Question

1. Why is the genetic code described both as degenerate and unambiguous?
2. The original enzyme used in PCR reaction is/are known as?
3. A dna codon consist of ?
4. What are the three basic steps of conventional PCR?
5. A 20 uear old male with anaemia is found to have an abnormal form of beta globin that is 172 amino acid long, rather thean the 144 found in the normal protein, which of the following point mutation is consistent with this abnormality?

1. CGAaUGA
2. GAUaGAC
3. GCAaGAA
4. UAAaCAA
5. UAAaUAC

6. Transmission of the genetic information from mRNA to protein is
7. A 5 year old male has been refeeed to the haematalogical department due to the splenomegaly and sever anaemia, which lab test is recommended to confirm this diagnosis

1. Protein electrophoresis
2. Polymerase chain reaction
3. Western blot
4. Southern blot
5. Northern blot

8. The sequence of part of the DNA is the following ATTCGATTGCCCAGGT, when this strand is used as a template, for DNA synthesis, the product will be which of the following

1. TAAGCTAACGGGTGCA
2. UAAGCUCGGGUGCA
3. ACGUGGGCAAUCGAAU

9. A man with a bacterial infection was prescribed ciprofloxacin to resolve the infection. Ciprofloxacin does not affect eukaryotic cell due what?
10. A mutation which also results in the disturbance of activity of the normal gene or protein due to loss of function mutation in the heterozygote state is
11. A heterozygote deletion that removes an allele and results in clinical problem is
12. A mutation which result in a decrease protein activity is
13. A point of mutaion that leads to failure of expression of ones gene product is
14. A 45 year old man is diagnosed with cancer of the proximal portion of the colon. His father died of colon cancer at the age of 52. He has three siiblings. His 55 year old brother has not been diagnosed with cancer, but his 57 year old sister has an endometrial carcinoma, and the other sister died of ovarian cancer. A diagnose of hereditary non polyposis colorectal cancer (HNPCC) is made which type of mutation is occurring in this family
15. Large triplet repeat expansion can be detected by ?
16. In meosis, recombination occurs in where?
17. A nonsense mutaion involve

1. A regulatory sequence
2. An AG splice acceptor site
3. The creation of different amino acid
4. The creation of stop codon

18. What is the sequence( convensionally written) of the RNA product of the DNA template sequence, GATCTAC?

1. CGAaUGA
2. GAUaGAC
3. GCAaGAA
4. UAAAaUAG
5. AUAAaCAA

Answer 1

1. The genetic code is unambiguous: A single codon clearly encodes a specific amino acid without ambiguity in all the organisms. Unambiguity is essential as the translation process should not incorporate a wrong amino acid into the protein.
Genetic code is degenerate: Several codons encode a same amino acid.
Ex: GGG, GGC, GGU, and GGA = Glycine.
Degeneracy of the genetic code provides buffering space for mutations.

2. Taq Polymerase is used in PCR.

3. A DNA codon consists of 3 nucleotide sequence that specifies a single amino acid.

4. PCR is used to amplify target gene sequences. It is an invaluable technique used in molecular biology and genetics.
PCR reaction components:
i. Taq polymerase
ii. Buffer
iii. dNTPs
iv. Primers
v. Template

PCR steps:
i. Denaturation (92'C to 94'C): Unwinding of the DNA duplex
ii. Annealing (50'C to 65'C): Binding of the primer to the template DNA
iii. Extension (70'C to 72'C): Extension of the primer by Taq polymerase
iv. Repeat

Primer is a short oligonucleotide sequence (15 to 30 ntd) that binds specifically to the template DNA using sequence complementarity. The primer binds to the template DNA only when the temperature is below the Tm of the DNA-primer duplex.

The Taq polymerase is a thermostable DNA polymerase isolated from Thermus aquaticus. The enzyme shows optimum activity at 72’C which is required at the elongation step of the PCR reaction. Normal DNA polymerases isolated from mesophilic organisms would generally be denatured at this temperature. Hence Taq polymerase is used.