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Genetics > Week 12 > Flashcards

Week 12 Flashcards

1
Q

Sexual Dimorphism

A

Differences in phenotype of the two reproductive species

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2
Q

Bipotential Gonads

A

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.

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3
Q

Male development

A

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)

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4
Q

Female development

A

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

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5
Q

How does sec determination occur?

A

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

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6
Q

Genetics of Sex determination

A

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

2- DNA sequence variations have clear phenotypes

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7
Q

Androgen insensitivity syndrome

A

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

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8
Q

Heterogametic systems (humans/drosophila)

A

Male (heterogametic): XY

Females (homogametic): XX

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9
Q

Heterogametic systems (Birds/Butterfly)

A

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

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10
Q

X0 and Haplodiploid systems

A

Male: X0
Female: XX

Male: 1n
Female: 2n

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11
Q

Gated Systems

A

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

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12
Q

Which Chromosome is humans is repsonsible for determining sex?

A

The presence of the Y chromosome

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

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13
Q

XX Male

A

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

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14
Q

XY female

A

Deletion of sry on the y chromosome

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15
Q

SRY

A

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

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16
Q

Sex determination in drosophila

A

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

17
Q

Drosophila primary sex determination

A

Polyploid in drosophila

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

18
Q

0.5/1 Ratio

A

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

19
Q

SXL males

A

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

20
Q

SXL in females

A

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.

21
Q

TRA

A

transformer protein is produced when SXL tf binds

TRA activates TRA2 when it binds to it

22
Q

Doublesex (dsx)

A

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

23
Q

Loss of DSX function

A

Partially formed male sexcombs

male claspers and vagina,

male pigmentation

genitals are both male and female

24
Q

DSXM

A

Suppresses female differentiation

male sex combs
no vagina
male colouring
claspers

25
Q

DSXF

A 
Surpresses male differentiation
no sex combs
femlae colouring
no male genetalia
vagina
26
Q

Double sex genes in turtles

A

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

27
Q

Behaviour

A

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)

28
Q

Behavioural genetics

A

Analysis of genes required for behaviour

29
Q

Drosophila male courtship behaviour

A 
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

30
Q

Genes responsible for male courtship behaviour

A

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

31
Q

Fru gene

A

Multiple promoters

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

32
Q

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

A

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

33
Q

What would happen if the TRA2 binding sites were removed?

A

The splicing machinery cannot be forced to use the female splice site

Females exhibits male behaviour

34
Q

Connectomics

A

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

35
Q

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

A

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.

36
Q

Express proteins specifically in neurons

A

Binary system

driver and uas line

Visualize neurons expressing gal4, gives us info on where gal4 is expressed

Genetics (16 decks)

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