Question

If a bacterial cell undergoing binary fission failed to replicate its DNA before the division process occurred, what might result?
*Each daughter cell would continue on with one-half of the parent cell’s genes.
*One daughter cell would receive no DNA but would continue to survive because it acquired all other cell components.
*At least one cell would die because it would not have a complete copy of every gene.
*The cell would switch to a sexual mode of reproduction.
4. An advantage of sexual reproduction over asexual reproduction is that sexual reproduction...?
takes less time.
requires more time.
provides genetic diversity.
produces identical offspring.

Answer 1

3. C. at least one cell would die because it would not have a complete copy of every gene
4. C. provides genetic diversity

Answer 2

3. The right answer is At least one cell would die because it would not have a complete copy of every gene.

Although this is possible, it is very unlikely that replication stops occurring, thanks to the highly efficient replication and repair system.

The fidelity of replication is very large and it is largely due to the DNA polymerase, which incorporates the nucleic bases according to the complementarity of Watson-Crick pairings (A-T, C-G). Indeed, this very low error rate of DNA polymerase during replication is due to the fact that the replicative DNA polymerases have a replay activity that allows them to verify that the last nucleotide incorporated is the correct one.

In case of error, the DNA polymerases (I and III) correct them by means of their 3 '→ 5' exonuclease activity. This allows the polymerase to back up a notch by removing the incorrect nucleotide that is hydrolyzed, and then resume synthesis of the DNA strand.

Before this reading of the DNA the error rate is about 10-5 (one error per hundred thousand replicate bases) which is very little considering the number of bases replicated per second which is about 500 bases per second in bacteria. The replay step drops the replication error rate to about 10-7. Finally, the errors that may have escaped this control mechanism are then repaired in the double-stranded DNA by a specific mismatch repair mechanism (MR). The entire device is therefore an extremely efficient system since the error rate drops to about one mutation for 10 billion replicate bases.

4. The right answer is provides genetic diversity.

The advantages of sexual reproduction are:

• Produces a new organism that is a combination of traits from parents

• Creates increased genetic variability of organisms of the same species and even among the offspring of a single pair

• In the long term, allows the best adaptations to be spread within a species, especially in a changing environment

• The variability of organisms within a single sexed species ensures that a greater proportion will survive in perilous circumstances

• There may be two parents who look after the offspring