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Biology > Reproduction > Flashcards

Reproduction Flashcards

1
Q

What does diploid mean? Haploid?

A
  • Diploid (2n): 46 chromosomes (23 from each parent) in somatic cells
  • Haploid (n): 23 chromosomes (gametes)
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2
Q

What are the 4 stages of the cell cycle?

A

G1, S, G2 (interphase), and M

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3
Q

Characteristics of interphase

A
  • G1, S, G2
  • Longest part of the cell cycle
  • Chromosomes are less condensed as chromatin
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4
Q

What occurs during G0?

A

Cell is just living and functioning, not trying to divide

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5
Q

What occurs during G1?

A
  • Cells create organelles for energy/protein
  • Cells increase in size
  • Restriction point must be passed to enter S
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6
Q

What occurs during S?

A
  • Cell replicates DNA
  • Each chromosome now has two identical chromatids bound together at a region called the centromere
  • 92 chromatids, but 46 chromosomes
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7
Q

What occurs during G2?

A
  • Cell passes thru another checkpoint

- Cell checks that there are enough organelles and cytoplasm and that DNA replication happened correctly

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8
Q

What are the stages of mitosis?

A

Prophase, metaphase, anaphase, telophase, cytokinesis

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9
Q

What are the checkpoints in the cell cycle? What controls these?

A
  • G1/S: determines if DNA is good enough for synthesis; controlled by p53 protein
  • G2/M: cell checks if its big enough and has replicated organelles; also controlled by p53
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10
Q

Which molecules activate the cell cycle? How do they work?

A
  • Cyclins and cyclin-dependent kinases (CDK)
  • CDKs activate in the presence of cyclins, which increase/decrease at various points in the cycle
  • The activated CDK-cyclin complex phosphorylates transcription factors, which promote transcription of genes for the next stage of the cell cycle
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11
Q

What happens to result in cancer during the cell cycle?

A
  • Cell cycle control fails - damaged cells are allowed to undergo mitosis
  • p53 may be mutated - called TP53 - cell won’t stop to repair damaged DNA, and mutations accumulate
  • Rapid cell division results in tumors
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12
Q

What occurs during prophase?

A
  • Chromatin condenses into chromosomes
  • Centriole pairs in centrosome separate and move toward opposite poles
  • Centrioles begin to form spindle fibers - form asters (secure centriole to cell membrane) and attach to kinetochores (proteins on centromeres)
  • Nucleoli begins to disappear
  • Nuclear membrane breaks down
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13
Q

What occurs during metaphase?

A
  • Centriole pairs now at opposite ends

- Chromosomes aligned at metaphase plate

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14
Q

What occurs during anaphase?

A
  • Centromeres split so each chromatid has its own, and sister chromatids separate
  • They are pulled to opposite poles by shortening of kinetochore fibers
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15
Q

What occurs during telophase? (reverse prophase)

A
  • Spindle apparatus disappears
  • Nuclear membrane forms around each set of chromosomes
  • Nucleoli reappears
  • Chromosomes uncoil
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16
Q

What occurs during cytokinesis?

A

Cytoplasm and organelles separate, creating identical daughter cells with 46 chromosomes each

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17
Q

What are the two phases of meiosis?

A
  • Meiosis I (reductional division): homologous chromosomes separate, creating haploid daughter cells
  • Meiosis II (equational division): sister chromatids separate, ploidy stays the same
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18
Q

What does the gametocyte look like before undergoing meiosis?

A

After S, it has 92 chromatids, or 46 chromosomes, which are arranged into 23 homologous pairs (one from each parent)

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19
Q

What occurs during prophase I?

A
  • Chromatin condenses in chromosomes
  • Nucleoli/nuclear membrane disappear
  • Spindle apparatus forms
  • Synapsis: homologous chromosomes, held together and intertwined by synaptonemal complex, undergo crossing over - may occur at point of contact (chiasma)
  • This is genetic recombination: can unlink linked genes, increasing variety of combos
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20
Q

What is Mendel’s second law?

A

Law of independent assortment: the inheritance of one allele has no effect on the likelihood of inheriting certain alleles for other genes
-Genes located closer to each other are more likely to be inherited together, but crossing over means that genes get unlinked and creates a random mix of genes

21
Q

What occurs during metaphase I?

A
  • Tetrads align at metaphase plate
  • In mitosis, each chromosome is lined up by two spindle fibers, one from each pole. In meiosis, homologous chromosomes are held by 1 spindle fiber (from whichever pole is closer to it)
22
Q

What occurs during anaphase I?

A
  • Disjunction/segregation: homologous pairs separate

- So either paternal or maternal chromosome can end up in either daughter cell

23
Q

What is Mendel’s first law?

A

Law of segregation: each gamete has an equal probability of getting either allele (as there will be two copies for each gene)

24
Q

What occurs during telophase I?

A
  • Nuclear membranes form
  • Cells are now haploid - each has 23 chromosomes
  • Cytokinesis
  • Interkinesis: short rest period between divisions during which chromosomes partially uncoil
25
Q

What are the products of meiosis II?

A

Up to 4 unique haploid daughter cells are produced

26
Q

Why do females express X-linked disorders far less frequently than males?

A
  • Most sex-linked disorders are recessively inherited

- So if a male has a disease-causing allele on the unpaired part of an X, he will necessarily express it

27
Q

What information does the Y chromosome carry?

A

SRY (sex-determining region Y): codes for a transcription factor that starts testis differentiation and male gonads

28
Q

Describe the journey of a sperm cell from production to ejaculation.

A
  1. Sperm are produced in the coiled seminiferous tubules (testes), where they are nourished by Sertoli cells.
  2. The cells of Leydig (testes) secrete testosterone + androgens.
  3. Formed sperms passed to the epididymis, where their flagella gain motility, and they are stored there until ejaculation.
  4. During ejaculation, they travel thru the vas deferens and enter the ejaculatory duct at the edge of the prostrate gland. They will be carried out thru the urethra in the penis.
  5. As it leaves, it is mixed with seminal fluid from seminal vesicles (contribute fructose to nourish), prostrate gland (give it alkaline properties so it can survive in acidic female tract), and bulbourethral (Cowper’s) glands (produce clear fluid to clear out urine and lubricate).
29
Q

Why do the testes hang outside the body?

A
  • They are in the scrotum, which hangs below the body to keep the sperm at a lower temp than the body
  • A muscle around the vas deferens can lower/raise testis
30
Q

List the steps of spermatogenesis.

A
  1. Diploid stem cells called spermatogonia.
  2. Some differentiate into diploid primary spermatocytes.
  3. After meiosis I, they are haploid secondary spermatocytes.
  4. After meiosis II, they are haploid spermatids.
  5. After they mature, they are spermatozoa.
31
Q

What is the structure of a mature sperm cell?

A
  • Head with genetic material; has acrosome cap made from the Golgi that can penetrate ovum
  • Midpiece with lots of mitochondria that makes ATP from fructose
32
Q

Describe the female reproductive system.

A
  • Ovaries, which produce estrogen/progesterone, have thousands of follicles - sacs that contain and protect immature ova
  • One egg per month is ovulated into the peritoneal sac, which lines the abdominal cavity
  • It is then drawn into the fallopian tube/oviduct, which is lined with cilia to propel egg
  • Tubes are connected to uterus (site of fetal development)
  • Lower end of the uterus is the cervix, which connects to vagina
33
Q

Are eggs continuously produced in females?

A

No. All the oogonia a woman will ever have are formed during fetal development.

34
Q

List the steps of oogenesis.

A
  1. By birth, all oogonia have undergone DNA replication and are primary oocytes (2n). They are arrested in prophase I.
  2. Once a woman reaches menarche, one egg per month will undergo meiosis I, producing a secondary oocyte and a polar body (unequal cytokinesis). It stays arrested in metaphase II unless fertilization occurs.
35
Q

What are the 2 layers around the ovum?

A
  1. Zona pellucida: surrounds oocyte itself; an acellular mix of glycoproteins that protects egg and helps sperm binding
  2. Corona radiata: lies outside zona and is a layer of cells adhered to egg during ovulation; meiosis II is started when a sperm penetrates these layers with acrosomal enzymes
36
Q

What does the ovum contribute to the zygote? What does the sperm contribute?

A

The ovum contributes half of DNA and all cytoplasm, organelles, RNA. Sperm gives half DNA.

37
Q

Which brain structure controls sexual development in the body? What hormones are involved?

A
  • Before puberty, the hypothalamus restricts production of GnRH
  • At puberty, it releases GnRH, which triggers anterior pituitary gland to make and release FSH and LH
  • These trigger production of sex hormones
38
Q

What is the process of male sexual development (effects of FSH and EH)?

A
  • During fetal period, androgens are made, causing male differentiation
  • Testosterone production increases and sperm production begin during puberty
  • FSH stimulates Sertoli cells and triggers sperm maturation
  • LH causes cells to produce testosterone
  • Secondary sexual characteristics result from testosterone
39
Q

What is the process of female sexual development (effects of FSH and EH)?

A
  • FSH causes estrogen secretion and female secondary sex characteristics
  • Estrogen in embryo creates reproductive tract; in adults leads to thickening of uterus lining (endometrium) in preparation of zygote
  • LH tells corpus luteum (remains of ovarian follicle after ovulation) to make progesterone, which develops and maintains the endometrium
40
Q

What are the 4 phases of the menstrual cycle?

A
  1. Follicular phase
  2. Ovulation
  3. Luteal phase
  4. Menstruation
41
Q

What occurs during the follicular phase of menstruation?

A
  • Begins when menstrual flow begins
  • Decreased concentrations of est/progest causes hypothalamus to make more GnRH –> more LH and FSH
  • FSH/LH develop ovarian follicles, which produce estrogen
  • Est has negative feedback effects and causes GnRH, LH, FSH concentrations to level off
42
Q

What occurs during the ovulation phase of menstruation?

A
  • Later in the follicular phase, the follicles secrete more and more est, which can also have a positive feedback effect –> GnRH, LH, FSH levels spike
  • LH surge induces ovulation (release of ovum from ovary into peritoneal cavity)
43
Q

What occurs during the luteal phase of menstruation?

A
  • After ovulation, LH causes ruptured follicle to form the corpus luteum, which secrets progesterone
  • Progest maintains uterine lining
  • Progesterone levels rise, est levels stay high
  • High levels of progest cause GnRH, LH, FSH to decrease, so another egg is not ovulated
44
Q

What occurs during the menstruation phase?

A
  • If no implantation, the corpus luteum loses its stimulation from LH, progest levels decline, and uterine lining comes off
  • Est/progest decrease so GnRH can start next cycle
45
Q

What does the graph of hormone blood concentrations look like during the follicular phase?

A
  1. FSH and LH at baseline levels to develop follicle; more LH than FSH.
  2. Estrogen levels increasing as follicles secrete it; making a new layer of endometrium
  3. As more estrogen is produced, it exerts a negative feedback effect on FSH and LH, which dip/level off.
  4. Estrogen reaches its highest point in the cycle at the end of the phase
46
Q

What does the graph of hormone blood concentrations look like during the ovulation phase?

A
  1. As estrogen has been increasing, it exerts a positive feedback effect as well
  2. Causes FSH and LH levels to spike, which starts ovulation; both hit their highest point
47
Q

What does the graph of hormone blood concentrations look like during the luteal phase?

A
  1. The increased LH causes corpus luteum to secrete lots of progesterone - hits its peak
  2. Estrogen levels remain high
  3. High level of progesterone causes negative feedback on FSH and LH, which decrease
48
Q

What occurs during pregnancy (hormonally)?

A
  • Zygote will implant and release hCG, an analog of LH, which maintains the corpus luteum
  • Corpus luteum secretes est/progest which keep uterine lining in plce
  • hCG levels decline by second trimester because placenta secretes enough progest/est then
  • High levels of est/progest serve as negative feedback on GnRH still
49
Q

What occurs during menopause (hormonally)?

A
  • Ovaries become less sensitive to FSH and LH, leading to atrophy
  • As est/progest levels drop, the endometrium also atrophies, and menstruation stops
  • As negative feedback on FSH and LH is gone, they rise - this is menopause
  • At ages 45-55: leads to physical/physiological changes

Biology (14 decks)

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