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Gemma Natori

on 26 April 2010

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Transcript of Reproduction

Spermatogenisis Spermatogonium Spermatogonia Primary Spermatocyte Secondary Spermatocyte Spermatids Spermatozoa Found at or near the basement membrane High rate of cell division by MITOSIS to produce spermatogonia Mitosis Cell Growth Grows to form Primary Spermatocyte (Completed S-Phase) Cell Cycle Prophase, Metaphase, Anaphase, Telophase Spindle microtubules grow Chromosomes become shorter and fatter by supercoiling PROPHASE Spindle fibers extend from each pole to the equator METAPHASE Nuclear membrane breaks down Chromosomes move to the equator Spindle fibres attach to each centromere on opposite sides ANAPHASE Centromes divide and chromatids become chromosomes Spindle fibers pull the genetically identical chromosomes to opposite sides TELOPHASE All chromosomes reach poles and nuclear membranes form around them Spindle microtubules break down Chromosomes uncoil Cell divides (cytokinosis) to form two cells genetically identical Meiosis 1 Reduce chromosome number by half from diploid (2n) to a haploid (n) Increases genetic diversity PROPHASE 1 Chromosomes coil up
Homologous chromosomes pair up Corssing over occurs Centrioles move to poles Nucleoli break down METAPHASE 1 Chromosomes continue to shorten Spindle microtubules attach to centromeres ANAPHASE 1 The two homologous chromosome pairs move to opposite poles TELOPHASE 1 Nuclear membrane form around the chromosomes at each pole Cell divides to form two haploid cells Meiosis 2 PROPHASE 2 Chromosomes become shorter Centrioles move to poles Nuclear membrane breaks down METAPHASE 2 Spindle fibers attach to centromeres Chromosomes line up on equator Centromeres divide ANAPHASE 2 Chromatids of each chromosome moves to opposite poles Two cells divide into four cells in total Chromosomes uncoil Nucleoli appears Develops into gamete TELOPHASE 2 Nuclear membrane form around chromatids at each pole Cell differentiation CROSSING OVER Context Prophase 1 of Meiosis Homologous chromosomes pair up Sections of chromatid are exchanged Two homologous chromosomes become tightly paired up together. This is called synapsis
The DNA molecule of one of the chromatid is cut. A second cut is made at exactly the same point in the DNA of a non-sister chromatid
The DNA of each chromatid is joined up to the DNA of the non-sister chromatid. Swap section of DNA between the chromatids
Homologous chromosomes become loose. Sister chromatids remain tightly connected
Crossing-over creates an X-shaped structure called a chiasma. PROCESS The spermatids are found in association with the sertoli cells which nourish the spermatids as they differentiate into spermatozoa. Testosterone Follicle-stimulating hormone (FSH) Interstitial cells Pituitary Luteinizing hormone (LH) Testosterone Testes produce testosterone Role of Testosterone
develops male genitalia in fetus
rising testosterone levels in puberty cause male secondary sexual characteristics to develop
during adulthood, maintains sex drive
stimulates sperm production Female Sex Hormones Follicle Stimulating Hormone (FSH)
development of follicles
Luteinizing Hormone (LH)
follicles to become mature
release egg (ovulation)
develop into corpus luteum Female Sex Hormones Menstrual Cycle
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