Genetics Answers

a.    which diagram(s) shows synapsis? (1 Mark)

b.    Which diagram(s) starts with a haploid cell? (1 Mark)

c.    In which diagram did segregation of both chromosome pairs occur? (1 Mark)

d.    What phenomenon occurred in division # IV? (1 Mark)

If a dog has 39 chromosomes in its sex cell how many chromosomes are in its body cell

Skin colour in humans ranges from very dark to very light. Which of the following most likely describes how skin colour is inherited?

4. In Jimsonweed, purple flower color (P) is dominant over white (p) and spiny pods (S) over smooth pods (s). These pairs of alleles are not linked. A Jimsonweed of genotype PPss is crossed with one of ppss. What is the genotype of the F1 generation? The phenotype?

5. In peas, the gene for tall plants (T) is dominant over the gene for dwarf plants (t) and round seed (R) is dominant over wrinkled seed (r). If one crosses a homozygous tall, wrinkled-seeded plant with a homozygous dwarf, round-seeded plant, what is the phenotype of the F1? The genotype of the F1? The phenotypic ratio of the F2?

6. If the cross BbDD X bbDd is made, which of the following would not be represented in the offspring?

a. BbDD; b. BbDd; c. bbDD; d. bbDd; e. BBDd

Four o'clocks exhibit incomplete dominance. Thus, if a plant with red flowers is crossed with a plant with white flowers, the offspring will all produce pink flowers. What offspring would you expect if you crossed a red-flowered plant with a pink-flowered plant?

II. DIHYBRID CROSSES

3. How many different kinds of gametes can an organism of genotype RrSS produce? List them.

1. Most individuals of a certain wild flower have white petals, but a few are blue. Crosses have shown that the blue color is due to a recessive allele. Use "W" for white and "w" for blue.

a. What is the genotype of a blue-flowered plant and what gametes would it produce as a result of meiosis?

b. What is/are the genotype(s) of each of a blue-flowered plant's parents?

c. If a blue-flowered plant has two white-flowered parents, and the parents produced many offspring, what fraction of them would you expect to be blue?

d. If a blue-flowered plant is crossed with its white-flowered parent, what fraction of their offspring would have the genotype "ww"?

e. If two blue-flowered plants cross, what fraction of their offspring will be blue? White?

The following pedigree analysis shows the inheritance of a recessive trait.

a. If individuals III-3 and III-8 marry, what is the probability of them having a child who phenotypically expresses the trait?

b. If individuals IV-1 and IV-10 marry, what is the probability of them having a child who phenotypically expresses the trait?

Q1. The following diagrams represent cells from a diploid organism with (2n=4) undergoing different stages of a division designated as (I,II, III,IV): 

a.      for each of the divisions, describe and conclude the type of division and its specific stage. (1.5 Marks each)

Draw two diagrams and label them indicating eukaryotic DNA replication and theta replication in E. coli. Highlight the similarities and differences. 

One type of conditional mutation is a temperature-sensitive mutation, which expresses the mutant phenotype only at certain temperatures. Strains of E. coli have been isolated that contain temperature-sensitive mutations in the genes encoding different components of the replication machinery. In each of these strains, the protein produced by the mutated gene is non-functional under the restrictive conditions. These strains are grown under permissive conditions and then abruptly switched to the restrictive condition. After one round of replication under the restrictive condition, the DNA from each strain is isolated and analysed. What characteristics would you expect to see in the DNA isolated from each strain with a temperature sensitive mutation in its gene that encodes a) DNA polymerase III, b) primase and c) initiator protein?