DNA EXAM PT. 3 Flashcards
RNA does not bind to the nucleotide base thymine. What does it bind to instead?
Uracil (U) - it also binds to the other three bases, adenine, cytosine and guanine.
What are the three types of RNA?
Messenger RNA (mRNA) Transfer RNA (tRNA) Ribosomal RNA (rRNA)
Describe mRNA..
The functions molecule connected with DNA.
Structure is similar to DNA but usually shorter.
It functions as a template formed from the DNA by RNA polymerase. This template is the template from which proteins are formed.
Describe tRNA..
Relatively small and there is one version of tRNA for each of the different amino acids that go into making proteins.
tRNA transports the amino acids to the ribosomes for the manufacture of the protein.
Describe rRNA…
Acts more as a catalyse for the production of protein and is one of the major components of the ribosome.
What is semi conservative replication?
When more DNA is needed and the molecule forms two complete double helixes from one
Describe and breakdown the process of DNA replication…
This involves different enzymes performing different roles in order to unzip the DNA strand, add new bases and then zip up the two new DNA strands.
First, the enzyme DNA topoisomerase breaks one strand of the DNA allowing it to unravel.
The DNA unzips, turning the double helix into a replication fork.
The enzyme DNA helicase breaks the hydrogen bonds between the base pairs and the strands start to separate.
A small primer made of 5 base pairs of RNA attach where the 5’ end would be, opposite the 3’ end of the other strand. This forms a basis for the enzyme DNA polymerase to start the replication.
DNA polymerase attaches to the 3’ end just on the end of the primer and starts adding the complimentary base pairs for each.
Phosphate bonds the sugars as before, building a new strand of DNA.
Some of the DNA polymerases have a special function allowing them to ‘proofread’ for errors and in some cases repair damaged DNA, making the process rapid and accurate at the same time.
On the other strand, instead of occurring the single chain, the primers attach toward the 3’ end of the molecule, but the DNA polymerases attach in fragments called Okazaki fragments. These are several thousand base pairs in length, heading towards the 3’ end, making up the other strand in pieces rather than a long and single piece.
Another enzyme called DNA ligase then joins the ends of these fragments together to form another DNA helix.
How does RNA differ from DNA?
RNA is single stranded
The sugar units are ribose instead of deoxyribose
The ribose sugar backbone in RNA has a hydroxyl (-OH) group that DNA does not
What is another name for the replication fork? What does it do?
The replication bubble.
It’s the join between the unzipped DNA and the area where the two strand are still zipper together.
What is another name for the replication fork? What does it do?
The replication bubble.
It’s the join between the unzipped DNA and the area where the two strand are still zipper together.
