CBG16

Question 1

In honet bees what is the gene to determine sex?

Answer 1

complementary sex determining gene csd

Question 2

How does csd gene work?

Answer 2

targets feminizer gene needed for female development
which then makes product that acts on double sex gene.
haploids are hemizygous and become males as dont produce feminizer gene
alternative splicing in males adds stop codons into feminizer coding sequence
females=2n males=n

Question 3

When might a male honey bee be produced by fertilisation?

Answer 3

the locus for csd is honey bees is highly variable. - 13 alleles
generally females are heterozygous at the locus.
in an inbred population the locus can be homozygous
which can result in male production from fertilisation as stop codon stops feminzer.
- ussually the males die, as lethal

Question 4

What is the default sex in drosophilia?

Answer 4

male

Question 5

how are females produced in drosophilia?

Answer 5

sex lethal sx1 gene starts cascade of mRNA alternate splicing to produce female specific proteins.
female double sex represses male genes and activates female.
* male double sex represses female genes*

Question 6

What are the chromosomes for male and female in grasshoppers?

Answer 6

female = XX
male = X0

Question 7

What are the chromosomes for male and female in humans?

Answer 7

female = XX, XXX, X0
male = XY, XXY

Question 8

What are the chromosomes for male and female in drosophillia?

Answer 8

Male = XY X0
female = XX, XXY
metafemale = XXX

Question 9

What are the chromosomes for male and female in birds?

Answer 9

male = ZZ
female = ZW

Question 10

What is a metafemale?

Answer 10

low viability fruit fly with female phenotype

no. of sex chromosomes exceeds number of autosomes.

Question 11

How is sex identified?

Answer 11

1. anatomy
2. endocrinology, conc of sex hormones
3. chromosomes
4. genes, eg. genes in testes development pathway.

Question 12

What is the SRY+ gene?

Answer 12

male determining gene
y genes not found on X active only in testes
if present inhibits od - ovary development gene
shows homology to SOX3 in playpus

Question 13

What determines sex in humans?

Answer 13

sry gene in males
od -ovary development gene in females
if sry present it inhibit od -> gonads, testes - boy 8weeks
if by week 13 there is no sry gene, od is switched on = ovaries- girl.

Question 14

what is dsd?

Answer 14

disorder of sexual development

- difference between internal/external chromosomal gender identity

Question 15

What sex do these chromosomes represent:
XYSRY+
XXSRY+
XYSRY-
XXSRY-

Answer 15

XYSRY+ normal male
XXSRY+ translocation from y-x
XYSRY- deletion/mutation of sry gene
XXSRY- normal female

Question 16

What leads to intersex or DSD?

Answer 16

uncoupling of human chromosomal and phenotypic sex.

Question 17

What is androgen insensitivity syndrome?

Answer 17

recessive mutation that causes 46XY SRY+ chromosomal males to be insensitive to androgens
leading to phenotypic female AIS
complete AIS genitalia female - no female internal organs
partial AIS = can be male female or in the middle

Question 18

When can 46XY SRY+ be phenotypically female?

Answer 18

AIS
if DAX1 gene is duplicated on X chromosome
= anti testis gene

Question 19

What is required to maintain testic function in adult males?

Answer 19

DMRT1
female specific genes are blocked
fox12
b-catenin
-rspof

Question 20

What does X0SRY- genotype produce?

Answer 20

female

but 2X chromosomes are required for functioning ovaries.

Question 21

What is required to prevent trans differentiation to testes in females?

Answer 21

on going presence of foxl2 in ovaries r

Question 22

Give 2 examples of ESD?

Answer 22

environmental sex determination
eg. parthenogenetic females produce clonal females (Daphnia) but males in stress
larval setting behaviour in green spoon worm
- free swimming in sea = female
large probiscus
land on prodbiscus and become male - sperm donor. - tiny

Question 23

How are turtles under the influence of ESD?

Answer 23

egg incubation critical at certain times in embryonic development
eg. CXPIA gene priduces aromatase converts testosterone to estradiol in gonads.
low temperates correlate with female development

Question 24

What is protoandry give an example?

Answer 24

protoandry
begin life as male and change into female
eg. clown fish.

Question 25

In what species does protogyny occur?

Answer 25

wrasse

female - male