BIO FINAL EXAM 2 Flashcards
(187 cards)
1
Q
What is the structure of nucleic acids?
A
Long chains of nucleotides with a sugar, phosphate group, and nitrogen base; DNA is double-stranded, RNA is single-stranded.
2
Q
What is chromatin?
A
DNA wrapped around histone proteins, found in the nucleus.
3
Q
What is a gene?
A
A segment of DNA that codes for a protein.
4
Q
What is a genome?
A
The complete set of DNA (all genes) in an organism.
5
Q
How does DNA replication occur?
A
DNA unzips, and each strand serves as a template to build a new complementary strand using DNA polymerase.
6
Q
What is semi-conservative replication?
A
Each new DNA molecule has one old strand and one new strand.
7
Q
Where does DNA replication occur in eukaryotic cells?
A
In the nucleus.
8
Q
What is the role of DNA polymerase?
A
It adds nucleotides to build the new DNA strand and proofreads for errors.
9
Q
What is complementary base pairing?
A
A pairs with T, and C pairs with G (in RNA, A pairs with U).
10
Q
What are the types of RNA and how are they different from DNA?
A
mRNA: Carries message from DNA to ribosomes.
tRNA: Transfers amino acids during protein synthesis.
rRNA: Makes up ribosomes.
RNA is single-stranded, has uracil instead of thymine, and uses ribose sugar.
11
Q
How does transcription occur?
A
RNA polymerase uses one DNA strand as a template to make mRNA.
12
Q
What is a ‘template’ strand?
A
The DNA strand used to create complementary mRNA.
13
Q
Where does transcription occur in eukaryotic cells?
A
In the nucleus.
14
Q
What does RNA polymerase do?
A
It builds RNA using the DNA template.
Similar to DNA polymerase: both synthesize nucleic acids. Different: RNA polymerase makes RNA, doesn’t need a primer, and doesn’t proofread.
15
Q
A
16
Q
What is the leading strand?
A
The strand synthesized continuously in the 5’ to 3’ direction, toward the replication fork.
17
Q
What is the lagging strand?
A
The strand synthesized in short fragments (Okazaki fragments), away from the replication fork.
18
Q
What are Okazaki fragments?
A
Short DNA segments formed on the lagging strand; later joined together.
19
Q
In what direction are Okazaki fragments built?
A
Each fragment is built in the 5’ to 3’ direction.
20
Q
What enzyme joins Okazaki fragments?
A
DNA ligase — it connects the fragments into a continuous strand.
21
Q
What enzyme builds new DNA strands?
A
DNA polymerase III — adds nucleotides to the growing strand.
22
Q
What enzyme creates the RNA primer?
A
Primase — it lays down a short RNA sequence to start replication.
23
Q
What is the function of the primer?
A
Provides a starting point for DNA polymerase to begin synthesis.
24
Q
What is the replication fork?
A
The area where the DNA double helix is unwinding for replication.
25
Why can’t DNA polymerase start replication on its own?
It needs an RNA primer to begin adding nucleotides — it can only extend, not start synthesis.
26
How does translation occur?
mRNA binds to a ribosome. tRNA brings amino acids to match codons, forming a polypeptide chain.
27
Where does translation happen in eukaryotic cells?
In the cytoplasm, at the ribosome.
28
What are the components involved in translation?
mRNA, ribosome, tRNA, amino acids, enzymes.
29
What is a codon?
A three-base sequence on mRNA that codes for one amino acid.
30
How do you use a codon table?
Match the three-letter mRNA codon to its corresponding amino acid on the chart.
31
What does the codon table represent?
It shows the amino acids based on mRNA codons.
32
What happens if the DNA sequence changes?
It can alter the codon, changing the amino acid in the protein — this is called a mutation.
33
Types of mutations
Silent: No change in amino acid.
Neutral: New amino acid, no big effect.
Missense: One amino acid is changed — may affect function.
Nonsense: Changes to a stop codon — ends translation early.
34
What happens if a base is added or deleted?
Causes a frameshift mutation, changing the entire reading frame of the mRNA.
35
Example of a point mutation disorder
Sickle cell anemia — caused by a single base change in the gene for hemoglobin.
36
What is the purpose of cell division?
To allow growth, repair, reproduction, and maintenance of organisms.
37
What is the difference between mitosis and meiosis?
Mitosis produces 2 identical cells (for growth/repair). Meiosis produces 4 genetically different gametes (for reproduction).
38
What is the cell cycle?
A series of phases (G1, S, G2, M) a cell goes through to grow and divide.
39
What is the appearance of a cell during interphase?
Nucleus is visible, DNA is in chromatin form, and the cell is growing and copying DNA.
40
What happens in G0, G1, and G2 phases?
G0: Cell rests or exits cycle. G1: Cell grows and prepares for DNA replication. G2: Final preparation before mitosis (organelles replicate).
41
What is the function of mitosis?
To divide the nucleus and ensure each daughter cell gets the same DNA.
42
What are the stages of mitosis and what happens?
Prophase: Chromosomes condense, spindle forms. Metaphase: Chromosomes line up at the center. Anaphase: Sister chromatids separate. Telophase: Nuclei reform, chromosomes uncoil.
43
How do chromosomes move during mitosis?
Spindle fibers (microtubules) pull them apart using kinetochores.
44
Why are daughter cells from mitosis identical?
They receive exact copies of DNA unless mutations occur.
45
What is the cell cycle control system?
A set of checkpoints and regulatory proteins that control cell progression.
46
What is cytokinesis?
The division of the cytoplasm into two separate cells.
47
What is the difference in cytokinesis between animal and plant cells?
Animal: Cleavage furrow pinches the cell in two. Plant: Cell plate forms to divide the cell.
48
What is the function of meiosis?
To produce haploid gametes (sperm or eggs) for sexual reproduction.
49
Why is meiosis necessary?
It ensures that offspring have the correct number of chromosomes by halving the number in gametes.
50
What are sister chromatids?
Identical copies of a chromosome joined at the centromere.
51
What are homologous chromosomes?
Chromosomes with the same genes but possibly different alleles — one from each parent.
52
What is synapsis?
Pairing of homologous chromosomes during prophase I of meiosis.
53
What is crossing over?
Exchange of genetic material between homologous chromosomes, increasing variation.
54
What is a chiasma (plural: chiasmata)?
The point where crossing over occurs between homologous chromosomes.
55
What is a tetrad?
A group of four chromatids (two homologous chromosomes, each with two sister chromatids) during meiosis I.
56
What is disjunction?
Proper separation of homologous chromosomes or sister chromatids during meiosis.
57
What is non-disjunction?
Failure of chromosomes to separate properly, leading to gametes with the wrong number of chromosomes.
58
What is independent assortment?
Random orientation of homologous chromosomes during metaphase I — contributes to genetic diversity.
59
What happens during meiosis?
Meiosis I: Homologous chromosomes separate.
Meiosis II: Sister chromatids separate (like mitosis).
60
What’s the difference between haploid and diploid?
Haploid (n): One set of chromosomes (gametes).
Diploid (2n): Two sets (one from each parent).
61
Differences between mitosis and meiosis I?
Mitosis: No pairing of homologs or crossing over.
Meiosis I: Homologs pair, cross over, and separate.
62
Comparison of meiosis II and mitosis?
Both separate sister chromatids, but meiosis II happens in haploid cells.
63
Consequences of non-disjunction in meiosis I vs. II?
Meiosis I: All gametes affected.
Meiosis II: Only half affected.
64
Sources of genetic variation in meiosis?
Crossing over
Independent assortment
Random fertilization
65
Do plants and animals have different sexual life cycles?
Yes — plants alternate between haploid and diploid generations, while animals are mostly diploid.
66
In what type of tissues does meiosis occur?
Meiosis occurs in germinal (germ line) tissues.
67
Where does meiosis take place in animals?
In the ovaries and testes.
68
Where does meiosis take place in plants?
In the pistils and anthers.
69
How many nuclear divisions occur during meiosis?
Two successive nuclear divisions occur: meiosis I and meiosis II.
70
How many times are chromosomes duplicated during meiosis?
Chromosomes are duplicated only once, before meiosis I begins.
71
What type of division is meiosis considered?
Meiosis is considered a reduction division because it reduces the chromosome number from diploid (2n) to haploid (n).
72
What makes reduction division possible in meiosis?
It is made possible by the way homologous chromosomes uniquely pair and align during meiosis I.
73
How do chromosomes behave differently in mitosis compared to meiosis?
In mitosis, individual chromosomes line up and sister chromatids separate.
In meiosis, homologous chromosomes align and separate in meiosis I, followed by separation of sister chromatids in meiosis II.
74
How many daughter cells are produced at the end of meiosis, and what is their chromosome number?
Four daughter cells are produced, each with half the number of chromosomes as the original parent cell.
75
How many daughter cells are produced at the end of mitosis, and what are they like?
Two identical diploid daughter cells, genetically the same as the parent cell.
76
Why are the daughter cells produced by meiosis genetically different?
Because of crossing over and independent assortment during meiosis I.
77
What is crossing over?
The exchange of genetic material between homologous chromosomes during prophase I of meiosis.
78
What is independent assortment?
The random distribution of homologous chromosomes during metaphase I of meiosis, contributing to genetic variation.
79
If a cell has 8 chromosomes at metaphase of mitosis, how many chromosomes will it have during anaphase?
16 chromosomes – because each sister chromatid is now considered a separate chromosome.
80
How do the daughter cells at the end of mitosis and cytokinesis compare with the parent cell when it was in G1 of the cell cycle?
They have the same number of chromosomes and the same amount of DNA.
81
What is the centromere?
The centromere is the region where chromatids are attached to one another.
82
At what phase of mitosis do chromosomes align at the center of the cell?
Metaphase
83
In mitosis, are the daughter cells haploid or diploid?
Diploid — they have the same number of chromosomes as the parent cell.
84
Are the chromosomes in daughter cells genetically identical to the parent cell in mitosis?
Yes, they are genetically identical, unless a mutation occurred.
85
What is the Law of Segregation?
Each individual has two alleles for a trait, and these alleles separate during gamete formation.
86
What is the Law of Independent Assortment?
Alleles of different genes separate independently during gamete formation.
87
What is a character in genetics?
A heritable feature (e.g., flower color).
88
What is a trait?
A specific version of a character (e.g., purple or white flowers).
89
What is a gene?
A segment of DNA that codes for a trait.
90
What is an allele?
Different versions of the same gene.
91
What is a locus?
The physical location of a gene on a chromosome.
92
What is phenotype?
The observable traits (e.g., tall, round).
93
What does dominant mean?
An allele that expresses its effect even when only one copy is present (e.g., A).
94
What does recessive mean?
An allele that is only expressed when two copies are present (e.g., a).
95
What is a true breeding variety?
An organism that always passes down the same traits to offspring (homozygous).
96
What does homozygous mean?
Having two identical alleles (AA or aa).
97
What does heterozygous mean?
Having two different alleles (Aa).
98
What is the P generation?
The parental generation in a genetic cross.
99
What are the F1 and F2 generations?
F1: First generation of offspring from P.
F2: Offspring of F1 × F1 cross.
100
What is a hybrid generation?
Offspring resulting from the cross of genetically different parents.
101
What is a Punnett square used for?
To predict possible genotypes and phenotypes of offspring.
102
How do you calculate genetic probabilities?
Use rules of probability (multiplication and addition) to determine the chance of genotypes/phenotypes from monohybrid and dihybrid crosses.
103
What is a test cross?
Crossing an individual with an unknown genotype with a homozygous recessive to determine its genotype.
104
What is incomplete dominance?
A blend of traits (e.g., red + white = pink flowers).
105
What is codominance?
Both alleles are fully expressed (e.g., AB blood type).
106
What are multiple alleles?
More than two possible alleles for a gene (e.g., blood types A, B, O).
106
What is expressivity?
The degree to which a trait is expressed.
107
What is multifactorial inheritance?
Traits influenced by genes and environment.
108
What is sex-linked inheritance?
Traits associated with genes on the sex chromosomes (often X-linked).
109
Why are human blood groups genetically and clinically important?
They determine compatibility for blood transfusions and reflect codominance and multiple allele inheritance.
110
What is an autosomal recessive pattern of inheritance?
A condition appears only when both alleles are mutated (aa).
Example: Cystic fibrosis.
111
What is an autosomal dominant pattern of inheritance?
Only one mutated allele (Aa or AA) causes the condition.
Example: Huntington’s disease.
112
What is a sex-linked recessive pattern?
The gene is on the X chromosome; more common in males.
Example: Hemophilia.
113
What is a sex-linked dominant pattern?
A dominant gene on the X chromosome; can affect both sexes, but more severe in males.
Example: Rett syndrome.
114
How can you deduce the mode of inheritance from a pedigree?
Skips generations: likely recessive.
Affects both sexes equally: likely autosomal.
More males affected: likely X-linked recessive.
Affected fathers passing to daughters but not sons: X-linked dominant.
115
What are changes in chromosome structure or number called?
Chromosomal mutations — including deletions, duplications, inversions, and translocations; number changes include aneuploidy and polyploidy.
116
What is aneuploidy?
An abnormal number of chromosomes (e.g., 45 or 47 instead of 46).
Example: Trisomy 21 (Down syndrome).
117
What are the consequences of aneuploidy?
Can lead to developmental disorders, miscarriages, or genetic syndromes.
118
Why are chromosomal deletions often lethal?
Losing essential genes can disrupt key biological functions, leading to death or severe disorders.
119
What is polyploidy?
Having more than two complete sets of chromosomes (e.g., 3n, 4n).
Common in plants, rare and often lethal in animals.
120
What is the theory of natural selection?
It is the process where organisms better adapted to their environment survive and reproduce more successfully.
121
What observations did Darwin make on the HMS Beagle?
He noticed variations in species across different environments, such as finch beak shapes in the Galápagos Islands.
122
How did Darwin arrive at his theory of natural selection?
By observing variation among species and recognizing that traits aiding survival become more common over generations.
123
Why is variation important in natural selection?
It provides the raw material for evolution—without variation, natural selection can't act.
124
What is natural selection?
The process by which individuals with favorable traits are more likely to survive and reproduce, passing those traits on.
125
What are homologous structures?
Structures that are similar in form and origin but may have different functions (e.g., human arm and bat wing).
126
What are analogous structures?
Structures that have similar functions but different evolutionary origins (e.g., bird wings and insect wings).
127
What is the pentadactyl limb?
A five-digit limb structure found in many vertebrates, evidence of a common ancestor.
128
What is the fossil record?
The fossil record shows preserved remains of ancient organisms and the order in which they appeared.
129
How is relative dating used in fossils?
By comparing the placement of fossils in sedimentary layers using index fossils to determine age.
130
How does radioactive dating help with fossils?
It measures the decay of radioactive isotopes to determine the actual age of rocks and fossils.
131
Why is the fossil record of macroevolution incomplete?
Not all organisms fossilize, and many fossils are yet to be found or have been destroyed over time.
132
What is biogeography?
The study of the geographic distribution of species across Earth.
133
How does continental drift affect evolution?
It rearranges landmasses, isolating populations and leading to new species through geographical isolation.
134
What is the difference between homologous and analogous structures?
Homologous: Same origin, different function (e.g., whale flipper and human arm) — from divergent evolution.
Analogous: Different origin, same function (e.g., bird and insect wings) — from convergent evolution.
135
What are vestigial structures?
Structures with no current function but that were useful to ancestors (e.g., human appendix, whale pelvis).
136
How does molecular biology support evolution?
Similar DNA, proteins, and genes among species show common ancestry (e.g., humans and chimps share ~98% DNA).
137
What is the carbonaria form of Biston betularia (peppered moth)?
A darker-colored moth that became more common during industrialization due to better camouflage on soot-covered trees — an example of natural selection in action.
138
How does evolution explain drug and pesticide resistance?
Random mutations allow some organisms to survive drugs or pesticides, and these traits spread through reproduction.
139
How does population genetics contribute to our understanding of evolution?
It shows how allele frequencies change over time in populations, explaining how evolution works on a genetic level.
140
What conditions must be met for the Hardy-Weinberg theorem to apply?
No mutation, random mating, no natural selection, large population, and no gene flow.
141
What causes microevolution?
Changes in allele frequencies due to mutation, selection, gene flow, genetic drift, and non-random mating.
142
How can genetic variation occur?
Through mutations, sexual reproduction, gene shuffling, and recombination.
143
What is a gene pool?
All the alleles in all individuals of a population.
144
What is a species?
A group of organisms that can breed and produce fertile offspring.
145
What is genetic drift?
Random changes in allele frequencies in small populations.
146
What is the founder effect?
When a new population is started by a few individuals, causing limited genetic variation.
147
What is the bottleneck effect?
When a population's size is drastically reduced, leading to reduced genetic diversity.
148
What is gene flow?
The movement of alleles from one population to another.
149
What is differential mating?
When certain traits make individuals more likely to mate and pass on genes.
150
How does migration affect allele distribution?
It introduces new alleles or changes frequencies by adding or removing genes.
151
How does genetic drift affect allele distribution?
It changes allele frequencies by chance, especially in small populations.
152
How does randomness affect allele distribution?
Random events can increase or decrease allele frequencies unpredictably.
153
How does natural selection affect how alleles are passed to the next generation?
It increases the frequency of beneficial alleles and decreases harmful ones.
154
What is genetic polymorphism? Give an example.
The existence of two or more forms of a gene in a population (e.g., blood types).
155
What is balanced polymorphism? Give an example.
When multiple alleles are kept in a population due to selective advantages (e.g., sickle cell trait vs. malaria resistance).
156
What is heterozygote advantage? Give an example.
When heterozygous individuals have a survival advantage (e.g., sickle cell carriers resist malaria better).
157
How does selective pressure affect adaptation?
It favors traits that help survival and reproduction, causing those traits to become more common.
158
What is stabilizing selection?
It favors the average traits and reduces variation.
159
What is directional selection?
It favors one extreme trait over others.
160
What is diversifying (disruptive) selection?
It favors both extremes of a trait and selects against the average.
161
What is sexual selection and how does it cause sexual dimorphism?
It’s when traits increase mating success. It causes males and females to look different.
162
What is speciation?
The formation of new species from existing ones.
163
What is the difference between morphological and biological species?
Morphological species are based on physical traits; biological species are based on the ability to breed and have fertile offspring.
164
How do isolating mechanisms maintain species integrity?
They prevent mating or successful reproduction between different species.
165
What is gradual speciation?
A slow and steady evolution of species over time.
166
What is punctuated speciation?
Sudden changes in species followed by long periods of no change.
167
What are prezygotic barriers?
Barriers that prevent fertilization (like timing or mating behavior).
168
What are postzygotic barriers?
Barriers that occur after fertilization (like infertile offspring).
169
What is allopatric speciation?
Speciation caused by geographic separation.
170
What is sympatric speciation?
Speciation without geographic separation, often due to behavioral or genetic differences.
171
What is parapatric speciation?
Speciation in neighboring populations with limited mating.
172
What is phylogeny?
The evolutionary history of a species or group.
173
What is a phylogenetic tree?
A diagram showing evolutionary relationships between species.
174
What features are shared by all animals?
Multicellular, heterotrophic, and cells without cell walls.
175
What are invertebrates?
Animals without a backbone.
176
What is segmentation?
Division of the body into repeated parts or segments.
177
What is radial symmetry?
Body parts arranged around a central axis (like a starfish).
178
What is bilateral symmetry?
Body has left and right sides that are mirror images (like humans).
179
What are the four characteristics of chordates?
1.Notochord
2.Dorsal, hollow nerve cord
3.Pharyngeal slits or clefts
4.Muscular, post-anal tail
180
What are some specializations that evolved in vertebrates?
-Backbone (vertebral column)
-Skull and brain protection
-Jaws
-Paired appendages
-Complex organs
181
What is the phylogenetic relationship of major vertebrate classes?
They evolved from a common chordate ancestor and diverged into groups like fish, amphibians, reptiles, birds, and mammals.
182
How do members of the vertebrate class differ from non-vertebrates?
They have a backbone, more complex nervous systems, and internal skeletons.
183
What does "tetrapod" mean?
It means "four feet" – vertebrates with two pairs of limbs (like amphibians, reptiles, birds, and mammals).
184
How did jaws evolve in gnathostomes (placoderms)?
Jaws evolved from gill arches in early jawless fish, allowing better feeding and survival.
185
What is the Class Chondrichthyes?
Cartilaginous fish like sharks and rays – the first vertebrates to have jaws.
186
What are features of Chondrichthyes?
-Cartilage skeleton
-Jaws
-Paired fins
-Gill slits
-No swim bladder
