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

What is not relevant to DNA double helix ?

  1. One turn every 34

  2. Diameter 20

  3. Distance between adjacent nucleotides 3.4

  4. Back bone has alternate ribose sugar and phosphate

  5. Sugar molecules are joined by phosphodiester bonds
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The DNA backbone consists of alternating deoxyribose sugar and phosphate groups, not ribose sugar (which is found in RNA).

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

TACAAAGGGTTTCAACCC is the sequence of nucleotides in a DNA strand. Predict the sequence of amino acids found in a protein formed from it

  1. Proline, phenylalanine, lysine, methionine, glycine, valine

  2. Methionine, phenylalanine, glycine, valine, lysine, proline

  3. Valine, glycine, proline, lysine, phenylalanine, methionine

  4. Methionine, phenylalanine, proline, lysine, valine, glycine
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Translating the sequence TAC AA A GGG TTT CAA CCC: TAC (Methionine/Start), AAA (Phenylalanine), GGG (Proline), TTT (Lysine), CAA (Valine), CCC (Glycine). Note: The codon table mapping confirms this sequence.

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

Identify the DNA segment which is not pallindromic

  1. 5'-GAATTC -3'

    3'-CTTAAG-5'

  2. 5'-CCCGGG-3'

    3'-GGGCCC-5'

  3. 5-GGATCC-3'

    3' GGTACC-5'

  4. 5'-GCGGCCGC-3'

    3-CGCCGGCG-5'
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A palindromic DNA sequence reads the same in the 5' to 3' direction on both strands. Option C is not palindromic because the complementary strand of 5'-GGATCC-3' is 3'-CCTAGG-5', which does not match the provided sequence.

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

Which one of the following alternations in DNA is likely to be lethal?

  1. Substitution of adenine for cytosine

  2. Substitution of methyl cytosine for cytosine

  3. Deletion of thee nucleotides

  4. Insertion of one nucleotide
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Insertion or deletion of a single nucleotide shifts the reading frame of the entire downstream genetic sequence, resulting in a frameshift mutation that drastically alters all subsequent amino acids and is usually lethal or severely dysfunctional. Substitutions or deletions of three nucleotides affect only single amino acids or remove a single codon.

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

An increased melting temperature for duplex DNA results from a high content of _________________.

  1. Adenine$+$ guanine
  2. Cytosine$+$thymine
  3. Cytosine$+$guanine
  4. Adenine$+$ cytosine
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cytosine and guanine base pairs are held together by three hydrogen bonds, whereas adenine and thymine pairs have only two. Consequently, DNA strands with a higher G-C content require more thermal energy to break the hydrogen bonds, resulting in an increased melting temperature.

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

The successive nucleotides of RNA are covalently linked through ______________.

  1. Glycoside bonds

  2. Hydrogen bonds

  3. Phosphodiester bonds

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

Successive nucleotides in both RNA and DNA chains are covalently joined together by phosphodiester bonds, which form between the 3 prime carbon of one sugar and the 5 prime carbon of the next. Glycoside bonds link bases to sugars, and hydrogen bonds hold complementary strands together non-covalently.