Sex determination in mammals and drosophila 3

Question 1

Which two promoters does Sxl have?

Answer 1

An early one and a late one

Question 2

Which promoter of Sxl do sisterless homodimer proteins activate?

Answer 2

The early promoter

Question 3

What happens to individuals who has XX:AA chromosomes who have a mutation in the tra gene?

Answer 3

They develop as males

Question 4

In which sex(es) is the tra gene transcribed?

Answer 4

Both

Question 5

In which sex(es) is the tra gene functional?

Answer 5

Females

Question 6

Why is the tra gene only functional in females?

Answer 6

The Sxl gene regulates the splicing of the tra transcript so it is only functional in females

Question 7

How does the Sxl splice the tra gene so it is functional in females?

Answer 7

It splices out an exon that has a premature termination codon

Question 8

Which tra gene (tra or tra2) binds to RNA?

Answer 8

Tra2

Question 9

Which type of domain does tra2 have 2 of?

Answer 9

SR domains (serine/arginine rich domains)

Question 10

Between which two organisms is the tra-2 gene highly conserved?

Answer 10

Humans and flies

Question 11

What is tra2 gene dysfunction in humans associated with?

Answer 11

A range of cancers

Question 12

Which gene does tra2 regulate the splicing of?

Answer 12

Doublesex

Question 13

What is the difference in the doublesex protein between the sexes?

Answer 13

Females–> exons 1,2,3,4 Dsx-F
Males–> exons 1,2,3,5 DsxM

Question 14

What is the same between Dsx-F and Dsx-M proteins?

Answer 14

They have the same DNA-binding domain and dimerization domain

Question 15

What is different between Dsx-F and Dsx-M proteins?

Answer 15

C-termini

Question 16

What does the c terminus of the female doublesex protein bind to?

Answer 16

intersex

Question 17

How do the Dsx-F and Dsx-M proteins control female- and male- specific differentiation?

Answer 17

DSXF and DSXM could be recruited to different loci, bind to different genes in different tissues,

Question 18

Which genes absence is responsible for the dark pigmentation present on male drosophila?

Answer 18

Bric a Brac

Question 19

In which sex is the bric a brac gene expressed in?

Answer 19

females

Question 20

How is DSXF related to the absence of dark pigmentation on a female drosophila?

Answer 20

DSXF bind to an intron on bric a brac (which suppresses the dark pigmentation) and promotes its transcription

Question 21

How is DSXM related to the absence of dark pigmentation on a female drosophila?

Answer 21

DSXF bind to an intron/enhancer on bric a brac (which suppresses the dark pigmentation) and promotes its transcription

Question 22

How are x-linked genes expressed at the same rate in male and female drosophila?

Answer 22

The x chromosome in males undergoes dosage compensation–> it is transcribed at twice the rate of females

Question 23

Which genes control the dosage compensation of x linked genes in male drosophila?

Answer 23

male specific lethal (msl) 1,2,3 and male-less (mle)

Question 24

What happens if msl and mle are absent in males?

Answer 24

Dosage compensation in males does not occur so not enough x-linked proteins are synthesised in males

Question 25

Role of the msl 2 gene?

Answer 25

It encoded a ring finger DNA binding protein that binds at hundreds of sites along the male x chromosome

Question 26

What type of protein is MOF?

Answer 26

Histone acetyl transferase

Question 27

How is Sxl linked to msl-2?

Answer 27

It controls translation of the msl-2 mRNA

Question 28

How does Sxl regulate msl-2 translation?

Answer 28

Sxl binds to the 3' untranslated region and represses translation

Question 29

Msl2 mechanism of action?

Answer 29

It forms part of the complex that acetylases histone H4 which opens up chromatin and increases transcription at a specific loci