8.1 -> 8.2 dna

Question 1

gene

Answer 1

base sequence of dna(section) that contains coded info for amino acid seqeunce of polypeptide or functional rna

each gene occupies specific position(locus) along dna molecule

Question 2

triplet code

Answer 2

minimum of 3 bases that code for each amino acid

Question 3

why scientists decided must be triplet code

Answer 3

1. only 20 amino acids regularly occur in proteins
2. each amino acid must have own bases
3. only 4 bases in DNA(could only code 4 amino acids)
4. 3 bases produce 64 codes

Question 4

degenerate code

Answer 4

amino acids coded for by more than one triplet

Question 5

features of triplet code

Answer 5

1. always read in one direction along DNA strand
2. start of DNA sequence for polypeptide is same triplet for methionine
3. 3 triplets don’t code for any amino acid and are stop codes
4. code is non-overlapping
5. code is universal

Question 6

DNA in prokaryotes

Answer 6

dna molecules are shorter, form circle and aren’t associated with protein molecules

don’t have chromosomes

Question 7

DNA in eukaryotes

Answer 7

dna molecules are longer, form a line and occur in associations with the protein histone to form chromosomes

Question 8

DNA in eukaryote chloroplast and mitochondria

Answer 8

dna molecule is short, circular and not associated with proteins- no chloroplasts

Question 9

chromosome structure

Answer 9

dna double helix is wound around histones to fix in position

dna-histone is then coiled

the coil is looped and further coiled before being packed into chromosome

two chromatids joined at centromere

Question 10

allele

Answer 10

one of a number of alternative forms of a gene