Sex Determination (12,13) Flashcards
What does ‘dominant male’ system refer to?
a. The absence of SRY leads to the development of the testis
b. The male phenotype is the default pathway
c. If SRY is present, a male should develop
d. Someone needs two copies of SRY to develop a male phenotype
c. If SRY is present, a male should develo
What is a feature of the SRY location?
a. It is within the PAR on the q arm of the Y chromosome
b. The location means that crossing over between X and Y chromosomes will never result in the exchange of SRY
c. It is close to the PAR on the Y chromosome p arm
d. It is in region 1A2 on the q arm of the Y chromosome
c. It is close to the PAR on the Y chromosome p arm
What was involved in cloning and identifying the SRY location?
a. Looking for the smallest deleted region on Y chromosomes in male carriers
b. Looking for the smallest fragments of Y chromosomes added to X chromosomes in the females
c. Finding the region that was present in the XY females and absent in the XX males
d. Determining that the SRY was in the region where the smallest insert made XX male and shortest deletion made XY female overlap
d. Determining that the SRY was in the region where the smallest insert made XX male and shortest deletion made XY female overlap
What is involved in the development of testes or ovaries?
a. After 5 weeks, a gonadal ridge forms from the mesonephros and germ cells migrate to the ridge
b. Sex is majorly determined by growth rate, which is more rapid in females
c. Ovary differentiation begins at 6 weeks, weeks before testes tissue differentiation
d. Females secret androgens and antimullerian hormone (AMH) to prevent to development of the mullerian duct
a. After 5 weeks, a gonadal ridge forms from the mesonephros and germ cells migrate to the ridge
What makes up the SRY gene?
a. It has several TATA boxes that are conserved between species
b. It has a conserved 80AA HMG box that shares high homology to the SRY of other mammals
c. It has several exons but little homology between species
d. It has a conserved SOX-box which shares high homology with other human genes
b. It has a conserved 80AA HMG box that shares high homology to the SRY of other mammals
What is false about SOX genes?
a. They have a Sox box which is an HMG box 70% homologous to that of SRY
b. SOX stands for SRY related box
c. SOX 3 is thought to be an ancestor of SRY and functions in brain development
d. 50% of XY females have mutation in SOX9 or SOX8
d. 50% of XY females have mutation in SOX9 or SOX8
What is false about the action of SRY as a transcription factor?
a. It binds to the minor groove of DNA and bends it at a 60 degree angle
b. The TAACAATAG binding site is also recognised by SOX genes
c. In mice, it contains a glutamine repeat region essential for testis development
d. The Sip-1 sequence in SRY is an important nuclear localisation signal
d. The Sip-1 sequence in SRY is an important nuclear localisation signal
• On day 11 of development, mice have 1500 sexually dimorphic genes expressed even though the gonad is morphologically indistinct.
T
• Female mice express one gene that alters the expression of 1500 genes in the ovary.
F (200)
• The events for correct gonadal development of secondary characteristics for a male or female phenotype are classified as part of sex determination. (differentiation)
F
• 50-70% of genes are expressed in a sex biased manner, although the mean difference is only 10%.
T
• Bovines have 1274 transcribed Y chromosome genes which are mostly expressed during testis development.
T
• The male phenotype is the default pathway in humans.
F
• XY females and XX males can result from a crossover that transfers the SRY locus to the X chromosome.
T
• Homology between mammals is greatest at the level of DNA.
F
• For the first 5 weeks, there is no detectable morphological difference between male and female destined embryos.
T
• Male reproductive tracts develop from the Mullerian duct and female reproductive tracts develop from the Wolfian duct.
F
