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Objectives, 9/18/08: Mitosis 1. Apply appropriate terminology to describe genetic characteristics of cells. 2. Model and explain how genetic information is transferred from one generation of cells to the next through the process of mitosis. - Use a diploid cell that is heterozygous for two genes located on separate chromosomes (unlinked). G1: Cell’s DNA is unduplicated t T f F G2: DNA is duplicated T t T t f F F f Metaphase - duplicated chromosomes line up at equatorial plane (centromeres align) t t f f T T F F Metaphase Anaphase - sister chromatids separate at centromere - chromatids move into daughter cells t t f f T T F F Products: 2 cells formed t t T F f T f F Use the information in the table above to answer questions about Rascal. Rascal is a large, black dog with a pointy nose and droop-down ears. Important notes: - Rascal’s mother is small and yellow and has a flat nose. - Ear and nose shape are linked, meaning they occur at different loci on the same chromosome (see above for example of linked genes). Genes for size and color occur on separate chromosomes. (Hint: you will draw 3 homologous pairs.) 1. What is Rascal’s genotype? 2. Cell at G1 3. Cell at G2 4. Cell at metaphase of mitosis 5. Cell products of mitosis 1. What is Rascal’s genotype? Rascal is a: large black dog with a pointy nose and droop-down ears. Important notes: - Rascal’s mother is small and yellow and has a flat nose. Phenotype Dominant Alleles Recessive Alleles Nose Shape Pointy (N) Flat (n) Ear Shape Upright (E) Down (e) Fur Color Black (B) Brown (b), Yellow (b’), White (b’’) Size Large (L) Small (l), Medium (l’) *Nose shape and Ear shape are linked on the same chromosome KEY Rascal is a large, black dog with a pointy nose and droop-down ears. Important notes: - Rascal’s mother is small and yellow and has a flat nose. 1. What is Rascal’s genotype? Phenotype Genotype Rascal’s genotype is: L l B b’ N n e e large L l black B b’ pointy nose N n droop‐down ears e e In order to express the phenotype of droop-down ears, Rascal must have only recessive alleles of the ear shape gene. Rascal is homozygous recessive for ear shape. All of Rascal’s other genotypes must be heterozygous. We know this because the phenotypes of large, black, and pointy nose are associated with dominant alleles, therefore Rascal must have at least one dominant allele for each. However, we are also given information about Rascal’s mom – she has only recessive traits, so can only pass on recessive alleles to her offspring. Rascal must have inherited dominant alleles from his father. KEY 2. Cell at G1 e b’ N L B e n l KEY 3. Cell at G2 e e N N e n b’ b’ L L B e n l l B KEY 4. Cell at Metaphase of Mitosis KEY 5. Products of mitosis