Chapter 6 pt 1 (sex det) Flashcards
“Sexual reproduction is the masterpiece of nature”
Erasmus Darwin
I tis quatrain to notice that that the number of speculations connected with the nature of sex have well-nigh doubled since drelincourt, in the 18th century brought together 262 groundless hypothesis
JA Thomsom
_______ claimed sex was determined by the heat of the male partner during intercourse. The more heated the passion, the greater the probability of producing male offspring. Elderly men should try to conceive in the summer if they wish to have sons
Aristotle
When were the X and Y chromosomes identified in humans?
early 1900’s
In _______, the presence of a second X and or presence of Y determines sex
Mammals
-XX = female
-XY = male
In _______, males have two similar sex chromosomes (ZZ) while females have unmatched sex chromosomes (ZW)
birds
In _______, Y chromosome does not appear to play a major role. Sex is determined by the number of X chromosomes
Drosophilia
- XX = female
- X_ = Male
In _______, fertlized diploid eggs will develop as female, while unfertilized haploid eggs become male
many insects
- hymenopterans (bees, ants, wasps)
What is primary sex determination in mammals?
determination of the gonads
The Y chromosome is critically important in mammals because it produces _______, which organizes the gonad into testes
Testes determination factor
What is secondary sex determination in mammals?
development of sexual phenotype
- male female duct system and genetalia
Mammalian gonads originally are formed indifferent with no sex chosen this is an example of _______
bipotential gonad
(indifferent gonad)
in male mammals:
_____ cells secrete _______ that block the formation of the female duct system from the _______ duct. The _______ duct differentiates into the vas deferens
1) sertoli
2) anti-mullerian factor
3) mullerian duct
4) wolffian duct
In female mammals:
in the absence of testosterone, the _______ duct degenerates while the _______ duct differentiates into the oviducts, uterus, cervix, and upper vagina
1) wolffian
2) Mullerian
In mammals, maleness is determined by the presence or absence of _______
testis
- y chromosome
_______: sex determining region of the Y chromosome
SRY gene
_______ cell of the testis secretes testosterone
Leydig
Testosterone is _______ meaning it is a male determining hormone
androgenic
In males (XY), _______ gene on the Y chromosome is activated by a series of factors in the early stages of genital ridge formation
SRY
SRY protein binds to _______ promotor, increasing its expression
SOX9
- Sry is only active for a few hours
In males, _______ and _______ both act to block the ovary forming pathway by blocking the function of β-catenin
Sox9 and Fgf9
In females (XX) ________ is critical in activating further ovary development and blocks the synthesis of Sox 9
β-catenin
β-catenin is activated through a _______ pathway
Wnt4/Rspo1
β-catenin can stimulate the production of _______ and other genes that lead to ovary formation
Follistatin
In lab experimental situations, a delay of Sry expression by as little as __-hours caused testis to fail to develop nad the gonads instead to become ovaries
6
_______ the development of male and female phenotypes in response to hormones secreted by the ovaries and testis
Secondary sex determination
What are the 2 major phases of secondary sex determination?
1) embryogenesis
2) puberty
_______ stimulates the mullerian ducts to differentiate into the uterus, cervix, oviducts, and upper vagina
Estrogen
In females, the ______ differentiates into clitoris, while in males it differentiates into the penis
genital tubercle
The androgen insensitivity syndrome results in __ individuals that have the SRY gene with testis and testosterone. However, they develop externally as _______
XY
female
- sterile women that lack uterus, oviducts, and have testes in abdomen
_______: male and female traits seen in the same individual
intersex
_______: only one type of gonad, but the secondary sexual characteristics depart from what is expected when carrying that type of gonad
pseudo-hermaphroditism
- androgen insensitivity
- mutation in testosterone synthesis
What is a cause of pseudo-hermaphroditism? (2)
1) androgen insensitivity syndrome
2) mutation in testosterone synthesis
_______: when gonadal sex is female but externally shows male phenotypes.
female pseudo-hermaphroditism
- can be caused by overproduction of androgens from adrenal glands or ovaries
What is a cause of female pseudo-hermaphroditism
overproduction androgen in adrenal glands or ovaries
_______: A genetic deficiency of an enzyme responsible for metabolizing cortisol steroids in the adrenal gland. In the absence of this enzyme, testosterone-like steroids accumulate masculinizing the fetus.
congenital adrenal hyperplasia
In drosophila, examination of _______ (mosaic individuals with both male and female cells in the same body) suggests that in insects, each individual cell makes its own decision about sex
gynandromorphs
the critical gene in drosophila sex determination is the _______ gene that encodes the _______ protein
Sxl gene
sex-lethal
Transcription of the Sxl gene is controlled by what two promoters?
1) PE (early)
- only activated in XX female cells
2) PL (late)
- activated in both XX and XY cells
What are the 4 transcription factors responsible for stimulating sxl transcription?
1) SisA
2) Scute
3) Runt
4) unpaired
In drosophila XY cells, transcription of Sxl from PE (is/isnt) sufficiently stimulated
isnt
- haploinsufficient
- XX has double the amount of TF which allows for XX PE transcription
The SXL protein is an RNA-binding protein that directs the splicing of sxl mRNA molecules produced from the _______ promoter
PL
In the absence of the SXL protein, sxl mRNA’s produced from the PL promoter are spliced in a manner that maintains a _______ present in exon 3 resulting in _______ additional functional SXL protein being produced
stop codon
- in males
no
In the presence of the SXL protein, sxl mRNA’s produced from the PL promoter are alternatively spliced in a manner that removes a _______ present in exon 3 resulting in _______ functional SXL protein being produced
stop codon
- in females
additional
Females have _______ and _______ Sxl protein while males have _______ sxl protein
early and late
non-functional
The pre-mRNA of the _______ gene is produced in both male and female cells and is a target of Sex-lethal
transformer (tra)
- produces another splicing factor
In female cells the presence of SXL protein directs the splicing apparatus to an alternate splice site producing the female-specific _______ protein. In male cells, the premature stop codon is not spliced out and no functional _______ protein is produced
TRA
- for both
TRA works to alternatively splice the pre-mRNA of the _______ gene to produce both male and female specific versions
double-sex (dsx)
- transcription factor
In females the _______ protein acts as a TF to activate female-specific genes and repress male-specific genes
DSXf
In males the _______ protein acts as a TF to activate male-specific genes and repress female-specific genes
DSXm
briefly explain sex-specific RNA splicing in drosophila
4 mRNA (sex-lethal, transformer, doublesex, fruitless) are spliced differently
- sex lethal affects sex lethal and transformer
- transformer affects doublesex, and fruitless
The dsx gene is processed in a sex-specific manner by _______ and _______
tra and tra2
DsxF in association with the _______ protein creates a TF complex that activates female-specific genes
intersex (Ix)
_______ is an enzyme that converts testosterone into estrogen
aromatase
In turtles, @ 25°C aromatase activity is _______
very low
Hot chicks, cool dudes
In turtles, @ 30°C aromatase activity _______
increases
Hot chicks, cool dudes
Aromatase control happens via what two mechanisms?
1) temp-dependent transcription
2) temp-dependent enzyme activity
Work done by _______ and colleagues has shown a link between _______ and sex determination
tyrone hayes
atrazine
atrazine produced sexual anomalies in males frogs like _______ and _______
testicular dysgenesis and conversion to ovaries
