1-Describe process of DNA replication.
- Discuss nature of gene.
- Write note on genetic code.
- Describe transcription.
- Describe process of protein synthesis.
- Describe regulation of gene expression in prokaryotes. Or discuss lac operon.
- Discuss control of gene expression in eukaryotes.
- Name different enzymes involved in replication of DNA.
Ans: DNA polymerase I, DNA polymerase II, Primase and DNA I igase.
- Why is RNA primer synthesized?
Ans: The DNA polymerase III can add nucleotides only to a 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.
- Differentiate 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.
- What are Okazaki fragments? Why are they formed?
Ans: Lagging strand is synthesized discontinuously. A series of short segments are synthesized. These segments are connected later on. These segments are called Okazaki fragments.
- What is gene expression?
Ans: The central dogma is composed of transcription and translation. These two steps of central dogma are also collectively called gene expression.
- What is translation?
Ans: The synthesis of mRNA from the DNA is called transcription.
- What is promoter?
Ans: Transcription starts at the promoter on the DNA template strand. Promoter is the RNA polymerase binding site.
- What is rRNA?
Ans: It is found in ribosome. The rRNA provide
- What is the function of tFtNA?
Ans: Transfer RNA molecules read massage (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.
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 tip 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. 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 Mr genetic codes?
Ans: Three 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 occurs continuously.
18-What are terminations or nonsense 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 but in mitochondria 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 sequence. 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
25-What is initiation factor?
Ans: A proteins initiation factor control the attachment of the
tRNA on the ribosomal surface at the P site.
26-What is translocation?
Ans: During Translocation, the ribosome now moves (translocates) to next code along the mRNA molecule in the
5′ 3′ direction.