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Building blocks of life > Genetics of sex > Flashcards

Genetics of sex Flashcards

1
Q

what is sex defined as?

A

combing of two individual genome to make a new individuals genome

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2
Q

what makes human unique?

A

polymorphism in human genes means no two humans are genetically identical

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3
Q

what is recombination

A

a part of sex that means genes meet up in new combinations

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4
Q

how do bacteria recombine genes?

A

swap them through mechanisms such as a pillus

take up DNA from the environment and incorporate this into their genome

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5
Q

what does meiosis make?

A

haploid cells which join together in sex

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6
Q

how can recombination occur?

A

segregation or crossing over between linked genes

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7
Q

what is anisogamy?

A

differences between the gametes

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8
Q

what passes on an autosomal mutation?

A

individulas to half of offspring

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9
Q

what passes on an X chromosome mutations

A

mothers of half of offspring
fathers to daughters but not sons
males hemizygous, unmasking recessive mutations

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10
Q

how is Y chromosome mutations passed on?

A

fathers to sons

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11
Q

how is a mitochrondria mutations passed on

A

mothers to all offspring

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12
Q

example of autosomal disorder

A

cystic firbosis

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13
Q

example of X linked disease

A

colour blindness

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14
Q

what is the main consequence of being a sexual species?

A

reproduction becomes as important as surival in terms of evolution

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15
Q

what is the down side to sex/

A

it can spread diseases such as pathogens and parasites easily

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16
Q

what is another smaller issue of having sex?

A

a species genome has to be able to make both sexes

this is an issue for gene regulation

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17
Q

what size is the human male gene?

A

40mb

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18
Q

is there any recombination in the male gene?

A

no

only the pseudoautosomal regions marked PAR at the ends do and these parts alow it to connect with the X

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19
Q

whatis SRY?

A

sexdetermining region of the Y chromosome

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20
Q

what is PAR

A

pseudoautosomal region

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21
Q

what is MSY?

A

male-specific region of the y chromosome

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22
Q

how was it known that the Y turns something on in embryos?

A

studys of the karyotype of people with sex chromosome aneuploidy

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23
Q

hwo did karotypes of sex chromosome aneuploidies demonstrate Y turns something on to make males?

A

XO females have turners syndrome
so having only one X doesnt make you male
XXY are males with a syndrome so it isnt two X’s making you female
so the Y must turn something on to male the embryo male

24
Q

how was SRY located

A

finding rare people with sex reversal syndromes

25
Q

what is a sex reversal sydrome?

A

wrong sex phenotype for their karyotype

some has translocation: part of Y attached to other chromosomes, became males.

26
Q

how did sex reversal translocations help find SRY

A

by finding out which parts of the Y had translocated they were able to narrow down the region of SRY and find the gene responsible

27
Q

what actually is SRY?

A

sex determining gene
short protein of 204 amino acids
transciption factors for turning off or on genes

28
Q

when is the bipotential stage?

A

in a mammalian gonad this is around 4-7 week

it can take the male or female route

29
Q

what way of at the bipotential stage does SRY go?

A

male

30
Q

how does SRY make males

A

switches on SOX9
this is also a transciponal factor and autoregulatory
positive feedback loop created
embryo stays male

31
Q

what does autoregulatory mean for SOX 9

A

it can switch other genes on or off but aso turn itself futher on
it increases the transciption of SOX9 even more creating a positive feedback loop

32
Q

what does SOX make the cell do?

A

switches on growth factors that make the undiffertiated cell in the gonad secrete hormones turning it into a teste making testosterone

33
Q

without SOX9 what happens to the gonad cells?

A

undifferentiated gonad cells turn on genes such as ESR1 and FOXL2 that keep sox9 turned off

34
Q

controlling sex with chromsomes causes another issue…

A

gene dosage

35
Q

what is down syndrome

A

a form of aneuploidy

they have an extra chromosome

36
Q

how do mammals deal with gene dosage

A

shut on X down entireley at random in each cell
this way males and females only have one X active and everything is equal
this happens in embroygenesis

37
Q

how is X inactivation show in female mammals>

A

heterochromatic lump called a Barr body

38
Q

what is Xic

A

the X inactivation centre

39
Q

what does Xic contain?

A

4 genes:
Xist
Tsix

40
Q

what is a holiday junction?

A

chromosomes connecting with each other via an intermediate

41
Q

what can be a purpose of a holiday junction?

A

recombination

if the junctions are resolved in oppsosite orientations recombination occurs

42
Q

what is heteroduplex dna?

A

areas of homologous DNA that are mostly similar can form DNA duplexes with mismatches in them

43
Q

what turns a heteroduplex into a homoduplex?

A

cells have systems to detect and mend mismatched DNA and sort these issues out

44
Q

what proofreads and mends DNA?

A

DNA polymerases can do this job and then mismatch enzymes can help

45
Q

when can DNA damage occur?

A

DNA replication most commonly

then after replication

46
Q

what kind of dna damage can occur after replication?

A 
abnormal base
single strand breaks
base adducts
thymidine dimers
chemical mutagens
interstrand crosslinks
double strand breakd
base insertions
base deletions
AG/ TC missmatches
47
Q

what causes damage after replication?

A

spontaneous or UV light

48
Q

what do chemical mutagens do

A

attack dna or interfere with replication

49
Q

what encodes reverse transciptase

A

retrviruses and retrotransposons

50
Q

what is a processed pseudogene?

A

mRNA after introns are removed is sometime transcribed and accidentally incorporated into the chromosome

51
Q

what makes ectopic recombination more likely?

A

areas of high similarity in the genome

52
Q

what is ectopic recombination?

A

regions of homology on chromsomes that are similar enough for recombination to occur causing abnormalities or deletions.

53
Q

how can mutations affect mutation rates?

A

mutations can abolish proofreading ability of DNA polymerasse resulting in higher mutation rates

54
Q

how can bacteria get around mutation rates?

A

some will be deficient and error prone and will die rather than mutating so their mutation rates are very low

55
Q

what affects mutation rates?

A

selection for accuracy
trade-off against replication speed
genetic drift

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