Genetics Exam 3

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tetrads

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Biology

Dr. sweet

102 Terms

1

tetrads

at the pachytene stage, the homologous chromosomes form these; also called bivalents

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2

synaptonemal complex

zipper-like proteins connecting tetrads

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3

crossing over

recombination by ___

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4

autosome

chromosome pairs 1-22

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5

sex chromosome

chromosome pair 23

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6

allosome

another name for sex chromosome

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7

heteromorphic

one chromosome is smaller and one is larger

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8

heterogametic sex

the sex with both heteromorphic chromosomes

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9

homogametic sex

the sex with homomorphic chromosomes

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10

heterogametic sex chromosomes

which type of sex chromosome has very little recombination occur?

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11

pseudoautosomal regions (PAR)

where does recombination occur in heterogametic sex chromosomes?

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12

y-linked genes

genes on the y chromosome

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13

SRY gene

sex determining region of the y; determines the sex in XY systems

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14

testis determining factor (TDF)

sry gene codes for this transcription factor; controls the expression of other genes coded on autosomes

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15

males can be XX if the SRY gene is present; females can be XY if the SRY gene is absent

examples of exceptions to the XX and XY rule

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16

errors in recombination, deletions, and mutations in autosomes

reasons for exceptions to the XX and XY rule

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17

hemizygous

y-linked genes are this; only ever one copy of the y chromosome

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18

through male lineage

how are y chromosomes passed down?

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19

haplotypes

group of genes or sites inherited together from a single parent

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20

mitochondrial haplotypes to look at haplogroups

what genetic marker could we use from maternal lineage?

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21

y adam

most recent male that is the common male ancestor of all living humans (>200kya)

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22

mitochondrial eve

most recent female that is the common female ancestor of all living humans (180kya)

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23

human X chromosome

females have 2 copies and inherited from either father or mother; males have 1 copy inherited from their mother

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24

x-inactivation

one copy of the x chromosome in females randomly inactivates by compacting one chromosome into heterochromatin

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25

mosaicism in x-linked traits

what can x-inactivation lead to?

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26

lyonization

what is another term for x-inactivation?

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27

part of x-linked genes are still active

why is turner syndrome a thing if one of the x-chromosomes gets inactivated anyway?

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28

Nettie Stevens; mealworms

who first discovered x and y chromosomes? what organism did she find them in?

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29

thomas hunt morgan

hypothesized about sex-linked traits; based his work on color on the eye of fruit flies

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30

w+

allele for red eyes; wild type

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31

w

allele for white eyes; mutant type

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32

females had all red eyes, but males were 50/50; concluded that gene for eye color was a sex-linked trait; XW+ or XW

what did thomas hunt morgan find out when concluding his fruit fly experiment?

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33

color blindness

x-linked trait, tends to affect males; affect opsin genes

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34

OPN1LW

red cones; affected by color blindness

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35

OPN1MW

green cones; affected by color blindness

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36

male pattern baldness

x-linked; likely partly responsible in many cases

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37

hemophilia

blood does not clot well; x-linked trait

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38

inbreeding

reason for hemophilia in european royal families

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39

ZW/ZZ system; females are the heterogametic sex

sex determining system of birds, lepidopterans, some reptiles, and some crustaceans

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40

X0 system;; males are X0

sex determining system of insects, and arachnids

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41

haplo-diploid

sex determining system of hymenopterans; males are typically haploid from an unfertilized egg

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42

paternal genome elimination

sex determining system in many types of arthropods; males inherit but do not pass on their father’s genetic material

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43

5 sets of X and Y

sex determining system of monotreme mammals; X and Y are not comparable to the X and Y in therian mammals; do not have SRY gene

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44

temperature during development; can still have X/Y or Z/W chromosomes

sex determining system of some reptiles

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45

muller’s ratchet

process through which, in the absence of recombination, and accumulation of irreversible deleterious mutations result

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46

gregor mendel experiments

experiments crossing pea plants and counting the phenotypic ratios of the offspring

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47

phenotype

physical trait of an organism

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48

law of dominance, law of segregation, law or, law of independent assortment

mendel’s three principles of inheritance

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49

law of segregation

alleles segregate into separate gametes during meiosis, only one allele per gamete

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50

law of independent assortment

alleles at 2 different genes sort into gametes independently of one another

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51

unlinked genes

assumption for dihybrid crosses

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52

dihybrid cross

cross between two individuals with two different traitd

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53

9:3:3:1

phenotypic ratio for a dihybrid cross

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54

polygenic trait

more than 1 gene is responsible for the trait

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55

human height, eye color, and skin color

examples of polygenic traits

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56

incomplete dominance

heterozygotes express an intermediate trait

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57

carl correns

who experimented with incomplete dominance using 4 o’clock plants?

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58

overdominance

heterozygotes have greater reproductive success than either the homozygote genotypes, also known as heterozygote advantage

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59

codominance

heterozygote expresses phenotypes from both alleles

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60

rhesus (Rh) factor

type of protein on the outside of your red blood cells

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61

second pregnancy; the mother to be Rh- and the fetus to be Rh+; mother produces antibodies that can attack the fetus’ blood cells

what happens with incompatibilities of Rh factor?

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62

ABO and Rh factors

what makes up blood type?

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63

O-

universal donor

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64

AB+

universal recipient

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65

thelytoky

female birth; virgin birth

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66

automixis

fusion of 2 gametes in a single individual

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67

apomixis

generation of seeds without meiosis and fertilization (in plants); female clones

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68

arrkenotoky

form of parthenogenesis where males develop from unfertilized eggs (and are haploid, or in some cases homozygous for sex determining gene)

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69

pseudo-arrhenotoky

males inherit but do not pass on their father’s genetic material; functionally equivalent to haplo-diploidy

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70

meiotic drive

unequal segregation of chromosomes or alleles that allow for the overrepresentation of the element

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71

monkeyflowers, stalk-eyed flies, neurospora fungi

examples of meiotic drive

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72

lethal alleles

allele that can cause the death of an individual; often but not always recessive

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73

Achondroplasia

type of dwarfism; homozygous dominant is lethal; around 80% are from a novel mutation in the FGFR3 gene

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74

chiasmata

what do homologous chromosomes form during the pachytene stage

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75

homologous chromosomes

what do pairs of chromosomes exchange genetic material through?

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76

diplotene

during what stage does the synaptonemal complex begin to disappear?

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77

sister chromatid exchange

recombination between sister chromatids; does not result in a new combination of alleles

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78

genetic recombination

recombination does result in new combination of alleles

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79

holliday model of recombination

described by Robin Holliday in fungi; original description involved single-stranded break

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80

single-stranded break

homologous chromatids are nicked at the same location

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81

holliday junctions

strands to the left of the nicks invade corresponding chromatids and form what?

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82

2 heteroduplex regions

what does branch migration create?

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83

nonhomologous end joining

broken ends are pieced back together; DNA polymerase fills in the gap and phosphodiester bonds connected with ligase; may result in a small deletion in the region

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84

The double-stranded break repair model

strand invasion and formation of D-loop; resolution of Holliday junctions results in either non-recombinant or recombinant chromosomes; formation of double holliday junctions

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85

synthesis-dependent strand annealing (SDSA) model

formation of a single holliday junction; release from HJ; DNA polymerase fills the gaps; results in not true recombination

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86

RecBCD

three proteins that find and/or cause DSB

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87

RecA

promotes strand invasion in single-stranded DNA

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88

single stranded binding proteins (SSB)

prevents strand degradation

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89

RuvABC

protein complex that promotes branch migration in Holliday junctions

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90

gene conversion

one allele is converted to the allele on the homologous chromosome

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91

gene conversion by mismatch pair

corrects mismatches in heteroduplex regions, which can lead to gene conversion; also scenarios with repair without gene conversion

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92

gene conversion by gap year

DNA polymerase uses the allele from the homologous chromosome as a template to fill in a gap

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93

G-C

gene conversion tends to be ___ biased

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94

mutation process; can lead to a false signal of positive selection; GC biased gene conversion can happen irrespective of the fitness of the organism

why does gene conversion tend to be GC-biased

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95

unequal crossing over

between non-equivalent sequences, can lead to deletion and/or duplications

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96

inversion

can be caused by crossing over; pericentric and paracentric

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97

pericentric

includes centromere

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98

paracentric

does not include centromere

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99

translocation

parts of different chromosomes rearrange; can be caused by non-homologous recombination

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100

robertsonian translocation

extreme version of translocation; entire arm that fuses to another chromosome; down syndrome can be caused by this

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