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Genetics and Evolution Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a gene’s locus?

A
  • its location on a specific chromosome

- the normal locus of a gene is the same across all humans

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2
Q

How many alleles does one inherit per gene?

A

-2 alleles as we all have 2 copies of each chromosome (homologues) - except for male sex chromos

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3
Q

What is a hemizygous genotype?

A

-only one allele is present for a given gene, like parts of the X chromo in males

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4
Q

What is complete dominance?

A

-only one dominant and one recessive allele exist for a given gene, so presence of dominant will mask recessive if it’s present

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5
Q

What is codominance?

A

-when more than one dominant allele exists for a given gene, like A and B for AB blood type

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6
Q

What is incomplete dominance?

A

-when a heterozygote expresses a phenotype that is intermediate between the two homozygous genotypes - like Rr is pink

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7
Q

What is penetrance?

A
  • population parameter: probability that, given a particular genotype, a person will express the phenotype
  • can be full (100% of those who have it express it), high, reduced, low, or even nonpenetrance
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8
Q

What is expressivity?

A
  • varying phenotypes despite identical genotypes
  • if constant, then all individuals with a given genotype express the same pheno
  • if variable, there can be diff phenos
  • is on more individual level than penetrance
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9
Q

What is Mendel’s first law? With which phase of meiosis does it correlate?

A
  • Law of segregation
    1. Genes exist in alternative forms (alleles).
    2. An organism has 2 alleles for each gene - one inherited from each parent
    3. The 2 alleles segregate during meiosis, resulting in gametes that carry only 1 allele for any inherited trait
    4. If the 2 alleles are different, only one will be expressed (dominant) while the other is silent (recessive)
  • anaphase I of meiosis
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10
Q

What is Mendel’s second law? With which phase of meiosis does it correlate?

A
  • Law of independent assortment
  • inheritance of one gene does not affect the inheritance of another gene
  • recombination - results in novel allele combinations that were not present in the original chromosome
  • prophase I of meiosis
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11
Q

What did Frederick Griffith do and discover?

A
  • Worked with virulent and nonvirulent strains of bacteria causing pneumonia
    1. Rats injected with NV strain - lived
    2. Rats injected with V strain - died
    3. Rats injected with heat-killed V strain - lived
    4. Rats injected with heat-killed V strain and live NV strain - died and found live bacteria with smooth capsules (that V used to have) inside
  • found transformation principle
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12
Q

What did Avery, MacLeod, and McCarty discover?

A
  • separated cellular components of heat-killed V into extracts
  • found one particular extract that when added to NV bacteria killed rats
  • when this substance was treated with enzymes to degrade DNA, the bacteria was not transformed and mice lived
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13
Q

What did Hershey and Chase do in 1952?

A
  • created bacteriophages with radio-labeled DNA and protein
  • one group had radio-labeled S (in protein but not DNA), the other radio-labeled P (in DNA but not protein)
  • let the phages infect bacteria and found that radio-labeled DNA had entered them
  • concluded that DNA was heritable genetic material
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14
Q

What is the gene pool? What is a wild-type allele?

A
  • gene pool: all alleles that exist within a species

- wild-type: alleles considered normal and prevalent

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15
Q

How can mutations be introduced to DNA?

A
  • mutagens: UV light, chemicals, radiation
  • DNA polymerase making errors during replication
  • transposons inserting themselves in the middle of a coding sequence
  • incorrect nucleotide pairing during transcrip/translat, tRNA with incorrect amino acid for anticodon
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16
Q

What are the point mutations (silent, missense, nonsense)?

A
  • when one nucleotide is switched for another
    1. Silent: has no effect on final protein; commonly occurs when changed nucleotide is the third one in a codon bc there is degeneracy (wobble) in genetic code
    2. Missense: change results in substituting one AA for another in final protein
    3. Nonsense: results in substituting a stop codon for an AA in final protein
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17
Q

What is a frameshift mutation?

A
  • nucleotides are inserted or deleted
  • this shifts reading frame as mRNA is read in 3 letter codons
  • can cause changes in AA sequence, premature truncation from a nonsense mutation
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18
Q

What are the chromosomal mutations (deletion, duplication, inversion, insertion, and translocation)?

A
  1. Deletion: large segment of DNA is lost
  2. Duplication: segment of DNA is copied multiple times
  3. Inversion: segment is reversed within chromosome
  4. Insertion: segment is moved from one chromosome to another
  5. Translocation: segment from one chromo is swapped with segment from another
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19
Q

What is an example of an advantageous mutation?

A
  • sickle cell disease is a single NT mutation

- those who are heterozygous for sickle cell disease have minor symptoms + resistance to malaria

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20
Q

What is an example of a deleterious mutation?

A
  • XP: inherited defect in which UV radiation DNA damage cannot be repaired
  • can cause cancer
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21
Q

What are inborn errors of metabolism?

A
  • defects in genes required for metabolism
  • children who have these need early intervention against buildup of metabolites
  • Ex: PKU - AA phenylalanine accumulates, causing lots of disabilities
22
Q

What is genetic leakage? What are hybrids?

A
  • flow of genes between species
  • individuals from different species can mate to produce hybrid offspring, often infertile due to odd # of chromosomes, sometimes fertile with a member of one parent species or the other
23
Q

What is genetic drift?

A
  • changes in the composition of the gene pool due to chance

- more pronounced in smaller populations

24
Q

What is the founder effect?

A
  • extreme case of genetic drift
  • small population of a species in reproductive isolation due to natural barriers, catastrophic events, or other bottlenecks that drastically reduce population available
  • inbreeding may occur in later generations - encourages homozygosity
  • leads to reduction in genetic diversity
25
Q

What is inbreeding depression vs. outbreeding?

A
  • inbreeding depression: loss of genetic variation causing reduced fitness in a population
  • outbreeding/outcrossing: introduction of unrelated individuals into a breeding group leading to increased variation/fitness within a gene pool
26
Q

What are generations called in Punnett squares?

A
  • P generation - parent
  • F generation - filial
  • if grandparents are P, your parents are F1 and you are F2
27
Q

What are the genotypic and phenotypic ratios that result from crossing 2 heterozygotes?

A
  • 1:2:1 for genotypes

- 3:1 for phenotypes

28
Q

What is a test cross/back cross?

A
  • used to determine an unknown genotype
  • organism w/ unknown crossed with homozygous recessive organism
  • if all kids dominant, unknown is homozygous dom
  • if 1:1 dom to rec in kids, unknown is hetero
29
Q

What is a dihybrid cross?

A
  • used to chart inheritance of 2 different genes

- 2 heterozygotes create 9:3:3:1

30
Q

What are sex-linked traits?

A
  • females can be homo or hetero
  • males just have one X so are hemizygous for many X traits
  • having only 1 recessive allele is enough for expression of the recessive phenotype in males
31
Q

What is recombination frequency (theta)?

A
  • likelihood that 2 alleles are separated from each other during crossing over
  • is proportional to distance between genes on the chromosome
  • so tightly linked genes have theta around 0
32
Q

What is a genetic map?

A
  • represents relative distance between genes on a chromosome
  • one map unit or centimorgan corresponds to 1% chance of recombination
  • so if two genes 25 map units apart, 25% of total gametes would show recombination somewhere between the two genes
33
Q

What is Hardy-Weinberg equilibrium? What conditions must be met?

A
  • gene frequencies of a population are not changing, gene pool is stable, and evolution is not occurring
    1. population is very large (no genetic drift)
    2. there are no mutations that affect the gene pool
    3. mating between individuals in the population is random (no sexual selection)
    4. there is no migration of individuals into or out of the population
    5. the genes in the population are all equally successful at being reproduced
34
Q

What are the Hardy-Weinberg equations?

A

-p is frequency of dominant allele, q is frequency of recessive allele
-p+q = 1 (tells us allele frequency)
square both sides and get p2 + 2pq + q2 = 1
-p2 is frequency of homo dom, 2pq is frequency of heterozygous, q2 is frequency of homo rec

35
Q

How are natural selection and evolution different?

A

natural selection is a mechanism for evolution

36
Q

What is the modern synthesis model / neo-Darwinism?

A
  • adds that when mutation/recomb results in favorable changes, that change is more likely to pass on; the opposite is also true
  • called differential reproduction; eventually, those successful traits will be ubiquitous in the pool
  • populations evolve, not individuals
  • basically, Darwin thought natural selection was the only driving force of evolution, but modern genetics taught us that genetic recomb and mutations drive
37
Q

What is inclusive fitness?

A
  • added to neo-Darwinism
  • measure of an organism’s success, based on number of offspring, success in supporting offspring, and the ability of the offspring to then support others
  • like altruism
38
Q

What is punctuated equilibrium?

A

-suggests that changes in some species occur in rapid bursts rather than evenly over time

39
Q

What is stabilizing selection?

A
  • one method of natural selection
  • keeps phenotypes within a specific range by selecting against extremes
  • like human birth weight
  • normal curve
40
Q

What is directional selection?

A
  • one method of natural selection
  • can lead to emergence and dominance of an initially extreme phenotype
  • like bacteria that are antibiotic resistant
  • normal curve shifted to the right or left
41
Q

What is disruptive selection? What is adaptive radiation?

A
  • one method of natural selection
  • two extreme phenotypes are selected
  • Darwin finches - beak size either large or small, no medium
  • facilitated by polymorphisms - naturally occurring differences in form between members of the same pop
  • adaptive radiation - describes rapid rise of a number of different species from a common ancestor; allows diff species to occupy diff niches
  • niche: specific environment (habitat, resources, predators) for which a species adapted
  • curve with two peaks
42
Q

How does speciation occur?

A
  • if two populations from the same species are separated geographically for a long time, diff evolutionary pressures = diff adaptive changes
  • in enough time, isolation would occur - progeny of the two species could not breed
43
Q

What are prezygotic mechanisms for reproductive isolation, and what are some examples?

A
  • prevent formation of zygote completely
  • like temporal isolation - breeding at diff times
  • like ecological isolation - living in diff niches within the same territory
  • like behavioral isolation - lack of attraction between members of the two species
  • like reproductive isolation - incompatibility of reproductive anatomy
  • like gametic isolation - intercourse can occur, but fertilization cannot
44
Q

What are postzygotic mechanisms for reproductive isolation, and what are some examples?

A
  • allow for gamete fusion but yield either nonviable or sterile offspring
  • like hybrid inviability (zygote that can’t develop)
  • hybrid sterility (offspring that can’t reproduce)
  • hybrid breakdown (forming first-gen hybrid offspring that are viable and fertile, but second-gen hybrids that are inviable or infertile)
  • like mules - horse + donkey produces viable mule, but mule is sterile
45
Q

What is divergent evolution?

A

-independent development of dissimilar characteristics in two or more lineages sharing a common ancestor

46
Q

What is parallel evolution?

A

-related species evolve in similar ways for a while due to similar environmental selection pressures

47
Q

What is convergent evolution?

A

-independent development of similar characteristics in two or more lineages not sharing a recent common ancestor

48
Q

How is the rate of evolution measured?

A

-rate of change of a genotype over a period of time and is related to severity of evolutionary pressures

49
Q

What is the molecular clock model?

A
  • DNA compared between different species to quantify degree of similarity
  • correlate degree of similarity with the amount of time since the two species split off from a common ancestor
  • more similarity = more recent split
50
Q

What is a species?

A

the largest group of organisms capable of forming fertile offspring

Biology (14 decks)

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