54357.The first genetic material could be
protein
carbohydrates
DNA
RNA
Explanation:
There are enough evidences to suggest that RNA was the first genetic material. But, RNA being a catalyst was quite reactive and hence unstable.Therefore, DNA has evolved from RNA with chemical modifications that make it more stable.DNA being double-stranded and having complementary strand further resists changes by
evolving a process of repair.
There are enough evidences to suggest that RNA was the first genetic material. But, RNA being a catalyst was quite reactive and hence unstable.Therefore, DNA has evolved from RNA with chemical modifications that make it more stable.DNA being double-stranded and having complementary strand further resists changes by
evolving a process of repair.
54358.Which of the following statements is the most appropriate for sickle-cell anaemia?
It cannot be treated with iron supplements
It is a molecular disease
It confers resistance to acquiring malaria
All of the above
Explanation:
Sickle cell anaemia is a genetic disorder and hence cannot be treated with iron supplements.
Altered shape of RBCs confer resistance to malaria in people suffering from sickle cell anaemia.
Sickle cell anaemia is a genetic disorder and hence cannot be treated with iron supplements.
Altered shape of RBCs confer resistance to malaria in people suffering from sickle cell anaemia.
54359.While analysing the DNA of an organism a total number of 5386 nucleotides were found out of which the proportion of different bases were Adenine = 29%, Guanine = 17%,Cytosine = 32%, Thymine = 17%. Considering the Chargaffs rule it can be concluded that
it is a double-stranded circular DNA
it is single-stranded DNA
it is a double-stranded linear DNA
No conclusion can be drawn
Explanation:
According to Chargaff s rules of base pairing.
(i) The amount of adenine is always equal to the amount of thymine and the amount of guanine is always equal to the amount of cytosine.
(ii) Adenine is joined to thymine with two hydrogen bonds and guanine is joined to cytosine by three hydrogen bonds.
(iii) The ratio of adenine to thymine and that of guanine to cytosine is always equal to one,A/T=G/C=1
In the given organism, the DNA is not following the Chargaff s rule, hence it can be concluded that it is a single-stranded DNA, not double-stranded
According to Chargaff s rules of base pairing.
(i) The amount of adenine is always equal to the amount of thymine and the amount of guanine is always equal to the amount of cytosine.
(ii) Adenine is joined to thymine with two hydrogen bonds and guanine is joined to cytosine by three hydrogen bonds.
(iii) The ratio of adenine to thymine and that of guanine to cytosine is always equal to one,A/T=G/C=1
In the given organism, the DNA is not following the Chargaff s rule, hence it can be concluded that it is a single-stranded DNA, not double-stranded
54360.Which of the following steps in transcription is catalysed by RNA polymerse?
Initiation
Elongation
Termination
All of these
Explanation:
The DNA dependent RNA polymerase helps in DNA replication by catalysing the polymerisation in only one direction,i.e., 5 ->3 .
The DNA dependent RNA polymerase helps in DNA replication by catalysing the polymerisation in only one direction,i.e., 5 ->3 .
54361.Regulatory proteins are the accessory proteins that interact with RNA polymerase and affect its role in transcription. Which of the following statements is correct about regulatory protein?
They only increase expression
They only decrease expression
They interact with RNA polymerase but do not affect the expression
They can act both as activators and as repressors
Explanation:
Regulatory proteins control the functions of structural genes and are at called regulatory
genes.The important regulatory genes are promoters, terminators, operators and repressor.
To regulate the process of transcription, transcription factors (a sequence of specific DNA-binding factor) alone or with other proteins, promoter (as on activator)or stop as a repress or the binding site of RNA polymerase to DNA.
Regulatory proteins control the functions of structural genes and are at called regulatory
genes.The important regulatory genes are promoters, terminators, operators and repressor.
To regulate the process of transcription, transcription factors (a sequence of specific DNA-binding factor) alone or with other proteins, promoter (as on activator)or stop as a repress or the binding site of RNA polymerase to DNA.
54362.In a DNA strand the nucleotides are linked together by
glycosidic bonds
phosphodiester bonds
peptide bonds
hydrogen bonds
Explanation:
In a DNA strand the nucleotides are linked together by 3’-5’ phosphodiester linkage.
In a DNA strand the nucleotides are linked together by 3’-5’ phosphodiester linkage.
54363.The fact that a purine always paired base through hydrogen bonds with a pyrimidine base leads to, in the DNA double helix
the antiparallel nature
the semiconservative nature
uniform width throughout DNA
uniform length in all DNA
Explanation:
The diameter of the strand is always constant due to a pairing of purine (adenine and guanine)
and pyrimidine (cytosine and thymine). This specific bonding gives uniform width to the DNA.
The diameter of the strand is always constant due to a pairing of purine (adenine and guanine)
and pyrimidine (cytosine and thymine). This specific bonding gives uniform width to the DNA.
54364.A nucleoside differs from a nucleotide. It lacks the
base
sugar
phosphate group
hydroxyl group
Explanation:
A nitrogenous base is attached to the pentose sugar by an N-glycosidic linkage to form a nucleoside, i.e., Nucleoside = Nitrogen base + Pentose sugar. On the other hand a phosphate group is attached to the 5 -OH of a nucleoside through phosphodiester linkage to form a nucleotide,
i.e., Nucleotide = Nitrogen base + Pentose sugar + Phosphate (PO4).
A nitrogenous base is attached to the pentose sugar by an N-glycosidic linkage to form a nucleoside, i.e., Nucleoside = Nitrogen base + Pentose sugar. On the other hand a phosphate group is attached to the 5 -OH of a nucleoside through phosphodiester linkage to form a nucleotide,
i.e., Nucleotide = Nitrogen base + Pentose sugar + Phosphate (PO4).
54365.DNA is a polymer of nucleotides which are linked to each other by 3 -5 phosphodiester bond. To prevent polymerisation of nucleotides, which of the following modifications would you choose?
Replace purine with pyrimindines
Remove/Replace 3 OH group in deoxy ribose
Remove/Replace 2 OH group with some other group in deoxy ribose
Both (b) and (c)
Explanation:
The enzyme called DNA polymerase progressively adds deoxyribonucleotides to the free 3 -end of the growing polynucleotide chain so, that replication of the 3 -5 strand of the DNA molecule is continuous. So, to prevent polymerisation of nucleotides 3 OH group in deoxyribose should be replaced/removed.
The enzyme called DNA polymerase progressively adds deoxyribonucleotides to the free 3 -end of the growing polynucleotide chain so, that replication of the 3 -5 strand of the DNA molecule is continuous. So, to prevent polymerisation of nucleotides 3 OH group in deoxyribose should be replaced/removed.
54366.With regard to mature mRNA in eukaryotes
Exons and introns do not appear in the mature RNA
Eexons appear but introns do not appear in the mature RNA
introns appear but exons do not appear in the mature RNA
both exons and introns appear in the mature RNA
Explanation:
In eukaryotes, the monocistronic structural genes have interrupted coding sequences i.e., the genes in eukaryotes are split. The coding sequences or expressed sequences are defined as exons.These sequences (exons) appear in mature or processed RNA.The exons are interrupted by introns or intervening sequences which do not appear in mature or processed RNA.
In eukaryotes, the monocistronic structural genes have interrupted coding sequences i.e., the genes in eukaryotes are split. The coding sequences or expressed sequences are defined as exons.These sequences (exons) appear in mature or processed RNA.The exons are interrupted by introns or intervening sequences which do not appear in mature or processed RNA.
54367.Which was the last human chromosome to be completely sequenced?
Chromosome 1
Chromosome 11
Chromosome 21
Chromosome-X
Explanation:
Chromosome 1 was the last completed chromosome, sequenced two decades after the beginning of the human Genome Project (hGP). It is the designation for the largest human chromosome.
Chromosome 1 was the last completed chromosome, sequenced two decades after the beginning of the human Genome Project (hGP). It is the designation for the largest human chromosome.
54368.Who amongst the following scientists had no contribution in the development of the double helix model for the structure of DNA?
Rosalind Franklin
Maurice Wilkins
Erwin Chargaff
Meselson and Stahl
Explanation:
It was only in 1953 that James Watson and Francis Crick, based on the X-ray diffraction data
produced by Maurice Wilkins and Rasalind Franklin, proposed a very simple but famous double helix model for the structure of DNA.
Erwin Chargaff observed that for a double-stranded DNA, the ratios between adenine and thymine and guanine and cytosine are constant and equals one.
On the other bond Matthew Meselson and Franklin Stahl in 1958 performed experiments on E.coli to prove that DNA replication is semi-conservative. But they had no contribution it the development of double helix model.
It was only in 1953 that James Watson and Francis Crick, based on the X-ray diffraction data
produced by Maurice Wilkins and Rasalind Franklin, proposed a very simple but famous double helix model for the structure of DNA.
Erwin Chargaff observed that for a double-stranded DNA, the ratios between adenine and thymine and guanine and cytosine are constant and equals one.
On the other bond Matthew Meselson and Franklin Stahl in 1958 performed experiments on E.coli to prove that DNA replication is semi-conservative. But they had no contribution it the development of double helix model.
54369.Which of the following are the functions of RNA?
It is carrier of genetic information from DNA to ribosomes synthesising polypeptides
It carries amino acids to ribosomes
It is a constituent component of ribosomes
All of the above
Explanation:
rRNA,mRNA and tRNA are major classes of RNAs that are involved in gene expression. rRNAs bind protein molecules and give rise to ribosomes.mRNA carries coded information for translation into polypeptide formation.
rRNA is called soluble or adaptor RNA and carries amino acids to mRNA during protein synthesis.
rRNA,mRNA and tRNA are major classes of RNAs that are involved in gene expression. rRNAs bind protein molecules and give rise to ribosomes.mRNA carries coded information for translation into polypeptide formation.
rRNA is called soluble or adaptor RNA and carries amino acids to mRNA during protein synthesis.
54370.Discontinuous synthesis of DNA occurs in one strand, because
DNA molecule being synthesised is very long
DNA dependent DNA polymerase catalyses polymerisation only in one direction (5->3)
it is a more efficient process
DNA ligase has to have a role
Explanation:
DNA polymerase adds deoxyribonucleotides to the free 3 -end of the growing _ polynucleotide chain so, that replication of the 3 -5 strand of the DNA molecule is continuous (growth of the new strand in 5 ->3 direction).
Since, DNA dependent DNA polymerase catalyses polymerisation only in one direction(5 ->3’), discontinuous synthesis of DNA occurs in the other strand.
DNA polymerase adds deoxyribonucleotides to the free 3 -end of the growing _ polynucleotide chain so, that replication of the 3 -5 strand of the DNA molecule is continuous (growth of the new strand in 5 ->3 direction).
Since, DNA dependent DNA polymerase catalyses polymerisation only in one direction(5 ->3’), discontinuous synthesis of DNA occurs in the other strand.
54371.Both deoxyribose and ribose belong to a class of sugars called
trioses
hexoses
pentoses
polysaccharides
Explanation:
Both deoxyribose and ribose belong to the class pentoses as both of them are 5-carbon sugars.
Both deoxyribose and ribose belong to the class pentoses as both of them are 5-carbon sugars.
54372.The net electric charge on DNA and histones is
both positive
both negative
Both (a) and (b)
zero
Explanation:
DNA consists of a nitrogenous base, pentose sugar and a phosphate group. DNA has negative
charge due to the presence of phosphate group (PO43-).
Histones are rich in the basic amino acid residues lysines and arginines, which carry positive
charges in their side chains. Therefore, histones are positively charged.
DNA consists of a nitrogenous base, pentose sugar and a phosphate group. DNA has negative
charge due to the presence of phosphate group (PO43-).
Histones are rich in the basic amino acid residues lysines and arginines, which carry positive
charges in their side chains. Therefore, histones are positively charged.
54373.The promoter site and the terminator site for transcription are located at
3 (downstream) end and 5 (upstream) end, respectively of the transcription unit
5 (upstream) end and 3 (downstream) end, respectively of the transcription unit
the 5 (upstream) end
the 3 (downstream) end
Explanation:
The promoter is the binding site for RNA polymerase for initiation of transcription.The promoter is located towards 5-end (upstream) of the structural gene of coding strands and provides the binding site for RNA polymerase.
The promoter is the binding site for RNA polymerase for initiation of transcription.The promoter is located towards 5-end (upstream) of the structural gene of coding strands and provides the binding site for RNA polymerase.
54374.Control of gene expression takes place at the level of
DNA-replication
transcription
translation
None of these
Explanation:
Transcription is the first step of gene expression. In this process, a particular segment of DNA is copied into mRNA
Transcription is the first step of gene expression. In this process, a particular segment of DNA is copied into mRNA
54375.One of the following is true with respect to AUG
it codes for methionine only
it is also an initiation codon
it codes for methionine in both prokaryotes and eukaryotes
All of the above
Explanation:
Polypeptide synthesis is signalled by two initiation codons commonly AUG or methionine codon and rarely GUG or valine codon. Since there are 64 triplet codons and only 20 amino acids, the incorporation of some amino acids must be influenced by more than one codon.
Polypeptide synthesis is signalled by two initiation codons commonly AUG or methionine codon and rarely GUG or valine codon. Since there are 64 triplet codons and only 20 amino acids, the incorporation of some amino acids must be influenced by more than one codon.
54376.The human chromosome with the highest and least number of genes in them are respectively
chromosome 21 and Y
chromosome 1 and X
chromosome 1 and Y
chromosome X and Y
Explanation:
In humans, chromosome 1 has highest genes (2968 approx.) and chromosome Y has the least number of genes (231 approx.).
In humans, chromosome 1 has highest genes (2968 approx.) and chromosome Y has the least number of genes (231 approx.).