Reproduction Flashcards
diploid cells (2n)
contain two copies of each chromosome
haploid (1n)
contain only one copy of each chromosome
cell cycle
eukaryotic cell replication; G1, S, G2, M phases
interphase
G1, S, G2; longest part of the cell cycle
G0 stage
cell is simply living and serving its function, without any preparation for division
chromatin
less condensed form of chromosomes
G1 stage
cells create organelle for energy and protein production while also increasing their size
restriction point
governs pass from G1 into S phase; certain criteria must be met
S stage
cell replicates its genetic material so that each daughter cell will have identical copies
sister chromatids
identical chromatids bound to each other after replication
centromere
specialized region that holds sister chromatids together
G2 stage
cell passes through another quality control checkpoint; cell checks to ensure that there are enough organelles and cytoplasm to divide between two daughter cells; also checks to make sure that DNA replication proceeded correctly
M stage
consists of mitosis as well as cytokinesis
p53
main protein in control of repairing DNA at the restriction point
cyclin dependent kinases (CDK)
responsible for the control of the cell cycle; presence of the right cyclins are required to activate them
transcription factors
promote transcription of genes required for the next stage of the cell cycle
cancer
result of damaged cells being allowed to undergo mitosis
TP53
gene that makes p53; when this is mutated, cell cycle is not stopped to repair DNA; allows mutations to accumulate, eventually resulting in a cancerous cell that divides uncontrollable
tumor
result of cancerous cell undergoing rapid cell division
metastasis
spread of cancerous cells through the blood stream or lymph systems
mitosis
process by which two identical daughter cells are created from a single cell
somatic cells
cells not involved in sexual reproduction
Prophase
- condensation of the chromatin into chromosomes
- centriole pairs separate, move toward opposite sides of cell
- spindle fibers begin to form
- nuclear membrane dissolves
- kinetechores appear at the centromere
centrosome
region that contains paired cylindrical organelles called centrioles; responsible for correct division of DNA
spindle fibers
made up of microtubules
asters
anchor centrioles to cell membrane
kinetochores
protein structures located on the centromeres that serve as attachment points for kinetochore fibers
Metaphase
kinetochore fibers interact with the fibers of the spindle apparatus to align the chromosomes at the metaphase plate
Anaphase
- centromeres split so that each chromatid has its own distinct centromere
- sister chromatids separate, pulled toward opposite poles of the cell by shortening of kinetochore fibers
telophase
- spindle apparatus disappears
- nuclear membrane reforms around each set of chromosomes, nucleoli reappear
- chromosomes uncoil, resuming chromatin form
- Each nucleic has received a complete copy of the genome identical to the original genome
cytokinesis
separation of the cytoplasm and organelles so that each daughter cell has sufficient supplies to survive
gametocytes (germ cells)
cells related to sexual reproduction
gametes (sex cells)
sperm and eggs, in humans
Meiosis I
homologous chromosomes are separated, generating haploid daughter cells; reductional division
Meiosis II
separation of sister chromatids; equational division
homologous pairs
a pair of chromosomes, each of which contains one chromosome inherited from each parent
Prophase I
- chromatin condenses into chromosomes
- spindle apparatus appears
- nucleoli and nuclear membrane disappear
- crossing over
synapsis
process of homologous chromosomes coming together and intertwining
tetrad
the result of synapsis; four sister chromatids
synaptonemal complex
group of proteins holding homologous chromosomes together
chiasma
point of contact between homologous chromosomes
crossing over
when chromatids of homologous chromosomes break at the chiasma, exchanging equivalent pieces of DNA
genetic recombination
happens during crossing over; increasing the variety of genetic combinations that can be produced during gametogenesis
Mendel’s second law of independent assortment
explained by crossing over; states that the inheritance f one allele has no effect on the likelihood of inheriting certain alleles for other genes
metaphase I
homologous pairs align at he metaphase plate, each pair attaches to a separate spindle fiber by its kinetochore
anaphase I
homologous pairs separate and are pulled to opposite poles of the cell; called segregation
Mendel’s first law of segregation
accounted for by disjunction during anaphase I; distribution of two intermediate daughter cells is random with respect to parental origin
disjunction
each chromosome of paternal origin disjoints from its homologue of maternal origin; either can end up in either daughter cell
telophase I
- nuclear membrane forms around each new nucleus
- cell divides into two (1n) daughter cells by cytokinesis
interkinesis
short rest period between M1 and M2 where chromosomes partially uncoil
prophase II
nuclear envelope dissipates, nucleoli disappear, centrioles migrate to opposite poles, spindle apparatus forms
metaphase II
chromosomes line up on metaphase plate
anaphase II
centromeres divide, separating chromosomes into two sister chromatids
telophase II
nuclear membrane forms around each new nucleus, followed by cytokinesis; four new daughter cells are formed
sex
23rd chromosome; XX=female, XY=male
sex-linked disorders
mutations to genes on X chromosome
hemizygous
males are considered this with respect to many genes on the x chromosome because they only have one copy
carriers
females carrying a diseased allele on the x chromosome but not exhibiting that disease
Y chromosome
carries very little genetic information
sex-determining region Y (SRY)
notable gene on Y chromosome which codes for a transcription factor that initiates testis/male gonads formation
seminiferous tubules
sperm are produced here
Sertoli cells
nourish perm
interstitial cells (of Leydig)
secrete testosterone and other male hormones
androgens
male sex hormones
scrotum
external pouch that holds the testes and hangs below the penis; maintains a temp 2-4 degrees lower than body
vas deferens
can lower/raise testis to maintain proper temp for sperm development
epididymis
sperm flagella gain motility here; stored here until ejaculation
ejaculation
sperm travel through the vas deferens to the ejaculatory duct and out the urethra
urethra
two ejaculatory ducts fuse to form this
seminal fluid
produced through a combined effort by the spinal vesicles, prostate gland and bulbourethral gland; mixed with sperm during ejaculation
seminal vesicles
contribute fructose to nourish sperm; give fluid mildly alkane properties
prostate gland
give semen mildly alkane properties
bulbourethral (Cowper’s) glands
produce a clear viscous fluid that cleans out any remnants of urine and lubricates the urethra during sexual arousal
semen
combination of sperm and seminal fluid
spermatogenesis
formation of haploid sperm through meiosis
spermatogonia
diploid stem cells
primary spermatocytes
spermatogonia after S stage
secondary spermatocytes
spermatogonia after M1
spermatids
spermatogonia after M2
spermatozoa
spermatids undergo maturation to become these
mature sperm
very compact; made up of midpiece, head, and flagellum
sperm midpiece
filled with mitochondria, which generate energy to be used as the sperm swims through the female reproduction tract; generates ATP from fructose
sperm head
part that actually penetrates egg
acrosome
structure that covers the sperm head and is derived from the Golgi; necessary to penetrate the ovum
ovaries
produce progesterone and estrogen
follicles
multilayered sacs found in the ovaries that contain, nourish, and protect immature ova (eggs)
ovulation
happens once per month between puberty and menopause
peritoneal sac
lines the abdominal cavity; egg is ovulated into it
fallopian tube (oviduct)
egg goes into this and is propelled forward by cilia
uterus
muscular; site of fetal development
cervix
lower end of the uterus; connects to vaginal canal
vaginal canal
where sperm are deposited during intercourse
vulva
external female anatomy
oogenesis
production of female gametes
primary oocytes
all eggs are at this stage by birth; have already undergone DNA replication; arrested in prophase I
menarche
first menstrual cycle; after this, one primary oocyte will complete MI per month
secondary oocyte
result of a primary oocyte undergoing MI; becomes arrested in metaphase II and does not complete meiosis II unless fertilized
polar body
does not produce any viable gametes
zona pellucida
surrounds oocyte itself and is an acellular mixture of glycoproteins that protect the oocyte and contain compounds necessary for sperm cell binding
corona radiata
lies outside the zona pellucida and is a layer of cells adhered to the oocyte during ovulation
mature ovum
very large; contains half of the DNA, all the cytoplasm, organelles, RNA and space for zygote
zygote
result of the haploid pronuclei of the sperm and the ovum joining
gonadotropin-releasing hormone (GnRH)
repressed until puberty; when released by the hypothalamus, the anterior pituitary is triggered to release follicle stimulating hormone (FSH) and luteinizing hormone (LH); these hormones trigger production of sex hormones
Testosterone
produced by the testes; increases dramatically during puberty when sperm production begins; also results in secondary sexual characteristics such as facial hair, arm hair, voice and growth patterns
estrogens
secreted in response to FSH; result in maintenance and development of female reproductive system as well as secondary sexual characteristics such as breast growth, hip widening, changes in fat distribution; also lead to thickening of endometrium to prepare for zygote
endometrium
lining of the uterus
Follicle stimulating hormone (FSH) and luteinizing hormone (LH)
both are controlled by anterior pituitary gland and play a role in reproductive growth and maintenance
progesterone
secreted by corpus luteum in response to LH; involved in the maintenance and development of the endometrium but not the thickening;
corpus luteum
remnant follicle that remains after ovulation; atrophies after the placenta begins to provide progesterone
menstrual cycle
follicular phase, ovulation, luteal phase and menstruation
follicular phase
begins when the menstrual flow, which sheds the uterine lining of the previous cycle, begins; GnRH secretion raises in response to the decrease in LH and FSH; LH and FSH begin to rise, working in concert to develop several ovarian follicles; follicles begin to produce estrogen, which has negative feedback effects and causes the GnRH, LH, and FSH to level off; estrogen works to regrow the endometrial lining
ovulation
estrogen interestingly grows to a high level and reaches a threshold, resulting in positive feedback, causing GnRH, LH and FSH levels to spike; surge in LH causes ovulation, the release of the ovum
luteal phase
after ovulation, LH causes ruptured follicle to form corpus luteum, which secretes progesterone; progesterone begins to rise and estrogen remains high; GnRH, FSH and LH are again repressed
menstruation
assuming implantation doesnt occur, the corpus luteum loses its stimulation from LH, progesterone levels decline and uterine lining is sloughed off; next cycle begins
pregnancy
zygote develops into blastocyte, implants into uterine lining and secretes human chorionic gonadotropin (hCG)
human chorionic gonadotropin (hCG)
analog of LH; maintains the corpus luteum so it can produce estrogen and progesterone to keep uterine lining in place; by 2nd trimester, hCG levels decline because the placenta has grown to a sufficient size and can secrete progesterone/estrogen by itself
menopause
ovaries become less sensitive to FSH and LH, resulting in ovarian atrophy; menstruation stops; blood levels of FSH and LH rise, accompanied with flushing, hot flashes, bloating, headaches and irritability; usually between 45-55 yrs
