DNA Structure

Question 1

what are Chargaff 2 significant findings

Answer 1

1. the number of adenine units approximately equals number of thymine and vice versa with guanine units and cytosine units
2. the composition of DNA varies between species

Question 2

the 3 findings in the first x-ray of the DNA molecule

Answer 2

1. helical structure
2. bases perpendicular to the length of the DNA molecule
3. double stranded

Question 3

what bases are pyrimidines

Answer 3

cytosine and thymine

Question 4

what bases are purines

Answer 4

adenine and guanine

Question 5

how are nucleotide monomers joined together

Answer 5

• joined together with phosphodiester bonds to form a nucleic acid
• the hydroxyl group on the 3rd carbon of one nucleotide reacts with the phosphate group attached to the 5th carbon on another nucleotide

Question 6

explain the structure of the DNA strand

Answer 6

is a double-stranded helical structure, composed of 2 linear DNA strands that are anti-parallel orientated to each other
sugar-phosphate backbone on the outside and bases inside

Question 7

how many bonds are between the 2 complimentary bases

Answer 7

A=T have 2 hydrogen bases
C=G have 3 hydrogen bases

Question 8

what is the function of the nucleotide bases in the DNA structure

Answer 8

to stabilise the DNA structure

Question 9

what is the semi-conservative model of replication

Answer 9

each DNA strand of the double helix is used as a template strand for the synthesis of 2 new strands