Week 12

Question 1

Sexual Dimorphism

Answer 1

Differences in phenotype of the two reproductive species

Question 2

Bipotential Gonads

Answer 2

Mullerian duct
Wolffian duct
Exist in both males and females during fetal development, set of cells make up either gonads.

During fetal development males and females are indistinguishable.

Question 3

Male development

Answer 3

Secretion of Testosterone and antimullerian duct hormone trigger regression of the mullerian duct (MIH) and development of the wolffian duct into the urethra and vas deferens (testosterone)

Question 4

Female development

Answer 4

Wolffian duct is degraded due to the lack of testosterone and the mullerian duct develops into parts of the vagina, uterus and cervix due to the lack of MIH

Question 5

How does sec determination occur?

Answer 5

sex of the gonad cells can influence the development of the bipotential gonad, these sex hormones control secondary sex characteristics

Question 6

Genetics of Sex determination

Answer 6

1- DNA sequence variations affecting sex determination are generally viable but may be sterile

2- DNA sequence variations have clear phenotypes

Question 7

Androgen insensitivity syndrome

Answer 7

XY
Testes
Female secondary sex (genitals) characteristics

Androgens are secreted, the gene encoding androgen receptors on the X-chromosome is inactive. The presence of androgens can be detected.

testosterone cannot act because there were no receptors

-no wolffian duct, no mullerian duct, just testes and urethra

Question 8

Heterogametic systems (humans/drosophila)

Answer 8

Male (heterogametic): XY

Females (homogametic): XX

Question 9

Heterogametic systems (Birds/Butterfly)

Answer 9

Male (homogametic): ZZ
Female (heterogametic): WZ
many mechanisms determines sex

Question 10

X0 and Haplodiploid systems

Answer 10

Male: X0
Female: XX

Male: 1n
Female: 2n

Question 11

Gated Systems

Answer 11

Temperature and social systems in turtles (temperature) and fish (social systems)

Question 12

Which Chromosome is humans is repsonsible for determining sex?

Answer 12

The presence of the Y chromosome

One X is sufficient for female development (Turner’s syndrome)

Question 13

XX Male

Answer 13

Sex reversal gene on the Y chromosome (sry) translocation of sry onto the X chromosome

Question 14

XY female

Answer 14

Deletion of sry on the y chromosome

Question 15

SRY

Answer 15

Encodes a transcription factor. Secretion of androgens and anti-mullerian hormone present in male gonads but not in females

Question 16

Sex determination in drosophila

Answer 16

the presence of the Y chromosome is not important for male development, the y chromosome has some gene that are important for fertility but not sex determination

Question 17

Drosophila primary sex determination

Answer 17

Polyploid in drosophila

X;A, 0.5 = males
XX; AA 1>= Females

Question 18

0.5/1 Ratio

Answer 18

In males the 0.5 ratio does not transcribe enough tf to bind to the sxl gene promoter no sxl is produced

In females the 1 ratio is enough to produce the tf required for sxl gene expression and sxl product

Question 19

SXL males

Answer 19

Binds to intron of TRA pre-mrna

in males there is no SXL to bind to the intron of TRA pre-mRNA and U1 binds to the 5’ss and U2AF binds to the male 3’ss

Mature tra messenger rna with an early stop codon resulting in an inactive truncated tra protein

Question 20

SXL in females

Answer 20

SXL binds to the intron of TRA pre-mRNA

SXL pushes U2 to use a 3’SS furhter down the pre-mRNA. SXL blocks the use of the male 3’SS

When SXL protein is present the female transcript is produced resulting in the expression of TRA protein.

Question 21

TRA

Answer 21

transformer protein is produced when SXL tf binds

TRA activates TRA2 when it binds to it

Question 22

Doublesex (dsx)

Answer 22

Alternative splicing of dsx is responsible for the last important step of somatic sex determination.

TRA2 is expressed in both males and females

no tra in males to activate tra2

tra2 is inactive in males leading to splicing that results in male dsx

Question 23

Loss of DSX function

Answer 23

Partially formed male sexcombs

male claspers and vagina,

male pigmentation

genitals are both male and female

Question 24

DSXM

Answer 24

Suppresses female differentiation

male sex combs
no vagina
male colouring
claspers

Question 25

DSXF

Answer 25

``` Surpresses male differentiation no sex combs femlae colouring no male genetalia vagina ```

Question 26

Double sex genes in turtles

Answer 26

Red eared turtle 26 c- male: dmrt is expressed, loosens chromatin (euchromatin;epigenetic phenomenon) 31 c-female

Question 27

Behaviour

Answer 27

Responses of an organism to stumuli includes neurobiology but is not exclusive to neurobiology you don't need to have a nervous system (chemotaxis, mating pheromones, sunflowers following the sun)

Question 28

Behavioural genetics

Answer 28

Analysis of genes required for behaviour

Question 29

Drosophila male courtship behaviour

Answer 29

``` Vibrate wings to sing tapping orienting licking attempting copulation ``` if the female is receptive to courtshil behaviour they will receive the male, if not the female will kick the male in the head

Question 30

Genes responsible for male courtship behaviour

Answer 30

Tra+Tra2 in females force the splicing of the fruitless mRNA so that no aactive gene product is formed

Question 31

Fru gene

Answer 31

Multiple promoters | fru loss-of-function alleles results in a lack of male courtship behaviour

Question 32

Splicing transcripts from the P1 fru promoter (alternative _' splicing)

Answer 32

5' splicing fru female TRA+TRA2 results in extra information in female transcript, no product is detected from the transcript even is it can be translated (tra2+tra forces the splice machinery to use 5' splice site further 3') in males tra2 binds to the binding sites in the extra region to splice it out

Question 33

What would happen if the TRA2 binding sites were removed?

Answer 33

The splicing machinery cannot be forced to use the female splice site Females exhibits male behaviour

Question 34

Connectomics

Answer 34

Systematic mapping of the neurons and synapses in an organism. Sliced the nematode worm in crossections and at each section they are able to track the neuronal by stakcing them against one another, giving a neural representation of the neurons of the c.elegans brain

Question 35

How can the presynaptic neuron be activated independently of a signal?

Answer 35

Light activated pores can be used to stimulate action potential. Opsin’s are activated by a center wavelength of light to allow ions to flow Used in vertebrates to manipulate the activity of neurons, used a focused beam of light to stimulate cells expressing opsin.

Question 36

Express proteins specifically in neurons

Answer 36

Binary system driver and uas line Visualize neurons expressing gal4, gives us info on where gal4 is expressed