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Human Genetics and Sex-Linked Traits

Human Genetics and Sex-Linked Traits. Human Chromosomes. Humans have 46 (23 pairs) of chromosomes These 46 chromosomes contain over 100,000 genes Human chromosomes come in homologous pairs – one from mom, one from dad – they are similar in size, shape and the genes they contain.

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Human Genetics and Sex-Linked Traits

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  1. Human Genetics and Sex-Linked Traits

  2. Human Chromosomes • Humans have 46 (23 pairs) of chromosomes • These 46 chromosomes contain over 100,000 genes • Human chromosomes come in homologous pairs – one from mom, one from dad – they are similar in size, shape and the genes they contain

  3. Determination of Gender • Sex chromosomes are the only pair of chromosomes in which the members of a pair do not always match together • Sex chromosomes = X and Y • All other chromosomes = autosomes • The presence of the Y chromosome determines “maleness”

  4. Turner Syndrome • One X chromosome, no other sex chromosome • Individuals with Turner Syndrome are physically female but never develop physically past childhood

  5. Klinefelter Syndrome Other Sex Chromosome abnormalities XXX XXXX XYY – 1/1000 male births; XXYY • XXY • Less facial and body hair • Usually less muscular due to less testosterone being produced • Usually infertility is a symptom

  6. Sex – Linked Traits • The X chromosome is large and carries many genes • The Y chromosome is small with few genes • If an allele is on an X chromosome and not the Y, then a man will express that allele – regardless of whether it is dominant or recessive

  7. Sex – Linked Traits Colorblindness Hemophilia Hemophilia is a blood clotting disorder where the blood does not clot (at all) 1/10,000 men 1/100,000,000 women • XC = color vision • Xc = color blind • In females: • XCXC = Normal vision • XCXc = normal vision (carrier) • XcXc = color blind • In Males: • XCY = normal vision • XcY = color blind

  8. Muscular Dystrophy • A disorder in which the muscles degenerate over time • Caused by a problem with a gene that codes for a certain muscle protein • Located on the X chromosome

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