DNA

Question 1

DNA replication model answer

Answer 1

Double helix untwisted/ (gyrase enzymes unwind)
DNA unzipped when hecilase enzymes break down the hydrogen bonds between the base pairs
both strands act as a template for the free DNA.
free DNA nucleotides align and complementary base pair.
hydrogen bonds between bases form in 5’ - 3’
DNA polymerase catalyses the addition of nucleotides and joins the sugar phosphate backbones together on the new strands with covalent bonds
the molecules twist back into a double helix
there are now 2 identical DNA molecules
which is semi conservative.

Question 2

Transcription

Answer 2

protein synthesis
DNA unwinds and unzips - hydrogen bonds break
RNA nucleotide align with complementary base pairs
catalysed by RNA polymerase temporary hydrogen bonds form
MRNA leaves nucleus and attaches to ribosome

Question 3

Translation

Answer 3

At the ribosome the anti-codon on the TRNA binds to the temporary hydrogen bonds.
complementary codon on the MRNA bringing the Amino acid coded for by the MRNA codon
adjacent AA’s form peptide bonds

Question 4

DNA replication VS protein synthesis

Answer 4

DNA rep.
product DNA
uses DNA
DNA polymerase

protein synthesis
product: protein
uses RNA
RNA polymerase

Question 5

structure of RNA nucleotide

Answer 5

one phosphate group
one nitrogenous base (AUGC)
both joined to one ribose pentose sugar
joined with one covalent bond each

Question 6

difference between structure of DNA and RNA

Answer 6

RNA has ribose instead of deoxyribose
RNA has uracil instead of thymine
RNA is single stranded rather than double stranded
RNA is a smaller molecule

Question 7

structure of a nucleotide chain (One backbone of DNA)

Answer 7

2 nucleotides are joined together with a covalent bond
between the phosphate group of 1 and the pentose sugar of the other
the backbone of a nucleic acid is a sugar phosphate backbone

Question 8

how two nuclei chains in DNA are bonded together (double helix)

Answer 8

• hydrogen bonds between bases
• complementary base paring
• purine to pyrimidine
• A-T AND G-C
• 2 hydrogen bonds between A/T
• 3 hydrogen bonds between C and G

Question 9

structure of DNA molecule

Answer 9

• DNA has a double helix structure - two polynucleotide strands twisted round one another in a double helix structure
• the two strands run anti-parrallel to one another
• the two strands are held together by complementary base pairs which join together with weak hydrogen bonds
  A-T and G-C
  purine to pyrimidine
  2 hydrogen bonds between a-t and 3 g-c

Question 10

why DNA replication is known as semi-conservative replication

Answer 10

this is because 2 identical DNA molecules are made with 1 strand from the original molecule (the conserved strand) which acted as a template strand and 1 new strand