No tail (Manx) is a dominant trait and its allele is represented by M The presence of a tail is recessive and its allele is represented by m

Transcription

1 Lab #4: Extensions to Mendelian Genetics Exercise #1 In this exercise you will be working with the Manx phenotype. This phenotype involves the presence or absence of a tail. The Manx phenotype is controlled by a single gene with two alleles: M and m. No tail (Manx) is a dominant trait and its allele is represented by M The presence of a tail is recessive and its allele is represented by m What are the possible genotypes of a Manx cat? What is the genotype of a cat with a tail? Make ten Manx cats: To make a Manx cat, click on: Male or Female, lacks a tail, all-white Determine the genotype of your ten Manx cats. Manx cats Genotype of the Manx parent

2 Exercise #2: In this exercise you will be working with the white-spotting phenotype (called white areas in the CATLAB program). This phenotype involves the extent of white spotting on a cat s coat. The white-spotting phenotype is controlled by a single gene with two alleles: S and s. The Extensive white-spotting allele is represented by S The No white spots allele is represented by s Make two gray cats, each with extensive white areas. Click on: male; has a tail; not all white; extensive white areas; No tabby stripes; gray Click on: female; has a tail; not all white; extensive white areas; No tabby stripes; gray Set litter size to 7 and produce three litters. Record your results. Clear the screen and repeat three more times. Make new parents each time and be sure to record all of your results. Based on your results, what do you think the genotype of the parents are? Maintain the current screen and make two gray cats, each with no white areas. Click on: male, has a tail, not all white, no white areas, No tabby stripes, gray Click on: female, has a tail, not all white, no white areas, No tabby stripes, gray Mate these cats and produce three litters. Record your results. Based on your results, what is the genotype of each parent. Choose a male parent with extensive white areas and a female parent with no white areas. Do not mate them yet. Assume that the male (extensive white areas) is homozygous dominant and that the female is homozygous recessive. Predict the genotypes of their offspring. Mate the cats and produce three litters. Record the phenotypes of the offspring.

3 Exercise #3: In the first CATLAB you discovered that the mackerel tabby striping pattern is dominant to the blotched tabby striping pattern. The relationship between tabby striping pattern and the relevant alleles is: Trait Mackerel Blotched Allele T t These alleles follow traditional Mendelian rules (i.e., no co-dominance or incomplete dominance) What are the possible genotypes of a Mackerel cat? What is the genotype of a blotched cat? What are the possible genotypes and phenotypes of a mating between a mackerel cat and a blotched cat? (predict the outcome for both possible mackerel cats) Make the following cats: Click on: male, has a tail, not all white, no white areas, blotched, gray Click on: female, has a tail, not all white, no white areas, mackerel, gray Mate the cats and produce 20 kittens. Pay attention only to the tabby striping phenotype of the offspring. In order to do this exercise, you need to have parents that can produce a litter with some kittens that completely lack a tabby striping pattern (a cat with no tabby striping pattern will have a blank under the column Pattern ). Are there any such kittens in your set of offspring? If not, make new mackerel and blotched parents (use the instructions given above) and mate them. Continue making new parents until you find two that can have kittens with no tabby striping pattern. Once you find suitable parents, mate them until you have 35 kittens. Record the results of the cross below. Phenotype Number of Kittens Mackerel Blotched No Tabby Pattern

4 Exercise #4 When cats have the homozygous recessive genotype (dd ) for the dilute gene, their coat color is expressed as cream or gray. Whether they actually are cream or gray depends on the Orange gene. Note: do not be confused by the name orange. The orange coat color phenotype is only expressed when the dilute gene is homozygous dominant (DD) or heterozygous (Dd). You will be working strictly with dd cats and therefore coat color will be expressed as cream or gray. The Orange gene has two alleles: O o and O +. Trait cream Allele O o gray O + Generate a cream female and a gray male: Click on: female; has a tail; not all white; some white areas; blotched, cream Click on: male; has a tail; not all white; some white areas; blotched, gray Set the litter size to 7 and generate three litters. Record the phenotypes of all kittens below. Now generate a gray female and a cream male. Click on: female; has a tail; not all white; some white areas; blotched, gray Click on: male; has a tail; not all white; some white areas; blotched, cream Set the litter size to 7 and generate three litters. Record all phenotypes of your kittens. Quiz #5

5 1. Questions related to Exercise #1 a) What is the genotype of each of the original ten Manx cats? b) Why do none of the original Manx cats have the MM genotype? 2. Questions related to Exercise #2. a) Based on your results, what is the genotype of a cat with extensive white areas? b) Based on your results, what is the genotype of a cat with no white areas? c) What are the genotype and phenotype of offspring from mating a cat with extensive white areas to a cat with no white areas? d) This is an example of? 3. Record your results for exercise #3 below. Phenotype Number of Kittens Mackerel Blotched No Tabby Pattern (a) What is the explanation for producing some kittens with no tabby striping pattern? (b) Propose a genotype for the mackerel parent? (c) Propose a genotype for the blotched parent? (d) Represent the cross with a branch diagram.

6 (e) Propose a genotype for a cat with no tabby striping pattern? 4. The following questions concern Exercise #4. a) Which allele is dominant, O o or O +? b) On what chromosome is the orange gene located? a) What is the genotype of the cream female parent? b) What is the genotype of the gray male parent? c) What are the genotypes of the male and female kittens from a cross of a cream female parent and a gray male parent?