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Biology - MCAT > Class Six > Flashcards

Class Six Flashcards

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1
Q

what are alleles

A

different versions of a gene

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2
Q

what is a genotype

A

DNA sequence of alleles that a person carries

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3
Q

heterozygote

A

a person carrying 2 different allele at a given locus

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4
Q

homozygote

A

individual carrying 2 identical alleles at a locus

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5
Q

what is a phenotype

A

the physical expression of the genotype

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6
Q

dominant allele

A

if it is expressed in the phenotype regardless of the second allele

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7
Q

recessive allele

A

an allele that is not expressed in the heterozygous state

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8
Q

what cells undergo meiosis

A

spermatogenic and oogonia

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9
Q

main difference between mitosis and meiosis

A

mitosis = one round of cell division

meiosis = two rounds

in meiosis, recombination can occur between homologous chromosomes

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10
Q

what phase takes the longest in meiosis and why?

A

prophase due to the crossing over/recombination

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11
Q

when does the synaptonemal complex form

A

meiotic prophase I

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12
Q

purpose of the formation of the synaptonemal complex

A

mediates synapsis

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13
Q

formation of the synaptonemal complex

A

SYCP2 and SYCP3 attach to the homologous chromatin (lateral element)

SYCP1 (central region) attaches the lateral regions

works as a zipper to connect homologous chromosomes

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14
Q

SC formation and recombination relationship

A

when one is inhibited, the other is disturbed

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15
Q

what is nondisjunction

A

failure of chromosomes to separate during meiosis

(either during meiosis I or II)

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16
Q

gametes resulting from nondisjunction

A

will have 2 copies or no copies of a given chromosomes

can fuse with a normal gamete → 3 copies or 1

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17
Q

what results in Down syndrome

A

trisomy of chromosome 21

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18
Q

Turner syndrome

A

only one X chromosome and no Y

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19
Q

Mendel’s law of segregation

A

two alleles of an individual are separated and passed onto the next generation singly

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20
Q

at what stage of meiosis are different alleles of a gene separated

A

meiosis I - when homologous chromosomes separate

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21
Q

Mendel’s law of independent assortment

A

alleles of one gene will separate into gametes independently of alleles for another gene

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22
Q

testcross

A

when one individual is crossed to another individual that has a homozygous recessive genotype

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23
Q

rule of multiplication

A

probability of both of 2 independent events happening

multiply the odds of either event

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24
Q

rule of addition

A

used to calculate the chances of either of 2 events happening

add the two probabilities together

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25
Q

incomplete dominance

A

the phenotype of a heterozygote is a blended mix of both alleles

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26
Q

codominance

A

two alleles are expressed but not blending

e.g. blood

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27
Q

pleiotropism

A

when a gene alters other unrelated aspects of an organism’s phenotype

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28
Q

polygenism

A

complex traits that are influenced by many different genes

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29
Q

penetrance

A

likelihood that a person with a given genotype will express the expected phenotype

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30
Q

epistasis

A

expression of alleles of one gene is dependent on a different gene

31
Q

recessive lethal alleles

A

mutant alleles that can cause death when presented homozygously

32
Q

what determines the sex of an embryo

A

male gamete

33
Q

linkage

A

failure of genes to display independent assortment

seen in genes located on the same chromosome

34
Q

when is recombination more likely to occur

A

the farther apart two genes are on a chromosome, the more likely recombination will occur

35
Q

how to calculate recombination frequency

A

number of recombinants / total number of offspring

36
Q

autosomal traits

A

caused by genetic variation on the autosome (22 pairs)

can be dominant or recessive

no sex bias for these traits

37
Q

mitochondrial traits

A

rare, inherited from mothers (affected mothers have affected offspring)

mt prefix

example of hemizygosity

38
Q

sex linked traits

A

traits that are determined by genes located on the X or Y chromosome

39
Q

Y linked traits

A

rare

can only be passed from fathers to male children (no Y for females)

40
Q

X linked traits

A

can be recessive or dominant

males always express it even if its recessive (only 1 copy)

41
Q

population genetics

A

describe the inheritance of traits in populations over time

42
Q

Hardy Weinberg law

A

frequencies of alleles in the gene pool of a population will not change over time

43
Q

assumptions of the Hardy Weinburg law (5)

A

no mutation

no migration

no natural selection

random mating

population is large enough to prevent random drift in allele frequencies

44
Q

Hardy Weinburg equation

A

p2 + 2pq + q2 = 1

p = dom

q = ress

45
Q

when does a population reach Hardy Weinburg

A

after one generation

46
Q

two sources of genetic diversity in a population

A

new alleles

new combinations of existing alleles

47
Q

directional selection

A

extreme phenotype is favoured over others

e.g. giraffes get taller as short giraffes die due to lack of food

48
Q

divergent selection

A

middle members are removed

splits the population in two extremes

49
Q

stabilizing selection

A

both extremes of a trait are selected against

drives population to the average

50
Q

artificial selection

A

humans using artificial selection to achieve desired traits through controlled mating

51
Q

sexual selection

A

animals choose their mates depending on certain characteristics

52
Q

kin selection

A

animals sacrificing themselves for the sake of the alleles they share with others

53
Q

reproductive isolation

A

keeps existing species separate

54
Q

2 types of reproductive isolation

A

prezygotic and posyzygotic

55
Q

prezygotic barriers

A

prevent the formation of a hybrid zygote

e.g. ecological, temporal, behavioural

56
Q

postzygotic barriers

A

prevent the development/survival/reproduction of hybrid individuals

e.g. don’t mature properly, incapable of breeding, 2nd gen is defective

57
Q

speciation

A

creation of a new species

58
Q

cladogenesis

A

one species diversifies and becomes 2 or more new species

59
Q

anagenesis

A

one biological species becomes another (lots of changes)

60
Q

allopatric isolation

A

type of cladogenesis

initiated by geographical location

61
Q

sympatric speciation

A

when a species gives rise to a new species in the same geographical area

62
Q

homologous strucurtes

A

physical feature shared by 2 different species bc of a common ancestor

63
Q

analogous structures

A

structures that serve the same function in different species but no common ancestor

64
Q

convergent evolution

A

2 different species having similar analogous structures due to selective pressures

65
Q

opposite of convergent evolution

A

divergent evolution

66
Q

parallel evolution

A

2 species going through similar evolutionary changes to similar selective pressures

67
Q

taxonomic categories (8)

A

domain

kingdom

phylum

class

order

family

genus

species

68
Q

anaphase I failure =

A

4 abnormal gametes

69
Q

anaphase II failure =

A

2 abnormal gametes

70
Q

polymorphic

A

trait with many different forms

71
Q

epistasis

A

dominance between different genes (not between different alleles of one gene)

72
Q

unlinked ratio for F1 X F1

A

9:3:3:1

73
Q

the smaller the recombination frequency..

A

the closer they are together

74
Q

how many generations to reach new equilibrium

A

1 gen

Biology - MCAT (11 decks)

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