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Biology MCAT > Evolution and Genetics > Flashcards

Evolution and Genetics Flashcards

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1
Q

Chromosomes

A

Contain genes in a linear sequence

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2
Q

Carrier

A

Holds a recessive allele that is not expressed

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3
Q

Alleles (types)

A

Alternative forms of a gene

1) Dominate alleles
2) Recessive alleles

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4
Q

Dominant alleles

A

Require only one copy to be expressed.

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5
Q

Recessive alleles

A

Require two copies to be expressed.

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6
Q

Genotype (types)

A

A combination of alleles one has at a given genetic locus.

Types:
1) Homozygous
2) Heterozygous
3) Hemizygous

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7
Q

Homozygous

A

Having two of the same allele

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8
Q

Heterozygous

A

Having two different alleles

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9
Q

Hemizygous

A

Having only one allele (i.e. male-sex chromosome- X)

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10
Q

Phenotype

A

An observable manifestation of a genotype.

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11
Q

Patterns of dominance

A

Patterns:

1) Complete dominance
2) Codominance
3) Incomplete dominance

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12
Q

Complete dominance

A

One dominate allele and one recessive allele. Dominant will mask the recessive allele.

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13
Q

Codominance

A

Has more than one dominant allele.
*co-parenting: still have both parents; still have full expression of each genes in certain areas (some parts completely white, some parts completely black)

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14
Q

Incomplete dominance

A

Has no dominant alleles; heterozygotes have intermediate phenotypes.

Results in a mixture of the two alleles (i.e., pink flowers out of red and white).

*could not be completely white or completely red=incomplete color change

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15
Q

Penetrance

A

A population measure defined as the proportion of individuals in the population carrying the allele who actually expresses the phenotype (with a genotype who express the phenotype)

probability that given a genotype, a person will express the phenotype.

Full Penetrance- 100%

High Penetrance- most but not all

Reduced/low/ nonpenetrance- fewer sequence repeats

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16
Q

Expressivity

A

Refers to the varying phenotypic manifestations of a given phenotype.

Constant- everyone with a given genotype, express the same phenotype

Variable- same genotype, variable phenotypes

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17
Q

Penetrance and Expressivity overview

A
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18
Q

Mendel’s first law

A

Mendel’s first law, of segregation
States that an organism:

1) Genes exist in alternative forms (alleles)
2) Has two alleles for each gene; one inherited from each parent.
3) Which segregate during meiosis resulting in gametes that carry only one allele for a trait (Anaphase 1)
4) if the 2 alleles are different only one will be expressed- dominant

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19
Q

Mendel’s second law

A

Mendel’s second law, of independent assortment

States that the inheritance of one gene does not affect the inheritance of another gene

Daughter strand held to parent strand by centromere (together known as sister chromatid). During Prophase 1, homologous chromosomes pair up to form tetrads where they exchange genetic material (recombination).
PS

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20
Q

1st and 2nd law of Mendel do what to genetic diversity?

A

Increase diversity

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21
Q

Gene pool

A

All of the alleles in a given population

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22
Q

Mutations def and types

A

Changes in the DNA sequence. Multiple types:

1) Point mutations
2) Frameshift mutations
3) Missense mutations
4) Nonsense mutations

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23
Q

Mutagens are

A

substances that cause mutations

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24
Q

Transposons

A

insert or remove themselves from the genome.

if it is inserted in the middle of the coding sequence, the mutation will disrupt that gene.

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25
Q

Point mutations

A

A nucleotide mutation that involves the substituting of one nucleotide for another.

Leads to silent mutations in wobble codon.

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26
Q

Missense mutations

A

Results in the substitution of one amino acid for another.

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27
Q

Nonsense mutations

A

Result in the substitution of a stop codon for an amino acid.

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28
Q

Frameshift mutations

A

Moving the three-letter transcriptional reading frame by inserting or removing a codon. Often causes a misfolded protein

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29
Q

Chromosomal mutations (types)

A

Larger-scale mutations that affect whole segments of DNA.

Include:

1) Deletion mutations
2) Duplication mutations
3) Inversion mutations
4) Insertion mutations
5) Translocation mutations
Did it

30
Q

Deletion mutations

A

Occurs when a large segment of DNA is lost.

31
Q

Duplication mutations

A

Occurs when a segment of DNA is copied multiple times.

32
Q

Inversion mutations

A

Occurs when a segment of DNA is reversed.

Least likely to cause an abnormality

33
Q

Insertion mutations

A

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

34
Q

Translocation mutations

A

Occurs when a segment of DNA is swapped with a segment of DNA from another chromosome.

35
Q

Genetic leakage

A

The flow of genes between species through a hybrid offspring.

36
Q

Genetic drift

A

Occurs when the composition of the gene pool changes as a result of chance.

37
Q

Founder effect

A

Results from a bottleneck that suddenly isolates a small population, leading to inbreeding and increased prevalence of certain homozygous genotypes.

38
Q

Parent generation

A

Represented by P1

39
Q

Filial generations

A

offspring generations
Represented by F1, F2, and so on.

40
Q

Monohybrid cross

A

Accounts for one gene

A cross between individuals that involves one pair of contrasting traits

41
Q

Phenotypic ratio for monohybrid cross?

A
42
Q

Dihybrid cross

A

Accounts for two genes

Cross or mating between organisms involving two pairs of contrasting traits

43
Q

Phenotypic ratio for dihybrid cross?

A
44
Q

Test cross

A

Breeding the unknown parent with a homozygous recessive

45
Q

Sex-linked crosses

A

Sex chromosomes are usually used to indicate sex as well as genotype

SeX linked is X linked

X-linked trait is recessive

46
Q

unless stated, all sex linked traits are considered

A

recessive

47
Q

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 (Hardy-weinberg equilibrium).

48
Q

Recombination frequency

A

The likelihood of two alleles being separated during crossover by meiosis.

25 map units apart= 25% of the total gametes to show recombination

Genes that are close to each other have low recombination frequency because they are unlike to cross-over separately

49
Q

What is the maximum recombination frequency?

A

50% because it is a random process

50
Q

Gene maps

A

Maps made using recombination frequencies as the scale, in centimorgans.

Genes organized in linear fashion on chromosomes. During Prophase 1, alleles are swapped and those close together on a chromosome are less likely to be separated. Further apart 2 genes are, the more likely that there will be a point of crossing over (chiasma)

51
Q

Hardy-weinberg equations

A
52
Q

Hard-weinberg criteria

A

5 criteria:

1) Population is large
2) No mutations
3) Mating is random
4) No migration into/out of the population
5) No natural selection

53
Q

Natural selection

A

States that the chance variations that exist between individuals, and the advantageous variations– those that increase an individuals fitness for the environment– afford the most opportunity for reproductive success.

54
Q

Modern synthesis model (neo-darwinism)

A

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

55
Q

differential reproduction

A

when mutation or recombination results in a change that is favorable to the organism’s reproductive success, that change is more likely to pass on to the next generation

56
Q

Inclusive fitness

A

Considers an organisms success to be based on:

1) Number of offspring
2) Success in supporting offspring
3) Ability of offspring to reproduce
4) Survival of offspring

promotes idea of altruistic behavior to benefit offspring

57
Q

Natural selection (types)

A

Different types of selection lead to changes in phenotype:

1) Stabilizing selection
2) Directional selection
3) Disruptive selection
4) Adaptive selection

58
Q

Stabilizing selection

A

Keeps the phenotypes in a narrow range, excluding extremes.

59
Q

Directional selection

A

Moves the average phenotype toward one extreme.

60
Q

Disruptive selection

A

Moves toward two different phenotypes at the extremes and can lead to speciation.

61
Q

polymorphisms

A

facilitates disruptive selection
naturally occurring difference in form between members of the same population

light/dark coloration of the same species of butterflies

62
Q

Adaptive radiation

A

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

63
Q

niche

A

specific environment, including habitat, avail resources, and predators, for which a species can be specifically adapted

64
Q

Species

A

The largest group of organisms capable of breeding to form a fertile offspring.

If you separate two populations of the same species long enough the changes would be sufficient enough to lead to isolation (no longer freely interbreed)

1) Reproductively isolated from each other by pre- and post zygotic mechanisms.

65
Q

Pre zygotic mechanisms

A

Prevent formation of zygote

Ecological-living in different niches within same territory
Temporal-breeding at different times
Behavioral-a lack of attraction between members of the two species due to differences in pheromones, courtship displays, and so on
Mechanical- reproductive- anatomies differ
Gametic- intercourse can occur, but fertilization cannot

66
Q

Isolation

A

when 1 species is separated, different evolutionary pressures leads to isolation, in which the progeny of these populations can no longer interbreed

67
Q

Post zygotic mechanisms

A

allows gamete fusion but yield nonviable or sterile offspring.

Hybrid inviability- zygote doesn’t develop to term
sterility
hybrid breakdown- forming first generation and second generation offspring that are inviable or infertile

68
Q

Evolution (types)

A

1) Divergent evolution
2) Convergent evolution
3) Parallel evolution

69
Q

Divergent evolution

A

Occurs when two species sharing a common ancestor become more different.

70
Q

Convergent evolution

A

Occurs when two species not sharing a recent ancestor evolve to become more similar due to analogous selection pressures.

71
Q

Parallel evolution

A

Occurs when two species sharing a common ancestor evolve in similar ways due to analogous selection pressures.

Biology MCAT (12 decks)

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