You are interested in a new type of autosomal dominant mutation that gives purple eyes in Drosophila. You have a true-breeding purple-eyed line carrying a mutation that you call pr-1. You have isolated a second purple-eyed mutation that you call pr-2, which you have established in a true-breeding line that also carries a recessive marker st, which gives stubby legs. You cross a fly from the pr-1 line to a fly from the st, pr-2 line producing F1 females which you then cross to males from a true breeding st line (normal eyes). From this cross, 1000 progeny flies can be categorized into four different phenotypic classes:

                             

Normally, 3-factor crosses give eight different phenotypic classes, why does this particular cross give only four?

#Question id: 3824

#Unit 3. Fundamental Processes

State whether the following statements is true/false regarding DNA replication.

1. The polymerization of DNA is essentially irreversible due to the hydrolysis of pyrophosphate.

2. On average about twenty errors are made during each replication of the human genome.

3. DNA polymerase I possesses 5ʹ → 3ʹ exonuclease activity.

4. All DNA ligase enzymes use ATP as a cosubstrate.

5. The purpose of SSB is to prevent single-stranded DNA from folding back on itself to form double-helical regions.

#Question id: 3825

#Unit 3. Fundamental Processes

Telomeres are the repetitive sequence of T's and G's that are present in the eukaryotes to protect the random cleavage from nucleases. These telomeres are synthesized by the enzyme telomerase. Which of the following are the properties of enzyme telomerase?

#Question id: 3826

#Unit 3. Fundamental Processes

Which scientists first gave experimental evidence that DNA is the genetic material?

#Question id: 3827

#Unit 3. Fundamental Processes

It takes about the same amount of time for eukaryotic chromosomes to be replicated in vivo as it does for E. coli. Why is this true?

#Question id: 3828

#Unit 3. Fundamental Processes

Why does E. coli need both DNA polymerase III and DNA polymerase I?

#Question id: 3829

#Unit 3. Fundamental Processes

Why is only one copy of DNA made per cell division cycle in eukaryotes despite the presence of multiple origins of replication?