Biology

Molecular Genetics

917 Questions

Molecular genetics explores the mechanisms of genetic information transfer, including DNA replication, transcription, and translation. It is a core component of biology syllabi. These concepts frequently appear in general science sections of major competitive exams.

DNA replicationTranscription processTranslation processRNA typesCentral dogma

Molecular Genetics Questions

Multiple choice expression of gene inherited changes biology

In Prokaryotes, the predominant site for control of gene expression is 

  1. Transcriptional intimation

  2. Processing level

  3. Transfer of mRNA from nucleus to the cytoplasm

  4. Translation initiation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Regulation of gene expression refers to a very broad term that may occur at various levels. In prokaryotes, control of the rate of transcriptional initiation is the predominant site for control of gene expression. 
Considering that gene expression results in the formation of a polypeptide, it can be regulated at several levels. In eukaryotes, the regulation could be exerted at
(i) transcriptional level (formation of primary transcript),
(ii) processing level (regulation of splicing),
(iii) transport of mRNA from the nucleus to the cytoplasm,
(iv) translational level.

So, the correct option is 'Transcriptional intimation'.

Multiple choice expression of gene inherited changes biology

Choose the correct answer from the alternatives given :
Control of gene expression takes place at the level of

  1. DNA-replication

  2. Transcription

  3. Translation

  4. None of the above.
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

Regulation of gene expression refers to a very broad term that may occur at various levels. In eukaryotes the gene expression can be regulated at transcriptional level, processing level, transport of mRNA from nucleus to the cytoplasm, and translational level whereas in prokaryotes, control of the rate of transcriptional initiation is the predominant site for control of gene expression.

So, the correct answer is 'Transcription and Translation'.

Multiple choice expression of gene inherited changes biology

When Tryptophan is present

  1. repressor is unable to bind to the operator

  2. transcription of structural genes occurs

  3. repressor is able to bind to the operator

  4. both (a) and (b)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The Trp operon is an example of a repressible operon; it is on unless turned off by a repressor protein. The repressor protein is synthesized by trpR. While the repressor protein is always present in the cell, it is synthesized in an inactive form. When a corepressor is present, in this case, tryptophan, it binds to the repressor protein in an allosteric site. This changes the conformation of the protein such that it can bind to the operator and block transcription by preventing the binding of RNA polymerase to the promoter. In this way, the cell saves energy by not producing tryptophan when it is already present.

So, the correct option is 'repressor is able to bind to the operator'.

Multiple choice zoology structure of chromosome, cell cycle and cell division structure of dna nucleic acid heredity and inheritance

Histone proteins are associated with

  1. DNA

  2. mRNA

  3. rRNA

  4. snRNA

  5. tRNA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Nucleosomes are fundamental organizational units of chromatin which appear as “beads-on-a-string” arrangement. Here beads represent complexes of histones and DNA. Each bead contains a core of histone octamer: two copies each of H2A, H2B, H3, and H4; out of 200 bp DNA, 146 bp DNA is bound tightly around the histone core and the remainder serve as linker DNA between nucleosomal beads. The H1 histone associates with the linker DNA to pack adjacent nucleosomes together and forms a compact 30-nm chromatin fiber. Thus, the correct answer is A.

Multiple choice zoology structure of chromosome, cell cycle and cell division structure of dna nucleic acid heredity and inheritance

DNA is directly involved in the synthesis except that of

  1. DNA

  2. Protein

  3. tRNA

  4. mRNA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
DNA is genetic material found in the living cell. It helps to carry characters from one generation to the other. The process by which the DNA replicated and forms another DNA molecule is known as replication. Parent strand of the DNA strand act as a template for synthesis of another DNA molecule.
Transcription is the process by which DNA is converted into RNA. The enzyme RNA polymerase plays an important role in transcription. The sequence of the nitrogenous base on the DNA acts as a template and determines the sequence of the nitrogenous base on the RNA. The RNA formed by the DNA are messenger RNA, t- RNA and ribosomal RNA.
Protein is formed by the m-RNA by process of translation.
So, the correct answer is option B.
Multiple choice zoology structure of chromosome, cell cycle and cell division structure of dna nucleic acid heredity and inheritance

Major and minor grooves can be seen in

  1. Polypeptide

  2. RNA

  3. DNA

  4. Chromatin
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
DNA has the double helical structure where the two strands are tightly coiled over each other. B- DNA has right-handed helix with the major and minor groove. The diameter of the DNA is 20 A$^o$. The number of base pairs in one turn is 10 and the distance between base pairs is 3.4 A$^o$. At major grooves, the base pairs are far apart while at minor groove the base pairs are closer. Major grooves have base pairs at a distance the DNA binding protein can easily interact with the bases.
So, the correct answer is option A.
Multiple choice structure of dna and rna nucleic acids and polynucleotides nucleic acids and protein synthesis molecular biology biology

The transforming substance in Griffith's experiment is 

  1. protein

  2. DNA

  3. mRNA

  4. polysaccharide
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The transforming principle in Griffith's experiment is DNA. Griffith conducted an experiment in 1928. In this experiment he chose two strains of Stephylococcus pneumoniae bacteria. One of them was a smooth strain which was virulent and the other one was a rough strain which was non-virulent. The smooth strains caused pneumonia when they were injected to the mice, and the rough strains did not cause pneumonia in mice. Griffith heat killed the smooth strain bacteria and injected them into mice and he observed that pneumonia was not caused in them. He mixed the heat killed smooth strain and rough strain and injected the mixture into mice and this mixture caused pneumonia in mice. When he tested the blood of the mice, he saw both rough and smooth strains of bacteria. This implied that some factor from the dead smooth bacterial strain had taken entry into the rough strains and converted them into smooth strains. He called this factor as Transforming principle.

Later in 1944 scientists, Avery, MacLeod, and McCarty conducted an experiment to find out what the transforming principle was, They selected DNA, Proteins and RNA. They eliminated proteins by adding proteases and the strains were able to perform the transformation, they eliminated RNA with RNase the strains were still able to perform the transformation, they eliminated DNA with DNase and now the smooth strains lost the ability to transform Rough strains and hence it was proved that the DNA was the transforming principle. 
Therefore the right option is option B, DNA. 

Multiple choice structure of dna and rna nucleic acids and polynucleotides nucleic acids and protein synthesis molecular biology biology

Select the correct option

  1. Direction of RNA Synthesis ----- Direction of reading of template DNA Strand

    3 5------5 3

  2. Direction of RNA Synthesis ----- Direction of reading of template DNA Strand

    5 3------5 3

  3. Direction of RNA Synthesis---- Direction of reading of template DNA Strand

    3 5------3 5

  4. Direction of RNA Synthesis - ---- Direction of reading of template DNA Strand

    5 3 ----- 3 5
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

RNA synthesis occurs in the 5' to 3' direction, and the template DNA strand is read in the 3' to 5' direction to ensure antiparallel alignment.

Multiple choice structure of dna and rna nucleic acids and polynucleotides nucleic acids and protein synthesis molecular biology biology

The terminator/stop codons UGA, UAG and UAA

  1. Initiate translation

  2. Do not code for any amino acid

  3. Code for only one amino acid

  4. Code for more than one amino acid

  5. Initiate transcription
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

UGA, UAG, and UAA are known as stop or nonsense codons. They signal the termination of protein synthesis and do not code for any amino acid.

Multiple choice botany the world of microbes bacteria - introduction, shape and structure bacteria: types and structure bacteria; benefits and harmful effects non cellular organism : virus world of virus

Sex factor of bacteria is

  1. RNA

  2. Sex pili

  3. F-factor

  4. Chromosome replicon
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

F-factor is also called as fertility factor. It is the sex factor of bacteria. It allows the transfers of genes from one bacterium carrying the factor to another bacterium lacking the factor by the process of conjugation. It is found in some bacteria only.

Thus, the correct answer is 'F-factor.'

Multiple choice biology cell-the basic unit of life nucleus organelles in cell membranous and non-membranous organells

The thread like structure present in the nucleus are

  1. Nucleolus

  2. Genes

  3. Chromosomes

  4. Ribosomes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The thread like structure present in the nucleus are called the chromosomes or the chromatin, when the degree of condensation is very less.

A. Nucleolus is the region on the chromosomes that codes for the ribosomal RNA. 
B. Genes are the segments of DNA that code for the proteins. These are located on the chromosomes.
C. The chromosomes are the thread like structures made up of DNA and proteins and are present in the DNA.
D. Ribosomes are the ribo-nucleoproteins present in the cytoplasm that take part in protein formation.
Hence, the correct answer is 'Chromosomes'

Multiple choice biology cell-the basic unit of life nucleus organelles in cell membranous and non-membranous organells

Cell nucleus is the site for

I. RNA synthesis 
II. Proteins synthesis 
III. DNA synthesis

  1. I only

  2. II only

  3. III only

  4. I and III only

  5. I, II and III
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The nucleus is the important structure of the cell and fully enclosed in a nuclear membrane. It contains the cells' genetic material organized as DNA and variety of proteins to form chromosomes. This is major site for cell reproduction. The genes are first transcribed, where DNA is read by RNA polymerase to produce messenger RNA (mRNA). The nucleus is therefore the site of RNA and DNA synthesis. Whereas protein is synthesized from the mRNA in the cytoplasm. Thus, the correct answer is option D.