Biology

Molecular Biology and Genetics

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

In the speculation concering the origins of life, one theory states that the combination of purines, pyrimidines, sugars, and phosphates is called as______________.

  1. Nucleotides

  2. Nucleosides

  3. Carbohydrates

  4. Fats

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

Nucleotides are formed by the combination of purines or pyrimidines (nitrogenous bases), sugars (pentose), and phosphates. Nucleosides lack the phosphate group, making option A the correct answer.

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

If one strand of DNA sequence is - 5'-GAATTG-3' - then the sequence of the opposite strand is

  1. 5'-CAATTC-3'

  2. 5'-CTTAAC-3'

  3. 5'-GAATTG-3'

  4. 5'-GTTAAG-3'

  5. 5'-TAATTC-3'
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A DNA strand is complementary. This means adenine pairs with thymine and cytosine pairs with guanine in the opposite strand. The given strand has a sequence 5'-GAATTG-3'. Hence the complementary strand will have a sequence 5'-CAATTC-3'. Thus the correct answer is option A.

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

A $340\overset{o}{A}$ long segment of DNA molecule has $20$ thymine nitrogenous bases, what will be the number of guanine nitrogen bases in the same segment?

  1. $10$
  2. $40$
  3. $30$
  4. $160$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Option (C) 30

$ 34A = 10 $ nucleotides
$ 340A = 100 $ nuclotides
$ A = T = 20 $
$ 100-40 = 60 $ nucleotides
$ G = C = 60 $
Hence $ G = 60/2 = 30 $ nuclotides
Multiple choice zoology structure of chromosome, cell cycle and cell division structure of dna nucleic acid heredity and inheritance

The DNA strands are antiparallel because of the presence of

  1. H-bonds

  2. Peptide bonds

  3. Disulphide bonds

  4. Phosphate-diester bonds

  5. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When DNA strands run in opposite direction one strand from 5 prime to 3 prime and another strand from 3 prime to 5 prime is called as antiparallel. The 5 prime end have phosphate in 5$^{th}$position of sugar and 3 prime end have a hydroxyl group on 3$^{rd}$ position of sugar. DNA strands are antiparallel because of the presence of hydrogen bond. Hydrogen bond binds the complementary bases (purine and pyrimidine)

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

In DNA, adenine pairs with

  1. Guanine

  2. Thymine

  3. Cytosine

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

The nitrogenous bases present in the DNA are purines and pyrimidines. The purines are adenine and guanine. The pyrimidines are thymine and cytosine. The purines are double ring structure while the pyrimidines are the single ring made up of carbon and nitrogen. Purines pair with the pyrimidines by hydrogen bonds. Adenine pairs with thymine by two hydrogen bond while the cytosine pairs with the guanosine by three hydrogen bonds.

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

DNA is composed of repeating units of

  1. Ribonucleosides

  2. Deoxyribonucleosides

  3. Ribonucleotides

  4. Deoxyribonucleotides
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
DNA is a chain of polynucleotide which are joined by the phosphodiester bonds. The nucleotide consists of a deoxyribose sugar, nitrogenous bases, and phosphate.The two nucleotide is linked by the phosphodiester bond. It is formed by the linkage between the 3' carbon atom of one sugar molecule and the 5' carbon atom of another. Two hydroxyls (OH) groups on the phosphate molecule bind to the 3’ and 5’ carbons on two independent pentose sugars to form a bond.
So, the correct answer is option D.
Multiple choice zoology structure of chromosome, cell cycle and cell division structure of dna nucleic acid heredity and inheritance

Base pairs present in one turn of DNA are

  1. $12$
  2. $11$
  3. $10$
  4. $9$
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 distance between base pairs is 3.4 A$^o$. The total length of one turn of DNA is 34 A$^o$. The total number of the base pair in each turn is 34/3.4 = 10.
So, the correct answer is option C.
Multiple choice zoology structure of chromosome, cell cycle and cell division structure of dna nucleic acid heredity and inheritance

The similarity between bacterial and eukaryotic DNA is that both are

  1. Circular

  2. Single stranded

  3. Double stranded

  4. All the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Nucleic acids are DNA and RNA. DNA is a genetic material which is mainly present in the nucleus of the cell in eukaryotes like mammals. The genetic material is covered by a nuclear membrane. In prokaryotes like bacteria the genetic material lie freely in the cytoplasm. The region where the nucleic acid are present is known as nucleoid. The similarity between bacterial and eukaryotic DNA is that both are double stranded DNA.
So, the correct answer is option C.
Multiple choice zoology structure of chromosome, cell cycle and cell division structure of dna nucleic acid heredity and inheritance

Length of one turn of DNA is

  1. $34 \mathring{A}$
  2. $3.4 \mathring{A}$
  3. $0.34 \mathring{A}$
  4. $20 \mathring{A}$
Reveal answer Fill a bubble to check yourself
A 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$^o$. So the total length of one turn of DNA is 10 x 3.4 =  34 A$^o$.
So, the correct answer is option A.
Multiple choice zoology structure of chromosome, cell cycle and cell division structure of dna nucleic acid heredity and inheritance

The two strands of DNA are held together by bonds of

  1. Nitrogen

  2. Oxygen

  3. Hydrogen

  4. Carbon
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The nitrogenous bases present in the DNA are purines and pyrimidines. Purines are double ring while pyrimidines are single ring structure. Adenine and guanine are purines while thymine, uracil, and cytosine are pyrimidines. A purine is attached to pyrimidine by hydrogen bond. Adenine is attached to thymine by two hydrogen bonds while three hydrogen bond is present between guanine and cytosine.
So, the correct answer is option C.
Multiple choice zoology structure of chromosome, cell cycle and cell division structure of dna nucleic acid heredity and inheritance

DNA is very long. It is accommodated in small sized nucleus by

  1. DNA-ase digestion

  2. Super coiling

  3. Elimination of repetitive DNA

  4. Deletion of non-essential genes
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

DNA is very long. It is accommodated in the small-sized nucleus by super coiling. The enzyme topoisomerase helps in the supercoiling of the DNA which helps in packaging and some biological process. The super coiled DNA is uncoiled during the process of transcription and translation. During transcription the enzyme helicase cuts the phosphate backbone and separates the two super coiled DNA strands while the topoisomerase balances the strain and prevents the recoiling of the DNA.

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

A $68nm$ length double stranded DNA has 24 adenine nucleotices. What must be the number of guanine nucleotides?

  1. $48$
  2. $72$
  3. $76$
  4. $176$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Length of $3.4 nm $ includes $10$ base pairs.So, $68 nm $ will include $200$ base pairs that is $400$ bases.

A=T AND G=C,
A+T+G+C=$400$,
$24$+$24$+$2G$=$400$.,
$2G$ = $352$.
So, Guanine nucleotides would be $176$.
Hence, the correct answer is option D.

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

The genetic information in the body is encoded in the

  1. Structural proteins

  2. Enzymes

  3. DNA

  4. DNA and enzymes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Deoxyribose Nucleic Acid or DNA carries the genetic information in the form of small segments known as genes and is also the genetic material in various organisms including humans.

Structural proteins and enzymes are the gene products that are synthesised from DNA through the process of translation.
Hence, the correct answer is 'DNA'.

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

Which of the following general statement about the structure of DNA is true?

  1. The hydrogen bonds connecting base pairs exist in a polar environment.

  2. Both major and minor grooves are formed between the phosphate-sugar backbone.

  3. The same C and N atoms are present in each groove.

  4. The amount of energy required to break down the AT and GC pairs is the same.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The DNA double helical structure has two different environments. The nitrogenous bases have an aromatic ring structure and are hydrophobic and interact with each other through base pair stacking interactions. At the same time, the back bone of DNA formed by phosphodiester bonds is hydrophilic and interacts with water. The nitrogenous bases of one nucleotide chain form hydrogen bonds with the nitrogenous bases present directly opposite them on the other chain. The hydrogen bonds are formed in polar aqueous environment. The adenine base pairs with thymine with two hydrogen bonds and guanine base pairs with cytosine with three hydrogen bonds.
So, the correct answer is option A.