Lecture 9: Sex Determination File

Question 1

Females determine sex in what species ?

Answer 1

birds, some fish and insects

Question 2

Explain sex determination in worms

Answer 2

XX is hermaphrodite
XO is male
Males have more neurones as they a re required to find a partner

Question 3

Explain sex determination in bees

Answer 3

Males = hemigametic (haploid X) 
Females= homogametic (diploid XX)

Question 4

Explain sex determination in alligators

Answer 4

Its temperature dependant
<30 degrees = female
>34 degrees = male

Temperature sensitive period between 7 and 21 days of incubation

Question 5

Whats strange about black sea bass ?

Answer 5

Born as females, turn into males between 2 and 5 years old

Question 6

Explain sex determination in flies

Answer 6

XX= female 
XY= male 
although Y is not sex determining, so:
X = male 
XXY= female

Question 7

XX transformer mutants are ?

Answer 7

normal, large sterile males

Question 8

XY transformer mutants are ?

Answer 8

normal males

Question 9

What is the transformers function ?

Answer 9

Directs female development

Question 10

What does the transformer gene do in female flies ?

Answer 10

Sxl represses exon 2 splice, function tra protein

Question 11

What does the transformer gene do in male flies ?

Answer 11

default splice, short non-functional tra protein

Question 12

what does the double-sex gene do in flies ?

Answer 12

directs sex-specific morphology

Question 13

what does the fruitless gene do in flies ?

Answer 13

directs sexual orientation

Question 14

Explain turners syndrome

Answer 14

XO (missing sex chromosome)

Develop as female

Question 15

Explain kleinfelters syndrome

Answer 15

XXY

Develop as male

Question 16

What are sex reversed mutant mice ?

Answer 16

males are XX, females are XY because of an inherited condition due to a single gene

Question 17

How could we get XY females ?

Answer 17

Mutation or deletion of the male determining gene (SRY), develop as female

Question 18

How could we get XX males ?

Answer 18

translocation of the male determining gene (SRY), develop as male

Question 19

What does the SRY gene do ?

Answer 19

Converts developing embryo from female to male

Question 20

What does SRY protein do ?

Answer 20

Is a transcription factor that switches on genes that force gonads to develop in male fashion and produce testosterone

Question 21

What does testosterone do ?

Answer 21

Travels round bloodstream, enter cells via receptors and switches on male genes