Question

question 17
what enzyme is responsible for adding nucleotides to a growing dna chain during replication?
○ dna polymerase
○ rna primase
○ rna polymerase
question 18
2 pts
in pea plants, the allele for round peas (r) is dominant to the allele for wrinkled peas (r). a gardener has a plant he got from his neighbor that produces round peas, but he does not know its genotype. what simple procedure could he do to determine the genotype of his new plant?
○ perform a dihybrid cross—if only 1 out of 16 offspring are wrinkled, then the new plant’s genotype is rr.
○ perform a test cross with a plant that has wrinkled peas—if any offspring give wrinkled peas, then the new plant’s genotype is rr.
○ perform a test cross with a plant that has an rr genotype—if all of the offspring give round seeds, then the new plant’s genotype is rr.

Explanation:

Question 17

To determine the enzyme adding nucleotides to a growing DNA chain during replication, we analyze each option:

• DNA polymerase: Its role is to synthesize new DNA strands by adding nucleotides complementary to the template strand during replication.
• RNA primase: Synthesizes RNA primers, not adding DNA nucleotides to the growing DNA chain.
• RNA polymerase: Involved in transcription (synthesizing RNA from DNA), not DNA replication's nucleotide addition to DNA chains.

So the correct enzyme is DNA polymerase.

To determine the genotype of a round - pea plant (dominant trait, so genotype could be RR or Rr), we analyze each option:

• Option 1 (Dihybrid cross): A dihybrid cross involves two traits, but here we are dealing with a single trait (pea shape). Also, the logic about the ratio is incorrect for determining the genotype of a single - trait dominant plant.
• Option 2 (Test cross with wrinkled - pea plant, genotype rr): If the unknown plant is Rr, when crossed with rr, the offspring genotypes will be Rr (round) and rr (wrinkled) in a 1:1 ratio. If the unknown plant is RR, all offspring will be Rr (round). So if any offspring have wrinkled peas, the unknown plant must be Rr.
• Option 3 (Test cross with Rr plant): Crossing with Rr does not effectively determine if the unknown is RR or Rr, as both RR and Rr can produce round - seeded offspring when crossed with Rr.

So the correct procedure is the test cross with a wrinkled - pea plant.

Answer:

A. DNA polymerase

Question 18