Nucleic Acids expeirmnt

Question 1

function of DNA (1 marks)

Answer 1

holds genetic information which codes for polypeptides

Question 2

function of RNA (1 marks)

Answer 2

transfer genetic information from DNA to ribosomes

Question 3

what are ribosomes made of (2 marks)

Answer 3

-RNA
-proteins

Question 4

draw a nucleotide

Answer 4

check google

Question 5

what is in a DNA nucleotide (3 marks)

Answer 5

-deoxyribose sugar
-phosphate group
- nitrogenous base

Question 6

what is in a RNA nucleotide (3 marks)

Answer 6

-ribose sugar
-phosphate group
- nitrogenous base

Question 7

what nitrogenous base is in DNA (4 marks)

Answer 7

-thymine
-adenine
-cytosine
-guanine

Question 8

what nitrogenous base is in RNA (4 marks)

Answer 8

-uracil
-adenine
-cytosine
-guanine

Question 9

describe how nucleotides join together to form polynucleotides (3 marks)

Answer 9

-condensation reaction, removing water molecules
-between phosphate group of one nucleotide and deoxyribose of another
-forming phosphodiester bonds

Question 10

describe structure of DNA (5 marks)

Answer 10

• polynucleotide
• has deoxyribose, phosphate group and base
  -phosphodiester bonds join adjacent nucleotides
  -bases held by hydrogen bonds
  -between specific complementary base a-t g-c
  -double helix

Question 11

describe structure of RNA (5 marks)

Answer 11

• polynucleotide
  -ribose, phosphate group, base
• bases uracil, adenine, guanine, cytosine
  -phosphodiester bonds joins adjacent nucleotides
  -single helix

Question 12

compare RNA and DNA (5 marks)

Answer 12

dna rna
pentose sugar deoxyribose ribose
base thymine adenine uracil adenine
double helix single helix
long short
has hydrogen bonds doesn’t

Question 13

DNA structure and function (6 marks)

Answer 13

• two strands
  -> act as templates for semi-conservative replication
• hydrogen bonds
  ->separated by dna helicase
  ->strong/stable molecule
• complementary base
  ->accurate replication
• double helix
  ->compact
• sugar phosphate backbone
  -> protects bases/ hydrogen bonds
• long
  ->stores lots of genetic information

Question 14

why is semi-conservative replication important (1 marks)

Answer 14

ensures genetic continuity between generations of cells

Question 15

describe process of semi-conservative replication (6 marks)

Answer 15

-DNA helicase breaks hydrogen bonds in bases, unwinding hydrogen bonds
-both strands act as template
-free DNA nucleotides join to complementary base pair
-hydrogen bonds form between bases (a-t, g-c)
-dna polymerase joins adjacent nucleotides on new strand by condensation reactions
-forming phosphodiester bonds

Question 16

what does semi-conservative mean (1 marks)

Answer 16

each new dna molecule with 1 old and 1 new strand

Question 17

what enzymes in dna replication (3 marks)

Answer 17

• dna helicase (unwinds strands, breaks h-bonds)
  -dna polymerase (joins adjacent nucleotides, condensation reaction, phosphodiester bonds)
  -dna ligase

Question 18

why dna polymerase enzyme moves in opposite direction of dna strand (4 marks)

Answer 18

-dna has antiparallel strands
-so arrangements of base are different on both ends
-dna polymerase is enzyme with specific shaped active site
-so can only bind to substrate with complementary shape (phosphate end)

Question 19

name 2 scientists for model of dna replication (1 marks)

Answer 19

watson and crick

Question 20

what were the other models for dna replication (4 marks)

Answer 20

-dispersive
-completely new dna strands
-conservative
-dna completely of original strand

Question 21

describe how the experiment was used to provide evidence for semi-conservative replication. (3 marks)

talk about 3 samples, generations, % of dna in each and centrigue tube

Answer 21

• Sample 1. DNA from bacteria grown for several generations in a nutrient solution containing 15N → DNA molecules contain 2 ‘heavy’ strands.
  -Sample 2. DNA from bacteria grown originally in a nutrient solution containing 15N, then transferred for one division to a solution containing 14N → DNA molecules contain 1 original ‘heavy’ and 1 new ‘light strand.
  -Sample 3. DNA from bacteria grown originally in a nutrient solution 15N, then transferred for two divisions to a solution containing 14N → 50% DNA molecules contain 1 original ‘heavy’ and 1 new ‘light’ strand, 50% contain both ‘light’ strands.

Question 22

describe the experiment carried out by Meselson & Stahl

Answer 22

• Bacteria grown in a nutrient solution containing heavy nitrogen (15N) for several generations.
• Nitrogen incorporated into bacterial DNA bases.
  -Bacteria then transferred to a nutrient solution containing light nitrogen (14N) and allowed to grow and divide twice.