Topic 4 - DNA, Genes and Chromosomes

Question 1

What is a fixed position occupied by a gene in a DNA molecule called?

Answer 1

locus/ loci

Question 2

Describe how a gene is a code for the production of a polypeptide. (not transcription and translation)

Answer 2

• because the seq of bases
• in triplets
• determines seq of AA

Question 3

Define the term exon.

Answer 3

Base sequence coding for polypeptides.

Question 4

Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule.

Answer 4

• condensation reaction
• between phosphate and deoxyribose
• catalysed by DNA ribose.

Question 5

Name the protein associated with DNA in a chromosome

Answer 5

Histone

Question 6

Three differences between DNA in plant cell nucleus vs DNA in prokaryotic cell.

Answer 6

Plant cell:
- Linear
- No plasmids
- Histones
Prokaryotic Cell:
- Circular
- Plasmids
- No Histones

Question 7

Describe “non-coding base sequences” and where age non-coding multiple repeats are positioned within the genome.

Answer 7

• DNA that doesn’t code for proteins
• Positioned between genes

Question 8

3 ways chloroplast DNA is diff to nucleus DNA

Answer 8

Chloroplast:
- circular DNA
- fewer genes
- no introns
Nucleus:
- linear DNA
- more genes
- has introns

Question 9

One difference between structure of DNA nucleotide and RNA nucleotide

Answer 9

• deoxyribose - DNA
• ribose - RNA

Question 10

Why don’t all mutations in nucleotide seq of a gene cause a change in the structure of a pp?

Answer 10

• Genetic code = degenerate so diff base seq can code for same AA
• if in non-coding region - won’t code for protein

Question 11

Differences and similarities between Eukaryotic DNA and Prokaryotic DNA

Answer 11

Eukaryotic DNA:
- linear
- longer
- contains introns
- associated w histones
Prokaryotic DNA:
- circular
- shorter
- no introns
- no histones
SIMILARITIES:
- nucleotide structure identical
- nucleotides joined by phosphodiester bonds

Question 12

Some stain used on chromosomes can give them a striped appearance. Suggest one way the structure of the chromosome could differ along the length to result in the stain binding more in some areas?

Answer 12

• differences in base seq

Question 13

What is a pair of homologous chromosomes?

Answer 13

• two chromosomes that carry two diff alleles for the same gene