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APS 136 animal physiology, reproduction & development > Lecture 2: Gametogenesis > Flashcards

Lecture 2: Gametogenesis Flashcards

1
Q

Gametogenesis is the process of

A

making sex cells.

  • meiosis (converting diploid cell into haploid cell)
  • spermatogenesis and oogenesis
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2
Q

Mitosis:

A

-homologous chromosomes
-DNA Replication = sister chromatids
- chromosome segregation (mitosis) sisters separate
= 2 IDENTICAL DAUGHTER CELLS, CLONES OF PARENT AND EACH OTHER

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3
Q

Meiosis:

A
  • homologous chromosomes
    -DNA Replication, RECOMBINATION = sister chromatids
    -chromosome segregation (meiosis 1) homologues separate, sisters remain attached
    -Chromosome segregation (meiosis 2) sisters separate
    === GAMETES (eggs or sperm)
    HAPLOID and NOT identical
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4
Q

fertilisation is when

A

haploid gametes (egg & sperm) –> Diploid zygote (fertilised egg)

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5
Q

what produce gametes i most species?

A

highly specialised organs (gonads)

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6
Q

Spermatogenesis:

A

process of making sperm

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7
Q

sperm are produced from

A

spermatogonial stem cells. Spermatogonial cells divide by MITOSIS initially, producing the diploid primary spermatocytes THEN MEIOSIS

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8
Q

each primary spermatocyte gives rise to

A

four sperm cells

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9
Q

Primary spermatocyte (diploid) –> sperm (haploid)

A 
Meiosis: 
primary spermatocyte (diploid) - meiosis -> secondary spermatocytes (diploid) -> spermatids (haploid) -> develop into sperm (haploid)
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10
Q

is spermatogenesis exactly the same throughout all taxa?

A

NO

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11
Q

Spermatogenesis in insects (e.g. fruit fly)

A
  • occurs in cysts within testes
  • spermatogenesis from distal to proximal (long tube) -starts at larval stage
  • sperm produced in a few days
  • ~<10,000 sperm / day
  • semen from accessory glands
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12
Q

Spermatogenesis in mammals (e.g humans)

A
  • Occurs in seminiferous tubules within testes
  • Spermatogenesis from periphery to lumen
  • starts in puberty
  • sperm produced in approx 74 days
  • ~300 million sperm per day
  • stored in epididymis for <4 weeks or reabsorbed
  • semen from seminal vesicles & prostate gland
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13
Q

is there much diversity own sperm morphology?

A

YES

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14
Q

sperm giantism:

A

type of fly??
body length = 3mm
sperm length = 60mm

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15
Q

sperm heteromorphism:

A

organism has multiple sperm morphologies used for blocking female tracts etc

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16
Q

oogenesis

A

production of the ovum (egg cell)

17
Q

1 primary oocyte gives rise to _ egg cells

A

JUST ONE.

more precious than sperm

18
Q

oogenesis stages:

A

meiosis 1:
-primary oocyte (diploid) –> secondary oocyte (diploid) and first polar body
(meiosis 2)
–> -ovum (haploid) and polar bodies –> just ONE egg (haploid)
- ovum (haploid)

19
Q

oogenesis in insects e.g. fruit fly

A
  • oogenesis from distal to proximal
  • start in larval stage
  • eggs produces in a few days
  • <100 per day
  • released into uterus for fertilisation
  • egg laid whether fertilised or not
  • oviparous (no pregnancy)
20
Q

oviparous:

A

producing young by means of eggs, which are hatched after being played by the parent.

21
Q

oogenesis in mammals e.g. humans

A
  • oogenesis within a follicle (one ova with cells to nourish)
  • 400,000 follicles at birth but ovulation starts at puberty
  • starts in puberty
  • 1 per month
  • follicle ruptures, oocyte enter Fallopian tube for fertilisation
  • If not fertilised, degenerates and prepared uterus lining (thick, vascular endometrium lining) sloughs away
22
Q

Control of gametogenesis hormones

A
  • At puberty, hypothalamus secretes gonadotrophin-realising hormone (GnRH)
  • GnRH stimulates FSH (follicle stimulating hormone) and LH (lutenizing hormone) from the anterior pituitary cells
23
Q

In spermatogenesis LH stimulates

A

LH – stimulates Leydig cells to secrete testosterone which stimulates spermatogenesis

24
Q

In spermatogenesis FSH stimulates

A

FSH –stimulates development of seminiferous tubules (where sperm form) and spermatogenesis acting together with testosterone by stimulating Sertoli cells

25
Q

In oogenesis LH -

A

LH – stimulates maturation of follicles, estrogen and progesterone, ovulation

26
Q

In oogenesis FSH =

A

FSH – stimulates development of follicles and secretion of estrogens

27
Q

role of estrogen:

A

enhances growth of follicles, grow endometrium

28
Q

progesterone:

A

endometrium for pregnancy, secretes nutrients for embryo

29
Q

oestrogen and progesterone fluctuate in

A

-28 day cycle in humans

30
Q

the ovary and uterus need to be…

A

coordinated. achieved by hormonal feedback

31
Q

if fertilised, embryonic placental cells secrete

A

chorionic gonadotropin to rescue the corpus luteum and maintains its function

32
Q

birth control pill works by

A

negative feedback to FSH and LH

APS 136 animal physiology, reproduction & development (17 decks)

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