Reproduction Flashcards
Diploid?
2n
autosomal cells
Haploid
one copy of each chromosome
n
Interphase?
G1, S, G2
Offshoot of G1 called…?
G0
Cell is simply living and carrying out its functions, without any preparation for division
Chromatin?
Chromosomes are in a less condensed form; DNA must be available to RNA polymerase so that genes can be transcribed
G1 stage
create organelles for energy and protein production; increases their size; in addition, passage into the S (synthesis) stage is governed by a restriction point
S stage
cell replicates its genetic material so each daughter will have identical copies
after replication, each chromosome will have two identical chromatids bound by a centromere
G2 stage
passes through another quality checkpoint, DNA was replicated in S stage, makes sure there are enough organelles and cytoplasm for two daughter cells, makes sure DNA is ok
M stage?
mitosis + cytokinesis 1. prophase 2. metaphase 3. anaphase 4. telophase cytokinesis
Protein in charge of stopping the cell cycle if DNA has damage?
p53–> plays a role in the G2/M checkpoint
Promote transcription of genes for next stage of the cell cycle?
Transcription factors
Cyclins and cyclin- dependent kinases?
Cyclins bind to CDKs, create an activated CDK-cyclin complex, help phosphorylate transcription factors
Cyclins drive the events of the cell cycle by partnering with a family of enzymes called the cyclin-dependent kinases (Cdks). A lone Cdk is inactive, but the binding of a cyclin activates it, making it a functional enzyme and allowing it to modify target proteins.
When cancer spreads through the bloodstream or lymphatic system?
metastasis
Genes that when mutated, actively promote cell divsion
oncogenes
Genes that, when mutated, lose their ability to regulate or arrest the cell cycle
tumor suppressor genes
ex. p53
mitosis
2 identical daughter cells from a single cell, 1. prophase 2. metaphase 3. anaphase 4. telophase occurs in somatic cells
prophase
condensation of chromatin into chromosomes, spindle forms, centrosome made up microtubules, can form asters that anchor the centrioles to the cell membrane, kinetochores appear at the centrosome
Kinetochores?
protein structures located on the centromeres that serve as attachment points for specific fibers of the spindle apparatus (called kinetochore fibers)
Metaphase
centriole pairs are at opposite ends of the cell, kinetochore fibers interact with the fibers of the spindle apparatus to align the chromosomes at the metaphase plate (equatorial plate)
Anaphase
centromeres split so that each chromatid has its own distinct centromere, thus allowing the sister chromatids to separate, the sister chromatids are pulled toward opposite poles by shortening of the kinetochore fibers
Telophase
essential the reversal of prophase, spindle apparatus disappears, a nuclear membrane reforms around each set of chromosomes and the nucleoli reappear, chromosomes uncoil, returning to their interphase form
Cytokinesis
end of telophase, separation of the cytoplasm and organelles, giving each daughter cell enough material to survive on its own, each cell undergoes a finite number of cell divisions before programmed death (for human somatic cells - normally between 20-50)
Where does meiosis occur?
meiosis occurs in gametocytes (germ cells) and results in up to four nonidentical sex cells (gametes)
What does Meiosis I result in ?
Homologous chromosomes being separated, generating haploid daughter cell –> known as reductional division
goes from 2n –> n
What does Meiosis II result in?
Results in the separation of sister chromatids without a change in ploidy and is therefore known as equational division
n–> n
Meiosis I–> prophase 1?
chromatin condenses into chromosomes, homologous chromosomes come together and intertwine in a process called synapsis, crossing over, chiasma and exchange equivalent pieces of DNA, genetic recombination
Mendel’s Second Law of Independent assortment
states that the inheritance of one allele has no effect on the likelihood of inheriting certain alleles for other genes
Metaphase I?
Homologous pairs (tetrads) align at the metaphase plate, each pair attaches by a separate spindle fiber by its kinetochore
Anaphase 1?
homologous pairs separate and are pulled to opposite poles of the cell, process is called disjunction
Telophase 1?
a nuclear membrane forms around each new nucleus
Interkinesis?
short rest period between meiosis 1 and meiosis 2
What is meiosis II similar to?
mitosis –> sister chromatids rather than homologues are separated from each other
Meiosis II
- prophase II–> nuclear envelope dissolves, nucleoli disappear, the centrioles migrate to opposite poles, and the spindle apparatus begins to form
- metaphase II–> the chromosomes line up on the metaphase plate
- anaphase II–> the centromeres divide, separating the chromosomes into sister chromatids
- telophase II –> a nuclear membrane forms around each new nucleus
4 haploid daughters per gametocyte
Hemizygous
x linked genes for dudes, men only have 1 so are hemizygous
SRY
sex determining region –> part of Y chromosome that codes for a transcription factor that initiates testis differentiation and thus formation of male gonads, in absence of Y chromosome, all zygotes will be female
SEVE(N) UP
- Seminiferous tubules
- Epididymis
- Vas deferens (also called the ductus deferens)
- Ejaculatory duct
- (nothing)
- Urethra
- Penis
Where are sperm produced?
produced in seminiferous tubules, nourished by Sertoli cells
What do the cells of Leydig secrete?
Testosterone
Where are sperm stored until ejaculation?
Epididymis
Where do sperm travel through during ejaculation?
They were stored in the epididymis–> vas deferens–> ejaculatory duct –> urethra –> penis
Seminal vesicles contribute….?
Fructose to nourish sperm and mildly alkaline properties
Prostate gland …?
Gives the fluid mildly alkaline properties so the sperm can survive in the relative acidity of the female reproductive tract
Bulbourethral (Cowper’s) glands produce…?
clear, viscous fluid that cleans out any remnants of urine and lubricates the urethra during sexual arousal
Diploid stem cell are known as…?
spermatogonia
After S stage, spermatogonia develop into..
primary spermatocytes
After primary spermatocytes undergo the first meiotic division they are called…
secondary spermatocytes
After secondary spermatocytes undergo meiosis II they generate
spermatids
After spermatids undergo maturation they become..
spermatozoa
What are the parts of a sperm?
- head- contains genetic material, has a cap known as an acrosome, derived from the Golgi apparatus, necessary to penetrate the ovum
- midpiece- generates ATP from fructose, lots of mitochondria
- A flagellum (for motility)
Female gonads are called
ovaries
Ovaries can produce…?
estrogen and progesterone
Production of female gametes is known as ….?
oogenesis
By birth, all the oogonia have already undergone DNA replication and are considered…
primary oocytes (these cells are 2n), arrested in prophase I
first menstrual cycle is called…?
menarche
after menarche, once per month one primary oocyte will complete meiosis I producing a ….
secondary oocyte and a polar body
zona pellucida
surrounds the oocyte itself, acellular mixture of glycoproteins that protect the oocyte and contain compounds necessary for sperm cell binding
corona radiata
lies outsides the zona pellucida and is a layer of cells that adhered to the oocyte during ovulation
When is meiosis II triggered for an egg?
When a sperm cell penetrates these layers with the help of acrosomal enzymes
Ovum
very large cell contributes large quantities of cytoplasm and organelles to the zygote, RNA for early cellular processes, mitochondria, half of DNA
Pronuclei
the pronuclei of the sperm and ovum join to create a diploid zygote
At the start of puberty the hypothalamus ends the restriction of….
Gonadotropin-releasing hormone (GnRH)
GnRH triggers the anterior pituitary gland to synthesize and release
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH), these trigger the production of other sex hormones
Male sexual development
testosterone, produced by the testes, increases dramatically during puberty, and sperm production begins; also leads to the development of secondary sexual characteristics
What is secreted in response to FSH in women?
Estrogens, result in the development and maintenance of the female reproductive system and female secondary sex characteristics
What leads to the thickening of the endometrium (lining of the uterus)?
Estrogens…done in preparation for the implantation fo a zygote
The corpus luteum secretes ….?
Progesterone … it is involved in the development and maintenance of the endometrium, but not in the initial thickening of the endometrium (that’s estrogen)
Mnemonic:
ESTrogen ESTablishes and PROgesterone PROtects the endometrium
estrogen= thickens the endometrium progesterone= helps maintain the endometrium
Corpus luteum
the remains of the ovarian follicle following ovulation
Menstrual cycle
- Follicular phase
- Ovulation
- Luteal Phase
Follicular phase
begins with menstrual flow, sheds the uterine lining of the previous cycle, GnRH secretion from the hypothalamus increases in response to decreased concentrations of estrogen and progesterone (falls off at the end of each cycle)
estrogen stimulates regrowth of the endometrial lining, stimulating vascularization and glandularization of the decidua
Ovulation
Surge in LH induces ovulation
estrogen can have negative and positive feedback effects, eventually will hit positive feedback late in follicular phase, and GnRH , LH, and FSH levels spike
Luteal Phase
LH causes the ruptured follicle to form the corpus luteum, secretes progesterone
menstruation
if implantation doesn’t occur, they corpus luteum loses its stimulation from LH, progesterone levels decline, and the uterine lining is sloughed off
What is secreted if pregnancy occurs?
Human chorionic gonadotropin (hCG), maintains the corpus luteum, keeps the uterine lining in place
by second semester, hCG levels decline, bc the placenta has grown to a sufficient size to secrete enough progesterone and estrogen by itself
menopause
as a woman ages, her ovaries become less sensitive to FSH and LH, resulting in ovarian atrophy; estrogen and progesterone levels drop, endometrium also atrophies, menstruation stops, negative feedback on FSH and LH is removed, blood levels of these two hormones rise
