SMITH (2) DNA

Question 1

What is DNA made up of, and what is the structure of a nucleotide?

Answer 1

Nucleotide structure:
• Made up of 3 components:
1. Pentose sugar
2. Phosphate group
3. Nitrogen-containing organic base
§ Cytosine
§ Guanine
§ Adenine
§ Thymine

Question 2

How are the different components of DNA joined up?

Answer 2

Via condensation reactions

Question 3

What is the structure of RNA?

Answer 3

RNA structure:
• Polymer made up of nucleotides
• Single, short polynucleotide chain
• Pentose sugar = ribose
• Bases:
○ Cytosine
○ Guanine
○ Adenine
○ Uracil

Question 4

What is the structure of DNA?

Answer 4

DNA structure:
• Double helix structure
• Made up of 2 strands of polynucleotides
○ Joined via hydrogen bonds between complementary base pairings
§ C-G (3 bonds)
§ A-T (2 bonds)
• Extremely long strands
• Pentose sugar = deoxyribose
• Bases:
○ Cytosine
○ Guanine
○ Adenine
○ Thymine

Question 5

What are the 4 steps of DNA replication?

Answer 5

1) the strand is split by DNA helicase (which breaks the H-bonds between the bases) into two strands, forming a Y-shape
2) free nucleotides will join onto the original strands (which act as templates) where there is a complementary base, forming hydrogen bonds with their complementary base pairings
3) DNA polymerase will form phosphodiester bonds between the new nucleotides
4) there are now two identical double helix strands. this process is semi-conservative as only half of the original material is conserved

Question 6

What are the 5 steps of DNA transcription?

Answer 6

1. DNA helicase separate the strands of a section of the double stranded DNA molecule, leaving a now separated coding strand and template strand.
   
   2. At the same time, free RNA nucleotides will bond to their complementary base pairing, assisted by RNA polymerase, which will form the phosphodiester bonds between the bases.
   3. As the pre-mRNA is built, the DNA strands will rejoin behind it.
   4. Eventually, the RNA polymerase will reach a stop triplet and detach from the strand to release the pre-mRNA, allowing it to be spliced by enzymes, ridding of the introns and leaving the exons
   5. The mRNA will then leave the nucleus via a nuclear pore, moving into the ribosome

Question 7

What is splicing?

Answer 7

What is splicing?
- When transcription happens, only the exons of a DNA strand are required because they are required for coding
- The strand will be spliced, removing the introns (apart from at the end of the strand, which will stop the process) and leaving the exons

Question 8

What is the 6 step process of translation?

Answer 8

1. mRNA leaves the nucleus via a nuclear pore and attaches to a ribosome at the starting codon
2. A tRNA molecule carrying a specific amino acid will attach to the mRNA strand using its complementary anti-codon
3. The next tRNA molecule also carrying a specific amino acid will attach to the next codon of the mRNA using its complementary anti-codon
4. The ribosome will move down the RNA strand and form peptide bonds between the amino acids carried by the tRNA
5. The amino acids are joined using an enzyme and energy from ATP
6. Each tRNA molecule is released to bring another of its specific amino acid to the ribosome