Ch.6

Question 1

Chromosomal Sex

Answer 1

established at fertilization

Question 2

gonadal sex

Answer 2

• development of ovaries or testes from undifferentiated gonads
• initiated by gene expression pathways to form either male or female gonads

Question 3

Phenotypic sex

Answer 3

development of external reproductive structures

Question 4

Why are the stages of sexual differentiation not always correlated?

Answer 4

genetic variations, hormonal imbalances, timing issues, environmental issues, gene mutations, intersex conditions

Question 5

During the fifth week of prenatal development, all embryos develop 2 sets of

Answer 5

unspecialized gonads & reproductive ducts (Mullerian: female-specific & Wolffian: male-specific)

Question 6

SRY gene

Answer 6

sex-determining region of the Y chromosome

Question 7

The testis secretes which 2 hormones?

Answer 7

Testosterone & Anti-Mullerian Hormone (AMH)

Question 8

Testosterone

Answer 8

• stimulates the Wolffian ducts to develop into the male duct system
• stimulates the development of external male structures

Question 9

Anti-Mullerian Hormone (AMH)

Answer 9

stimulates regression of the Mullerian ducts

Question 10

SrY gene on Y chromosome

Answer 10

codes for a protein that directs the development of male anatomical features

Question 11

mutations can uncouple chromosomal sex from phenotypic sex

Answer 11

mutations can uncouple chromosomal sex from phenotypic sex

ex. gonadal intersexuality, complete androgen insensitivtiy

Question 12

X Chromosome

Answer 12

present in females and males, larger of the two sex chromosomes

Question 13

Anatomy of the Y Chromosome

Y Chromosome

Answer 13

The Y Chromosome has a very short arm and a long arm, present in males only, has few genes, contains the SRY gene

Question 14

Pseudoautosomal Regions (PAR1 and PAR2)

Answer 14

• 5% of the chromosome
• contain 63 genes shared with X chromosome (control bone growth, cell division, in both sexes)

Question 15

Male Specific Region (MSY)

Answer 15

• most of the chromosome
• three classes of DNA sequences (sequence almost identical to the X chromosome, somewhat identical to the X chromosome, palindromes)
• many of the genes are essential to fertility (including SRY)

Question 16

Hermaphroditism

Answer 16

individual w/ both male and female sexual structures

Question 17

Intersex

Answer 17

individuals whose internal structures are inconsistent with external structures, or whose genitalia are ambiguous

Question 18

Pseudohermaphroditism

Answer 18

individuals whose external genitalia appear to be of one sex, but they have the internal reproductive organs of another

includes:
- androgen insensitivity syndrome
- 5-alpha reductase deficiency
- congenital adrenal hyperplasia (enzyme bock causes androgens to accumulate, cause precocious puberty in males or male secondary sex characteristics to develop in females)

Question 19

Mutations that Affect Male Sexual Development

5- alpha Reductase deficiency

Answer 19

unable to convert testosterone to DHT, child has inside male anatomy but looks like girl on the exterior

Question 20

Mutations that Affect Male Sexual Development

Androgen Insensitivity Syndrome

Answer 20

mutation on androgen receptor

Question 21

Androgens

Answer 21

Include testosterone (T) and dihydrotestosterone (DHT)

Question 22

Steroid Receptor Family

Answer 22

sex steroid receptors:
androgen receptor (AR), estrogen receptor (ER), progesterone receptor (PR)

glucocorticoid recpetor (GR) and mineralocorticoid receptor (MR)

Question 23

Steroid hormone

Answer 23

steroid hormone - cytoplasm where steroid receptor connects w hormone (hormone-receptor complex) - nucleus where complex binds to sites on chromatin, activating mRNA transcription (nucleus response)

Question 24

Ligand

Answer 24

a molecule that binds to another (usually larger) molecule
ex. estrogen, progesterone, testosterone, RU 486 (abortion med- blocking progesterone action)

Question 25

Agonist

Answer 25

a substance that fully activates the receptor that it binds to ex. estrogen, progesterone, testosterone

Question 26

Antagonist

Answer 26

a substance that binds to a receptor but does not activate and can block the activity of other agonists ex. RU 486

Question 27

X Inactivation

Answer 27

balances inequality (females have 2 alleles for x chromosome genes but males only have 1) in expression of genes on the x chromosome alters the phenotype and not the genotype

Question 28

XIST gene

Answer 28

encodes an RNA binds to and inactivates the X chromosome

Question 29

Epigenetic Change

Answer 29

an inherited change that DOES NOT alter the DNA base sequence inactivated DNA is methylated

Question 30

Manifesting heterozygote

Answer 30

a female that expresses the phenotype corresponding to an X-linked gene ALWAYS

Question 31

Gene Imprinting

Answer 31

genes are expressed only from a single allele, not both. the other allele is silenced by DNA methylation

Question 32

DNA methylation

Answer 32

gene silencing = no/low gene expression the addition of methyl groups to cytosine bases in DNA - turns transcription off (binding to non-histone protein forms silent chromatin) - on CpG sites

Question 33

CpG Island

Answer 33

promoter to the gene for gene expression

Question 34

Imprinting

Answer 34

deletion on chromosome 15 reveals imprinting, can cause Prader-Willi syndrome if deletion comes from father or Angelman syndrome if it comes from the mother

Question 35

Prader-Willi Syndrome (PWS)

Answer 35

different alleles, caused by no gene expression on PWS region

Question 36

Angelman Syndrome (AS)

Answer 36

no gene expression on AS region; different alleles from father

Question 37

X inactivation normally occurs only in males.

Answer 37

False; X inactivation is a process that occurs in females

Question 38

X inactivation is a change in an individual's genotype

Answer 38

False; One of the X chromosomes becomes inactivated, which affects the expression of genes on that chromosome. In this way, the individual's phenotype, but not the genotype, is altered.

Question 39

The inactivated X chromosome is called a Barr body.

Answer 39

True

Question 40

The XIST gene encodes a protein that binds to the X chromosome.

Answer 40

False; The molecular basis of X inactivation involves the RNA produced from the XIST gene.This RNA does not encode a protein. Instead, the XIST RNA binds to the X chromosome and initiates the process of inactivation.

Question 41

Females are mosaics for the expression of most genes on the X chromosome.

Answer 41

True

Question 42

X inactivation is an example of an epigenetic change.

Answer 42

True

Question 43

Genomic imprinting is permanent in the somatic cells of a given individual.

Answer 43

True; Genomic imprinting silences the contribution of the allele inherited from one parent. After an imprinting pattern is established in an individual, it is permanent in his or her somatic cells.

Question 44

Genomic imprinting is permanent and affects future generations

Answer 44

False; If a gene is imprinted, the offspring can express either the maternal or the paternal allele, but not both.

Question 45

Methylation is the chemical change underlying genomic imprinting.

Answer 45

True; Methylation of genes is the molecular mechanism underlying genomic imprinting.

Question 46

If a gene is imprinted, the offspring can express both the maternal and paternal allele.

Answer 46

False