Tuesday, 15 December 2009

Biochemistry Exams - 2007/2008 3rd year Undenominated Science Semester I - Question 1 and 2

Hello Students,

Welcome again in the Biochemistry Exams Section. Today we will start to work with another Biochemistry Exam Sample Paper which you can find here Biochemistry Exams - 2007/2008 3rd year Undenominated Science Semester I.

Ok let's go team.

Question 1. The replication of eukaryotic chromosomes requires the cooperation of multiple
proteins. Discuss the activities of polymerases (DNA and RNA) in this process.

As you see Question 1 from this paper is exactly the same as on the paper we have already, previously exposed. To see the answer to the question go here DNA replication enzymes. If this question did show up last year and two years ago, we can conclude that a similar question can came up this year as well. So it is essential you get familiar with it:)

Ok that was easy:).

Question 2. Explain and discuss the term “junk DNA” OR Write an essay on protein folding and processing in eukaryotic cells and outline the role that chaperone proteins play in these events.

We will start with the essay part. As you probably noticed, we have already answered this question as well. Last paper had a similar problem to solve but this time you are asked to write an essay about protein folding and processing. Just go here Protein Folding, Processing ang Targeting (Part A of the question 4) and use the infromation provided to write nice essay.

Ok, let's explain what the junk DNA is?

Junk DNA - simply saying, it is a DNA which have no known function. About 95% of the human genome is considered as a junk DNA (about 5% encodes for the proteins, RNA's etc).
The best example of the junk DNA are introns. As you know most of the genes are composed of exons (protein coding sequence) and introns (non-coding sequence). After gene transcription (before protein synthesis), splicing machinery remove introns and join exons together to form a protein coding sequence. Because introns are removed in this process they are designated as junk DNA.
Pseudogenes are another example of the junk DNA. Pseudogene is a DNA sequence which is similar (sometimes almost identical) to another gene but it is never expressed (protein is never produced from this sequence). So this is like a copy of a particular gene but it is never used.

Why we actually need a junk DNA? We need it because we actually do not comprehend its function yet:) I am sure that these functions will be revealed in the future.
Remember that genomes are dynamic structures and junk DNA might be essential for them. Imagine that junk DNA might interfere with gene transcription (activation or deactivation). It is possible that junk DNA form complexes with DNA what is essential for genome metabolism or it is a platform for processes that regulates genome maintenance (etc).

This is it:) Soon next questions:)

Have a nice night:)


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