3.4.1 DNA, Genes And Chromosmes

Question 1

Compare the structure of DNA between EUK and PRO

Answer 1

Eukaryotes vs Prokaryotes,

Length: very long vs short
Shape: linear vs circular
No. Per cell: variable vs 1
Associated with proteins: histones vs no

Question 2

In Eukaryotes, DNA molecule + associated histones equals what ?

Answer 2

Chromosome

Question 3

Describe a gene (e.g. what it codes for)

Answer 3

• sequence of bases in DNA which code for
  . Amino acid sequence of a polypeptide
  . Functional RNA (e.g. rRNA, tRNA)
• occupies a fixed position on a chromosome (locus)

Question 4

What is a genetic code

Answer 4

3 bases in DNA = triplet = codes for a specific amino acid

Question 5

Describe the 3 types of genetic codes

Answer 5

1. Universal = same code in all species
2. Non-overlapping: each base is only part of 1 triplet
3. Degenerate: many amino acids are coded for by more than one triplet

Question 6

What are bases called in: DNA, mRNA & tRNA

Answer 6

• TRIPLET in DNA
• CODON in mRNA
• ANTICODON (at complimentary site only) in tRNA

Question 7

What are exons and introns

Answer 7

Exons = code for the polypeptide (coding)

Introns = between exons. Removed during splicing of pre-mRNA (non-coding)