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4.4 Gender Determination in Humans. Human Karyotype. During Mitosis, chromosomes look shorter & thicker (easier to see during cell division) Scientists use a microscope to take pictures of condensed chromosomes during metaphase. Human Karyotype.
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Human Karyotype • During Mitosis, chromosomes look shorter & thicker (easier to see during cell division) • Scientists use a microscope to take pictures of condensed chromosomes during metaphase.
Human Karyotype • Individual chromosomes can be cut out and homologous pairs matched by shape and size • This arrangement of an organisms chromosomes from one body cell is called the karyotype The human karyotype has 23 pairs or 46 chromosomes
Sex Chromosomes • One pair of chromosomes in the human karyotype has different sizes • These are the sex determining chromosomes • Both primary & secondary sexual characteristics in humans are controled by the two sex chromosomes ... • ... The X and Y chromosomes
Sex Determining Chromosomes See Fig. 2 Pg. 124 for X & Y Chromosomes at 35 000 x Larger X Smaller Y http://homepages.uel.ac.uk/V.K.Sieber/human.htm
Gender Determination See Figure 3, pg. 124 Females: X X chromosomes • Eggs contains one X chromosome • Meiosis produces: • one large haploid egg cell contain 23 pairs of chromosomes and most of the cytoplasm • Three tiny cells containing haploid nuclei which eventually disintegrate
Gender Determination See Figure 3, pg. 124 Males:X Y chromosomes • Sperm contain one X and one Y • Meiosis produces: • Four haploid sperm cells • contain 23 pairs of chromosomes