Topic 4: DNA, genes and chromosomes

Question 1

Define gene

Answer 1

a section of DNA that contains a code for making a polypeptide and functional RNA

Question 2

Define allele

Answer 2

a different form of the same gene

Question 3

Define homologous pair of chromosomes

Answer 3

a pair of chromosomes with the same genes, but might have different alleles

Question 4

Define locus

Answer 4

the location of a particular gene on a chromosome called the locus

Question 5

Define start codon

Answer 5

at the start of every gene, there are three bases which help to initiate translation

Question 6

define stop codon

Answer 6

A stop codon causes ribosomes to detach and therefore stop translation.

Question 7

Define genome

Answer 7

An organism’s complete set of DNA is one cell

Question 8

Define proteome

Answer 8

The full range of proteins a cell can produce

Question 9

Compare DNA in a eukaryote and prokaryote (5 marks)

Answer 9

Comparisons
1. nucleotide structure is identical
2. nucleotides joined by a phosphodiester bond
3. DNA in mitochondria/ chloroplasts same/ similar structure to DNA in prokaryotes

Contrasts
4. eukaryotic DNA is longer
5. eukaryotic DNA contains introns, prokaryotic DNA does not
6. eukaryotic DNA is linear, and prokaryotic DNA is circular
7. eukaryotic DNA is associated with/bound to protein/histones, prokaryotic DNA is not

Question 10

Compare the DNA in the nucleus and chloroplast of a eukaryote. (5 marks)

Answer 10

In chloroplasts
1. DNA shorter;
2. Fewer genes;
3. DNA is circular, not linear;
4. Not associated with protein/histones, unlike nuclear DNA; 5. Introns absent but present in nuclear DNA;