Module 10 human heredity

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  • You must learn the symbols of the pedigree charts before you can start to learn how to interpret it. These are the symbols that represent a male and a female.
  • These symbols also represent relationships between people. some may have to each other.
  • These are examples of different types of symbols. These symbols would be the same for males or for females, except for X-linked carrier which is only used for females. So an affected male would be a square that is filled in completely. A deceased female would be a circle with a diagonal slash.
  • Module 10 human heredity

    1. 1. Human Heredity
    2. 2. Chromosomes <ul><li>Every human cell has 46 chromosomes (23 pairs of chromosomes) </li></ul><ul><li>A karyotype is a picture of the 23 pairs of chromosomes. </li></ul>
    3. 3. Examples of Karyotypes Autosomes are the first 22 pairs of chromosomes (#1-#22) Sex Chromosomes determine the sex and are pair #23 XX-female XY-male Female (XX) Male (XY) <ul><li>Muskopf, Shannan. Online Images. The Biology Corner . 8 May 2007. http://www.biologycorner.com/bio1/celldivision-chromosomes.html </li></ul>
    4. 4. Pedigree Charts-shows genetic history of a family over many generations <ul><li>Muskopf, Shannan. Online Images. The Biology Corner . 8 May 2007. http://www.biologycorner.com/bio2/humangenetics.html </li></ul>Generation I Generation II Generation III
    5. 5. Symbols in a Pedigree Chart <ul><li>Female </li></ul><ul><li>Male </li></ul>
    6. 6. <ul><li>Married Couple </li></ul><ul><ul><li>horizontal line connects a married couple </li></ul></ul><ul><li>Siblings </li></ul>
    7. 7. <ul><li>Shaded: individual has the trait </li></ul><ul><li>Not shaded: does not have the trait </li></ul><ul><li>Half-shaded: carries the trait (heterozygous) </li></ul>
    8. 8. Pedigree Chart of a Dominant Trait <ul><li>Huntingtons disease is a dominant disease that damages the nervous system </li></ul><ul><li>One dominant allele means you get the disease </li></ul><ul><li>HH (homozygous) and Hh (heterozygous) will have the disease </li></ul><ul><li>hh (homozygous) will not have the disease </li></ul><ul><li>One parent has to have it to pass on to child </li></ul>What is the genotype of the father? What is the genotype of the son?
    9. 9. Pedigree Chart of a Dominant Trait The father does not have the dominant disease so he must have 2 recessive alleles; his genotype is hh The son has the dominant disease so he has to have at least one dominant allele. Is his genotype HH or Hh? One allele came from his father so his genotype is Hh.
    10. 10. Pedigree Chart of a Dominant Trait hh HH Hh What are the chances that future offspring of this couple will have this dominant disease? Use the genotypes of the parents to draw a punnett square.
    11. 11. Pedigree Chart of a Dominant Trait hh HH Hh All of the offspring have the dominant allele so 100% of their future children will have this dominant disease. H H h Hh Hh h Hh Hh
    12. 12. Pedigree Chart of a Recessive Trait <ul><li>Cystic fibrosis is a recessive disease causing digestive problems </li></ul><ul><li>HH (homozygous) and Hh (heterozygous) will NOT have the disease </li></ul><ul><li>hh (homozygous) will have the disease </li></ul><ul><li>Must inherit recessive allele from each parent to have the disease </li></ul>What is the genotype of the father? What is the genotype of the daughter?
    13. 13. Pedigree Chart of a Recessive Trait She must have 2 recessive alleles to have this disease. Her genotype is cc. The dad does not have this recessive disease so his genotype is either CC or Cc. Since he passed on one recessive allele to his daughter, his genotype is Cc.
    14. 14. Pedigree Chart of a Recessive Trait What are the chances that future offspring of this couple will have this recessive disease? Use the genotypes of the parents to draw a punnett square. Cc Cc cc
    15. 15. Pedigree Chart of a Recessive Trait Cc Cc cc C c C CC Cc c Cc cc Only 1 out of 4 offspring have the recessive disease (cc). There is a 25% chance of future offspring having the disease.
    16. 16. Sex-Linked Traits (X-linked) <ul><li>Sex-linked genes are located on the sex chromosomes (23 rd pair) and deal with the X and Y chromosome </li></ul><ul><li>A female is XX; a male is XY </li></ul><ul><li>Sex-linked genes are shown as superscripts on the X chromosome </li></ul>
    17. 17. Sex-Linked Traits in females <ul><li>If a disorder is caused by a recessive gene, a female’s genotype could be X B X B or X B X b and she will not have the disorder. The X B X b female would be a carrier. </li></ul><ul><li>A female with a sex linked disorder would be written as X b X b because she must have both recessive alleles. </li></ul>
    18. 18. Sex-Linked Traits in males <ul><li>The Y chromosome does NOT carry a gene. A male without the recessive sex-linked disorder would be X B Y. A male with the sex-linked disorder would be X b Y. </li></ul><ul><li>Sex-linked disorders are more common in males because males only need 1 copy of the recessive allele since they have only 1 X chromosome. Females must have 2 copies of the recessive allele since they have 2 X chromosomes. </li></ul><ul><li>Common sex-linked disorders include color blindness and hemophilia (a bleeding disorder) </li></ul>
    19. 19. Sex-linked pedigree for color blindness What is this male’s genotype? Colorblindness is a recessive sex-linked disorder This is a male so his sex chromosome is XY The square is shaded so this male is colorblind His genotype is X b Y (Remember, there are no superscripts on the Y chromosome) <ul><li>Muskopf, Shannan. Online Images. The Biology Corner . 8 May 2007. http://www.biologycorner.com/bio4/notes/inheritance3.html </li></ul>
    20. 20. Sex-linked pedigree for color blindness What is this male’s genotype? This is a male so his sex chromosome is XY The square is not shaded so this male has normal vision His genotype is X B Y <ul><li>Muskopf, Shannan. Online Images. The Biology Corner . 8 May 2007. http://www.biologycorner.com/bio4/notes/inheritance3.html </li></ul>
    21. 21. Sex-linked pedigree for color blindness What is this female’s genotype? This is a female so her sex chromosome is XX This female is not colorblind so her genotype is either X B X B or X B X b Her son is shaded so he is colorblind (X b Y) and inherited the Y chromosome from his father and the X b chromosome from his mother. The mother has to have a X b in her genotype Her genotype is X B X b <ul><li>Muskopf, Shannan. Online Images. The Biology Corner . 8 May 2007. http://www.biologycorner.com/bio4/notes/inheritance3.html </li></ul>
    22. 22. Practice What percentages can be expected in the offspring of a cross between a female carrier for color blindness and a male with a normal color vision? Show your work with a punnett square.
    23. 23. Practice What percentages can be expected in the offspring of a cross between a female carrier for color blindness and a male with a normal color vision? Color blindness is a recessive trait attached to the X chromosome. A female carrier means heterozygous. female carrier X B X b male with normal vision X B Y X B X b Y X B Y X b Y X B X B X B X B X b 25% colorblind males 25% carrier females 25% normal males 25% normal females
    24. 24. <ul><li>Karyotypes are used to determine if an offspring has the right number of chromosomes (46 in humans) </li></ul><ul><li>Down Syndrome </li></ul><ul><ul><li>47 chromosomes because there are 3 copies of chromosome #21 </li></ul></ul><ul><ul><li>Causes mental retardation </li></ul></ul>3 copies of #21 <ul><li>Muskopf, Shannan. Online Images. The Biology Corner . 8 May 2007. http://www.biologycorner.com/bio1/celldivision-chromosomes.html </li></ul>
    25. 25. <ul><li>Amniocentesis-during pregnancy, a small amount of fluid from the sac surrounding the embryo is used to make a karyotype to determine if the fetus has the correct number of chromosomes </li></ul>Diagnosis of Chromosomal Abnormality

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