Meiosis and Mitosis Flashcards
Look at the diagram of the testis
..
Spermatogenesis the hormones
- Hypothalamus secretes GnRH
- this stimulates the A.pit to secrete FSH and LH
- in the testes then…
- the leydig cells secrete testosterone
- and the sertoli cells carry out spermatogenesis
Meiosis- Prophase I
Homologus chromosomes appear, each made of 2 chromatids joined at the centromere
Meiosis- Metaphase I
Spindle forms and homologous pairs of chromosomes line up on the metaphase plane
Meiosis- Anaphase I
No centromere split, homologous pairs are pulled to opposite ends of the cell
Meiosis- Telophase I
Nuclear membrane reforms around the 2 haploid nuclei
Meiosis - Prophase II
- nuclear membrane starts to break down again
- the chromatids are still joined by the centromeres
- no DNA replication, no crossing over
Meiosis - Metaphase II
New spindles form and pairs of chromatids line up on metaphase plane
Meiosis - Anaphase II
Centromeres divide and the chromatids are pulled to opposite ends of the cell
Meiosis - Telophase II
nuclear envelope reforms and chromosomes uncondensed giving 4 haploid nuclei
-once the nuclear division is complete cytogenesis completes the division process to give 4 haploid nuclei
Mitosis- Interphase
Chromosomes duplicate, the copies remain attached to one another
Mitosis - Prophase
in the nucleus the chromosomes condense and become visible
spindle forms in the cytoplasm
when does the nuclear envelope break down during mitosis?
prophase, after the chromosomes have condensed
Mitosis - Metaphase
the chromosomes are aligned in the middle of the spindle
Mitosis - Anaphase
Chromosomes separate into 2 genetically identical groups and move to opposite ends of the spindle
Mitosis - Telophase
Nuclear membranes form around the 2 sets of chromosomes which then begin to spread out and the spindle begins to break down.
how many pairs of chromosomes do humans have?
23 pairs
when does crossing over occur in meiosis?
Prophase I
Spermatogenesis
- Primordial germ cell
- enters testes - spermatogonia
- spermatogonia proliferate by mitts division inside testis
- primary spermatocyte
- meitotic division I
- secondary spermatocytes
- meitotis division II
- Spermatids. differentiate into mature sperm
How long does it take to produce a mature germ cell?
75 days
and 21 days to transport that sperm to the t sack bit
How do low levels of FSH affect spermatogenisis
sperm levels can continue
How do low levels of testosterone affect spermatogenesis?
required absolutely for spermatogenesis
what does androgen binding protein do during spermatogenesis?
- produced by the sertoli cells
- ensures that the concentration of testosterone in the testes is high enough to maintain spermatogenesis.
what does mitosis produce?
2 identical daughter cells - diploid
