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MCAT Biology > Ch 12 - Genetics and Evolution > Flashcards

Ch 12 - Genetics and Evolution Flashcards

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1
Q

What do chromosomes contain?

A

genes in a linear sequence

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2
Q

What are alleles?

A

alternative forms of genes

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3
Q

What is the difference between dominant and recessive alleles?

A
  • dom require only one copy to be expressed

- rec require 2 copies

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4
Q

What is genotype?

A

the combination of alleles one has at a given genetic locus

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5
Q

What are homozygous, heterozygous, and hemizygous ?

A
  • homo have 2 of the same allele
  • hetero have 2 different alleles
  • hemi have only 1 allele (male sex chromosomes)
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6
Q

What is a phenotype?

A

the observable manifestation of a genotype

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7
Q

What is complete/incomplete dominance and codominance?

A
  • complete: when the effect of 1 allele completely masks the effect of another
  • codominance ahs more than one dominant allele
  • incomplete: has no dominant alleles; heterozygotes have intermediate phenotypes
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8
Q

What is penetrance?

A

the proportion of a population with a given genotype who express the phenotype

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9
Q

What is expressivity?

A

the varying phenotypic manifestations of a given genotype

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10
Q

How do the modern interpretations of Mendel’s laws help explain the inheritance of genes from parent to offspring?

A
  • 1st law (segregation): an organism has 2 alleles for each gene, which segregate during meiosis, resulting in gametes carrying only 1 allele for a trait
  • 2nd law (independent assortment): the inheritance of 1 allele does not influence the probability of inheriting an allele for a different trait
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11
Q

What did Griffith’s experiment show?

A

the transforming principle, converting non virulent bacteria into virulent bacteria by exposure to heat killed virulent bacteria

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12
Q

What did Avery-McLeod-McCarty’s experiment show?

A

DNA is the genetic material because degradation of DNA led to cessation of bacterial transformation

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13
Q

What did Hershey-Chase’s experiment show?

A

DNA is the genetic material because only radiolabeled DNA could be found in bacteriophage infected bacteria

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14
Q

What is a gene pool?

A

all of the alleles in a given population

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15
Q

What are mutations?

A

changes in DNA sequence

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16
Q

What are point and frameshift mutations?

A
  • point: substituting of one nucleotide for another

- frameshift: moving the 3 letter transcriptional reading frame

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17
Q

What is the silent mutation?

A

has no effect on the protein

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18
Q

What is the missense mutation?

A

substitution of one amino acid for another

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19
Q

What is the nonsence mutation?

A

substitution of a stop codon for another amino acid

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20
Q

What are insertions and deletions?

A

result in a shift in the reading frame, leading to changes for all downstream amino acids

21
Q

What are deletion mutations?

A

occur when a large segment of DNA is lost

22
Q

WHat are duplication mutations?

A

occur when a segment of DNA is copied multiple times

23
Q

What are inversion mutations?

A

occur when a segment of DNA is reversed

24
Q

What are insertion mutations?

A

occur when a segment of DNA is moved from one chromosome to another

25
Q

What are translocation mutaitons?

A

occur when a segment of DNA is swapped with a segment of DNA from another chromosome

26
Q

Why would genetic leakage in animals be rare prior to the last century?

A
  • genetic leakage requires the formation of a hybrid organism that can then mate with members of one or the other parent species
  • while hybrids existed historically, fertile hybrids were certainly rare before a more modern understanding of genetics
27
Q

What is a genetic drift?

A

occurs when the composition of the gene pool changes as a result of chance

28
Q

What does the founder effect come from?

A

results from bottlenecks that suddenly isolate a small population, leading to inbreeding and increased prevalence of certain homozygous genotypes

29
Q

What are punnett squares?

A

visually represent the crossing of gametes from parents to show relative genotypic and phenotypic frequencies

30
Q

How are generations represented in punnett squares?

A
  • parent (P)

- offspring (filial) F1, F2, and so on

31
Q

What are mono/dihybrid crosses?

A
  • mono accounts for 1 gene (3:1 phenotypic ratio)

- di accounts for 2 (9:3:3:1 phenotypic ratio)

32
Q

What are sex-linked crosses?

A

sex chromosomes are usually used to indicate sex as well as genotypes
- X lined on MCAT (Y linked rare)

33
Q

What is the recombinant frequency?

A

the likelihood of 2 alleles being separated during crossing over in meiosis

34
Q

How are genetic maps made?

A

can be made using recombination frequency as the scale of centimorgans

35
Q

What is the Hardy-Weinberg principle?

A

states that if a population meets certain criteria (aimed at a lack of evolution), then the allele frequencies will remain constant

36
Q

What is natural selection?

A

states that chance variations exist between individuals and that advantageous variations - those that increase an individual’s fitness for survival or adaptation to the environment - afford the most opportunities for reproductive success

37
Q

What does the modern synthesis model (neo-Darwinism) account for?

A

mutation and recombination as mechanisms of variation and considers differential reproduction to be the mechanism for reproductive success

38
Q

What does inclusive fitness consider?

A

an organism’s success to be based on the number of offspring, success in supporting offspring, and the ability of the offspring to then support others
- survival of offspring or relatives ensures appearances of genes in subsequent generations

39
Q

What does punctuated equilibrium consider?

A

evolution to be a very slow process with intermittent rapid bursts of evolutionary activity

40
Q

What is the difference between stabilizing, direction, and disruption selection in regards to changes in phenotypes?

A
  • stabilizing: keeps phenotypes in a narrow range, excluding extremes
  • directional: moves the average phenotype toward one extreme
  • disruptive: moves the population toward 2 different phenotypes at the extremes and can lead to speciation
41
Q

What is adaptive radiation?

A

the rapid emergence of multiple species from a common ancestor, each of which occupies its own ecological niche

42
Q

What are species?

A
  • the largest group of organisms capable of breeding to form fertile offspring
  • reproductively isolated from each other by pre- or postzygotic mechanisms
43
Q

What is the difference between divergent, parallel, and convergent evolution?

A
  • div: occurs when 2 species sharing a common ancestor become more different
  • par: occurs when 2 species sharing a common ancestor evolve in similar ways du eto analogous selection pressures
  • con: occurs when 2 species not sharing a recent ancestor evolve to become more similar due to analogous selection pressures
44
Q

What does the molecular clock model show?

A

the degree of difference in the genome between 2 species is related to the amount of time since the species broke off from a common ancestor

45
Q

What is a testcross?

A

used to determine an unknown genotype

  • unknown genotype is crossed with homozygous recessive
  • if all offspring are dominant phenotype, unknown is homozygous dominant
  • if 1:1 distribution of dominant to recessive, unknown heterozygous dominant
46
Q

What are the criteria for Hardy-Weinberg principle?

A
  • the population is very large (no genetic drift)
  • no mutations that affect the gene pool
  • mating between individuals in the population is random (no sexual selection)
  • no migration of individuals into or out of the population
  • genes in the population are all equally successful at being reproduced
47
Q

What are Hardy-Weinberg equations?

A

p + q = 1 (frequency of alleles)
p^2 + 2pq + q^2 = 1 (frequency of genotypes and phenotypes)
p is dominant allele and q is recessive allele

48
Q

At what point to 2 populations descended from the same ancestral stock considered to be separate species?

A

when they can no longer produce viable, fertile offspring

49
Q

What was Darwin’s main argument?

A
  • natural selection was the driving force of evolution
  • argues that change variations between organisms can help certain organisms survive to reproductive age and produce many offsprings, transmitting their variations to the next generation

MCAT Biology (12 decks)

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