Biology

Molecular Biology and Genetics

717 Questions

Molecular biology and genetics explore the structure and function of DNA, RNA, genetic mutations, and heredity. Understanding these building blocks of life is essential for most biology examinations. Review these practice questions to test your molecular genetics knowledge.

DNA structure and basesGenetic mutationsNucleic acids compositionDNA sequencing and replication

Molecular Biology and Genetics Questions

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

If the sequence of bases in coding strand of DNA is ATTCGATG, then the sequence of bases in mRNA will be

  1. TAAGCTAC

  2. UAAGCUAC

  3. ATTCGATG

  4. AUUCGAUG
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

mRNA strand is complementary to template strand of DNA, while coding strand has same sequence as RNA (except thymine at the place of uracil). Hence, the sequence of bases in mRNA will be AUUCGAUG.

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

If one strand of DNA has the base sequence AAGCAA, the complementary strand has which of the following sequences?

  1. UUCGUU

  2. TTCGTT

  3. AAGCM

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

The DNA (Deoxyribonucleic acid) molecules have four nucleotide bases along with sugar and phosphate backbone, these four bases are adenine, guanine, thymine, and cytosine. Adenine and thymine are bonded together by two hydrogen bonds while guanine and cytosine are bonded by three hydrogen bonds.

So, the correct option is 'TTCGTT'.

Multiple choice zoology global environmental change causes of greenhouse effect global warming adaptation in animals

Ultraviolet light causes

  1. Destruction of hydrogen bonds between complementary DNA strands

  2. Photodynamic action

  3. Sticky metaphases

  4. Formation of pyrimidines
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
DNA is one of the prime molecules and provides stability for proper functioning and existence of all living systems. Ultra-violet radiations are power molecules whose exposure breaks the hydrogen bonds of dna and thus altering its structure and affecting the genomic stability.
So, the correct answer is option A.
Multiple choice zoology global environmental change causes of greenhouse effect global warming adaptation in animals

Ultra-violet light causes

  1. Formation of pyrimidines dimers

  2. Sticky metaphases

  3. Photodynamic action

  4. Destruction of hydrogen bonds between complementary DNA strands
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The Ultra-violet radiations are the potent mutagens as they are capable of distorting the structure of the DNA. The UV radiations cause the adjacent pyrimidines residues (thymine and cytosine) to form hydrogen bonds with each other rather than the corresponding purine residues. Generally, the thymine dimers are seen as immediate effects of the UV radiations. Due to this type of mutation, the errors in replication of DNA are frequent to observe. The breaking of hydrogen bonds between the two complementary DNA strands occurs due to increase in temperature. This is not considered as a mutation because when normal conditions arrive the hydrogen bonds can be formed again.

Hence, the correct answer is 'Formation of pyrimidines dimers'.

Multiple choice biology biodiversity and classification monera five kingdoms of living organisms biodiversity and need of classification

Choose the correct answers from the alternatives given:
All monerans

  1. lack an endoplasmic reticulum

  2. contain DNA and RNA

  3. demonstrate a long circular strand of DNA not found enclosed in a nuclear membrane

  4. all of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • Monera is a kingdom that contains unicellular organisms with a prokaryotic cell organization such as bacteria. They are single-celled organisms with an absence of membrane-bound organelles. The nucleus and endoplasmic reticulum, as well as other organelles, are absent. 
  • Hence, the correct answer is 'All of the above'.
Multiple choice biology biodiversity and classification monera five kingdoms of living organisms biodiversity and need of classification

All monerans ___________________.

  1. Contain $DNA$ and $RNA$
  2. Demonstrate a long circular strand of $DNA$, not formed enclosed in a nuclear membrane

  3. Are bacteria

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Monerans are prokaryotes, meaning they lack a membrane-bound nucleus (they have a nucleoid with circular DNA). They are not exclusively bacteria (they include archaea), but the options provided are often grouped in general biology contexts.

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

Bacterial genome consist of 

  1. Circular, ssRNA

  2. Circular, dsDNA

  3. Linear, triple stranded DNA

  4. zig-zag DNA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Bacterial genome as that of a bacteria E.coli consists of Double-stranded DNA (ds DNA) which is circular which means it doesn't have ends like eukaryotic chromosomes. E.coli consists of 4.6 x 10$^6$ base pairs(bp).

So, the correct answer is 'Circular, dsDNA'.

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

DNA of Escherichia coli is

  1. dsDNA and circular

  2. dsDNA and linear

  3. ssDNA and linear

  4. ssDNA and circular.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Escherichia coli is a Gram-negative, facultatively anaerobic bacteria. It is found in the intestine of warm-blooded organisms. It has one circular chromosome. The chromosome contains double-stranded DNA. It may contain some circular plasmids as well as extrachromosomal material.

Thus, the correct answer is option A.

Multiple choice biology selection and evolution ethology animal behaviour natural selection

Which of the following codon does not justify degeneracy rule?

  1. UGG

  2. CUG

  3. GGG

  4. GAG.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Degeneracy is the rule in of genetic code which states that one amino acid can be produced by one or more codon. The example is UUU and UUG both code for same amino acid i.e phenylalanine.Tryptophan is only produced by UGG.
So the correct option is 'UGG'.
Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Polymerisation of DNA is in

  1. $3' \rightarrow 5'$ direction
  2. $5' \rightarrow 3'$ direction
  3. Both $3' \rightarrow 5'$ and $5' \rightarrow 3'$ direction

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
DNA polymerase has 5' $\rightarrow$ 3' activity. All known DNA replication systems require a free 3' hydroxyl group before synthesis can be initiated (note: the DNA temple is read in 3' to 5' direction whereas a new strand is synthesized in 5' to 3' direction).
So, the correct answer is "5' $\rightarrow$ 3' ".
Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Which one of the following palindromic base sequences in DNA can be easily cut at about the middle by some particular restriction enzyme?

  1. $5$' ______ GAATTC ________$3$

    $3$' _______ CTTAAG __________$5$'
  2. $5$' __________CACGTA _________ $3$'

    $3$'________ CTCAGT ________ $5$'
  3. $5$' ________ CGTTCG ________ $3$'

    $3$' _________ATGGTA _________$5$'
  4. $5$' _________ GATATG _________$3$'

    $3$'________CTACTA ________$5$'
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The sequence 5'-GAATTC-3' paired with 3'-CTTAAG-5' is the classic palindromic recognition site for the restriction enzyme EcoRI, which cuts between G and A.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Which of the following are all Nucleotides?

  1. Adenosine, Cytidylic acid, Cytosine

  2. Adenylic acid, Cytidylic acid, Guanylic acid

  3. Cytidine, Adenine, Adenylic acid

  4. Uracil, Thymidine, Thymidylic acid
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • Nucleotides are compound consisting of a nucleoside linked to a phosphate group. Nucleotides form the basic structural unit of nucleic acids such as DNA and RNA. For example, Adenylic acid, Guanylic acid, Thymidylic acid, and Cytidilic acid and 5'uridylic acid.
  • Hence Adenylic acid, Cytidilic acid, Guanylic acid are all Nucleotides.
  • So, the correct answer is 'Adenylic acid, Cytidilic acid, Guanylic acid'.
Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

Melting of DNA at 70$^o$ C is due to breakdown of

  1. Phosphodiester bonds

  2. Hydrogen bonds

  3. Glycosidic bonds

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

DNA denaturation involves the separation of the two strands of the double helix. This process is driven by the breaking of hydrogen bonds between complementary nitrogenous bases.

Multiple choice bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

At which temperature a DNA molecule is denatured by heat in PCR

  1. 70$^o$ - 80$^o$C
  2. 90$^o$ - 95$^o$C
  3. 42$^o$C
  4. 50$^o$ - 65$^o$C
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In the PCR process, the denaturation step requires high temperatures to break the hydrogen bonds between DNA strands. This typically occurs between 90 and 95 degrees Celsius.