Molecular Genetics Exam Questions

Following questions are the important for molecular genetics exam questions. Students can prepare these questions for their exams.

1. Name different enzymes involved in replication of DNA?

Ans: DNA Polymerase I, DNA polymerase II, Primase and DNA ligase.

2. Why is primer RNA is synthesized?

Ans: The DNA polymerase III can add nucleotides only to chain of nucleotides that is already paired with the parent strands. Hence DNA polymerase cannot itself initiate synthesis of DNA. Thus, another enzyme, primase synthesize an RNA primer.

3. Difference between leading strand and lagging strands?

Ans: Leading strand elongates toward the replication fork. In this case, the nucleotides are added continuously to its growing 3’ end. Lagging strand elongates away from the replication fork. molecular genetics

4. What are Okazaki fragments? Why are they formed?

Ans: Lagging strand s synthesized discontinuously. A series of short segments are synthesized. These segments are connected later on. These segments are called Okazaki fragments.

5. What is Gene Expression?

Ans: The central dogma consists is composed o transcription and translation. These two steps of central dogma are also collectively called gene expression.

6. What is transcription?

Ans: The synthesis of mRNA from the DNA is called transcription.

7. What is promoter?

Ans: transcription starts at the promoter on the DNA template strand. Promoter is RNA polymerase binding site.

8. What is rRNA?

Ans: It is found in ribosome. The rRNA provides the site for the synthesis of polypeptides during translation.

9. What is the function of tRNA?

Ans: Transfer RNA -molecules read message (code) on the mRNA and transport the amino acids to the ribosomes.

10. Differentiate between codes and anticodes?

Ans: Codes are present on mRNA and anticodes are present on tRNA.

11. What is the function of mRNA?

Ans: The mRNA is long strands of RNA. It is transcribed from DNA and it travels to the ribosomes and direct precisely which amino acids are assembled into polypeptide. molecular genetics

12. Differentiate between translation and transcription?

Ans: The synthesis of mRNA from DNA is called transcription. The synthesis of protein from mRNA is called translation.

13. Differentiate between template strand or the antisense strand and coding strand or the sense strand?

Ans: Template is the strand which is transcribed during transcription: The opposite strand is called coding or sense strand.

14. What is transcription bulb?

Ans: The DNA strands open up at the place where enzyme is attached with the template strand. It forms transcription bubble.

15. What is cap and tail of mRNA?

Ans: Cap is in the form of 7 methyl GTP., It is linked to 5′ end with the first nucleotide of mRNA. A Tail is in the form of poly A tail. It is linked to 3′ end of the RNA.

16. What is genetic code?

Ans: Genetic code is, a combination of 3 nucleotides, which specify a particular amino acid.

17. Why are three nucleotides taken as most appropriate for genetic codes?

Ans: The Nucleotides can form 43 Or 64 different combinations. It is more than enough to code for the 20 amino acids. Thus, genetic code is a triplet code and the reading occur continuously. molecular genetics

18. What are terminations or non-sense codes?

Ans: These are three codons UAA. UAG and UGA. They do not code for any amino acid. So, they are known as nonsense codon.

19. What is initiation codon?

Ans: It is present at the start of every gene. This initiation codon AUG. It encodes the amino acid methionine.

20. Are genetic codes universal?

Ans: No. genetic codes are not universal. The study of genetic code of mitochondrial DNA showed that genetic codes are not so universal. For example, UGA codon is normally a stop codon. it codes for tryptophan amino acid.

21. What is translation?

Ans:  The synthesis of protein, from mRNA is called translation.

22. What is anticodon?

Ans: The tRNA molecules possess complementary three nucleotide sequences. It is called anticodon

23. What is the function of P site (peptidyl site) of ribosome?

Ans: It is the Site of the ribosome where peptide bonds are formed.

24. What is the function of A site (aminoacyl site)?

Ans: This site contains Successive (next) amino acid with its rRNA.

25. What is initiation factor?

Ans: A proteins initiation factor control the attachment of the tRNA on the ribosomal surface at the P site. molecular genetics

26. What is translocation?

Ans: During Translocation, the ribosome now moves (translocates) to next code along the mRNA molecule in the 5′ —+ 3′ direction.