modification.
- The 5' end of the pre-mRNA is capped with an altered guanine (G) base, known as methyl guanosine/methyl cap. This cap protects the pre-mRNA from enzyme attack and contributes to its stability.
- The primary transcript is clipped at a specific point downstream of the coding region and a poly-adenine (A) tail is then added at the 3' end. The tail contributes to the stability of the mRNA.
- The regions in the pre-mRNA that corresponds to the introns are cut out and the remaining exons are spliced together. This cutting and splicing is done by spliceosomes, which recognize specific base sequences at the end of introns
291
True or False.
pre-mRNA is complementary to the base sequence of the DNA template strand, and "identical" to the DNA non-template strand
True.
292
What is alternative splicing?
Alternative splicing of the pre-mRNA molecule from a single gene at different areas explains how one gene produce different protein products at different development stages or in different tissues. Alternative splicing can occur during post-transcription modification of pre-mRNA. Different exons are combined to form several kinds of mRNA, each with a different base sequence. These different mRNAs are then translated into proteins that differ in their amino acid sequences.
293
Describe the process of translation.
1. The single-stranded mRNA molecule leaves the nucleus and attaches to a ribosome in the cytosol.
2. Each specific amino acid is brought to the mRNA molecule by the carrier molecule tRNA. At one end of each tRNA molecule are three bases that make up an anti-codon. At the other end of the tRNA molecule is a region that attaches to one specific amino acid.
3. Amino acids are released as the anti-codon pairs complementary with the codon on the mRNA strand. And these amino acids join together to form a polypeptide chain.
294
How many possible tRNA combinations?
64.
295
Which is always the first amino acid?
Methionine.
296
Comparison of DNA between prokaryotic and eukaryotic organisms?
Chromosomes exists as a circular molecule of DNA, plasmids are present, coding regions are uninterrupted, DNA is free within the cell, DNA comprises of unique nucleotide sequences.
297
Comparison of gene action between prokaryotic and eukaryotic organisms?
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