2. Genes and Chromosomes

Question 1

Define gene.

Answer 1

A sequence of DNA bases that codes for either a polypeptide or functional RNA.

Question 2

What does the sequence of amino acids in a polypeptide form?

Answer 2

The primary structure of a protein.

Question 3

What do different polypeptides have?

Answer 3

Different number and order of amino acids.

Question 4

What determines the order of amino acids in a particular polypeptide?

Answer 4

The order of the bases in a gene.

Question 5

How is each amino acid coded for?

Answer 5

By a sequence of 3 bases in a gene called a tripler or codon

Question 6

What is the first stage of protein synthesis that makes a polypeptide?

Answer 6

DNA copied into a messenger RNA.

Question 7

What do genes code for that don’t code for a particular polypeptide?

Answer 7

They code for functional RNA.

Question 8

What is functional RNA?

Answer 8

They’re RNA molecules other than mRNA, which preform special tasks during protein synthesis.
eg tRNA and rRNA which forms part of ribosomes.

Question 9

Genome.

Answer 9

Complete set of genes.

Question 10

Proteome.

Answer 10

Full range of proteins that the cell is able to produce.

Question 11

What is nuclear DNA?

Answer 11

DNA stored in the nucleus.

Question 12

In eukaryotes what does a lot of the nuclear DNA code for?

Answer 12

Polypeptides.
BUT.
Some genes don’t code for polypeptides at all ( they code for function RNA)

Question 13

Define intron.

Answer 13

A section of DNA within a gene that does not code for amino acids.
There can be several introns within a gene - purpose isn’t known for sure.

Question 14

What happens to the introns in eukaroyotes and prokaryotes?

Answer 14

In eukaryotes hey’re removed during protein synthesis - so they don’t affect amino acid order.
Prokaryotes don’t have introns.

Question 15

Define exon.

Answer 15

A section of DNA within a gene that codes for amino acids.

Question 16

What is non-coding DNA?

Answer 16

Regions of multiple repeats outside of the genes that don’t code for amino acids.

Question 17

Define allele.

Answer 17

An alternative from of gene.

Question 18

What are the bases like in alleles?

Answer 18

The order of the bases is slightly different in each allele, so they code for slightly different versions of the same polypeptide.

Question 19

EXAMPLE.

The gene that codes for blood.

Answer 19

Exists as one of three alleles.
One type = O
Another type = A
Other type = B.

Question 20

Define homologous pair.

Answer 20

A pair of matching chromosomes - each chromosome contains the same genes but could have different alleles.

Question 21

In a eukaryotic cell what is DNA stored as?

Answer 21

Chromosomes.

Question 22

What are pairs of matching chromsomes called?

Answer 22

Homologous chromosomes.

Question 23

In a homologous pair, alleles coding for the same characteristic will be found where?

Answer 23

Fixed in the same position on each chromosome.

Question 24

Define locus.

Answer 24

Position on a chromosome where a particular allele is found.