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Gender Determination in Humans

Gender Determination in Humans

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Gender Determination in Humans

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  1. Gender Determination in Humans BC Science Probe 9 Section 4.4 Pages 123-126

  2. The Human Karyotype • The arrangement of an organism’s chromosomes from one body cell is called a karyotype.

  3. The Human Karyotype • Scientists construct karyotypes by taking pictures of condensed chromosomes during metaphase, then cutting them out and arranging them.

  4. The Human Karyotype • This human karyotype has 23 pairs or 46 chromosomes.

  5. Sex Chromosomes • There is one pair of chromosomes that determine the gender of the individual. • These are called sex chromosomes.

  6. Sex Chromosomes • Both the primary and secondary sex characteristics are controlled by the 2 sex chromosomes.

  7. Sex Chromosomes • The 2 sex chromosomes are the X and the Y. • The X is the larger one. • The Y is the smaller one.

  8. Sex Chromosomes • Females have 2 X chromosomes. • Males have 1 X and 1 Y chromosome.

  9. Sex Chromosomes • The gametes that are produced during meiosis each get one sex chromosome from the parent. • All of the female’s eggs will have X’s • ½ of the male’s sperm will have X’s, the other ½ will have Y’s.

  10. Male Zygotes or Female Zygotes • Male or female all depends on which sperm fertilizes the egg. • Since all the eggs have a single X chromosome, it depends on whether it’s a sperm cell with an X or a Y that fertilizes it.

  11. Male Zygotes of Female Zygotes

  12. Male Zygotes or Female Zygotes • ½ the sperm produce male offspring • ½ produce female offspring • This means that there is a 50% chance that the child will be male and a 50% chance that the child will be female. • Gender is determined by the father.

  13. Sex-linked Characteristics • There are some traits that are more common in men than in women. • This is because the X and Y chromosomes are not homologous (they do not carry matching genes).

  14. Sex-linked Characteristics • Females get 23 pairs of homologs because of the 2 X’s. • The smaller Y that the males get are missing some information.

  15. Sex-linked Characteristics • Certain traits are controlled by the genes on the X-chromosome. • These are known as sex-linked characteristics. • They occur more frequently in males than in females.

  16. Sex-linked Characteristics • Examples: • Red-green colour blindness

  17. Sex-linked Characteristics • Examples: • baldness

  18. Sex-linked Characteristics • Examples: • hemophilia