DNA Structure - L4

Question 1

Describe the strucuture of DNA.

Answer 1

DNA is made up of nucleotides that each have a deoxyribose sugar, phosphate group and nitrogenous base. The nucleotides are held together by covalent bonds known as phosphodiester bonds. DNA has 5 prime to 3 prime end on strands that are the start and end.

Double stranded DNA forms a helix, with complementary antiparallel strands. A-T and G-C. Major and minor grooves in DNA double helix where there is a helical turn every 10.5 basepairs.

Question 2

What are purines and pyrimidines?

Answer 2

Purines have 2 carbon rings = Adenine and Guanine

Pyrimidines have 1 carbon ring = Cytosine and Thymine.

A-T has 2 base pairs.
G-C has 3 base pairs.

Question 3

What are the structural features of plasmids and chromosomes?

Answer 3

Prokaryotes - have plasmids, small circular DNA molecule.

Eukaryotes - chromosomes, linear molecules held in the nucleus of the cell.

Question 4

What are DNA binding domains in proteins and what are their roles?

What are the 3 DNA binding domain examples?

Answer 4

DNA binding domains in proteins have a general affinity for DNA (double or single stranded), that are sequence-specific.

They regulate gene expression, cut DNA at specific sequences and protect DNA.

examples are…

1. The sheltering complex
2. Transcriptional regulators
3. Histones