Molecular genetics: Practice Questions

The process of synthesizing RNA from a DNA template is known as:

During the process of protein synthesis, what is the specific role of the anticodon located on a tRNA molecule?

In DNA fingerprinting, a student observes several bands on an electrophoresis gel. These bands represent DNA fragments separated by size. Which of the following statements correctly explains the origin of these fragments?

Which of the following nitrogenous bases is found in RNA but not in DNA?

In a eukaryotic cell, a primary transcript (pre-mRNA) undergoes extensive processing before becoming a mature messenger RNA (mRNA). Which of the following sequences found within the initial primary transcript is typically retained and translated into a polypeptide?

Name the three components that make up a DNA nucleotide.

Given the messenger RNA (mRNA) sequence 5'-AUG CCG UAA-3', what is the corresponding amino acid sequence that it codes for?

Molecular genetics provides the basis for understanding how genetic information is stored, expressed, and applied in biotechnology. Consider a segment of a DNA template strand with the following sequence: 3'-TAC AAA CCG AGT ATT-5'.

(a) Using the genetic code provided below, determine the mRNA sequence transcribed from this segment and the resulting amino acid sequence of the polypeptide produced. (2 marks)
AUG = Methionine; UUU = Phenylalanine; UUC = Phenylalanine; GGC = Glycine; UCA = Serine; UAA = Stop.

(b) Suppose a substitution mutation occurs at the 6th position of the original DNA template strand, where Adenine (A) is replaced by Guanine (G). Describe the resulting change in the polypeptide and explain the property of the genetic code that accounts for this observation. (2 marks)

(c) If a deletion occurs at the 4th position (Adenine) instead of the substitution described in (b), explain how this change affects the translation process from that point onward and why this type of mutation is generally more likely to result in a non-functional protein. (2 marks)

(d) Biotechnology utilizes our understanding of DNA variations for identification. Explain how the presence of variable number tandem repeats (VNTRs) in non-coding regions allows scientists to distinguish between individuals using the technique of gel electrophoresis. (2 marks)

Molecular genetics involves understanding the flow of genetic information and the application of DNA technologies. Consider a segment of a DNA template strand with the following sequence:
3'- TAC GGC TTT ACC GGG ACT -5'

(a) State the mRNA sequence transcribed from this DNA segment and the resulting sequence of amino acids. (Codon reference: AUG = Methionine; CCG = Proline; AAA = Lysine; UGG = Tryptophan; CCC = Proline; UGA = Stop). (2 marks)

(b) If a mutation occurs where the 5th base (G) in the DNA template strand is substituted by 'A', determine the new mRNA codon at that position. Explain how this substitution mutation could lead to a change in the protein's overall three-dimensional shape. (2 marks)

(c) Explain the significance of the Human Genome Project (HGP) in advancing our ability to diagnose inherited diseases. (2 marks)

(d) Recombinant DNA technology often involves the use of plasmids as vectors. Describe how restriction enzymes and DNA ligase are used to insert a human gene into a bacterial plasmid. (2 marks)