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Human Heredity

Human Heredity. There are traits that are controlled by one gene with 2 alleles. Often, one is dominant and the other is recessive Example: widow’s peaks and dimples. Some traits are controlled by a gene with multiple alleles – 3 or more for a single trait.

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Human Heredity

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  1. Human Heredity

  2. There are traits that are controlled by one gene with 2 alleles. Often, one is dominant and the other is recessive • Example: widow’s peaks and dimples.

  3. Some traits are controlled by a gene with multiple alleles – 3 or more for a single trait. For example: blood types and skin color in humans.

  4. There are 44 chromosomes that we call autosomal chromosomes. • However, there are 2 chromosomes that determine our sex and we call them sex chromosomes. • These 46 chromosomes all carrier genes on them that determine our traits.

  5. Out of our 23 pairs of chromosomes, 1 pair is the sex chromosomes (X and Y). • Female = XX • Male = XY

  6. Question: What is the probability that your parents will have a boy or girl? • XY (dad) x XX (mom) Y X Phenotype: 50% boy 50% girl X XX XY Genotype: 50% XX 50% XY X XX XY

  7. Question? If my parents have 5 boys in a row, what is the chance they will have a girl the next time? 50%

  8. Sex-linked gene: • Some traits are carried on the sex chromosomes. Genes on the X or Y chromosomes are sex-linked genes. • These traits are passes on from parent to child. Sex- linked genes can be recessive or dominant. • MALES are more likely to have a sex-linked trait because they only have ONE X and Y. The allele is USUALLY on the X chromosome. • Ex. colorblindness, hemophilia, hairy ears, muscular dystrophy

  9. Are you colorblind? What numbers do you see?

  10. Carrier – person who has one recessive allele and one dominant allele for a trait or heterozygous for that trait (only women can be carriers). Example Hemophiliac carrier XHXh Colorblind carrier XBXb

  11. Sex linked Punnett Squares: Question: What is the probability that a carrier female and a colorblind male will have a girl who is colorblind (b = colorblind, B = normal)? Xb Y Phenotype: 25% normal boy 25% colorblind boy 25% normal girl 25% colorblind girl XBXb XBY XB Xb XbXb XbY

  12. Try this one on your own Question: What is the probability that a homozygous (normal vision) female and a colorblind male will have a girl who is colorblind (b = colorblind, B = normal)?

  13. Parents: XBXB x XbY Xb Y Phenotype: 50% normal girls 50% normal boys XBXb XBY XB XB XBXb XBY

  14. ?

  15. Pedigree • Simply a family tree describing the interrelationships of parents and children across the generations • Males – square • Females – circle • Past and future • Genotype and phenotype • Sex-linked or autosomal

  16. Carriers do not show that particular trait phenotypically but have a chance to pass the trait on to their child. Carrier – half colored

  17. Reading a Pedigree Task 1: Genotyping a pedigree chart • Task 2: • Take out your pedigree sheet. • Lets do the first one together. • Do # 2.

  18. Sex-linked-Practice on your own: • What is the probability of a female carrier of hemophilia and a normal male having a boy with hemophilia (X-linked recessive)? • What is the probability of a man with hairy ears and a woman having a son with hairy ears (Y-linked recessive)? • What is the probability of a carrier woman and a male with muscular dystrophy having a girl with muscular dystrophy (X-linked recessive)?

  19. Genetic Engineering

  20. Cloning – Ch. 13 • Donor cell taken from original animal • Fused with egg cell with no nucleus • Fused with electric shock • Dolly • First mammal cloned • Offspring genetically IDENTICAL to parent/donor

  21. CC (Copy Cat) • http://www.msnbc.msn.com/id/3076908/

  22. DNA Fingerprinting • Analyze sections of DNA that have little or no known function • Sections that vary widely from one individual to another • Positive ID has similar marker to mother AND father • Remember you get your chromosomes from both your mom AND your dad

  23. Uses gel electrophoresis – gel setup between two poles; positive charge on one end and negative on the other • Amino acids have different charges and travel along the gel depending on that charge • Figure 14-18: which suspect matches the evidence?

  24. Human Genome Project • Scientists working on full set of chromosomes/DNA sequence of humans • Look at haploid set of chromosomes • Human genome - ~3 billion base pairs

  25. Stem Cells • Unspecialized cells with the potential to become a variety of cells • Taken from embryos • Moral and ethical objections • Immune system may reject stem cells • Mouse cells to date

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