Nucleic acids

Question 1

Name the structural units in nucleic acids (1)

Answer 1

nucleotides

Question 2

Name the sugars in DNA and RNA (1)

Answer 2

• DNA - deoxyribose
• RNA - ribose

Question 3

Name the four nitrogenous bases in DNA (2)

Answer 3

• adenine
• guanine
• cytosine
• thymine

Question 4

Describe how nucleotides are arranged in DNA molecules (4)

Answer 4

• pairing A-T and C-G
• backbone formed by alternating sugar phosphate groups
• two chains connected
• hydrogen bonding
• two chains to form a helix / double helix

Question 5

Descirbe the function of DNA in molecules in cells (1)

Answer 5

• forming instructions for frotein synthesis

Question 6

Name complementary DNA to TATCG (1)

Answer 6

ATAGC

Question 7

What is meant by semiconervative replication (2)

Answer 7

• each strand of DNA used as a template to make a new DNA strand
• New DNA made of original strand linked to a new strand

Question 8

Name the part of the DNA that contained the N15 (1)

Answer 8

nitrogenous base

Question 9

If you wanted to show the relative position of DN from different sample of bacteria suggest two vairables wich would need to be controlled in the centrigation process (2)

Answer 9

• spin at same speed
• same time
• same density / concentration of gel
• same temperature

Question 10

Give the full name of ATP (1)

Answer 10

adenosine triphosphate

Question 11

Apart from muscle contraction name one other process in cells whcih require energy (1)

Answer 11

• protein synthesis
• biosynthesis
• active transport
• nerve conduction
• cell division

Question 12

State the type of base that cytosine belongs to (1)

Answer 12

pyrimidine

Question 13

Explain why there would be large numbers of different mRNA molecules in a cell only a maximum of 64 different types of tRNA molecules (3)

Answer 13

• different mRNA for every polyeppetide
• base triple code 4^3=64
• tRNA molecule have anticodons which have three bases which are complementary to condons / tRNA are specific to one amino acid

Question 14

What is the role of DNA Polymerase in DNA replication (1)

Answer 14

• join nucleotides together to form a new strand

Question 15

Describe three differences between structure of DNA and RNA (3)

Answer 15

DNA
* double stranded
* helical
* deoxyribose
* thymine
* only one tupe
* longer
RNA
* single stranded
* not helical
* ribose
* uracil
* 3 types mRNA, rRNA, tRNA
* smaller

Question 16

Explain how the Melesohn and Stahl’s exeriment explain how their environment and the results support the theroy of semi conservative repliaction. Predict how the result would have differed if the theroies had been correct. Explain your answer (9)

Answer 16

• description of experiment heavy and light isotopes of N and ultracentrifugation
• explanation of how bands seen in centrifuge tube are formed giving details of heavy and light isotopes of N
• the relative amount of DNA in each band are explained
  conservative replication
• always some heavy DNA present
• increasing mass of light DNA
• no intermediate DNA
• original heavy DNA is not split
  Dispersive replication
• apart from G0 all DNA would be itnermediate in molecular mass
• getting lighter between G0 and G3
• because original heavy DNA split between all new molecules