Q-161. All of the following amino acids are converted to succinyl-CoA EXCEPT
a) Methionine
b) Iso-leucine
c) Valine
d) Histidine
Answer: Histidine
Explanation:
Amino acids form succinyl Co-A:
Methionine
Iso-leucine
Valine
Threonine
Important point:
Histidine forms alpha keto-glutarate
Q-162. The amino acid which serves as a carrier of ammonia from skeletal muscle to liver is
a) Alanine
b) Methionine
c) Arginine
d) Glutamine
Answer: Alanine
Explanation:
Alanine serves as a carrier of ammonia from skeletal muscle to liver. Most other tissues however use glutamine.
Q-163. The long and short arms of chromosomes are designated respectively as
a) p and q arms
b) m and q arms
c) q and p arms
d) I and s arms
Answer: q and p arms
Explanation:
The short arm of chromosome is designated as p and the long arm is as q.
Q-164. Euchromatin is the region of DNA that is relatively
a) Uncondensed
b) Condensed
c) Over-condensed
d) Partially condensed
Answer: Uncondensed
Explanation:
Euchromatin stains weakly and is highly de-condensed chromatin.
Heterochromatin stains more strongly and is more condensed chromatin.
Q-165. Microsatellite sequence is
a) Small satellite
b) Extra chromosomal DNA
c) Short sequence (2-5) repeat DNA
d) Looped-DNA
Answer: Short sequence (2-5) repeats DNA
Explanation:
Microsatellites are short segments of DNA that have a repeated sequence such as CACACACA.
The majority of microsatellites occur in gene introns or other non-coding regions of the genome; thus variation in the number of repeats has no consequence on gene function.
Microsatellites are commonly used for mapping, linkage analysis and to trace inheritance patterns.
Q-166. Mitochondrial DNA is
a) Closed circular
b) Nicked circular
c) Linear
d) Open circular
Answer: Closed circular
Explanation:
The mitochondrial genome is built of double-stranded DNA, and it encodes genes. The mitochondrial genome is closed circular.
The mitochondrial genome is built of 16,569 DNA base pairs.
The mitochondrial genome contains 37 genes that encode 13 proteins, 22 t-RNAs, and 2 r-RNAs.
Mitochondrial DNA in humans is always inherited from a person’s mother.
Q-167. The sigma subunit of prokaryotic RNA polymerase
a) Binds the antibiotic rifampicin
b) Inhibited by alpha-amanitin
c) Specifically recognizes the promoter site
d) Part of the core enzyme
Answer: Specifically recognizes the promoter site
Explanation:
In prokaryotes, sigma subunits enables RNA polymerase core enzyme to recognize promoter region on the DNA. Sigma subunits are intimately involved in all aspects of transcription initiation.
Q-168. Which one of the following is the complementary sequence of 5’ TTAAGCTAC 3’?
a) 5’ GTACGCTTAA 3’
b) 5’ AATTCGCATG 3’
c) 5’ CATGCGAATT 3’
d) 5’ TTAAGCGTAC 3’
Answer: 5’ GTACGCTTAA 3’
Explanation:
Q-169. During replication of DNA which one of the following enzymes polymerizes the Okazaki fragments?
a) DNA Polymerase I
b) DNA Polymerase II
c) DNA Polymerase III
d) RAN Polymerase I
Answer: DNA polymerase III
Explanation:
Okazaki fragments are short, newly synthesized DNA fragments that are formed on the lagging template strand during process of replication of a ds-DNA.
They are complementary to the lagging template strand, together forming short double-stranded DNA sections.
Important points:
Okazaki fragments require RNA priming, which serves as the beginning of an Okazaki fragment polymerization.
This polymerization function is accompanied by DNA polymerase III.
These RNA primers are subsequently removed by DNA polymerase-I at the end of Okazaki fragment polymerization.
The complete but still separated Okazaki fragments are then joined into a single strand of DNA via the enzyme, DNA ligase.
Q-170. All of the following cell types contain the enzyme telomerase which protects the length of telomeres at the end of chromosomes except?
a) Germinal
b) Somatic
c) Hemopoietic
d) Tumor
Answer: Somatic
Explanation:
The telomeres are special structures on the chromosome ends that are essential for providing protection from enzymatic end-degradation and maintaining chromosomal and genomic stability.
Telomeres are composed of a DNA component characterized by non-coding repetitive sequences rich in guanine (G) and multiple protein components.
Important points:
Most human somatic cells do not produce active telomerase and do not maintain stable telomere length with proliferation.