Session 2-Introduction To DNA

Question 1

Which groove is used for DNA protein binding and why?

Answer 1

Major groove because it has the most space for protein to bind to

Question 2

How is 2m of DNA packaged in a cell?

Answer 2

DNA wraps around special proteins called HISTONES which form loops of DNA called NUCLEOSOMES. These nucleosomes coil and stack together to form fibres called CHROMATIN. This in turn forms larger loops and coils to form CHROMOSOMES.

Question 3

What is a gene?

Answer 3

Basic unit of genetic information, carried on a specific locus on a chromosome

Question 4

What are nucleic acids?

Answer 4

Polynucleotides (linear polymers of nucleotides)

Question 5

What are the two types of pentose sugars?

Answer 5

Ribose (in RNA)-OH on 2C

2-deoxyribose (in DNA)-H on 2C

Question 6

Which bases are purines? (Remember: angels are pure)

Answer 6

Adenine and Guanine

Question 7

Which bases are pyrimidines?

Answer 7

Cytosine
Thymine
Uracil (RNA)

Question 8

How are nucleotides joined?

Answer 8

Phosphodiester bonds

Question 9

Describe the polarity in a DNA molecule

Answer 9

The chain has a 5’P (phosphate end of the chain) and a 3’OH (OH on 3C in deoxyribose)

Question 10

How many hydrogen bonds are between G and C?

Answer 10

3

Question 11

How many hydrogen bonds are between A and T or A and U?

Answer 11

2

Question 12

What is the conventional way of depicting a DNA sequence?

Answer 12

5’ to 3’ from left to right and the top strand is always 5’ to 3’

NOTE: always write complementary strand from 5’, regardless of 3’ start