Sex Deter And Sexual Dx Flashcards
Gender vs. Sex
Gender
- subjective
- individual’s subjective perception of their sex and their sexual orientation
Sex
- objective
- more factual
- biological characteristics that distinguish female from male. Distinction may be made on the basis of chromosomes, gonads, and internal & external morphologies
Sex determination
- This is the role of the?
- What determines if you are a male or a female?
- Role of the CHROMOSOMES
2. Y chromosome and its SRY gene/testes determining factor
Sex determination
1. T or F. A person with both X and Y chromosomes always looks like a man.
- Chromosomal sex vs. gonadal sex vs. phenotypic sex vs. behavioral and metabolic sex
- F! You can have X and Y chromosomes but not look like a man because the aberrations can happen in each step.
- Sex determination in mammals is a process
- In other words, you can have X and Y but doesn’t mean that you will always look like a man bc the process takes many steps and in each step, aberrations can happen.
- Most obvious: Either you have XY or XX mix of sex chormosomes. This is called the genetic gametic for chromosomal sex. Your chromosomal sex is female bc you have XX chr. Now, the presence of the Y chromosomes will determine whether you are male bc in the Y chromosome you have the SRY (Sex determining region) in the Y which will code for the SRY protein. In this sense, after this is determined, there will now be the development of the gonads. When we were developing as fetuses, our gonads are initially bipotential (indifferent) gonads. Eventually bc of the SRY in males, there will be the development of the bipotential gonad into the testis. While in the females, bc there’s no SRY, the gonads develop in the ovary. At this pt, you are a female bc your gonads are developing into ovaries so that’s part of your gonadal sex.
Now, bc the ovary has been developing, there will be secretions by the cells of the ovary. There will be the secretions of hormones like E2 and progesterone that will also help in producing the external aspects of our sexual appearance that includes external genitalia. And eventually w/ puberty, your external sex characteristics.
So at this pt, from gonads to producing the genitalia that goes w/ the ovary (that’s your uterus, vagina, vulva), then you now have the start and the development of your phenotypic sex.
With your hormone, there’ll be behavioral and metabolic sex. So in guys, there’ll be the development of the testes and the testes will have cells that produce secretions (Leydig cells secrete testosterone and they help in further differentiating the male sexual organs into the genitalia eventually the external sex characteristics but again this testosterone has to be activated first into your 5-alpha-DHT; so 1 factor is if there is no activation, you can have high levels of testosterone but bc no activation to 5-alpha, your sex characteristics may be affected and so you also have a factor: MRF (mullerian regression factor) - the Sertoli cells will also aid in further increasing the rate of differentiation of the testis to actually produce the different components of the testis (spermatic cords, etc) this is the part of your phenotypic sex
>This part begins even in your childhood but will only be fully established during puberty meaning you reach the height of your adult appearance when puberty comes
What is your karyotype?
46, XX
Total number of chromosomes you have + sex chromosome combination
Y chromosome
- Position of the centromere?
- This chromosome is said to be very specialized to maleness. Why?
- Acrocentric
2. You have MSY (Male-specific region of the Y) which is 95% and PAR (Pseudoautosomal Region) is only 5%
Two general steps in sex differentiation?
- Gonadal sex differentiation
2. Development and maintenance of sexual dimorphism
Gonadal sex differentiation
Role of hormones
Males: If you have SRY -> indifferent/bipotential gonad, through the action of SRY, dx into a testes. The testes will now dx into special cells so it will have: Sertoli ang Leydig
Females: No SRY
Bipotential gonad dx into the ovary which has granulosa cells and theca cells.
Hormones:
Leydig will secrete testosterone which will aid in further developing the testis into its more specialized form. The cells in the ovary, on the other hand, will secrete 17B-Estradiol which helps in developing the follicles of the ovary.
Gonadal ridge importance
In the early embryo, you have production of the gonadal ridge which is empty. Then, primordial germ cells migrate there and eventually, it will be filled and dx into testes or ovary depending on the TFs that will dictate the change.
Origin of the Gonads?
The gonads originate as bilateral swellings in the intermediate mesoderm arising from the coelomic epithelium and underlying urogenital mesenchyme
Primordial Germ Cells (PGCs)
- T or F. They come immediately from the gonads.
- Migration begins when? Ends when?
- T or F. The PGCs become the sperm or the ova depending on the karyotype.
- False! The PGCs come from the yolk sac so they travel and dadaan pa sa mesentery
- Migration starts at the 5th week of embryo development and nakaabot na sila at 7th week
- F! These primordial germ cells become the sperm or the ova BUT the dx of these germ cells into the sperm or ova does NOT depend on XY or XX karyotype. SO IN OTHER WORDS, akala niyo basta XX or XY, okay na buhay niyo..NO!! Madami pang steps. Bc eventually when they reach the gonadal ridge, the cells there (neighboring somatic cells surrounding the gonads) will eventually have a greater influence on whether they will dx into ova or sperm so laking factor sila.
Gonadal sex differentiation
>What happens to the medulla and cortex when you have 46, XX? 46, XY?
> You have an inner medulla and outer cortex
So if you have 46, XY karyotype, the medullary portion of the gonad develops to become the testis and the cortex regresses
If you have a 46, XX karyotype, your cortex will be the one to develop and the medulla regresses
Development of genital ducts
When you still had undifferentiated gonads (gonads are still developing), there are 2 ducts that also develop: Mullerian and Wolffian duct.
> For males: bc of all the signals and TFs that was released, their Wolffian ducts are the ones that develop and Mullerian ducts regress.
Opposite in ladies: Mullerian ducts develop
Your Wolffian ducts develop into you epididymis, vas deferens, parts of seminal vesicles
In the females, since walang SRY and signaling so eventually their mullerian will form into the oviducts, uterus, and vagina
WOLFFIAN: Big bad wolf
Mullerian; Motherly
Phenotypic differentiation
>How many holes in the external genitalia of males? Females?
Males: 2 (Urethra and anus)
Females: 3 (Urethra, vaginal opening, anus)
SRY
- Encodes for?
- What does it do to testicular differentiation genes? ovarian differentiation genes?
- Main TFs in testis differentiation and regulation of their expression in Sertoli cells?
- SRY protein
- Activates testicular dx genes but represses ovarian dx genes throught the Wnt/Beta-catenin signaling pathway
- SRY and Sox9
You see here that there are two main TFs involved. In fact, once dx has begun, parang tapos na role ni SRY but in the processes of developing its actions, it turns off ovarian genes, it turns on testicular genes. It also promotes the transcription of the genes that will produce your Sox9 which is another TF. And your Sox9 together with SRY bind to promoters of many common targets involved in testis dx and regulate their expression (All the undx cell tinatarget para mapromote dx into maleness)
>So your Sox TF will now keep this off and turn on even more genes
>Bakit may circles? Your SRY has specific target cells/areas where it does all these things (383 identified). Your Sox9 targets 1903 areas na siya lang in charge to maintain the same thing na ginagawa ni SRY but specific to Sox9 so as seen here madaming possibilities for aberrancy.
>Between the two of them, they have a commonality ~907 targets.
The first thing that develops to aid in the bipotential gonad differentiation?
Sertoli cell
