3.4.1 DNA, genes and chromosomes

Question 1

outline the features of eukaryotic dna

Answer 1

• dna is wrapped around/associated with histone proteins
• a dna molecule and associated proteins forms a chromosome
• dna is long and linear
• dna is condensed so compact and can be stored in a small space

Question 2

outline the features of prokaryotic dna

Answer 2

• prokaryotes have no nucleus
• dna is short and circular
• not wrapped around/associated with histone proteins
• condensed by supercoiling
• dna found in chromosomes and plasmids
• similar to dna or chloroplasts and mitochondria

Question 3

define gene

Answer 3

a base sequence of DNA that codes for:
- an amino acid sequence of a polypeptide
- a functional RNA

Question 4

define locus

Answer 4

a fixed position on a chromosome that a gene occupies

Question 5

the name for a sequence of 3 dna bases

Answer 5

triplet

Question 6

what are the features of the genetic code?

Answer 6

• degenerate
• non-overlapping
• universal

Question 7

what does it mean for the genetic code to be degenerate?

Answer 7

some amino acids are coded for by more than one triplet code

Question 8

what does it mean for the genetic code to be non-overlapping?

Answer 8

the triplets are read in sequence and only once, the triplets do not share bases

Question 9

what does it mean for the genetic code to be universal?

Answer 9

the same specific base triplet codes for the same amino acid in all living organisms

Question 10

what are introns?

Answer 10

non-coding regions of DNA

Question 11

what are exons?

Answer 11

coding DNA

Question 12

what are the differences between eukaryotic DNA and mitochondrial & chloroplast DNA

Answer 12

eukaryotic :
longer
linear
associated with histones
has introns

prokaryotic / mitochondrial & chloroplast :
shorter
circular
no histones
no introns