Transcript Pedigrees
What is a pedigree? Pedigree: family history - shows how a trait is passed on through generations a graphic representation of a family tree Pedigree can tell you if a trait is passed on genetically and if the alleles are dominant or recessive How do you read a Pedigree? Generation Generation And Individual (III-1) Individual Analyze the Pedigrees In your group, analyze the 4 pedigrees in your IN Who’s affected? Every generation affected? How many males/females affected? Are there any carriers? Is the trait dominant or recessive? What are the four types of pedigrees? AUTOSOMAL DOMINANT ***Found in genes on chromosomes 1-22*** Who will express the trait more often... Males or Females? They are equally likely to have the trait Does the trait occur every generation or skip generations? Occurs every generation Which genotypes express the trait? Homozygous Dominant or Heterozygous AUTOSOMAL DOMINANT What’s the genotype for: • Individual I-1 aa •Individual I-2 Aa ***Use A or a for alleles*** •Individual II-7 Aa Autosomal Dominant Disorder Neurofibromatosis AUTOSOMAL RECESSIVE ***Found in genes on chromosomes 1-22*** Who will express the trait more often... Males or Females? They are equally likely to have the trait Does the trait occur every generation or skip generations? Skips generations Which genotypes express the trait? Homozygous Recessive If parents without the trait have children with the trait, what must be the genotype of both parents? Heterozygous If a Parent has the trait, their offspring who do not have the trait must have what genotype? Heterozygous AUTOSOMAL RECESSIVE What’s the genotype for: Individual I-2 Aa Individual II-3 aa ***Use A or a for alleles*** Individual III-2 AA or Aa Autosomal Recessive Disorder Albinism SEX-LINKED DOMINANT ***Found in genes on the X chromosome*** Will all daughters of males with the trait inherit the trait? YES!...Why? Can males pass the trait on to their sons? NO! Will all daughters and sons of females with the trait inherit the trait? Depends on the mother’s genotype SEX-LINKED DOMINANT What’s the genotype for: Individual I-1 XHy Individual II-3 Xhy Individual II-4 XHXh ***Use XH, Xh, and y for alleles*** Sex-Linked Dominant Disorder Rickets SEX-LINKED RECESSIVE ***Found in genes on the X chromosome*** Is the trait more common in Males than Females? Why? Males If a Male has the trait what will be genotype of his daughters? Heterozygous (Carriers) What is the chance that a son of a female carrier will inherit the trait? 50% SEX-LINKED RECESSIVE What’s the genotype for: Individual I-2 XhXh Individual II-2 Xhy Individual II-3 XHXh ***Use XH, Xh, and y for alleles*** What are the chances that Individual III-5 will have a son with the trait? 100% Sex-Linked Recessive Disorder Color-Blindness Are you Red-Green Colorblind? Pedigree Activity (Left-Side of your IN) Paste the pedigree above on the Left-Side of your IN and answer the following questions in your IN. Pedigree Activity 1. What type of pedigree is shown? Autosomal Recessive 2. How many children of individuals II-2 and II-3 have attached earlobes? None 3. How many children of individuals III-3 and III-4 have attached earlobes? Three 4. Is individual I-2 homozygous or heterozygous for free earlobes? Explain. Heterozygous – because the trait was passed on, so the recessive allele had to have been present Pedigree Activity 5. Can you be certain of the genotype of individual II-3? Explain. No, the recessive allele could be passed through individual II-2 or III-4 6. Predict the genotype and phenotype of individual V-1. genotype: homozygous recessive phenotype: attached earlobes 7. Are any of the descendants of individuals I-1 and I-2 homozygous for free earlobes (FF)? No Create a Pedigree • A man and woman marry. They have five children, 2 girls and 3 boys. The mother is a carrier of hemophilia, an Xlinked recessive 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 each (2 boys and a girl). The carrier daughter has one son with hemophilia. One of the non-carrier daughter’s sons marries a woman who is a carrier and they have twin daughters. • Draw this pedigree. Label the genotypes of the individuals above each circle or square. How many people are carriers of hemophilia? How many actually have the disease?