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Human Heredity Bell: What is the genotype of the possible children if a heterozygote for Widow’s peak marries a homozygous recessive (straight hairline)? Ww and ww What is/are the possible phenotype(s)? Widows peak and Straight hairline AGENDA 1. Independent Projects 2. Blood Typing 3. Pedigrees 4. Sex-linked traits Human Heredity Review: Just a reminder Human cell = How many chromosomes? 46 (23 pairs) 1 set from Mom (egg) : 1 set from Dad (sperm) 1 chromosome from each are known as sex chromosome Female = XX Male = XY Remaining 44 chromosomes = autosome Pedigree Def.- Chart that shows the relationships within a family Used to predict or determine the mode of inheritance of a trait Pedigree (cont.) Female = Affected Female = Male = Affected Male = If a heterozygote is known then half of the shape is shaded Complete: 1st side of Pedigree Practice Worksheet Pedigree Practice: Autosomal Dominant? A. B. C. rr rr rr rr rr rr rr Draw each pedigree and do the following for each one: 1. Assume that the affected trait is dominant. Write the genotypes beside each recessive individual (you choose the letters) 2. Is it possible for this trait to be autosomal dominant inheritance? Circle pedigree if possible or X pedigree if not possible Can two affected individuals have Yes - if both are heterozygous unaffected children? Pedigree Practice Autosomal Recessive? A. rr rr B. rr rr rr rr rr rr C. rr Assume the trait is recessive. Draw the pedigree and write the genotype beside each person. Is it possible for the trait to be recessive? - Circle if possible or X if not possible They are also If the trait is autosomal recessive, what can you conclude the children will be of two affected parents? affected Pedigree Practice Carrier Heterozygote that “carries” the affected allele, but does not express the allele (Allele remains hidden.) ** Who are the carriers? Is the affected trait autosomal dominant or recessive? Why? Recessive - Trait disappears for generations Sex-Linked Genes Pattern of inheritance is located on the Xchromosome or the Y- chromosome Y is much smaller Therefore, there are more X-linked disorders/traits What numbers to you See? Ex. Red-Green X-linked disorder Colorblindness Most common in ? Males (1/10) Females ( only 1/100) Allele Definition XN= Normal vision/dominant allele on X chromosome Xn = Colorblind/recessive allele on the X chromosome Y = male chromosome contains no allele for color vision Colorblind Problem Marian’s father is colorblind. Marian herself has normal color vision. Marian and her husband, Martin, who is also colorblind, have just had their first child; a son they have named Mickey. Write the genotypes of Marian and Martin. •Marian has normal vision = XN •Marian’s father is colorblind (XnY) and gave her the colorblind X chromosome = Xn •Therefore, Marian has genotype - XN Xn •Martin is colorblind - he has recessive X allele (Xn) • Martin is Male, so he has Y gene • Therefore Martin’s genotype is XnY Marian’s father is colorblind. Marian herself has normal color vision. Marian and her husband, Martin, who is also colorblind, have just had their first child; a son they have named Mickey. COMPLETE A PUNNET SQUARE a. What is the probability that their son is colorblind? 50% b. If Martin were not colorblind, how would this affect the prediction about Mickey? No Affect - Martin gives a Y to his son c. If Marian and Martin were to have a girl (who they would name Minnie) what is the probability that she would be colorblind? 1 out of 2 or 50% - Depends on Marian; Martin will give a colorblind X (Xn) Homework Complete blood typing and sex-linked genes worksheet - both sides (Will be checked on Monday)