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Building blocks of life > Genetics of sex > Flashcards

Genetics of sex Flashcards

(55 cards)

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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?

Study These Flashcards
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

Study These Flashcards
A

finding rare people with sex reversal syndromes

25
what is a sex reversal sydrome?
wrong sex phenotype for their karyotype | some has translocation: part of Y attached to other chromosomes, became males.
26
how did sex reversal translocations help find SRY
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
what actually is SRY?
sex determining gene short protein of 204 amino acids transciption factors for turning off or on genes
28
when is the bipotential stage?
in a mammalian gonad this is around 4-7 week | it can take the male or female route
29
what way of at the bipotential stage does SRY go?
male
30
how does SRY make males
switches on SOX9 this is also a transciponal factor and autoregulatory positive feedback loop created embryo stays male
31
what does autoregulatory mean for SOX 9
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
what does SOX make the cell do?
switches on growth factors that make the undiffertiated cell in the gonad secrete hormones turning it into a teste making testosterone
33
without SOX9 what happens to the gonad cells?
undifferentiated gonad cells turn on genes such as ESR1 and FOXL2 that keep sox9 turned off
34
controlling sex with chromsomes causes another issue...
gene dosage
35
what is down syndrome
a form of aneuploidy | they have an extra chromosome
36
how do mammals deal with gene dosage
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
how is X inactivation show in female mammals>
heterochromatic lump called a Barr body
38
what is Xic
the X inactivation centre
39
what does Xic contain?
4 genes: Xist Tsix
40
what is a holiday junction?
chromosomes connecting with each other via an intermediate
41
what can be a purpose of a holiday junction?
recombination | if the junctions are resolved in oppsosite orientations recombination occurs
42
what is heteroduplex dna?
areas of homologous DNA that are mostly similar can form DNA duplexes with mismatches in them
43
what turns a heteroduplex into a homoduplex?
cells have systems to detect and mend mismatched DNA and sort these issues out
44
what proofreads and mends DNA?
DNA polymerases can do this job and then mismatch enzymes can help
45
when can DNA damage occur?
DNA replication most commonly | then after replication
46
what kind of dna damage can occur after replication?
``` abnormal base single strand breaks base adducts thymidine dimers chemical mutagens interstrand crosslinks double strand breakd base insertions base deletions AG/ TC missmatches ```
47
what causes damage after replication?
spontaneous or UV light
48
what do chemical mutagens do
attack dna or interfere with replication
49
what encodes reverse transciptase
retrviruses and retrotransposons
50
what is a processed pseudogene?
mRNA after introns are removed is sometime transcribed and accidentally incorporated into the chromosome
51
what makes ectopic recombination more likely?
areas of high similarity in the genome
52
what is ectopic recombination?
regions of homology on chromsomes that are similar enough for recombination to occur causing abnormalities or deletions.
53
how can mutations affect mutation rates?
mutations can abolish proofreading ability of DNA polymerasse resulting in higher mutation rates
54
how can bacteria get around mutation rates?
some will be deficient and error prone and will die rather than mutating so their mutation rates are very low
55
what affects mutation rates?
selection for accuracy trade-off against replication speed genetic drift

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