Supplemental Instruction
Iowa State University / Leader: / Laura
Course: / Bio 313
Instructor: / Dr. Rodermel
Date: / 12/7/15
Warm-up:
What are the 3 main points about the Lyon Hypothesis?
1.
2.
3.
Answer the following questions about Calico Cats:
1. Coat color in cats is a codominant trait and is also located on the X chromosome. Cats can be black, orange or calico. A calico cat has black and orange splotches. In order to be calico. the cat must have an allele for the black color and an allele for the orange color. Use a punnett square to show why there are no male calico cats.
2. A female calico cat is crossed with a male black cat. What are the phenotypes of the offspring and in what proportion?
3. Also located on the X chromosome of a cat is a gene that codes for deafness. This gene is recessive. A black female cat that is heterozygous for deafness (Dd) is crossed with a orange male cat that is not deaf. Show the cross. What are the phenotypes of the offspring and in what proportion? Hint: place two letters on the X chromosome in your cross. (You will need to use two superscript letters on your X chromosome) the female cat has the following alleles BD and Bd; the male cat has only OD, setting up the square will show that the offspring will be:
4. Match the term with the definition:
Term / DefinitionPenetrance / A trait that is penetrant in males OR females
Expressivity / A trait that has a larger penetrance in males or females
Sex-limited trait / Causes death at an early stage in development, so some genotypes do not appear among the progeny
Epigenetics / Densely staining areas in the nuclei of females
Sex-influenced trait / Interactions between alleles of a single gene, or rather interactions between the gene products of these alleles
Barr Bodies / Heritable alterations in the DNA that do not involve base changes, but affect the way DNA sequences are expressed
Dominance / The degree to which a character is expressed
Lethal Allele / Percentage of individuals having a particular genotype that express the expected phenotype
5. Another type of non-mendelian trait: Multiple alleles. Human hair color is controlled by one gene with four alleles (with some incomplete dominance):
HBr = brown HBd = blonde hr = red hbk = black
The possible genotypes and phenotypes:
HBd HBd or HBdhbk= blonde HBdhr= strawberry blonde HBrhR = auburn
hRhR or hRhbk = red hbkhbk = black
What do you think your parent’s phenotypes and genotypes for hair color are?
6. What are your phenotype and genotype for hair color?
7. If someone with auburn hair has children with someone with red hair (but whose mother had black hair), what are the genotype and phenotype probabilities for their children?