molgen self evaluation

Which of the following are role(s) of the 5' cap?

The cap plays a role in the removal of introns. The cap protects the RNA from degradation. The cap acts as a binding site for the ribosome.

poly A tail function

1,The poly-A tail makes the RNA molecule more stable and prevents its degradation. 2, poly-A tail allows the mature messenger RNA molecule to be exported from the nucleus and translated.

Why do eukaryotic chromosomes have multiple origins of replication, whereas prokaryotic chromosomes typically have only one origin?

Eukaryotes have a very large genome and it would take to long if there was only one origin. Prokaryotes have a smaller genome and can have only one.

Briefly discuss the evidence for the semi-conservative replication of DNA

Experiments by Matthew Meselson and Frank Stahl allowed E. coli to be labeled with 15N and 14N and then followed the density of the daughter cells using cesium chloride gradient centrifugation. They predicted that parental DNA molecules of one density which were allowed to replicate in another medium of a different density will show daughter DNA molecules of intermediate density because half will be old DNA and the other half will be new DNA. Their results proved that indeed half was old and other half was new indicating DNA of intermediate density.