Determination Of Sex Flashcards
These are the chromosomes involved in the determination of sex
Sex chromosomes
What are autosomes?
All other chromosomes which are not involved in sex determination
In man 2n=46, how many are autosomes and sex chromosomes?
44 autosomes and 2 sex chromosomes
In drosophila, 2n=8 how many are autosomes and sex chromosomes?
6 are autosomes and 2 are sex chromosomes
Is colorblindness an x-linked recessive trait?
Yes
In drosophila, are the chromosomes labeled with roman numerals?
Yes
What are the different methods of sex determination?
Haploidiploidy, chromosomal methods of sex determination (XX-XO system, ZZ-ZW system, XX-XY system), genic balance in drosophila, environmental sex determination
Give an example of an organism that uses haplodiploidy as their method for sex determination
Bees
(Haplodiploidy) In bees, what is the sex if the egg is fertilized and forms a 2n individual?
Female (workers)
(Haplodiploidy ) If eggs are unfertilized in bees (parthenogenesis) and forms a 1n individual what is the sex?
Male (drone)
What method of sex determination do grasshoppers use?
XX-XO system
(XX-XO System) If the grasshopper has a sex of XX
Female
(XX-XO System) If the grasshopper has a sex of XO
Male
(XX-XO System) what does O stand for?
Non-x bearing
What system is utilized in birds for sex determination?
ZZ-ZW system
If the sex chromosomes are identical ZZ or homogametic it is
Male
If the sex chromosomes are not identical ZW or heterogametic it is
Females
For humans, when the sex if homogametic it is
Female
For humans, when the sex if heterogametic it is
Male
What determines the maleness in man?
Y chromosome
What is bipotentiality of sexes?
This is a phenomena during the indifferent stage where the gonads are neither testes or ovary, thus having the possibility to arise to either or even both
During the indifferent period are the presence of indifferent gonads, thus the presence of ________
2 ducts
What is the duct for females?
Mullerian or paramesonefric
What is the duct for males?
Wolfian or mesonefric duct
What occurs if something goes wrong in the differentiation of the gonads?
Hermaphroditism
This encodes a transcription factor that controls the expression of genes
SRY (sex-determining region Y) gene or formerly known as testes-determining factor (TDF)
The ______ gene is y-linked because it is only found in the y chromosome
SRY gene
How does the SRY gene stimulate male development?
It sends signals to indifferent gonads
The ______ in testis secrete the _____ which destroys the mullerian duct
Sertoli cells; anti-mullerian hormone/mullerian regression factor
________ in testis secrete testosterone which stimulates the development of male structures
Interstitial cells
Some testosterone are converted into ______ which causes _________
DHT (dihydrotestosterone); masculinization of external genitalia
What happens in females during sex differentiation?
The medulla regresses and the cortex progresses
What is secreted by the leydig cells that functions for muscularization of the male genitalia?
5a dihydrotestosterone
This is a genetic disorder where the individual is XY but has female features, because the XY fetuses becomes impassive to androgen
Androgen insensitivity syndrome
What does undescended testis mean?
Because the scrotum is a thermoregulator, when the testis is undescended it is found in the abdomen where the temperature is not ideal for spermatogenesis. Normally, it should descend because the torso has higher temperature
What phenomena did Dr. Julianne Imperato investigate in the Dominican Republic where children appearing to be girls turned into men at puberty?
Male pseudohermaphroditism
This means penis at 12 years
Guevadoces
What is the cause of the phenomena in the Dominican Republic?
Deficiency of the enzyme 5-alpha reductase which converts testosterone into dihydrotestosterone and inbreeding in which the gene can be traced back to 1 female
What is the barr body?
It is present in dosage compensation and it is the condensed inactive member of a pair of chromosomes in the cell. While the other x is not condensed and is active in transcription
What is the purpose of dosage compensation?
This balances the dose of x chromosome gene expression in females and males
Who discovered the barr body?
Dr. Murray Barr and Mary Lyon
A female is barr ______
Positive
A male is barr ______
Negative
how is the number of barr bodies computed?
no. of x chromosome - 1 you know I love unity you should know don’t mean
This states that the x inactivation occurs randomly in embryonic cells
The lyon hypothesis
What specific region shuts off much of the chromosome?
X-inactivation center (Xic)
This a gene that encodes an RNA that does not encode a protein, instead it coats the inactive x chromosome and promotes chromosomal compaction into a barr body
XIST (x-inactive specific transcript) gene
What happens once an x chromosome is inactivated 1 cell?
All its daughter cells will have the same x chromosome inactivated
Why is the calico color only found in female cats?
This is because it is a heterozygous trait that needs 2 Xs
Male cats are ______
Hemizygous
What do you call when sex is determined by balance between number of x chromosomes and number of sets of autosomes
Genic balance
Who discovered sex determination in drosophila?
Dr. Calvin blackman bridges
Is known for the fly room and morgan unit
Thomas hunt morgan
If X/A ratio=1, what is the sex?
Female
If X/A ratio=0.5, what is the sex?
Male
If X/A ratio is between 0.5 and 1, what is the sex?
Intersex
If X/A ratio is greater than 1, what is the sex?
Metafemale
If X/A ratio is lesser than 0.5, what is the sex?
Metamale
How many autosomes are grouped in A in drosophila?
3
What is the master switch gene for sex determination in drosophila melanogaster?
Sex-lethal (Sxl) gene
In xx animals, sxl becomes inactivated and imposes__________
Female development
In xy animals, sxl remains inactive and ________ ensues
Male development
When in homozygous recessive form, transforms females into sterile males.
Transformer (tra) gene on autosome 3
Transforms normal males and females into flies with intersex phenotypes
Double sex ( dsx) gene, recessive autosomal
AA XX tra tra
Males
AA XY tra tra
Male
AA XX Tra tra
Female
AAXX dsx dsx
intersex
AA XY dsx dsx
Intersex
AA XY Dsx dsx
Male
4 examples of environmental sex determination
Temperature dependent sex determination, location-dependent sex determination in Bonellia, equisetum, cucurbita pepo
Low temp 100% males, high temp 100% females for scripta, low and high temp 100% females and intermediate temp males for Macroclemys temmickii, and low temp 100% females and high temp 100% males for alligator mississippiensis
Temperature dependent sex determination
If bonellia larva settles on the floor, what is the sex?
Female
If bonellia larva settles on a female’s proboscis, and enters the mouth, migrates to the uterus, what happens?
It differentiates into a male
In equisetum, if grown under favorable conditions, what does it form?
Female
In equisetum, if grown under poor conditions, what does it form?
Male
In cucurbita pepo, during high temp and long days, what flowers are produced?
Male
In cucurbita pepo, during low temp and short days, what flowers are produced?
Female
