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Human Heredity

Human Heredity. 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 carry genes on them that determine our traits.

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Human Heredity

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  1. Human Heredity

  2. 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 carry genes on them that determine our traits.

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

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

  5. 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

  6. 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 passed 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

  7. 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

  8. 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

  9. 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)?

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

  11. Genetics Disorders and Mutations

  12. Mutations … • are changes in the genetic material • can be good or bad • can be on a single gene or the whole chromosome

  13. Genetic Disorder – abnormal condition that a person inherits through genes or chromosomes. They are caused by mutations or changes in a person’s DNA. Write down 3 disorders that have affected someone you know.

  14. Cystic Fibrosis • Genetic disorder where the body produces abnormally thick mucus in the lungs and intestines making respiration and digestion difficult • caused by a mutation in a gene. The product of this gene is a chloride ion channel important in creating sweat, digestive juices and mucus. • One in four babies are born with cystic fibrosis • Most common among Northern European descent

  15. Sickle Cell Anemia • Sickle cell is a genetic disorder that affects the blood’s hemoglobin. Hemoglobin is the protein in your blood that carries oxygen. • Sickle-cell anemia is caused by a point mutation in protein chain of hemoglobin, replacing the amino acid glutamic acid with the amino acid valine • The ‘sickle shape’ of the cell doesn’t allow the red blood cell to carry very much oxygen. • Most common among African American descent Famous People with Sickle Cell Disease Miles Davis, jazz musician. Paul Williams, singer (The Temptations) Georgeanna Tillman, singer (The Marvelettes) Tionne "T-Boz" Watkins, singer (TLC)

  16. Hemophilia • Hemophilia is a genetic disorder in which a person’s blood clots VERY slowly or not at all. • A person with hemophilia can bleed to death from a paper cut or scrape. • This is sex-linked disorder on the X chromosome. • Queen Elizabeth suffered from this disorder. This man received a vaccine. This is what having hemophilia did to is body.

  17. Down Syndrome • Down Syndrome is a genetic disorder that occurs when an individual receives an extra copy of a chromosome. • A mistake occurs during Meiosis I: the chromosomes failed to separate correctly (non-disjunction) therefore leaving an extra copy of chromosome #21.

  18. Doctor’s use tools like amniocentesis and karyotypes to helpdetect most diseases.

  19. What is a karyotype? • Picture of your chromosomes • Arranged from largest to smallest • quickly identify chromosomal changes

  20. 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? • What is the probability of a man with hairy ears and a normal female (not a carrier) having a child with hairy ears? • What is the probability of a carrier woman and a male with muscular dystrophy having a girl with muscular dystrophy?

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