CALM 5 Flashcards
During the ____ , all embryos develop two unspecialized gonads, which are organs that will develop as either testes or ovaries. Each such “indifferent” gonad forms near two sets
fifth week
one set of tube
Müllerian ducts
sexual structures characteristic of a female.
Müllerian ducts
If a gene on the Y chromosome called SRY (for “sex-determining region of the Y”) is activated,
hormones steer development along a male route.
In the absence of SRY activation,
a female develops.
Human males and females have equal numbers of autosomes
(44 or 22 pairs
two different sex chromosomes
heterogametic sex
two of the same sex chromosome
homogametic sex.
This symmetry in a DNA sequence, described by researchers as ___destabilizes DNA replication.
“a hall of mirrors”
The ___has a distinctive overall structure with a short arm and a long arm.
Y chromosome
At both tips of the Y chromosome are___ , termed PAR1 and PAR2.
pseudoautosomal regions
means that the DNA sequences have counterparts on the X chromosome and can cross over with them.
pseudoautosomal
lies between the two pseudoautosomal regions. It consists of three classes of DNA sequences.
male-specific region, or MSY
Many of the genes in the MSY are essential to fertility, including
SRY
The SRY gene encodes a very important type of protein called a ___, which controls the expression of other genes.
transcription factor
___cells in the developing testis secrete anti-Müllerian hormone, which destroys potential female structures (uterus, uterine tubes, and upper vagina).
sustentacular (Sertoli)
____ cells in the testes secrete testosterone, which stimulates the development of male structures (the epididymis, ductus deferentia, seminal vesicles, and ejaculatory ducts).
interstitial (Leydig)
embryos don’t have SRY, so they develop as females.
XX
embryos do have SRY, so they develop as male.
XY
caused by a mutation in a gene on the X chromosome, the absence of receptors for androgens (the male sex hormones testosterone and DHT) stops cells in early reproductive structures from receiving the signal to develop as male. The person looks female, but is XY.
androgen insensitivity syndrome (MIM 300068)
Is an older and more general term for an individual with both male and female sexual structures.
Hermaphroditism
Refers to individuals whose internal structures are inconsistent with external structures, or whose genitals are ambiguous. It is the preferred term outside of medical circles.
Intersex
Refers to the presence of both types of structures but at different stages of life.
Pseudohermaphroditism
Affected individuals have a normal Y chromosome, a wild type SRY gene, and testes.
5-alpha reductase deficiency
lack of__ causes the fetus to develop externally as female—that is, without DHT, a penis cannot form.
DHT
due to 21- hydroxylase deficiency (MIM 201910),
congenital adrenal hyperplasia (CAH)
a person’s phenotype & genotype are consistent, and physical attraction is toward members of the same sex.
homosexuality
Undifferentiated structure begins to develop as testis or ovary
Gonadal Sex
Development of external & internal reproductive structures continues as male or female in response to hormones
Phenotypic Sex
Strong feelings of being male or female develop
Gender Identity
Attraction to same or opposite sex
Sexual Orientation
predicts that populations should have approximately equal numbers of male and female newborns.
Mendel’s law of segregation
proportion of males to females in a human population
sex ratio
calculated as the number of males divided by the number of females multiplied by 1,000, for people of a particular age
sex ratio
The sex ratio at conception is called the
primary sex ratio.
Sex ratio at birth is termed
secondary
and at maturity is called
tertiary.
The human male is considered ))))for X-linked traits, because he has only one set of X-linked genes.
hemizygous
An enzyme deficiency blocks removal of cholesterol from skin cells, the upper skin layer cannot peel off as it normally does, appearing brown and scaly. It is transmitted as an X-linked recessive trait.
Ichthyosis
Is another X-linked recessive trait that does not hamper the ability of a man to have children
Color Blindness
Blood-clotting disorder.
Hemophilia A
In affected females, swirls of skin pigment arise when melanin penetrates the deeper skin layers.
Incontinentia Pigmenti
This condition produces many extra hair follicles, and hence denser and more abundant upper body hair.
Congenital generalized hypertrichosis
X-linked recessive trait generally is more prevalent in
males than females
affects a structure or function of the body that is present in only males or only females. Such a gene may be X-linked or autosomal.
sex-limited trait
sudden rise in blood pressure late in pregnancy.
preeclampsia
An allele is dominant in one sex but recessive in the other.
sex-influenced trait
balances this apparent inequality in the expression of genes on the X chromosome.
X inactivation
a random process that happens separately in individual cells during embryonic development.
X-inactivation
gene called ___controls X inactivation.
XIST
can alter the phenotype (gene expression), but not the genotype.
X inactivation
a ___does not have an inactivated X chromosome.
fertilized ovum
X inactivation is an example of an .____ one that is passed from one cell generation to the next but that does not alter the DNA base sequence.
epigenetic change i
The nucleus of a cell of a female, during interphase, has one dark-staining X chromosome
Barr body (a small, dense structure).
A female who is ___can express the associated condition if the normal allele is inactivated in the tissues that the illness affects.
heterozygous for an X-linked recessive gene
carrier of an X-linked trait who expresses the phenotype is called a
manifesting heterozygote.
Cells that make the enzyme readily send it to neighboring cells that do not, essentially correcting the defect in cells that can’t make the enzyme.
Hunter syndrome (mucopolysaccharidosis II),
Affected boys are deaf, mentally retarded, have dwarfism and abnormal facial features, heart damage, and enlarged liver and spleen.
Hunter syndrome (mucopolysaccharidosis II),
may develop mild symptoms of this disorder that causes skin lesions, abdominal pain, and kidney failure in boys.
Fabry disease (alpha-galactosidase A deficiency)
methyl (CH 3) groups cover a gene or several linked genes and prevent them from being accessed to synthesize protein
genomic imprinting
epigenetic alteration.
Imprinting
passed from cell to cell in mitosis, but not from individual to individual through meiosis.
Imprinting
controls placenta development
male genome
controls embryo development.
female genome
When two sperm fertilize an oocyte and the female pronucleus degenerates, an abnormal growth of placenta-like tissue called a ___forms
hydatidiform mole
due to a deletion in the copy of the chromosome he inherited from his father. Note his small hands.
Prader-Willi syndrome
caused by a deletion in the chromosome 15 that he inherited from his mother. He is mentally retarded.
Angelman syndrome
