DNA

Question 1

There is significant DNA _____ between _____

Answer 1

Variation
Species

Question 2

Chargaff’s findings

Answer 2

1st rule:
A=T
G=C

2nd rule:
The composition of DNA varies between species

Question 3

DNA structure

Answer 3

A double stranded helical molecule with particular features

Question 4

X-ray diffraction pattern of DNA

Answer 4

• helical structure
• bases perpendicular to the length of the DNA molecule
• double stranded

Question 5

Structure of purines vs pyrimidines

Answer 5

• PYRIMIDINES: have a single ringed 5 carbons - hexagon + pentagon
• Cytosine
  -Thymine
• urasial ????
• PURINES: two ringed 4 carbon molecule - hexagon
• Adenine
• Guanine

Question 6

The single unit building blocks of the macromolecule DNA are…

Answer 6

Nucleotides

Question 7

Formation of polynucleotide

Answer 7

Nucleotide monomers are joined together with PHOSPHODIESTER BONDS to form a polynucleotide = nucleic acid (deoxyribonucleic acid for DNA)

Sugar group leads to phosphate group of the next molecule

Question 8

How the phosphodiester bond forms

Answer 8

The hydroxyl group (OH) on the 3rd carbon of one nucleotide reacts (condensation reaction) with the phosphate group attached to the 5th carbon on another nucleotide

PHOSPHODIESTER LINKAGE

Question 9

What direction are the DNA and RNA synthesised in

Answer 9

5’———>3’ direction

Question 10

Each DNA strand has a ______
The two strands are ______________
I.e. ___________

Answer 10

Direction
Antiparallel

5’———-> 3’
3’———-> 5’

Question 11

What forms the double-stranded helix of DNA

Answer 11

The two antiparallel DNA strands

Question 12

The structure of the DNA molecule

Answer 12

• Pairs of complementary bases form hydrogen bonds that hold up two strands of the DNA double helix together
• T-A pairs have two hydrogen bonds
• C-G pairs have three hydrogen bonds
• The strands both in a 5’ to 3’ direction, they are antiparallel
• each phosphate group links the 3’ carbon of one sugar to the 5’ carbon of the next sugar along the backbone

Question 13

The Watson-Crick model of DNA structure

Answer 13

• DNA has a double stranded helical structure
• The sugar phosphate backbone is on the outside
• The bases are on the inside
• Stabilised by hydrogen bonds
• The two polynucleotide strands are oriented in opposite directions

Question 14

The Watson-Crick model provided:

Answer 14

• a stimulus for deciphering the genetic code
• a possible mechanism for the replication of DNA

Question 15

What kind of replication is in DNA

Answer 15

Semi-conservative model of replication

Question 16

What is semi-conservative replication

Answer 16

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

Question 17

Why does your cell replicate its DNA?

Answer 17

• because your body needs to make more cells during:
• different growth stages throughout life
• pregnancy
• repair of injury