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MCAT Biology > Ch 2 - Reproduction > Flashcards

Ch 2 - Reproduction Flashcards

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1
Q

What is the difference between a diploid and a haploid?

A
  • diploid (2n) cells have 2 copies of each chromosome

- haploid (n) cells have one copy

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2
Q

What are the 5 stages of the cell cycle?

A
  • G1: cells create organelles for energy and protein production and increase their size
  • S: DNA is replicated (strands of DNA - chromatids - are held together at the centromere) - only DNA molecules double, chromosome number stays the same
  • G2: further cell growth and replication of organelles in preparation for mitosis
  • M: mitosis and cytokineses occur
  • G0: cell performs its functions without preparing for division
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3
Q

What is interphase?

A
  • G1, S, and G2 phase
  • the DNA is uncoiled in the form of chromatin making the DNA available to the RNA polymerase so that the genes can be transcribed
  • individual chromosomes are not visible with light microscopy
  • longest part of cell cycle
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4
Q

What is p53?

A
  • plays a role in the 2 major checkpoints of the cell cycle (G1 to S and G2 to M)
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5
Q

What is the role of cyclins and CDK in the cell cycle?

A
  • the rise and fall during the cell cycle

- cyclins bind to the CDKs, phosphorylating and activating transcription factors for the next stage of the cell cycle

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6
Q

What is cancer and when does it occur?

A
  • occurs when cell cycle control become deranged, allowing damaged cells to undergo mitosis without regard to quality and quantity of the new cell produced
  • cancerous cells may begin to produce factors that allow them to delocalize and invade adjacent tissues or metastasize elsewhere
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7
Q

What does mitosis produce and where does it occur?

A
  • produces 2 genetically identical diploid daughter cells from a single cell
  • occurs in somatic cells
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8
Q

What are the 4 phases of mitosis?

A
  • Prophase: chromosomes condense, nuclear membrane dissolve, centrioles migrate to opposite sides of cells, spindle apparatus begins to form (kinetechore of each chromosome is contacted by a spindle fiber)
  • Metaphase: chromosomes line up along the metaphase plate
  • Anaphase: sister chromatids are separated and pulled to opposite poles
  • Telophase: nuclear membrane re forms, spindle apparatus disappears, cytosol and organelles are split between the 2 daughter cells through cytokineses
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9
Q

What does meiosis produce and where does it occur?

A
  • occurs in gametocytes (germ cells)

- produces up to 4 non identical haploid sex cells (gametes)

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10
Q

How many rounds to meiosis have and of what?

A
  • one round of replication

- 2 rounds of division ( the reductional and the equational)

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11
Q

What happens in meiosis 1?

A
  • homologous pairs of chromosomes (homologues) are separated from each other
  • homologues are chromosomes that are given the same number, but are of the opposite parental origin
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12
Q

What happens in prophase 1?

A
  • the same events as in prophase of mitosis, except the homologues come together and intertwine (synapsis)
  • the 4 chromatids are referred as a tetrad
  • crossing over exchanges genetic material between one chromatid and material from a chromatid in the homologous chromosome
  • mendel’s first law of independent assortment
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13
Q

Metaphase 1?

A

homologous chromosomes line up on opposite sides of the metaphase plate

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14
Q

Anaphase 1?

A

homologous chromosomes are pulled to opposite poles of the cell
- mendel’s first law of segregation

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15
Q

Telophase 1?

A

the chromosomes may or may not fully decondense and the cell may inter interkinesis after cytokineses

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16
Q

What happens in meiosis 2?

A
  • sister chromatids are separated from each in a process that is functionally identical to mitosis
  • sister chromatids are copies of the same DNA held together at the centromere
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17
Q

What chromosome determines biological sex?

A
  • 23rd pair of chromosomes in humans

- XX being female and XY being male

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18
Q

What do X chromosome carry? What affects to mutations to X linked genes cause?

A
  • carry a sizeable amount of genetic information
  • mutations can cause sex linked disorders
  • males are hemizygous with respect to the unpaired genes on the X chromosome, so they will express sex linked disorders, even if they only have one recessive diseases carrying allele
  • women with one copy of the affected allele are called carriers
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19
Q

What do Y chromosomes carry?

A
  • little genetic information, but does contain the SRY gene which causes gonads to differentiate into testes
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20
Q

Where are sperm developed and how are they nourished?

A
  • develop in the seminiferous tubulues in the testes

- nourished by Sertoli cells

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21
Q

What do interstitial cells of Leydig secrete and where are they located?

A
  • in the testes

- secrete testosterone and other male sex hormones (androgens)

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22
Q

Where are the testes located?

A

in the scrotum which hangs outside of the abdominal cavity and has a temperature 2-4 C lower than the rest of the body

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23
Q

Once formed, where do sperm gain motility?

A

epididymis and are stored there until ejaculation

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24
Q

What is the pathway for sperm during ejaculation?

A

SEVE(N) UP

  • through the Seminiferous tubules
  • Epididymis
  • Vas deferens
  • to the Ejaculatory duct
  • Nothing
  • and then to the Urethra
  • and out the Penis
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25
Q

What do the seminal vesicles contribute?

A

fructose to nourish sperm and produce alkaline fluid

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26
Q

What doe the prostate and bulbourethral glands produce?

A
  • prostate: alkaline fluid
  • bulbourethral: a clear viscous fluid that cleans out any remnants of urine and lubricates the urethra during sexual arousal
27
Q

What is semen compose of?

A

sperm and seminal fluid from prostate and bulbourethral glands

28
Q

What are the stages of spermatogenesis and what is produced?

A
  • after S stage, the germ cells are called primary spermatocytes
  • after meiosis 1, secondary spermadocytes
  • after meiosis 2, spermatids
  • after maturation, spermatozoa
  • producing 4 haploid sperm from a spermatogonium
29
Q

What are the 3 parts of sperm?

A
  • head: contains the genetic material and is covered with acrosome (a modified Goligi apparatus that contains enzymes that help the sperm fuse with and penetrate the ovum)
  • midpiece: generates ATP from fructose and contains many mitochondria
  • flagellum: promotes motility
30
Q

Where are ova produced?

A
  • eggs

- produced in follicles in the ovaries

31
Q

What happens to the eggs once each month?

A

an egg is ovulated into the peritoneal sac and is drawn into the fallopian tube or oviduct

32
Q

What are the fallopian tubes connected to?

A

the uterus, the lower end of which is the cervix

33
Q

Where does the vaginal canal lie and what happens there?

A

below the cervix

  • site where sperm are deposited during intercourse
  • site of natural childbirth
34
Q

What is the external female anatomy known as?

A

vulva

35
Q

What is formed in oogenesis?

A

one haploid ovum and a variable number of polar bodies are formed from an oogonium

36
Q

What is the process of oogenesis?

A
  • at birth, all oogonia have already undergone replication and are primary oocytes (they arrest in propase 1)
  • the ovulated egg each month is the secondary oocyte (arrests in metaphase 2)
  • if the oocyte is fertilized, it will complete meiosis 2 and become true ovum
  • cytokinesis is uneven in oogenesis, the cell receiving very little cytoplasm and organelles = polar body
37
Q

What surrounds an oocyte?

A
  • the zone pellucida: an acellular mixture of glycoproteins that protect the oocyte and contain the compounds necessary for sperm binding
  • corona radiata: a layer of cells that adhered to the oocyte during ovulation
38
Q

What does the Gonadotropin-releasing horomone (GnRH) from the hypothalamus cause?

A
  • the release of follicle stimulating hormones (FSH) and luteinizing hormone (LH), the functions of which depend on the sex of the individual
39
Q

What are the function of FSH and LH in males?

A
  • FSH stimulates the Sertoli cells and triggers spermatogenesis
  • LH causes the interstitial cells to produce testerone
40
Q

What is testosterone?

A

responsible for the maintenance and development of the male reproductive system and male secondary sex characteristics (facial and axillary hair, deepening of voice, increased bone and muscle mass)

41
Q

What are the functions of FSH and LH in females?

A
  • FSH stimulates development of ovarian follicles
  • LH: causes ovulation
  • these hormones also stimulate production of estrogen and progesterone
42
Q

What is the menstrual cycle?

A

a periodic growth and shedding of the endometrial lining

43
Q

What happens in the follicular phase of the menstrual cycle?

A
  • first step (follicles mature)
  • GnRH secretio stimulates FSH and LH secretion, which promotes follicle development
  • estrogen is released, stimulating vascularization and glandularization of the decidua
44
Q

What happens during ovulation of the menstrual cycle?

A
  • second step
  • stimulated by sudden surge in LH (around 14 days)
  • surge is triggered when estrogen levels reach a threshold and witch from negative to positive feedback effects
45
Q

What happens in the luteal phase of the menstrual cycle?

A
  • third step
  • LH causes the ruptured follicle to become the corpus luteum, which secretes progesterone that maintains the uterine lining
  • high estrogen and progesterone levels cause negative feedback on GnRH, LH, and FSH
46
Q

What happens during menstruation step if fertilization does not occur?

A
  • fourth step
  • as the estrogen and progesterone levels drop, the endometrial lining is sloughed off, and the block on GnRH production is removed causing LH and FSH levels to rise again
47
Q

What happens if fertilization does occur during the menstrual cycle?

A
  • the blastula produces human chorionic gonadotrophin (hCG) which, as an LH analog, can maintain the corpus luteum
  • near the end of the first trimester, hCG levels drop as the placenta takes over progesterone production
48
Q

When does menopause occur and what happens?

A
  • occurs when ovaries stop producing estrogen and progesterone, usually between 45-55
  • menstruation stops and FSH and LH levels rise
  • physical and physiological changes accompanying menopause include flushing, hot flashes, bloating, headache, irritability
49
Q

How many daughter cells are there after meiosis 1 v meiosis 2?

A
  • 1: 2 haploid daughter cells

- 2: 4 halpoid gametes

50
Q

What is the difference between homologous chromosomes and sister chromatids?

A
  • homologous: related chromosomes of opposite parental origin (X and Y)
  • sister: identical copies of the same DNA that are held together at the centromere
  • after S phase, a cell contains 92 chromatids, 46 chromosomes, and 23 homologous pairs
51
Q

What is the difference between prophase 1 and prophase?

A

in prophase 1, homologous chromosomes come together as tetrads during synapsis; crossing over

52
Q

What is the difference between metaphase 1 and metaphase?

A

in metaphase 1, homologous chromosomes line up on opposite sides of the metaphase plate rather than individual chromosomes lining up on the metaphase plate

53
Q

What is the difference between anaphase 1 and anaphase?

A

in anaphase 1, homologous chromosomes separate from each other; centromeres do not break

54
Q

What is the difference between telophase 1 and telophase?

A

in telophase 1, chromatin may or may not decondense; interkinesis occurs as the cell prepares for meiosis 2

55
Q

When does FSH increase/decrease throughout the menstrual cycle?

A
  • follicular: increase
  • ovulation: increase
  • luteal: decrease
  • menses: decrease
56
Q

When does LH increase/decrease throughout the menstrual cycle?

A
  • follicular: same
  • ovulation: increase a lot
  • luteal: same
  • menses: decrease
57
Q

When does estrogen increase/decrease throughout the menstrual cycle?

A
  • follicular: decrease then increase
  • ovulation: increase
  • luteal: increase
  • menses: decrease
58
Q

When does progesterone increase/decrease throughout the menstrual cycle?

A
  • follicular: decrease
  • ovulation: decrease
  • luteal: increase
  • menses: decrease
59
Q

What would excess estrogen cause?

A
  • estrogen known to cause growth of the endometrial lining during the follicular phase and its levels stay high during luteal phase to promote vascularization and glandularization
  • excess may provide a strong enough signal for cell growth to promote tumor formation or even cancer
60
Q

Upon ovulation, where is the oocyte released to?

A
  • the ruptured ovarian follicle releases an oocyte into the abdominal cavity, close to the entrance of the fallopian tube
  • with the aid of beating cilia, the oocyte is drawn into the fallopian tube through which it travels until it reaches the uterus
61
Q

What is the epididymis?

A
  • the side of sperm maturation at the posterior side of the testis
  • sperm gain mobility and are stored until ejaculation
62
Q

What is vas deferens?

A

surrounding by muscle that raises and lowers the testis to maintain constant temperature suitable for sperm production

63
Q

What happens in the first trimester?

A
  • the corpus luteum is preserved by hCG and progesterone secretion by corpeus lutem is maintained
64
Q

What happens in the second trimester?

A
  • hCG levels decline

- progesterone levels rise because the hormone is now secreted by the placenta itself

MCAT Biology (12 decks)

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