DNA and Protein Synthesis

Question 1

What monomers are DNA and RNA polymers of?

Answer 1

Nucleotides

Question 2

What are the 4 nitrogen containing bases called?

Answer 2

• Adeneine
• Thymine
• Guanine
• Cytosine

Question 3

What sugar is contained within a nucleotide of DNA?

Answer 3

Deoxyribose

Question 4

What is attached to the sugar contained within a nucleotide (of DNA)?

Answer 4

A phosphate group and nitrogen-containing base

Question 5

What components make up RNA?

Answer 5

• Sugar- ribose
• A phosphate group
• One of 4 bases: adenine, guanine, cytosine and uracil

Question 6

What bond forms between nucleotides in a condensation reaction?

Answer 6

Phosphodiester bond

Question 7

Describe the structure of DNA

Answer 7

• Double helix
• 2 polynucleotide chains
• Run antiparallel
• Joined by H bonds between complementary bases

Question 8

Describe the structure of RNA

Answer 8

• Single strand

- One polynucleotide chain

Question 9

How does prokaryotic DNA differ from eukaryotic DNA?

Answer 9

Prokaryotic DNA is..

• Circular
• Not associated with histones
• Does not have introns

Question 10

Describe the role of DNA polymerase in DNA replication

Answer 10

Joins nucleotides

Question 11

What enzyme unwinds the DNA helix?

Answer 11

DNA helicase, breaks hydrogen bonds

Question 12

How is DNA replicated?

Answer 12

Unwound strand acts as a template for a new strand, free nucleotides are joined according to complementary base pairing and bonded by DNA polymerase (forms hydrogen bonds)

Question 13

Describe the process of transcription

Answer 13

• Helicase unwinds DNA strand (breaks H bonds)
• RNA polymerase copies singular DNA template strand to create mRNA (complementary base pairing)
• mRNA exits nucleus via nuclear pores into cytoplasm
• Translation occurs in ribosomes

Question 14

Describe the process of translation

Answer 14

• Ribosomes and tRNA translate mRNA by reading strand
• tRNA has anticodons which complement codons on mRNA (introns and exons [coding])
• Each codon codes for 1 amino acid
• A chain of amino acids joined by peptide bonds forms
• Stop codon halts the process
• Polypeptide detaches into cytoplasm

Question 15

What is the difference between transcription in prokaryotes and eukaryotes?

Answer 15

• Prokaryotes: mRNA formed directly from DNA strand

- Eukaryotes: pre-RNA formed first, splicing occurs to remove introns

Question 16

How is RNA formed?

Answer 16

1. Helicase unwinds DNA (breaking H bonds)
2. mRNA produces by free nucleotides in cytoplasm
3. RNA polymerase builds strand by joining nucleotides together
4. Complementary base pairing
5. mRNA exits nucleus via nuclear pores

Question 17

DNA vs RNA

Answer 17

mRNA- single stranded, uracil, ribose, short

DNA- double stranded, thymine, deoxyribose, long

Question 18

What is semi-conservative replication?

Answer 18

DNA is semi conservative because every new strand is paired with a strand from a previous generation (old and new)

Question 19

Testing for semi conservative replication

Answer 19

1) centrifugation of nitrogen- 15, ‘heavy’ DNA, all of it is from N-15, so it is dense. Low band
2) transfer cells into N-14 and centrifuge. Middle band because DNA is hybrid with 14 and 15
3) transfer into N-14 again, two bands, one higher and one lower (hybrid), old and new strands

Question 20

How is the structure of tRNA related to its function?

Answer 20

• Clover leaf structure
• Allows the exposure of three bases (anticodon) which are complementary to a codon on mRNA
• Amino acid attached to tRNA, dependent on anticodon.
• Complementary base pairing stimulates condensation reaction of that amino acid with the adjacent amino acid to form a peptide bond