2. Gametogenesis Flashcards
What are gametes?
Haploid sex cells. (Eggs and sperm)
What are the stages of gametogenesis?
- The extraembryonic origin of the germ cells (primordial germ cells) and their migration to the gonads.
- Increase in # of germ cells by mitosis.
- A reduction in chromosomal # by meiosis.
- Structural & functional maturation of the eggs and sperms.
The first stage of gametogenesis is ………. In males and females. Whereas they differ in the…………?
In the first stage…(primordial germ cells & migration) they are identical. They differ in the last 3 stages, mitosis, meiosis, and the structure & function.
In phase 1 of gametogenesis, the primordial germ cells migrate to?
The gonads.
What are the carriers of genetic material?
Chromosomes
Humans have approximately …… genes? And how many chromosomes?
35,000 genes and 46 chromosomes
22 pairs of chromosomes are called? And how many pairs of sex chromosomes?
Autosomes.
1 pair of sex chromosomes
One chromosomes of EACH pair is derived from?
A maternal gamete (oocyte) and a paternal gamete (sperm)
T or F?
Each gamete contains haploid number of 23 chromosomes.
True.
What happens to each chromosome before mitosis?
DNA replication
What is a diploid progeny?
Each daughter cell receives the complete complement of 46 chromosomes. DIPLOID
T of F? explain why?
The pattern of mitotic divisions differ from male and female germ cells.
True. For males, happens after puberty, for females, before birth ( 5 days after conception)
What is the longest phase of mitosis?
Prophase ( where duplication and condensation happens)
What is meiosis?
Cell division that takes place in germ cells to generate male and female gametes.
T or F?
It requires 1 cell division to reduce the number of chromosomes to the haploid number of 23?
False. It requires 2 cell devision to produce 4 haploid daughter cells.
Is the homologous pair of chromosomes in meiosis 1 haploid or diploid?
Haploid but they structurally haven’t separated yet.
Meiosis 2 then separate sister chromatids, where each gamete contains 23 chromosomes.
:)
What is a crossover?
Crossover are critical events in mitosis 1. It is the interchange of chromatid segments between paired homologous chromosomes.
How is genetic variability enhanced?
Through random distribution and random crossover.
What happens after meiosis for an oocyte?
1 primary oocyte gives rise to four daughter cells. Only one develops into a mature gamete and the other 3 are polar bodies. All are (22+ X)
What happens after meiosis of a spermatocyte?
Gives 4 spermatids ( all are mature gametes ) 2 are 22 + X / 2 are 22+ Y
of germ cells peak from the …… to the ……. Month of pregnancy?
Second to fifth month.
What is atresia?
Is is where Numerous ooginia undergo programmed degeneration until menopause.
T or F?
Spermatogonia maintain the ability to divide throughout postnatal life?
True.
Atretic follicles are the highest during?
- prepubertal
- adult
- post menopausal
Post menopausal
Does the prepubertal phase have growing and ovulated follicles?
No.
what phase has the most follicular pool?
Prepubertal
What happens After oogonia undergoes mitotic divisions.
It is arranged in clusters surrounded by a layer of flat epithelium.
Primary oocytes together with flat epithelial cells is called a?
A primordial follicle.
At birth, all primary oocytes are arrested in…? And they enter ……….. stage until puberty
Prophase 1. Diplotene stage .
Most oocytes become …………. During childhood (before puberty)
Atretic. (To die off)
Secondary oocyte is arrested at……………….. until fertilization?
Metaphase 2
Each month 15 to 20 follicles begin to mature and pass through 3 stages which are?
- Primary ( preantral)
- Secondary (antral)
- Preovulatory (graafian follicle)
The primary oocyte grows, Making the surrounding follicular cells to change from flat to?
Cuboidal to produce stratified epithelium of granulosa cells.
