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Transcript
11/20/2013 Genetics Unit A pedigree is a chart that shows which members of a family have a certain trait. Male without the trait Male with the trait Female without the trait I. 1 2 3 4 Female with the trait II. 1 2 3 4 5 6 7 III. 1 2 Examples of connected symbols: Marriage Female (mom) Children Fraternal twins Identical twins Male (dad) Offspring Female (mom) Male (dad) Offspring 1 11/20/2013 A and B are grandparents. Who are their children? What is the sex of their children? Do their children have the trait? KEY 1 2 Normal male Affected male 3 4 5 6 Normal female A B C D E F G H Affected female 7 If 8 9 10 11 12 a trait is DOMINANT Disorder: Achondroplasia A = trait a = no trait Cause: mutation in FGFR3 gene for protein receptor on cells Symptoms: limited height, disproportionately short arms and legs, large head due to improper function of protein involved in signaling to regulate bone growth Location: Chromosome 4 If I a trait is RECESSIVE A = no trait a = trait Achondroplasia (dwarfism) is a dominant disorder What would the pedigree of the family be? Roloff Family Pedigree 2 11/20/2013 THIS is WHY dwarfs can have NORMAL sized children…EVEN twins What would be the genotype for each individual in this family? aa Describe the family in words Aa Aa Aa or AA aa aa What would the genotypes be if the trait is dominant? A= B= C= D= B A C A B C D D What would the genotypes be if the trait is dominant? A= aa B= aa C= Aa D=aa What would the genotypes be if the trait is recessive? A= B= C= D= A B A B C D C D 3 11/20/2013 What would the genotypes be if the trait is recessive? A= Aa B= Aa C= aa D= Aa Can this be a dominant trait, a recessive trait, or both? CAN “aa” have a child that is “Aa” or “AA” A B A B C D C D Can this be a dominant trait, a recessive trait, or both? RECESSIVE!! A Dominant or Recessive? A B C D B Dominant 4 11/20/2013 Dominant or Recessive? Recessive Classify pedigrees as autosomal dominant, autosomal recessive, or sex-linked Males: XY Females: XX 5 11/20/2013 1/10 males in the US cannot see the 16 females cannot see the 16 1/100 WHY THE DIFFERENCE? Disorder: colorblindness Deleted genetic material in the gene opsin 1 medium-wave-sensitive (OPN1MW) that codes for the green color receptors (cones) Location: X chromosome Cause: Sex-linked genes are genes that are located on the X-chromosome The human Y chromosome is much smaller than the X chromosome and appears to contain only a few genes. 6 11/20/2013 Males have just one X chromosome. Thus, all X (sex-linked) alleles are expressed in males, even if they are recessive. Colorblindness is a sex-linked trait. A colorblind man (XcY) marries a woman who is heterozygous for colorblindness (XCXc). Which of the following could NOT be a genotype of their offspring? XcY XCXc XCXC XCY In chickens, a dominant gene (F) on the X chromosome results in silver feathers. Its recessive allele (f) results in gold feathers. What are the 2 possible F1 generations that would result from a cross between a golden rooster and a silver hen? (Hint: 2 possible genotypes for a silver hen) Disorder: hemophilia lack of blood clotting. No proteins produced to properly clot simple cuts Locations: X chromosome Symptoms: Husband Husband They They was Albert (normal XY) had 9 kids. Leopold was the only child with hemophilia, why? Daughter: Beatrice was a carrier Daughter: Alice is a carrier as well. She married Louis of Hesse. **Focus** Louis of Hesse had 6 kids Daughter: Irene was a carrier Son: Fred HAD hemophilia and died Daughter: Alix is a carrier. She married Nikolas II of Russia ** 7 11/20/2013 Husband: Nickolas II of Russia had 5 kids 4 girls and 1 boy Son: Alexis has hemophilia but was executed at the age of 14 along with the rest of his family. They Grand Duchess Anastasia, Nickolas II youngest daughter was believed to never have been executed. Her body had never been recovered, and who was believed by some to have managed to survive the revolution Royalty of Great Britain Future King of England (no hemophilia) 8 11/20/2013 Pedigrees are family trees that explain your genetic history. Pedigrees are used to find out the probability of a child having a disorder in a particular family. To begin to interpret a pedigree, determine if the disease or condition is autosomal or Xlinked and dominant or recessive. A man and woman marry. They have five children, 2 girls and 3 boys. The mother is a carrier of hemophilia, an X-linked disorder. She passes the gene on to two of the boys who died in childhood and one of the daughters is also a carrier. Both daughters marry men without hemophilia and have 3 children (2 boys and a girl). Create a pedigree for the family describe. (Be sure to shade individuals affected with hemophilia) Determine the genotypes of the family members. List the genotypes on your pedigree. What is the chance the carrier daughter will have a son with hemophilia? 9