Gametogenesis and puberty (cell b) Flashcards
Oogenesis
Somatic cells
- pairs of ? chromosomes (2n)
- each chromosome has one chromatid
Human body cells have 46 chromosomes (chromatids) or #? pairs
Oogenesis Mitosis
* Part of cell ?
* Two genetically identical ? cells
* No ?
* ? get separated
* ** Generate 2 ? cells (46 chromosomes) with 46 chromatids **
* 2n & 2c
Oogenesis
Somatic cells
- pairs of homologous chromosomes (2n)
- each chromosome has one chromatid
Human body cells have 46 chromosomes or 23 pairs
Oogenesis Mitosis
* Part of cell cycle
* Two genetically identical daughter cells
* No crossing over
- chromatids get separated
** Generate 2 diploid cells (46 chromosomes) with 46 chromatids ** - 2n & 2c (46 chromosomes and 46 chromatids)
Meiosis
* Special form of cell division that ? chromosome
* Creates #? haploid daughter cells
* Each genetically distinct
* Crossing ? (? I)
- Before parturition, the fetus’ oogonia (2n) starts meiosis I – prophase I (duplication of DNA – 2n & 4C -> so 4 diploid chromosomes)
- Homologous chromosomes get separated
- Generate 2 haploid cells (23 chromosomes) but 46 chromatids
- N & 2C
- Before parturition, the fetus’ oogonia (2n) starts meiosis I – gets arrested in Prophase I (duplication of DNA – 2n & 4C)
- Chromatids get separated
- Generate 2 haploid cells (23 chromosomes) with 23 chromatids
*N & C
Meiosis
* Special form of cell division that reduces chromosome
* Creates 4 haploid daughter cells
* Each genetically distinct
* Crossing over (prophase I)
Fetal life
Ovum development in fetal life
- Primary germ cells originate near ? sac and migrate to the developing ? (genital ridge)
- Differentiate to oogonia and multiply by ?
- Oogonia: diploid cells (2N & 2C).
- Enter prophase of first meiotic division (primary oocytes) –
most mammals are born
Absence of
✔? determining factor
✔AMH - ?? what is this
✔ ?
? is required for genetic variation and continuity of all living organisms.
? = genetic variation doesn’t change
Fetal life
Ovum development in fetal life
- Primary germ cells originate near yolk sac and migrate to the developing ovary (genital ridge)
- Differentiate to oogonia and multiply by mitosis
- Oogonia: diploid cells (2N & 2C).
- Enter prophase of first meiotic division (primary oocytes) –
most mammals are born
Absence of
✔testes determining factor
✔AMH - what is this?
✔ testosterone
MEIOSIS is required for the genetic variation and continuity of all living organisms.
mitosis = genetic variation doesn’t change
Oocyte developmental events
- ** Most mammals are born with ? at the beginning of ? – Primary oocyte **
- Oocytes get arrested until puberty in ? (2N & 4C) 4 diploid chromosomes
Oocyte developmental events
- ** Most mammals are born with oogenesis at the beginning of Meiosis I – Primary oocyte **
- Oocytes get arrested until puberty in prophase I (2N & 4C) 4 diploid chromosomes
MEIOSIS
PROPHASE
* Homologous ? (“Chromosomal ?”)
- Not at random points: ? (chiasmata)
* Multiple crossovers occur per homologue ?
* Introduces variation into ? reproduction
Many genetically different ? cells are possible.
* Homologous pairs line up in random orientation
-> For each chromosome, it is ? as to whether the maternally or paternally derived chromosome goes to each daughter cell
-> For human, with 23 chromosome pairs, this allows over 8 ? variations (223)
- Add in recombination (“?”) and you have a virtually infinite number of genetically distinct gametes
MEIOSIS
PROPHASE
* Homologous recombination (“Chromosomal crossover”)
- Not at random points: chiasma (chiasmata)
* Multiple crossovers occur per homologue pair
* ** Introduces variation into sexual reproduction **
Many genetically different daughter cells are possible.
* Homologous pairs line up in random orientation
-> For each chromosome, it is random as to whether the maternally or paternally derived chromosome goes to each daughter cell
-> For human, with 23 chromosome pairs, this allows over 8 million variations (223)
- Add in recombination (“crossover”) and you have a virtually infinite number of genetically distinct gametes
POSTNATAL OOCYTE DEVELOPMENT
Primary oocyte (Meiosis I)
-> ? the DNA (Interphase) -
Chromosomal complement is #?N & #?C
-> ? (Prophase)
- Meiosis resumed at the ovulatory surge of ? (Puberty) *
- Meiosis I results in a ? oocyte (n & 2C) and a ? (will degenerate)
POSTNATAL OOCYTE DEVELOPMENT
Primary oocyte (Meiosis I)
-> duplicates the DNA (Interphase) -
Chromosomal complement is 2N & 4C
-> crossing over (Prophase)
- Meiosis resumed at the ovulatory surge of LH (Puberty) *
- Meiosis I results in a secondary oocyte (n & 2C) and a polar body (will degenerate)
Oocytes
Polar body
* Formed after ? divisions
* Important for ? the genetic material
* Embryo development requires the oocyte ?
-> Polar bodies ?
Oocytes
Polar body
* Formed after meiotic divisions
* Important for reducing the genetic material
* Embryo development requires the oocyte cytoplasm
-> Polar bodies degenerate
Postnatal oocyte development
Secondary oocyte (Meiosis II)
* The secondary oocyte is the cell that is formed by ? in oogenesis.
Thus, it has only #? of each pair of homologous chromosomes (after crossing over). However, each chromosome still has two chromatids, making a total of #?chromatids (2C).
* The secondary oocyte continues the second stage of meiosis (meiosis II), however, gets arrested at ?; until they meet the sperm in the fallopian tube.
- ? occurs during the second Meiotic division
- imp -> Meiosis II is completed at the time of ?.
- Results in an ? (n) and a polar body (will degenerate)
Postnatal oocyte development
Secondary oocyte (Meiosis II)
* The secondary oocyte is the cell that is formed by Meiosis I in oogenesis.
Thus, it has only 1 of each pair of homologous chromosomes (after crossing over). However, each chromosome still has two chromatids, making a total of 46 chromatids (2C).
* The secondary oocyte continues the second stage of meiosis (meiosis II), however, gets arrested at ?; until they meet the sperm in the fallopian tube.
- Ovulation occurs during the second Meiotic division
- imp -> Meiosis II is completed at the time of fertilization.
- Results in an Ovum (n) and a polar body (will degenerate)
Ovulation
- Release of the oocyte from the ?
- Oocyte and cumulus mass moved into the infundibulum of uterine tube by fimbria
- Meiosis continues to the second meiotic metaphase (blocked there unless fertilized)
- Fertilization occurs in * ? * of uterine tube
- long or short? window for fertilization (6-12 h)
Ovulation
- Release of the oocyte from the follicle
- Oocyte and cumulus mass moved into the infundibulum of uterine tube by fimbria
- Meiosis continues to the second meiotic metaphase (blocked there unless fertilized)
- Fertilization occurs in * ampulla * of the uterine tube
- short window for fertilization (6-12 h)
Male fetal life
✔? determining factor
- ? development (Sertoli cells)
✔?
Development of the Leydig cells – Testosterone – Male duct system
Male fetal life
- testes determining factor
-> testis developement (sertoli cells) - AMH
-> development of the leydig cells- testosterone - male duct system
Fetal life - MALE
Spermatogonium development in fetal life
- Primary germ cells originate near the ? sac and migrate to the developing ? (genital ridge)
- Differentiate to spermatogonium and multiply by ?
-> Diploid cells (2N) - Male mammals are born with ? that can undergo multiple mitosis
- ? determining factor
- ?
- ?
Fetal life
Spermatogonium development in fetal life
- Primary germ cells originate near the yolk sac and migrate to the developing ovary (genital ridge)
- Differentiate to spermatogonium and multiply by mitosis
-> Diploid cells (2N) - Male mammals are born with spermatogonium that can undergo multiple mitosis
- testis determining factor
- AMH
- testosterone
Sperm function requires development and maturation through the testis and epididymis
Overall #?ish days
Temperature
* Lower than ? temperature (34 °C/93 °F)
Hormone-dependent
* ?
- Spermatocytogenesis
-> Formation of spermatid from
? - Spermiogenesis
-> Morphological change of spermatid into ?
Sperm function requires development and maturation through the testis and epididymis
Overall 60ish days
Temperature
* Lower than body temperature (34 °C/93 °F)
Hormone-dependent
* testosterone
- Spermatocytogenesis
-> Formation of spermatid from
spermatogonia - Spermiogenesis
-> Morphological change of spermatid into spermatozoa
spermatogonia -> spermatid (cyto) -> spermatozoa
- Inside of the seminiferous tubules
- First haploid cell – ? spermatocyte
- ? is the last cell after cell Division
- Spermatids undergo morphological changes to become a ?
- Sertoli cells - a “?” cell of the testicles that is part of a ? tubule and helps in the process of spermatogenesis – produces ? and ?; Phagocytose residual cytoplasm
- Spermatogonium - ? male germ cell (2n)
- ? ? barrier (Lamina propria) - Prevents ? response to sperm
- ? cells - primary source of ? or androgens in males.
- Inside of the seminiferous tubules
- First haploid cell – secondary spermatocyte
- spermatid is the last cell after cell Division
- Spermatids undergo morphological changes to become a spermatozoa
- Sertoli cells - a “nurse” cell of the testicles that is part of a seminiferous tubule and helps in the process of spermatogenesis – produces inhibin and estradiol; Phagocytose residual cytoplasm
- Spermatogonium - undifferentiated male germ cell (2n)
- blood testis barrier (Lamina propria) - Prevents autoimmune response to sperm
- Leydig cells - primary source of testosterone or androgens in males.
Sperm cell
head: acrosome
miedpiece
tail
Spermatogenesis
Epididymis
- transit takes about #? weeks
- sperm acquire capability for ? and ?
- sperm are stored in ? of epididymis
PUBERTY
The acquisition of ? competence
* Production of ?
* ? behavior
* ** Ability to produce sufficient ? - ? **
* ? hypothalamic sensitivity to negative
feedback by ?/estradiol - FSH
- Onset of ? in females
- ? sperm in males
Spermatogenesis
Epididymis
- transit takes about 2 weeks
- sperm acquire capability for motility and fertilization
- sperm are stored in the tail of epididymis
PUBERTY
The acquisition of reproductive competence
* Production of gametes
* mating behavior
* ** Ability to produce sufficient GnRH - LH **
* Decreased hypothalamic sensitivity to negative feedback by testosterone/estradiol - FSH
- Onset of cyclicity in females
- mature sperm in males
Puberty
What mediates puberty?
? maturation – ? secretion/synthesis
- There is no “? immaturity” of
- ?
- ?
- Animals may be forced to ovulate by appropriate stimulation of prepubertal ?
- Pituitary transplants (!!) in mice prove that prepubertal pituitary can drive cyclicity when transferred to ? recipient
Puberty
What mediates puberty?
Hypothalamus maturation – GnRH secretion/synthesis
- There is no “intrinsic immaturity” of
- Gonads
- Pituitary
- Animals may be forced to ovulate by appropriate stimulation of prepubertal ovaries
- Pituitary transplants (!!) in mice prove that prepubertal pituitary can drive cyclicity when transferred to adult recipient
Frequency of LH pulses in heifers prior to the onset of puberty. Note the substantial time needed for the pulse frequency to become high enough for puberty to be achieved. The variation in LH pulse frequency after puberty reflects cycle.
