Chapter 2: Reproduction Flashcards
What is diploid?
2 copies of each chromosome
What is haploid?
1 copy of each chromosome
Are autosomal cells haploid or diploid?
Diploid (2n)
Are germ cells haploid or diploid?
Haploid (n)
What are the 4 stages of the cell cycle?
G1
S
G2
M
Which of these stages comprise interphase? : G1, S, G2, M
G1, S, G2
Interphase is the (longest/shortest) part of the cell cycle. Actively dividing cells spend 90% of their time in interphase.
Longest
Cells that do not divide spend all of their time in an offshoot of G1 called ____, where the cell simply lives and carries out its functions, without preparing for division.
G0
During interphase, individual chromosomes are in a less condensed form known as ____________.
Chromatin
not visible by light microscopy
During mitosis, it is preferable to condense DNA into tightly coiled ________________ to avoid losing any genetic material during cell division.
Chromosomes
What occurs during the G1 stage?
- Cells create organelles for energy and protein production
- Cells increase in size
Passage into the S (synthesis) stage is governed by a ______________ ________.
Restriction point
What occurs during the S stage?
Cell replicates its genetic material so that each daugher cell has identical copies
After replication in the S stage, each chromosome consists of 2 identical ________________ that are bound together at a specialized region known as the ________________.
chromatids; centromere
Does the ploidy of cells change after replication in G1?
No, it simply has more DNA, but still only has 46 chromosomes.
Cells entering G2 have ________ as much DNA as cells in G1.
Twice
During the G2 stage, DNA has been duplicated, and the cell checks to ensure there are enough ________________ and ________________ for 2 daughter cells. It also checks to make sure that DNA replication proceeded correctly.
Organelles and cytoplasm
What are the 4 phases of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What are the 2 primary checkpoints in the cell cycle?
G1/S and G2/M
What does the cell check for at the G1/S checkpoint, i.e. restriction point?
If the condition of the DNA is good enough for synthesis
If the DNA is damaged at the G1/S checkpoint, what happens? What protein is in control of this?
The cell cycle goes into arrest until the DNA is repaired. p53 is the main protein.
What does the cell check for at the G2/M checkpoint? What protein is involved?
If it has achieved adequate size and the organelles have been properly replicated to support 2 daughter cells. p53 is also at play.
Which 2 molecules are responsible for the cell cycle?
- Cyclins
- Cyclin-dependent kinases (CDK)
How are CDKs activated?
They require the presence of the right cyclins
During the cell cycle, concentrations of various cyclins increase and decrease. These cyclins bind CDKs, creating an activated _________ - __________ ___________, which can then phosphorylate _______________ _________.
CDK-cyclin complex; transcription factors
What is a common mutation of p53 that can cause cancer?
TP53
What occurs in TP53 mutation?
The cell cycle is not stoppped to repair damaged DNA, allowing mutations to accumulate, resulting in a cancerous cell that divides continuously, creating tumors
List 4 steps
What occurs during prophase?
- Chromatin condenses into chromosomes
- Centrioles separate and migrate to opposite poles
- Centrioles begin to form spindle fibers
- The nuclear membrane dissolves, allowing these spindle fibers to contact the chromosomes
Centrioles are located outside the nucleus in a region known as the ________________ and are responsible for the correct division of DNA.
Centrosome
What are spindle fibers made of ?
Microtubules
Since spindle fibers are made of microtubules, the centrosome is one of two ___________________ ______________ _________ of the cell.
Microtubule organizing centers
Besides the centrosome, what is the other microtubule organizing centers of the cell?
The basal body of a flagellum or cilium
Some microtubules form ________ that anchor the centrioles to the cell membrane.
asters
________________, which appear at the centrosome, are protein structures located on the centromeres of chromosomes that serve as attachment points for specific fibers of the ____________ ________________ (kinetochore fibers).
Kinetochores; spindle apparatus
2 steps
What happens during metaphase?
- Centriole pairs are at opposite poles
- Kinetochore fibers interact with the fibers of the spindle apparatus to align the chromosomes at the metaphase plate.
2 steps
What happens during anaphase?
- Centromeres split so that each chromatid has its own distinct centromere
- Sister chromatids are pulled toward the opposite poles of the cell by the shortening of kinetochore fibers
4 steps
What occurs during telophase?
- Spindle apparatus disappears
- Nuclear membrane reforms around each set of chromosomes
- Nucleoli reappear
- Chromosomes uncoil
What is cytokinesis?
Separation of cytoplasm and organelles
Meiosis occurs in germ cells and results in up to (how many?) nonidentical sex cells (gametes).
4
How many rounds of replication and division does mitosis have?
1 round of replication and 1 round of division
How many rounds of replication and division does meiosis have?
1 round of replication, 2 rounds of division
Meiosis I results in homologous chromosomes being separated, generating haploid daughter cells; this is known as ____________________ division.
Reductional
Meiosis II is most similar to mitosis, in that it results in the separation of sister chromatids without a change in ploidy, and is therefore known as ____________________ division.
Equational
What are homologous pairs of chromosomes?
Each pair contains 1 chromosome inherited from each parent
In meiosis, after S phase, there are (how many?) chromatids organized into (how many?) chromosomes, which are organized into (how many?) homologous pairs.
92, 46, 23
What are the 3 main events in Prophase I?
- Chromatin condenses into chromosomes
- Spindle apparatus forms
- Nucleoli and nuclear membrane disappear
During Prophase I, the homologous chromosomes come together and intertwine in a process called _____________.
Synapsis
At this point, each chromosome is made up of 2 chromatids, so each synaptic pair contains (how many?) chromatids and is referred to as a _____________.
4; tetrad
The homologous chromosomes are held together by a group of proteins called the ____________________ ___________.
Synaptonemal complex
Chromatids of homologous chromosomes may break at the point of contact, called the ____________, and exchange equivalent pieces of DNA.
Chiasma
plural: chiasmata
What is the process of exchanging chromatids exchanging DNA called?
Crossing over
What is crossing over characterized by?
The number of crossover events that occur in one strand of DNA
Crossing over can unlink linked genes, thereby increasing the variety of genetic ________________ that can be produced by gametogenesis.
Recombination
What is gene linkage?
Tendency for genes to be inherited together
Genes that are located farther from each other physically are (more/less) likely to be inherited together, and (more/less) likely to undergo crossing over relative to each other.
less; more
What is the unit of measurement for distance between genes on the chromosome?
Centimorgans
What does Mendel’s second law of independent assortment state?
Has to do with crossing over
The inheritance of one allele has no effect on the likelihood of inheriting certain alleles for other genes
What are the 2 main steps in Metaphase I?
- Tetrads (homologous pairs) align at the metaphase plate
- Each pair attaches to a separate spindle fiber by its kinetochore
What occurs during Anaphase I?
- Homologous pairs separate and are pulled to opposite poles of the cell
This is disjunction
What is Mendel’s first law of segregation?
during gamete formation, the two alleles at a gene locus segregate from each other; each gamete has an equal probability of containing either allele
What occurs during disjunction?
Each chromosome of paternal origin separates from its homologous of maternal origin, and eater chromosome can end up in either daughter cell. Thus, the distribution of homologous chromosomes to the 2 intermediate daughter cells is random with respect to parental origin.
What is the separation of 2 homolgous chromosomes called?
Segregation
What occurs during Telophase I?
- A nuclear membrane forms around each new nucleus
- The cell divides into 2 daughter cells by cytokinesis
After Telophase I, are the cells haploid or diploid?
Haploid
Only n chromosomes are found in each daugher cell (23 in humans)
Between cell division, there may be a short rest period, or ________________, during which the chromosomes partially uncoil.
Interkinesis
What occurs in Meiosis II?
Sister chromatids separate from each other
4 phases
What occurs during Prophase II?
- Nuclear envelope dissolves
- Nucleoli disappear
- Centrioles migrate to opposite poles
- Spindle apparatus begins to form
What occurs during Metaphase II?
Chromosomes line up on metaphase plate
What occurs during Anaphase II?
- Centromeres divide, separating chromosomes into sister chromatids
- Chromatids are pulled to opposite poles by spindle fibers
What occurs during Telophase II?
- A nuclear membrane forms around each new nucleus
- Cytokinesis follows, and 2 daughter cells are formed per each
Which pair of chromosomes determine chromosomal sex?
23rd
Mutations in the genes of the X chromosome can cause ___-___________ disorders.
aka?
sex-linked
X-linked
Males are termed ________________ with respect to many of the genes on the X chromosome because they only have one copy.
Hemizygous
What is one major consequence of males only having one X chromosome?
They tend to express X-linked disorders more frequently than females.
dominantly or recessively?
Most X-linked disorders are ________________ inherited.
recessively
The (X or Y?) chromosome contains very little genetic information.
Y
A notable gene on the Y chromosome is ________, which codes for a transcription factor that initiates testis differentiation and thus, the formation of male gonads.
what does it stand for?
SRY
sex-determining region Y
What is the pathway of sperm through the male reproductive system?
SEVE(N) UP
- Seminiferous tubules
- Epididymis
- Vas deferens (also called ductus deferens)
- Ejaculatory duct
- (Nothing)
- Urethra
- Penis
In males, the primitive gonads develop into the ________.
Testes
The testes have 2 functional components, the ________________ tubules and the interstitial cells of ____________.
seminiferous; Leydig
Where are sperm produced?
In the highly coiled seminiferous tubules
____________ cells nourish the sperm in the seminiferous tubules.
Sertoli
The cells of Leydig secrete ________________ and other male sex hormones known as ____________.
testosterone; androgens
The testes are located in the ____________, an external pouch that hangs below the ________, which allows it to maintain a temperature 2-4 deg C cooler than the body.
scrotum; penis
The ____ ____________ has a layer of muscle that can raise and lower the testis to maintain the proper temperature for sperm development.
aka?
vas deferens
ductus deferens
Once sperm are formed in the seminiferous tubules of the testes, they are passed to the ____________________, where their flagella gain motility. They are stored there until ______________.
epididymis; ejaculation
During ejaculation, sperm travel through the ____ ____________ and enter the ______________ ______ at the posterior edge of the prostate gland.
vas deferens; ejaculatory duct
The 2 ejaculatory ducts fuse to form the ________, which carries sperm through the penis.
urethra
As sperm pass through the reproductive tract, they mix with ____________ ________, which is produced by what 3 things?
seminal fluid; seminal vesicles, prostate gland, and bulbourethral gland
The seminal vesicles contribute ____________ to nourish sperm, and both the seminal vescles and ____________ gland give the fluid mildly alkaline properties so they can survive the relatively acidic female reproductive tract.
fructose; prostate
The ________________ glands produce a clear viscous fluid that cleans out any remnants of urine and lubricates the urethra during sexual arousal.
aka?
bulbourethral
Cowper’s
The combination of sperm and seminal fluid is ________.
Semen
In males, the diploid stem cells are known as _________________.
Spermatogonia
After spermatogonia replicate their genetic material (S stage), they develop into (diploid or haploid?) ____________ ______________________.
diploid primary spermatocytes
The first meiotic division of primary spermatocytes results in (diploid or haploid?) __________________ ______________________.
haploid secondary spermatocytes
Secondary spermatocytes undergo meiosis II to generate (diploid or haploid?) ______________.
haploid spermatids
The spermatids then undergo maturation to become mature ________________.
spermatozoa
Spermatogenesis results in (how many?) functional sperm for each spermatogonoium.
4
What are the 3 main parts of sperm?
- Head
- Midpiece
- Flagellum
What is contained in the sperm head?
Genetic material
What is inside the sperm midpiece and what do they generate?
Mitochondria generates ATP from fructose for swimming.
Each sperm head is covered by a cap known as a ____________. It is necessary to penetrate the ovum.
Acrosome
The female gonads, known as ____________, produce ____________ and ____________________.
ovaries; estrogen and progesterone
The ovaries are located in the __________ _________.
Pelvic cavity
Each ovary consists of thousands of ____________, which are multilayered sacs that contain, nourish, and protect immature ____.
follicles; ova
One egg per month is ____________ into the ________________ sac, which lines the abdominal cavity.
ovulated; peritoneal
Upon ovulation, the egg is drawn into the ______________ ______, or ________, which is lined with cilia to propel the egg forward.
fallopian tube; oviduct
The fallopian tubes are connected to the muscular ________, where the fetus develops.
Uterus
The lower end of the uterus, known as the ________, connects to the ____________ ________, where sperm are deposited during intercourse.
cervix; vaginal canal
The production of female gametes is known as ____________.
oogenesis
By birth, all of a female’s oogonia have already undergone DNA replication and are considered ______________ __________.
primary oocytes
What is the ploidy of primary oocytes?
2n
Primary oocytes are arrested in ___________ __.
Prophase I
After menarche (first menstrual cycle), 1 primary oocyte per month will complete ____________ ____, producing a __________________ __________ and a ________ _______.
Meiosis I; secondary oocyte and polar body
Meiosis I in oocytes is characterized by unequal ________________. This causes ample cytoplasm to be distributed to 1 daughter cell (secondary oocyte) and nearly none to the other (polar body).
cytokinesis
What happens to the polar body?
It does not divide any further and does not produce functional gametes
What happens to the secondary oocyte?
It is arrested in metaphase II and does not complete meiosis II until fertilization occurs
What are the 2 layers surrounding oocytes?
zona pellucida and the corona radiata
What is the zona pellucida and what is it made of and what does it do?
Surrounds the oocyte itself and is an acellular mixture of glycoproteins that protects the oocyte and contains compounds necessary for sperm cell binding
What is the corona radiata?
Surrounds the zona pellucida; it is a layer of cells that adheres to the oocyte during ovulation
What triggers Meiosis II?
When a sperm cell penetrates the zona pellucida and corona radiata with the help of acrosomal enzymes
What happens after Meiosis II?
The secondary oocyte splits into a mature ovum and another polar body
What do the ovum and sperm each contribute to the zygote?
Ovum; half of DNA, all of cytoplasm/organelles/RNA
Sperm; half of the DNA
After Meiosis II, the (diploid/haploid?) ____________ of the sperm and the ovum join, creating a (diploid/haploid?) ____________.
haploid pronuclei; diploid zygote
What controls the ability to reproduce?
Hormones
Prior to puberty, the ________________ restricts production of ____________________-________________ hormone.
Hypothalamus; gonadotropin-releasing (GnRH)
At the start of puberty, the hypothalamus releases pulses of ________, which triggers the (anterior/posterior?) pituitary gland to synthesize and release _____________-_________________ hormone and ____________________ hormone.
GnRH; anterior; follicule-stimulating (FSH); luteinizing (LH)
What do FSH and LH do?
Trigger the production of other sex hormones
During the fetal period (9 weeks post-fertilization till birth), the presence of the Y chromosome in males leads to the production of ________________, which results in male sexual differentiation.
androgens
For the duration of infancy and childhood, androgen production is (high/low?).
Low
By puberty, the testes dramatically increase production of ____________________, and sperm production begins.
testosterone
During puberty, ____ stimulates the Sertoli cells and triggers what?
Whereas ____ causes the interstitial cells to produce what?
FSH, sperm maturation; LH, testosterone
The ovaries are also under the control of FSH and LH but they produce what instead?
Estrogens and progesterone
What does FSH stimulate the secretion of in females? What does this stimulate the development of in embroys? In adults?
estrogens; female reproductive tract; endometrial lining in preparation for zygote implantation
What do estrogen and progesterone do?
Est-est-pro-pro
Estrogen establishes and progesterone protects the endometrium.
Estrogen - thickens endomet.
Progesterone - develops/maintains endomet.
What is the corpus luteum?
The remains of the ovarian follicle following ovulation
What does LH stimulate the secretion of in females? From where?
Progesterone from corpus luteum
What are the 4 events of the menstrual cycle?
- Follicular phase
- Ovulation
- Luteal phase
- Menstruation
What marks the start of the follicular phase?
When the menstrual flow begins
uterine lining of previous cycle is shed
________ secretion from the hypothalamus increases in response to the decreased concentrations of ____________ and ________________, which fall off towards the end of each cycle.
GnRH; estrogen and progesterone
The higher concentrations of GnRH cause increased secretion of what in the hypothalamus?
FSH and LH
What do FSH and LH do in the follicular phase?
Develop several ovarian follicles which begin to produce estrogen
What do the follicles do in the follicular phase?
Produce estrogen, which causes GnRH, LH, and FSH concentrations to level off
negative feedback
What does estrogen do in the follicular phase?
Stimulates regrowth of the endometrial lining
Estrogen stimulates vascularization and glandularization of the ___________.
Decidua
thick layer of mucous membrane which lines uterus during pregnancy
Late in the follicular phase, the developing follicles secrete higher and higher concentrations of estrogen. This reaches a threshold that results in positive feedback, and GnRH, LH, and FSH levels spike. The surge in LH induces _____________.
ovulation
ovary releases ovum into abdominal cavity
After ovulation, LH causes the ruptured follicle to form the ________ ________, which secretes _________________.
corpus luteum; progesterone
During the luteal phase, progesterone levels (rise/fall?), while estrogen levels remain (high/low?).
rise; high
What do the high levels of progesterone do in the luteal phase?
Cause negative feedback on GnRH, FSH, LH, preventing ovulation of multiple eggs
If implantation does not occur, the corpus luteum loses its stimulation from LH, progesterone levels (rise/decline?) and the uterine lining is sloughed off.
Decline
The loss of high levels of estrogen and progesterone do what to GnRH?
Remove the block on GnRH, so that the next cycle can begin
If fertilization occurs, the zygote develops into a ____________ that will implant in the uterine lining and secrete __________ _____________ ___________________, which is an analog of LH and can stimulate LH receptors to maintain the corpus luteum.
blastocyst; human chorionic gonadotropin (hCG)
What is hCG important for in the first trimester?
Keeping the uterine lining in place by maintaining the corpus luteum (and allowing it to continue secreting estrogen and progesterone)
In the second trimester, why do hCG levels decline?
The placent has grown large enough to secrete enough progesterone and estrogen by itself
What do the high levels of estrogen and progesterone do during pregnancy?
Negative feedback on GnRH secretion
As we age, the ovaries become (more/less?) sensitive to FSH and LH, resulting in what?
Less; ovarian atrophy
As estrogen and progesterone levels drop as we age, the endometrium also atrophies, causing what?
The stopping of menstruation, aka menopause
What happens as a result of the removal of negative feedback on FSH and LH during menopause?
FSH and LH blood levels rise
