Chapter 3 Vocab Flashcards
EXAM 2
zygote
A prenatal human from the fertilized ovum stage until formation of the primordial embryo, at about 2 weeks.
sperm
The male sex cell (gamete).
oocyte
The female gamete (sex cell). An egg.
gamete
A sex cell.
gonads
Paired structures in the reproductive system where sperm or oocytes are manufactured.
testes
The male gonads.
ovaries
The female gonads.
homologous pair
Two chromosomes with the same gene sequence.
polyploid
A cell with one or more extra sets of chromosomes.
reduction division
The first meiotic division, which halves the chromosome number.
equational division
The second meiotic division, yielding four cells from two.
spermatozoon
A mature male reproductive cell (meiotic product).
independent assortment
Inheritance of a gene on one chromosome does not influence inheritance of a gene on a different chromosome (Mendel’s second law) because of the random arrangement of homologous chromosome pairs, in terms of maternal and paternal origin, down the center of a cell in metaphase 1.
crossing over
An event during prophase I when homologs exchange parts.
spermatogonium
An undifferentiated cell in a seminiferous tubule that can give rise to a sperm cell following meiosis and maturation.
spermatogenesis
Sperm cell formation and differentiation.
oogenesis
Oocyte (egg) formation.
oogonium
A cell in the ovary that gives rise to an oocyte, in meiosis.
polar body
A product of female meiosis that contains little cytoplasm and does not continue to develop into an oocyte.
embryo
In humans, the prenatal organism from fertilization until the end of the eighth week, when all basic structures are present.
fetus
The prenatal human after the eighth week of development, when structures grow and specialize.
cleavage
A series of rapid mitotic cell divisions after fertilization.
blastomere
A cell of a blastocyst.
ectoderm
The outermost primary germ layer of the primordial embryo.
inner cell mass
A clump of cells on the inside of the blastocyst that will continue developing into an embryo.
morula
The very early prenatal stage that resembles a mulberry.
blastocyst
A fluid-filled ball of cells descended from a fertilized ovum.
endoderm
The innermost primary germ layer of the primordial embryo.
mesoderm
The middle primary germ layer.
gastrula
A three-layered embryo.
primary germ layers
The three layers of an embryo.
epigenetic
Any effect that modifies gene expression without changing the DNA sequence, such as methylation.
dizygotic twins (DZ)
Twins that originate as two fertilized ova; fraternal twins.
monozygotic twins (MZ)
Twins that originate as a single fertilized ovum; identical twins
neural tube
A structure in the embryo that develops into the brain and spinal cord.
teratogen
A substance that causes a congenital disorder.
critical period
The time during prenatal development when a structure is sensitive to damage from a mutation or an environmental intervention.
Meiosis I, a __1__, halves the number of chromosomes. Meiosis II, an __2__, produces four cells from the two that result from meiosis I, without another DNA replication
1: reduction division
2: equational division
The male and female reproductive systems include paired __1__ and networks of tubes in which __2__ and __3__ are made.
1: Gonads
2: Sperm
3: Oocytes
