Genetics Flashcards
1
Q
Variation
A
There are differences between numbers of the same species i.e. a population
2
Q
Species
A
A group of organisms capable of interbreeding and producing fertile offspring.
3
Q
What must be for a new species to form?
A
For a new species to form , all offspring must be fertile
4
Q
Genetics
A
The study of heredity
5
Q
Heredity
A
The passing on of features from parents to offspring by means of genes (also called genetic inheritance)
6
Q
What is the unit of inheritance?
A
Gene
7
Q
Where is a gene found?
A
On a chromosome
8
Q
What does a chromosome contain?
A
a number of genes
9
Q
What do genes contain?
A
Instructions to make a particular protein
10
Q
What does a gene influence?
A
It directly influences the characteristics of an organism
11
Q
What are controlled by genes?
A
Characteristics are controlled by genes.
12
Q
What is an example of how characteristics are controlled by genes?
A
e.g. everyone has genes which determine hair colour
13
Q
What is an example of genes creating different characteristics?
A
There is more than one type of gene for hair colour that you could have
14
Q
Are all genes expressed?
A
Not all genes are expressed
15
Q
What do genes produce? Give an example.
A
Genes produces characteristics or traits that are inherited e.g. gene for tallness
16
Q
What influences characteristics?
A
Characteristics = heredity + environment
17
Q
What are chromosomes made up of?
A
Chromosomes are made up of 60% protein and 40% DNA.
18
Q
What are genes arranged along?
A
Genes are arranged along the DNA of the chromosome
19
Q
Describe the structure of chromosomes, what they contain, how they occur and where they are found.
A
Chromosomes are thread like structures that contain DNA and Genetic information. They occur in pairs and are found in the nucleus of all cells
20
Q
What are chromosomes?
A
Chromosomes are long pieces of DNA, with supporting proteins.
21
Q
What are genes?
A
A gene is a short length of DNA that codes for a specific protein and therefore genes hold the information needed to build and maintain the body
22
Q
Do genes locations change?
A
Genes have fixed locations: each gene is in a particular place on a particular chromosome.
23
Q
What chromosomes do diploids contain?
A
Diploids have 2 copies of each chromosome, one from each parent. This means 2 copies of each gene.
24
Q
How many chromosomes do we have?
A
We have 46 chromosomes, or 23 pairs.
25
What are 44 of the 46 chromosomes called? How are they labeled and what are their sizes?
44 of the 46 chromosomes are called autosomes and are numbered 1 through 22. Chromosome 1 is the longest, 22 is the shortest.
26
What are the other two chromosomes (not autosomes) called?
The other 2 chromosomes are the sex chromosomes: the X chromosome and the Y chromosome.
27
What sex chromosomes do males and females have?
Males have an X and a Y, females have 2 X's: XY vs. XX.
28
What is the basic rule of sex determination?
If a Y is present the person is male
29
What happens to the X and Y chromosomes in males for meiosis?
The X and Y chromosomes separate and go into different sperm cells
30
How many sperm carry the X and Y chromosomes?
1/2 the sperm carry the X and the other half carry the Y.
31
What do all eggs have with regard to chromosomes?
All eggs have one of the mother's X chromosomes.
32
What does the Y chromosome have on it?
The Y chromosome has the main sex-determining gene on it, called SRY.
33
What happens with regard to sex about 4 weeks after fertilization?
About 4 weeks after fertilization, an embryo that contains the SRY gene develops testes, the primary male sex organ.
34
If an embryo develops testes, what do they secrete?
The testes secrete the hormone testosterone.
35
What does testosterone do after it has been secreted by the testes of the embryo?
Testosterone signals the other cells of the embryo to develop in the male pattern.
36
What are the causes of inherited variations?
1. Sexual reproduction
2. The independent assortment of chromosomes when gametes are formed
3. Crossing over during Meiosis - this allows genes to move between chromosomes
4. Mutations
37
Are offspring identical to their parents?
Offspring are similar to their parents but are not identical
38
What are differences between parents and offspring caused by?
This is caused by crossing over
39
Can humans survive with 1 or 3 copies of any chromosome except for X and Y?
Except for the X and Y, humans don't survive with only 1 copy of any chromosome. Also, 3 copies is lethal in most cases.
40
What is Down-Syndrome and what is another name for it?
Down-Syndrome is the most common human aneuploidy. It is also called trisomy-21, meaning 3 copies of chromosome number 21.
41
What can chromosomes be broken by?
By X-rays and by certain chemicals.
42
What happens usually when chromosomes are broken?
The broken ends spontaneously rejoin, but if there are multiple breaks, the ends join at random.
43
If there are multiple breaks and the ends join at random, what does this lead to?
This leads to alterations in chromosome structure.
44
Are the syndromes with alterations in chromosome structure as well defined as with number variations? Explain.
There are lots of ways chromosomes can change structure, so the syndromes are not as well defined as with number variations.
45
What are point mutations?
These are changes in just one base pair of a gene.
46
What happens if a point mutation occurs in a gamete or in a cell that gives rise to gametes? Give an example.
If a point mutation occurs in a gamete or in a cell that gives rise to gametes, it may be transmitted to offspring and to a succession of future generations e.g. sickle cell anaemia.
47
How does a point mutation causing sickle cell anaemia affect a person?
Damage is caused to the red blood cell membrane, resulting in a cellular lifespan of only a few days. Due to the sickle cell shape, small capillaries may become blocked.
48
What are other causes of mutations?
Radiation, Sunlight (containing UV radiation), smoking
49
What does DNA stand for?
Deoxyribonucleic acid
50
What is DNA?
Hereditary material that carries and passes on genetic information. It is a nucleic acid made up of nucleotides.
51
What is the structure of DNA?
DNA is a double helix. It consists of two parallel strands each with a series of bases to the inside. The bases are directly opposite each other and they link each other in pairs. These links form the steps of the ladder.
52
What do the bases A, T, C and G stand for?
Adenine, Thymine, Cytosine, Guanine
53
What is the base pair rule?
Adenine can only join to Thymine and Guanine can only join to Cytosine.
54
What percent of DNA is composed of genes? What is the rest of DNA made up of?
Only about 3% of DNA is composed of genes. 97% of DNA is non coding DNA or junk DNA.
55
What are coding DNA and what are coding DNA in genes called?
The parts of DNA that contain information to make RNA or protein. Coding DNA in genes are called exons.
56
What are non coding DNA and what are non coding DNA in genes called?
The parts of DNA that do not contain critical information for the production of protein. They are now thought to play a role in gene expression. Non coding DNA within genes is called introns.
57
What are the differences between DNA and RNA?
DNA: Double strand, Sugar is deoxyribose, has Thymine, Very long, Self replicating, Found only in the nucleus.
RNA: Single strand, Sugar is ribose, Has Uracil, Short molecule, Not self replicating, Found in nucleus and cytoplam.
58
What are the similarities between DNA and RNA?
Both are nucleic acids.
Both contain adenine, guanine and cytosine nucleotides.
Operate together to produce specific proteins.
59
What are nucleotides?
Nucleotides are carbon ring structures containing nitrogen linked to a 5-carbon sugar (a ribose). 5-carbon sugar is either a ribose or a deoxyribose.
60
Draw a nucleotide
.
61
In eukaryotic cells what are nucleic acids?
In eukaryotic cells nucleic acids are either:
Deoxyribose nucleic acids (DNA)
Ribose nucleic acids (RNA)
62
Give examples of non-coding structures?
Sugar - Phosphate
63
Give examples of coding structures?
Base Sequences
64
What are Purine Bases (incl. examples)?
Double ringed molecular structures - Adenine and Guanine
65
What are Pyramidine bases (incl. examples)?
Single ringed structures - Thymine and Cytosine
66
Draw Adenine and Guanine (Purines) and Thymine, Uracil and Cytosine (Pyramidines).
.
67
How was base pairing discovered?
Number of Purine Bases = Number of Pyramidine Bases
68
Who discovered the model of DNA?
Watson and Crick
69
What is the model of DNA called?
The Watson-Crick Model of DNA
70
How do we get from genes to proteins (to protein synthesis)?
Processing the information contained in DNA into proteins involves a sequence of events known as gene expression and results in protein synthesis.
71
How are proteins built?
Proteins are not built directly from genes. Hereditary information is transferred from DNA to a working set of directions
- RNA
72
What two steps does gene expression occur in?
transcription and translation
73
Where are the genes directing protein production, the enzymes and amino acid building blocks found?
The genes directing protein production are in the nucleus. The enzymes and amino acid building blocks for proteins are found at the ribosomes in the cytoplasm.
74
What must happen before proteins are made from genes and how does this happen?
Before proteins are made from these genes an RNA molecule must be made. RNA, ribonucleic acid, is responsible for taking the genetic information from the DNA in the nucleus to the site of protein synthesis.
75
How does RNA differ from DNA?
RNA differs from DNA in three main ways:
- RNA is single stranded
- RNA contains ribose not deoxyribose
- RNA contains uracil (U) not thymine (bonds with adenine)
76
What types of RNA are essential for gene expression?
Three types of RNA are essential for gene expression:
- mRNA - carries information from DNA to ribosomes (working copy of DNA).
- tRNA - carries amino acids to ribosomes
- rRNA - plays a structural role in ribosomes
77
What happens in transcription and where does it happen?
- Cell assembles a molecule of RNA using DNA as a template.
| - In eukaryotic organisms this takes place in the nucleus
78
What are proteins made up of?
Proteins are made up of one or more polypeptides, each of which consists of a specific sequence of amino acids linked together by peptide bonds
79
What is genetic code made of and where do you find the stuff its made of?
All organisms have a genetic code made of three-nucleotide sequences called codons. The codon is located on the mRNA.
80
What is translation where does it happens and what are the tools of translation?
Cell produces a protein. Occurs at the ribosome in the cytoplasm where the cell keeps its supply of tRNA.
Tools of translation (in addition to mRNA)...
- tRNA
- Ribosomes (rRNA)
81
How does translation happen?
The ribosome translates the code. The code is used to assemble amino acids in the correct sequence. This forms a specific protein.
82
What happens to the structure of the new specific protein? What is this structure known as?
The new protein is folded to give the correct shape. This is known as the functional shape.
83
How does mRNA make a copy of one side of a DNA molecule?
DNA uncoils and unzips. The exposed DNA bases are matched up with RNA bases in the nucleus to form mRNA.
84
What is transcription and where does it take place?
Transcription takes places in the nucleus of the cell. It is the process by which the information from DNA is transferred to RNA.
85
What is the function of a messenger RNA and what is it made of?
Messenger RNA (mRNA) carries the information for a specific protein. Made up of 500 to 1000 nucleotides long. Made up of codons (sequences of three bases). Each codon is specific for one amino acid.
86
What is the function of a transfer RNA and what is it made of?
tRNA is made up of 75 to 80 nucleotides long. Picks up the appropriate amino acid floating in the cytoplasm. Transports amino acids to the mRNA. Has anticodons that are complementary to mRNA codons. Recognizes the appropriate codons on the mRNA and bonds to them with H-bonds.
87
What is the function of a ribosomal RNA (rRNA) and what is it made of?
rRNA is made up of 100 to 3000 nucleotides long. Important structural component of a ribosome. Associates with proteins to form ribosomes.
88
Where and how does translation occur?
In the cytoplasm, translation occurs. The mRNA binds to a ribosome. The strand of mRNA is pulled through the ribosome three bases at a time, in triplets. Each of these triplets on the mRNA strand is called a codon.
89
What is the first thing transfer RNA does?
Transfer RNA (tRNA), reads the strand of mRNA and translates it into a strand of amino acids.
90
What are the end products of protein synthesis?
A primary structure of a protein.
91
What is a primary structure of a protein?
A sequence of amino acids bonded together by peptide bonds.
92
What has to happen to the primary structure of a protein made by protein synthesis? Why?
The protein has to undergo folding and the addition of bonds. Folding allows the protein to reach its 3D (Tertiary Shape) which influences its function.
93
What does a molecule of tRNA have at one end, what is it called and what will it do?
A molecule of tRNA has at one end a set of three bases that will complement the mRNA strand; this is called the anticodon.
94
What happens if the 3 base anticodon of the tRNA complements the 3 base codon of the mRNA?
If the 3 base anticodon of the tRNA complements the 3 base codon of the mRNA, they briefly combine.
95
What happens when the tRNA leaves?
The amino acid is left behind when the tRNA leaves.
96
What happens as each codon is read?
As each codon is read, the next tRNA brings in a new amino acid and the polypeptide (protein) chain grows.
97
What does the next tRNA bringing in a new amino acid and the polypeptide (protein) chain growing require?
This requires enzymes and ATP.
98
What is the principle in DNA profiling?
All human chromosomes have sections of DNA with no known functions. These sections have short base sequences. These sequences repeat over and over. They are inherited from parents. Their length and position are unique to each person.
99
What is DNA profiling?
A process or technique of analysis revealing unique patterns of an individual's DNA involving non-coding regions.
100
What are the stages involved in DNA profiling?
Cells broken down to release DNA. DNA strands cut into fragments. Fragments separated. Pattern of fragments analysed.
101
What is electrophoresis?
Samples containing the fragments are placed into individual wells in a gel using a pipette. Fragments separated by length. DNA (negatively charged) moves towards + positive terminal. Shorter fragments move faster.
102
What happens in DNA transfer?
DNA split into single strands using alkaline solution
103
What happens in analysis?
Radioactive probe in solution binds to DNA -> X-ray film -> Revealing a pattern of bands
104
What are the Applications of Genetic Screening?
Paternity disputes, Forensic Science, Genetic Screening, Genetic Archaeology
105
What are common concerns of genetic profiling?
Quality of sample, Mistakes and inaccuracy, Interpretation, Privacy, Evidence from criminal investigation, Who should use DNA fingerprinting, Cost effective, Ethnic problems.
106
What is genetic screening?
Genetic screening is used to test individuals who are at high risk of having or passing on a specific genetic disorder.
107
What are screening tests that can be done?
Antenatal serum screening for Down Syndrome.
Antenatal carrier screening for Sickle Cell Anaemia.
Predictive testing for hereditary cancers.
Predictive testing for cystic fibrosis.
Newborn screening for phenylketonuria, cystic fibrosis and hypothyroidism.
108
Mendel's Peas - Why Peas?
- Pure lines with easily identifiable traits were available.
- Peas are self-fertilizing with a flower structure that minimizes accidental pollination.
- Peas can be artificially fertilized which allows specific crosses to be made. Peas have a short growth period.
- Peas produce large numbers of offspring.
109
What are Mendel's two laws?
The Law of Segregation
| The Law of Independent Assortment
110
Explain Mendel's First Principle
- Mendel assumed that the two "Factors" for each trait must exist in the parental cells producing the gametes.
- These "Factors" came from the parent's parents and were united in fertilization.
- In forming pollen and egg, the two "factors" for any trait must separate and go into different gametes.
- This became know as Mendel's "Principle of Segregation".
111
What is the Law of Segregation?
"Characteristics are controlled by pairs of factors; but only one factor can be carried in a gamete"
112
What is the Law of Independent Assortment?
"Where two or more characteristics are concerned, the "factors" for these enter the gametes independently of each other". States when gametes are formed either pair of factors is equally likely to combine with another pair of factors.
113
What is the Law of Independent Assortment?
Two characters are inherited independently
114
What is a dihybrid test cross?
In a dihybrid cross the test cross is made with an individual which is homozygous recessive for both characters (rryy)
115
What is the locus of a gene?
The locus of a gene is it's position on a chromosome
116
How many colour receptors do we have and where?
We have 3 colour receptors in the retinas of our eyes.
117
What colours do colour receptors respond best to?
They respond best to red, green and blue light.
118
What is each colour receptor made by?
Each receptor is made by a gene.
119
Where is the blue receptor?
On an autosome
120
Where are the red and green receptors? What does this mean?
The red and green receptors are on the X chromosome (sex-linked)
121
What type of vision does a heterozygous female have?
A heterozygous female has normal colour vision
122
Where do sons get their only X from?
Sons get their only X from their mother
123
What type of vision will the sons of a heterozygous mother have?
So, 1/2 of the sons of a heterozygous mother are colourblind, and 1/2 are normal
124
What is Non Nuclear Inheritance?
Non nuclear genes
Present in small circles of DNA
In mitochondria and chloroplasts
125
How are mitochondria and chloroplasts normally passed on to the next generation? What line on inheritance do they follow and why?
Mitochondria and chloroplasts are normally passed on to the next generation in the cytoplasm of the egg.
They follow a maternal line of inheritance because male gametes contribute only their nucleus to the zygote at fertilization.
126
What is evolution?
Evolution is the changing of one species into another that takes place through natural selection. It takes place over a long period of time.
127
What observations did Darwin make?
Over breeding
Population numbers remain constant
Inherited variations occur in populations
128
What is the mechanism of evolution?
Too many offspring are produced. This leads to competition. All populations have genetic variations. Individuals that are best adapted to the environment survive. As the environment changes new adaptations emerge. Over a long period of time a new species forms.
129
What evidence is there for evolution?
Fossils show changes compared to modern organisms. Some fossil organisms are extinct. Modern fossils show increased complexity. Fossil evidence can be linked to environmental change.
130
What is genetic engineering?
The simple addition, deletion, or manipulation of a single trait in an organism to create a desired change.
131
What is the altered DNA called?
recombinant DNA
132
What is recombinant DNA joined to? What is this called?
Recombinant DNA is joined to other unrelated DNA in the organism. This is called gene splicing.
133
What is gene splicing?
Recombinant DNA is joined to other unrelated DNA in the organism.
134
What do GMO and GEO mean?
GMO - genetically modified organism
| GEO - genetically enhanced organism
135
What are examples of transgenic organisms?
Plants that resists a particular type of weed killer.
| Sheep which makes some special substance in it's milk.
136
What are the 5 stages involved in GE?
1. Isolation 2. Cutting 3. Ligation and Insertion
4. Transformation 5. Expression
137
What is isolation? Give an example
Isolation of a specific gene from donor e.g. human
138
What is cutting?
Restriction enzymes act as molecular scissors and cut DNA at specific sites called restriction sites.
139
What is ligation?
Rejoining cut fragments of DNA and forming artificial recombinant molecules.
140
What is transformation?
Recombinant DNA introduced into bacterial cell.
141
Give examples of how animals are used in GE
The human gene to clot blood has been inserted into the DNA of sheep. Sheep produce human clotting factor needed for Haemophiliacs in their milk. Goats produce a protein to treat emphysema.
142
What are applications (micro-organisms) of GE?
Production of humulin used by diabetics by bacteria.
This prevented many diabetics from getting and allergic reaction to animal insulin. Bacteria make interferon which can fight virus infections and some cancers.
143
What is a plant application of GE?
Golden Rice - a possible solution to Vitamin A deficiency. The gene which produces vitamin A was taken from daffodils and put into rice to help prevent blindness.
Weedkiller resistant crops - weeds die but the crops survive.
