Unformatted text preview: L111 Lecture Quiz #1 ANSWER KEY For the following two questions, assume that black (B) is dominant to brown (b). 1. If two black dogs mate and have both brown puppies and black puppies, what are the genotypes of the parents? (1pt) Bb & Bb (both heterozygous) Explanation (not needed for credit): Both parents have to be heterozygous, in order to give at least one recessive allele to their offspring who are homozygous recessive. 2. A heterozygous black dog is mated with a brown dog. What is the predicted phenotypic and genotypic ratio of the offspring? Show your work. (2pts) Bb * bb B b b b Bb Bb bb bb Genotypic ratio: 1 (Bb) : 1 (bb) or Bb and bb Phenotypic ratio: 1 (black): 1 (brown) or black and brown 3. If a child has type AB blood, he or she could NOT have been produced by which set of parents? (circle all that apply) (1pt) a. Type A mother and type B father b. Type AB mother and type O father can't be parents c. Type B mother and type B father can't be parents d. Type A mother and type A father can't be parents e. Type A mother and type AB father f. Type AB mother and type B father 4. Black fur in mice (B) is dominant to brown fur (b). Short tails (T) is dominant to long tails (t). If you cross a mouse (parent #1) that is heterozygous for fur color, but homozygous recessive for tail, with an individual (parent #2) who is heterozygous for both traits..... (a) What are the genotypes for the parents? (1pt) Bbtt * BbTt (b) What are the possible gametes for each parent? (1pt) parent #1: Bt, bt parent #2: BT, Bt, bT, bt (c) What are the predicted genotypic ratio and the phenotypic ratios of the offspring? (2pts) (Make sure you indicate which ratio is the genotypic and which is phenotypic and label each of the #s within the ratios) SHOW YOUR WORK! Bt bt Bt bt BT BBTt BbTt BBTt BbTt Bt BBtt Bbtt BBtt Bbtt bT BbTt bbTt BbTt bbTt bt Bbtt bbtt Bbtt bbtt Genotypic Ratio Phenotypic ratio: BBTt 1/8 or 2/16 Black & short 3/8 or 6/16 BbTt 2/8 or 4/16 Black & tall 3/8 or 6/16 BBtt 1/8 or 2/16 Brown & short 1/8 or 2/16 Bbtt 2/8 or 4/16 Brown & tall 1/8 or 2/16 bbTt 1/8 or 2/16 bbtt 1/8 or 2/16 Genotypic ratio: 1:2:1:2:1:1 ratio BBTt (1):BbTt (2):BBtt (1): Bbtt (2): bbTt (1): bbtt (1) Phenotypic ratio: 3:3:1:1 ratio Black & short (3): Black & tall (3): Brown & short (1): Brown & tall (1) You did not have to have all of the different ways I have down here, as long as the have each ratio written down in a way that it is obvious you know what is the phenotype and genotype. 5. Demonstrate your knowledge of independent assortment by drawing the two possible alignments for this cell AFTER DNA duplication prior to the first division. (2pts) 6. On the next page, draw out meiosis using the cell at the top of the page as the starting point (two pairs of homologous chromosomes prior to DNA duplication). a. You MUST OBVIOUSLY label your drawing at some point (only once each) with: sister chromatids, homologous pair, gametes. (3 pts) b. You must also show and indicate when the following occur: DNA replication (1 pt) Sister Chromatids split (2 pt) Homologous pairs split (2 pt) c. SHOW crossingover for the "G/g" and the "R/r" genes ONLY (1pt) d. Indicate when the cell is diploid and when it is haploid (you can draw a bracket off to the side to show the change). (1pt) ...
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- Fall '11