DNA, Genes, Protein Synthesis

Question 1

What is a gene?

Answer 1

A section of DNA that contains coded information for making polypeptides and RNA

Question 2

Genetic code

Answer 2

The sequence of DNA triplets bases (or mRNA codons) that code for a specific amino acid.

Question 3

Degenerate coding

Answer 3

When an amino acid is coded for by more than one triplet

Question 4

Universal

Answer 4

All species have the same four bases, and each base sequence codes for the same amino acid in all species.

Question 5

Non Overlapping

Answer 5

The first three bases are read as one codon and the next three are read as another, so each base is only part of one codon.

Question 6

Exons

Answer 6

Sections of a gene: Coding sequences

Question 7

Introns

Answer 7

Sections of a gene: Non coding sequences

Question 8

Homologous pair

Answer 8

Two chromosomes that carry the same genes

Question 9

Allele

Answer 9

An alternative form of a gene

Question 10

Mutation

Answer 10

Changes in the base sequences that results in a different amino acid in chain causes diff. polypeptide which changes protein.

Question 11

Genome

Answer 11

Complete set of genes in a cell

Question 12

The function of Messenger RNA

Answer 12

Transfers DNA from nucleus to cytoplasm.

Question 13

Structure of tRNA

Answer 13

Small molecule

Single-stranded chain folded into a clover leaf shape

Amino acid binding site, one end of the chain extends beyond the other so that the amino acid can easily attach to

Question 14

Anticodon

Answer 14

sequence of three bases complementary to three bases on the codon

Question 15

Transcription

Answer 15

Process of making pre-mRNA:
DNA helicase causes two strands of DNA to separate

The bases on one side of the DNA pair with its complementary base.

RNA polymerase moves along the strand and joins them together to form pre mRNA
RNA polymerase reaches stop codon and pre mRNA detaches.

Question 16

Splicing

Answer 16

Formation of mRNA. Introns are removed from the pre-mRNA, exons are spliced together.

Question 17

Prokaryotes

Answer 17

No splicing, mRNA produced straight from DNA as it contains no introns.

Question 18

Translation

Answer 18

mRNA leaves nucleus through nucleus pore into cytoplasm.
At the ribosomes, anticodons on tRNA molecules complementary to codons on mRNA attach to codons and bring amino acids
Amino acids form peptide bonds, forming a polypeptide chain until stop codon.

Question 19

Role of ATP in translation

Answer 19

ATP is hydrolysed into ADP and a phosphate which:
1) provides the energy for the amino acids to bind to the tRNA at the amino acid binding site.
2) provides the energy for the formation of peptide bonds between the amino acids.

Question 20

Role of ribosomes in translation

Answer 20

• Attaches to mRNA and houses tRNA, allowing codon-anticodon complementary base pairing
• Allows peptide bonds to form between amino acids