DNA replication and mutations

Question 1

What does semi-conservative replication mean in DNA replication?

Answer 1

• semi-conservative DNA replication is a process in which the polynucleotide strands of DNA act as a template to make a new, complimentary strand
• each of the two, new DNA molecules now contains one ‘old’ strand and one ‘new’ strand.

Question 2

What is DNA helicase? What does it do?

Answer 2

DNA helicase is an enzyme which attaches to the DNA molecule and unwinds the double helix by breaking the hydrogen bonds between the complimentary bases

Question 3

What is DNA polymerase? What does it do?

Answer 3

• DNA polymerase is an enzyme which catalyses condensation reactions to link adjacent nucleotides together by phosphodiester bonds
• this enzyme synthesises new complimentary strands from the two template strands

Question 4

What is a nucleotide?

Answer 4

• a nucleotide is made of three components: phosphate group, a pentose sugar and a nitrogenous base
• nucleotides are the building blocks for DNA and RNA

Question 5

How is a phosphodiester bond formed?

Answer 5

• phosphodiester bond is formed by a condensation reaction between two nucleotides

Question 6

What do hydrogen bonds hold together in DNA and where are they found?

Answer 6

the two antiparallel DNA polynucleotide strands that make up the DNA molecule are held together by hydrogen bonds between the nitrogenous bases.

Question 7

Why is DNA semi conservative? Why is it important?

Answer 7

• as the DNA double helix is unwound by helicase, replication occurs separately on each template strand in antiparallel directions
• the semi-conservative mechanism minimizes errors in DNA replication, because the template gives DNA polymerase something accurate to copy from

Question 8

Explain why a mistake during DNA replication would potentially cause more problems than a mistake during protein synthesis

Answer 8

• it is more important to check for errors during DNA replication than during protein synthesis because errors in DNA replication can lead to mutations that affect the function and expression of genes
• errors in protein synthesis my result in misfolded or toxic proteins, but these are usually degraded or eliminated by the cell

Question 9

What are the similarities between DNA replication and transcription of a gene?