Sex determination in mammals and drosophila 3 Flashcards
Which two promoters does Sxl have?
An early one and a late one
Which promoter of Sxl do sisterless homodimer proteins activate?
The early promoter
What happens to individuals who has XX:AA individuals who have a mutation in the tra gene?
They develop as males
In which sex(es) is the tra gene transcribed?
Both
In which sex(es) is the tra gene functional?
Females
Why is the tra gene only functional in females?
The Sxl gene regulates the splicing of the tra transcript so it is only functional in females
How does the Sxl splice the tra gene so it is functional in females?
It splices out an exon that has a premature termination codon
Which tra gene (tra or tra2) binds to RNA?
Tra2
Which type of domain does tra2 have 2 of?
SR domains (serine/arginine rich domains)
Between which two organisms is the tra-2 gene highly conserved?
Humans and flies
What is tra2 gene dysfunction in humans associated with?
A range of cancers
Which gene does tra2 regulate the splicing of?
Doublesex
What is the difference in the doublesex protein between the sexes?
Females–> exons 1,2,3,4 Dsx-F
Males–> exons 1,2,3,5 DsxM
What is the same between Dsx-F and Dsx-M proteins?
They have the same DNA-binding domain and dimerization domain
What is different between Dsx-F and Dsx-M proteins?
C-termini
What does the c terminus of the female doublesex protein bind to?
intersex
How do the Dsx-F and Dsx-M proteins control female- and male- specific differentiation?
DSXF and DSXM could be recruited to different loci, bind to different genes in different tissues,
Which genes absence is responsible for the dark pigmentation present on male drosophila?
Bric a Brac
In which sex is the bric a brac gene expressed in?
females
How is DSXF related to the absence of dark pigmentation on a female drosophila?
DSXF bind to an intron on bric a brac (which suppresses the dark pigmentation) and promotes its transcription
How is DSXM related to the absence of dark pigmentation on a female drosophila?
DSXF bind to an intron on bric a brac (which suppresses the dark pigmentation) and suppresses its transcription
How are x-linked genes expressed at the same rate in male and female drosophila?
The x chromosome in males undergoes dosage compensation–> it is transcribed at twice the rate of females
Which genes control the dosage compensation of x linked genes in male drosophila?
male specific lethal (msl) 1,2,3 and male-less (mle)
What happens if msl and mle are absent in males?
Dosage compensation in males does not occur so not enough x-linked proteins are synthesised in males
Role of the msl 2 gene?
It encoded a ring finger DNA binding protein that binds at hundreds of sites along the male x chromosome
What type of protein is MOF?
Histone acetyl transferase
How is Sxl linked to msl-2?
It controls translation of the msl-2 to mRNA
How does Sxl regulate msl-2 translation?
Sxl binds to the 3’ untranslated region and represses translation
Why is msl-2 needed in males?
It forms part of the complex that acetylases histone H4 which opens up chromatin and increases transcription at a specific loci
