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Biology - MCAT > Class Six > Flashcards

Class Six Flashcards

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
incomplete dominance
the phenotype of a heterozygote is a blended mix of both alleles
26
codominance
two alleles are expressed but not blending e.g. blood
27
pleiotropism
when a gene alters other unrelated aspects of an organism's phenotype
28
polygenism
complex traits that are influenced by many different genes
29
penetrance
likelihood that a person with a given genotype will express the expected phenotype
30
epistasis
expression of alleles of one gene is dependent on a different gene
31
recessive lethal alleles
mutant alleles that can cause death when presented homozygously
32
what determines the sex of an embryo
male gamete
33
linkage
failure of genes to display independent assortment seen in genes located on the same chromosome
34
when is recombination more likely to occur
the farther apart two genes are on a chromosome, the more likely recombination will occur
35
how to calculate recombination frequency
number of recombinants / total number of offspring
36
autosomal traits
caused by genetic variation on the autosome (22 pairs) can be dominant or recessive no sex bias for these traits
37
mitochondrial traits
rare, inherited from mothers (affected mothers have affected offspring) mt prefix example of hemizygosity
38
sex linked traits
traits that are determined by genes located on the X or Y chromosome
39
Y linked traits
rare can only be passed from fathers to male children (no Y for females)
40
X linked traits
can be recessive or dominant males always express it even if its recessive (only 1 copy)
41
population genetics
describe the inheritance of traits in populations over time
42
Hardy Weinberg law
frequencies of alleles in the gene pool of a population will not change over time
43
assumptions of the Hardy Weinburg law (5)
no mutation no migration no natural selection random mating population is large enough to prevent random drift in allele frequencies
44
Hardy Weinburg equation
p2 + 2pq + q2 = 1 p = dom q = ress
45
when does a population reach Hardy Weinburg
after one generation
46
two sources of genetic diversity in a population
new alleles new combinations of existing alleles
47
directional selection
extreme phenotype is favoured over others e.g. giraffes get taller as short giraffes die due to lack of food
48
divergent selection
middle members are removed splits the population in two extremes
49
stabilizing selection
both extremes of a trait are selected against drives population to the average
50
artificial selection
humans using artificial selection to achieve desired traits through controlled mating
51
sexual selection
animals choose their mates depending on certain characteristics
52
kin selection
animals sacrificing themselves for the sake of the alleles they share with others
53
reproductive isolation
keeps existing species separate
54
2 types of reproductive isolation
prezygotic and posyzygotic
55
prezygotic barriers
prevent the formation of a hybrid zygote e.g. ecological, temporal, behavioural
56
postzygotic barriers
prevent the development/survival/reproduction of hybrid individuals e.g. don't mature properly, incapable of breeding, 2nd gen is defective
57
speciation
creation of a new species
58
cladogenesis
one species diversifies and becomes 2 or more new species
59
anagenesis
one biological species becomes another (lots of changes)
60
allopatric isolation
type of cladogenesis initiated by geographical location
61
sympatric speciation
when a species gives rise to a new species in the same geographical area
62
homologous strucurtes
physical feature shared by 2 different species bc of a common ancestor
63
analogous structures
structures that serve the same function in different species but no common ancestor
64
convergent evolution
2 different species having similar analogous structures due to selective pressures
65
opposite of convergent evolution
divergent evolution
66
parallel evolution
2 species going through similar evolutionary changes to similar selective pressures
67
taxonomic categories (8)
domain kingdom phylum class order family genus species
68
anaphase I failure =
4 abnormal gametes
69
anaphase II failure =
2 abnormal gametes
70
polymorphic
trait with many different forms
71
epistasis
dominance between different genes (not between different alleles of one gene)
72
unlinked ratio for F1 X F1
9:3:3:1
73
the smaller the recombination frequency..
the closer they are together
74
how many generations to reach new equilibrium
1 gen

Biology - MCAT (11 decks)

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