DNA and protein synthesis

Question 1

What is the difference between eukaryotic and prokaryotic DNA?

Answer 1

Prokaryotic: Shorter, circular, aren’t associated with proteins

Eukaryotic: Longer, linear, associated with proteins called histones which form chromosomes

Mitochondria/chloroplasts: Contain DNA which is like the DNA of prokaryotes

Question 2

Gene definition

Answer 2

DNA base sequence that codes for polypeptides or a functional RNA

Question 3

Allele definition

Answer 3

An alternative form of a gene

Question 4

What are sections of non-coding DNA called?

Answer 4

Introns

Question 5

What is the triplet code?

Answer 5

3 DNA bases (triplet) code for 1 amino acid

Question 6

Degenerate definition

Answer 6

Most amino acids are coded for by more than one triplet

Question 7

Non-overlapping definition

Answer 7

Each base is only read once

Question 8

Universal definition

Answer 8

Each triplet codes for the same amino acid in all organisms

Question 9

Genome definition

Answer 9

All the DNA in a cell

Question 10

Proteome definition

Answer 10

The whole range of proteins that a cell is able to produce

Question 11

What is the difference between mRNA and tRNA?

Answer 11

mRNA: Linear shape, has codons

tRNA: Clover leaf shape, has anticodons

Question 12

What does tRNA contain?

Answer 12

Anticodons, amino acid binding site

Question 13

What does transcription do?

Answer 13

DNA –> mRNA

Question 14

What are the 4 steps of transcription?

Answer 14

1. Hydrogen bonds between 2 strands are broken so DNA strands separate
2. 2 strands used as template strands
3. Complementary free RNA nucleotides join with exposed DNA bases via base pairing on template strand
4. RNA polymerase joins adjacent nucleotides via phosphodiester bonds

Question 15

What does splicing do?

Answer 15

*Removes introns from pre-mRNA so mRNA molecule only has coding regions
*mRNA passes out of the nucleus via a nuclear pore and goes to a ribosome
*Doesn’t occur in prokaryotes

Question 16

What does translation do?

Answer 16

mRNA –> polypeptide

Question 17

What are the 9 steps of translation?

Answer 17

1. mRNA attaches to ribosome
2. Ribosome moves to bind to a start codon
3. tRNA carrying specific amino acid binds to first codon on mRNA via complementary base pairing with its anticodon
4. Second tRNA does the same with the second codon
5. Enzymes join amino acids together forming a peptide bond using energy from the hydrolysis of ATP
6. Ribosome moves along mRNA to next codon
7. tRNA lost from the first codon to collect another of the same amino acid
8. Process repeats until stop codon is reached
9. Polypeptide is released