- Two-layered structure formed from trophoblast - Releases human chorionic gonadotropin (hCG) hormone that maintains uterine lining and stimulates endometrial cells to produce hormones - Grows and forms villi that exchange nutrients and wastes with maternal blood circulation, eventually forming the placenta

(12) Sex Determination Flashcards by Liam Rosenberg

The three major components of the human reproductive system

Gonads produce gametes (testes in males, ovaries in females)
Ducts to transport gametes
Genital structures for intercourse and fertilization

How well did you know this?

Not at all

Perfectly

The single cell produced by the fusion of a sperm and oocyte

The Zygote

How well did you know this?

Not at all

Perfectly

Gametes for
- Males:
- Females:

Male: Sperm
Female: Oocyte

How well did you know this?

Not at all

Perfectly

Organs where gametes are produced

Gonads

How well did you know this?

Not at all

Perfectly

Male gonads:
Female gonads:

Male: Testes (produce spermatozoa and male sex hormones)
Female: Ovaries (Produce oocytes and female sex hormones)

How well did you know this?

Not at all

Perfectly

Why female meiosis results in only one egg

Polar body found in the female gamete represents one of the four products of meiosis, and therefore is haploid. During cytokinesis of oogenesis there is uneven division of the cytoplasm, and a disintegration of one or two of the haploid polar bodies

How well did you know this?

Not at all

Perfectly

Time for spermatogenesis

~64 days

How well did you know this?

Not at all

Perfectly

Quantity of sperm produced by meiotic division

4 sperm

How well did you know this?

Not at all

Perfectly

Result produced by meiotic division in females

1 oocyte + 2-3 polar bodies

How well did you know this?

Not at all

Perfectly

Beginning of human development

Begins with fertilization and the formation of a zygote

How well did you know this?

Not at all

Perfectly

Fusion of two gametes to produce a zygote

Fertilization

How well did you know this?

Not at all

Perfectly

Fertilized egg that develops into a new individual

Zygote

How well did you know this?

Not at all

Perfectly

Name for the egg and sperm nuclei at fertilization (form the first 2n nucleus of the zygote)

Pronuclei

How well did you know this?

Not at all

Perfectly

The developmental stage at which the embryo implants into the uterine wall

Blastocyst

How well did you know this?

Not at all

Perfectly

A cluster of cells in the blastocyst that gives rise to the embryonic body

Inner cell mass

How well did you know this?

Not at all

Perfectly

Glycoprotein membrane surrounding the plasma membrane of the egg cell and early zygote

Zona Pellucida

How well did you know this?

Not at all

Perfectly

The embryo implants into the uterine wall, and membranes develop to support the embryo

Implantation

How well did you know this?

Not at all

Perfectly

Outer layer of cells in the blastocyst that gives rise to the membranes surrounding the embryo (i.e., the chorion and placenta)

Trophoblast

How well did you know this?

Not at all

Perfectly

The breaking open of the zona pellucida

Hatching

How well did you know this?

Not at all

Perfectly

What is the chorion?

Two-layered structure formed from trophoblast
Releases human chorionic gonadotropin (hCG) hormone that maintains uterine lining and stimulates endometrial cells to produce hormones
Grows and forms villi that exchange nutrients and wastes with maternal blood circulation, eventually forming the placenta

How well did you know this?

Not at all

Perfectly

Name for division stages of development

Trimesters

How well did you know this?

Not at all

Perfectly

What occurs in each of the first three months of development?

Month 1: Basic tissue layers form; most of the body is divided into paired segments; heart starts to beat
Month 2: Most major organ systems are formed; becomes a fetus at 11 weeks
Month 3: Sexual development initiated in the fetus

How well did you know this?

Not at all

Perfectly

What occurs in the second trimester of development?

Increase in size and organ-system development
Bony parts of skeleton form
Heartbeat is heard with a stethoscope
Fetal movements begin

How well did you know this?

Not at all

Perfectly

What occurs in the third trimester of development?

Rapid growth
Circulatory and respiratory systems mature

How well did you know this?

Not at all

Perfectly

A hormonal induced process at the end of the 3rd trimester

Birth

What is a teratogen?

Any physical or chemical agent that brings about an increase in congenital malformations

Provide examples of a teratogen

Radiation, viruses, medications, alcohol

Explain the context of Thalidomide as a teratogen

Introduced into the market in 1957 as a “wonder drug” against morning sickness. It is racemic, containing both right- and left-handed isomers in equal amounts. The R isomer is effective against morning sickness and the S isomer is teratogenic

What is fetal alcohol syndrome?

A constellation of birth defects caused by maternal alcohol consumption during pregnancy

Alcohol as the leading cause of preventable birth defects is an example of what genetic concept?

Teratogen

How is sex determined?

In humans, the presence of a Y chromosome is associated with male sexual development, and the absence of a Y chromosome is associated with female development

Explain how the ratio of males to females in humans changes throughout life

At fertilization, ratio is ~1:1, but ratio of females to males increases as population ages

When is chromosomal sex established?

Fertilization

Other than chromosomal sex, what do other aspect of sex depend on?

Interaction of genes and environmental factors, especially hormones.

Name the three levels at which sex of an individual is defined

i. Chromosomal sex ii. Gonadal sex iii. Phenotypic sex

Can the chromosomal sex of an individual differ from the phenotypic sex?

Yes

For how long does the embryo stay neither male or female?

The first 7 or 8 weeks of development.

During the first 7-8 weeks of development, which reproductive duct system(s) develops?

Both male and female

What causes glands to develop as testes or ovaries?

Genes

What establishes gonadal sex?

The genes that cause gonads to develop as testes or ovaries

Sex-determining region of the Y chromosome

SRY gene

Where is the SRY gene located?

Near the end of the short arm of the Y chromosome

What is the function of the SRY gene?

- Plays a major role in causing the undifferentiated gonad to develop into a testis - Encodes a transcription factor, known as the SRY protein or the testis determining factor (TDF)

What does the loss of the SRY gene region (i.e. through chromosomal deletion) result in?

A loss of “manliness” and a condition called Swyer syndrome, or XY gonadal dysgenesis

What does TDF stand for?

Testis determining factor

What is testosterone?

- A steroid hormone produced by the testis - The male sex hormone - Gets converted to DHT, a more potent form of testosterone

What does MIS stand for?

Müllerian inhibiting substance

What is MIS?

A hormone produced by developing testis that causes breakdown of Müllerian (female) ducts in the embryo

What does the female embryonic gonad develop as?

An ovary

For female development, what happens in the absence of testosterone?

The degeneration of the Wolffian duct system

In female development, what happens in the absence of MIH?

The Müllerian duct system forms the female reproductive system.

What is the collective term for hormones?

Androgens

Which hormones secreted by the testis control later stages of male sexual differentiation, including the development of phenotypic sex?

Testosterone & DHT

What does DHT stand for?

Dihydrotestosterone

What is AIS? (Both full name & explanation)

Name: Androgen Insensitivity Syndrome - X-linked genetic trait Role: Causes XY individuals to develop into phenotypic female

What is the result of a mutation in the X-linked androgen receptor gene (AR)?

Causes XY males to become phenotypic females

How does a mutation in the X-linked androgen receptor gene (AR) cause XY males to become phenotypic females?

Testosterone is produced, but not testosterone receptors; cells develop as females.

What enzyme causes testosterone to become DHT?

The enzyme 5-alpha-reductase

(T/F) The androgen receptor is always present, but needs to be activated

True

Consider a person who has the chromosomes of a woman, the ovaries of a woman, but external (outside) genitals that appear male. What is this condition caused by?

Usually caused by a female fetus having been exposed to excess male hormones before birth. SRY gene d, 46 XX intersex

Consider a person who has the chromosomes of a man, but the external genitals are incompletely formed, ambiguous, or clearly female. Name generally the main cause.

Deficiencies in enzymes required for testosterone biosynthesis. Uterine exposure to androgens, 46 XY Intersex

Explain dosage compensation?

- A mechanism that regulates the expression of sex-linked gene products - Human females have one X chromosome inactivated in all somatic cells to balance the expression of X-linked genes in males and females - Females have two X chromosomes, males have one; yet the amount of gene products is the same

A densely staining mass in the somatic nuclei of mammalian females; an inactivated X chromosome, tightly coiled

Barr body

(12) Sex Determination Flashcards

(64 cards)