DNA book 10

Question 1

DNA is made up of what monomers?

Answer 1

nucleotide

Question 2

Each nucleotide is made up of what?

Answer 2

a deoxyribose sugar, a phosphate group and a nitrogenous base

Question 3

Nucleotides are joined together by what?

Answer 3

condensation reactions for a polynucleotide strand

Question 4

What are the bases joined by?

Answer 4

many hydrogen bonds

Question 5

Change in base sequence causes what?

Answer 5

• change in primary structure
• change in hydrogen/ionic/disulphide bonds
• change in tertiary structure
• change in active site
• substrate no longer complementary
• no ES complexes can form

Question 6

Explain DNA replication

Answer 6

1. ) double helix is uncoiled by DNA helicase by breaking the hydrogen bonds between the complementary base pairs
2. ) each of the separate strands act as a template for the formation of the two new complementary strands
3. )free DNA nucleotides align next to each template according tp their specific complementary base pairing- AT, CG
4. ) hydrogen bonds reform between the complementary base pairs
5. ) these DNA nucleotides are joined together by the enzyme DNA polymerase by forming the sugar-phosphate backbone
6. ) two new DNA molecules are identical to each other and the original

Question 7

What is the difference between translation and transcription?

Answer 7

Transcription occurs in the nucleus and involves copying part of the DNA code into a strand of messenger RNA. Translation occurs in the cytoplasm and involves ribosomes joining amino acids together to form polypeptides.

Question 8

Explain transcription

Answer 8

1. ) DNA helicase enzyme causes the relevant part of the DNA molecule to uncoil, causing the 2 strands to separate as hydrogen bonds are broken.
2. ) One of the 2 acts as a template.
   3) individual mRNA nucleotides line uo alongside the DNA nucleotide bases on the template strand due to specific base pairing.
3. )The RNA nucleotides are joined together using the enzyme RNA polymerase, to form a strand of pre-messenger RNA.
   5) the pre-RNA molecule is spliced. this involves the removal of introns, producing mRNA made up of exons only.
4. ) mRNA leaves the nucleus and attaches to a ribosome in the cytoplasm.

Question 9

What does splicing do?

Answer 9

removes introns leaving only exons

Question 10

Explain translation

Answer 10

1. ) each tRNA molecule has a specific amino acid attached and 3 exposed bases known as an anticodon
2. ) a tRNA molecule with the complementary anticodon to the first codon on the mRNA strand moves to the ribosome bringing its specific amino acid.
3. ) other tRNA then join in the order determined by the codons on the mRNA strand. The amino acid on the first tRNA molecule is attached to the amino acid on the second tRNA molecule by a peptide bond.
4. ) this requires ATP and the action of an enzyme.
5. ) the first tRNA molecule detaches and moves away from the ribosome leaving the amino acid behind
6. ) it collects another molecule of the same amino from the amino acid pool in the cytoplasm
7. ) this process continues along the mRNA strabd, 2 codons at a time

Question 11

Causes of mutation?

Answer 11

• naturally

- can arise as a result of incorrect pairing during DNA replication

Question 12

substitution?

Answer 12

the replacement of 1 or more bases by different bases. it can result in;

• new triplet code resulting in non functional protein being formed
• formaton of nonsence triplet codes

Question 13

deletion?

Answer 13

the removal of bases- frame shift, which is the alteration In the base code from the deletion