DNA Genes Chromosomes

Question 1

Compare and contrast DNA in eukaryotic cells with DNA in prokaryotic cells

Answer 1

Similarities:
● Nucleotide structure is identical - deoxyribose attached to phosphate and a base
● Adjacent nucleotides joined by phosphodiester bonds, complementary bases joined by hydrogen bonds
● DNA in mitochondria / chloroplasts have similar structure to DNA in prokaryotes
○ Short, circular, not associated with proteins

Differences:
● Eukaryotic DNA is longer
● Eukaryotic DNA is linear, prokaryotic DNA is circular
● Eukaryotic DNA is associated with histone proteins, prokaryotic DNA is not
● Eukaryotic DNA contain introns, prokaryotic DNA does not

Question 2

What is a chromosome?

Answer 2

● Long, linear DNA + its associated histone proteins
● In the nucleus of eukaryotic cells

Question 3

What is a gene?

Answer 3

A sequence of DNA (nucleotide) bases that codes for:
● The amino acid sequence of a polypeptide
● Or a functional RNA

Question 4

What is a locus

Answer 4

Fixed position a gene occupies on a particular DNA molecule

Question 5

Triplet code

Answer 5

A sequence of 3 DNA bases, codes for a specific specific amino acid

Question 6

Universal

Answer 6

The same base triplets code for the same amino acids in all organisms

Question 7

Non-overlapping

Answer 7

Each base is part of only one triplet so each triplet is read as a discrete unit

Question 8

Degenerate

Answer 8

An amino acid can be coded for by more than one base triplet

Question 9

What are ‘non-coding base sequences’ and where are they found?

Answer 9

Non-coding base sequence- DNA that does not code for amino acid sequences / polypeptides:
1. Between genes - eg. non-coding multiple repeats
2. Within genes- introns

Question 10

Intron

Answer 10

Base sequence of a gene that doesn’t code for amino acids, in eukaryotic cells

Question 11

Exon

Answer 11

Base sequence of a gene coding for amino acid sequences (in a polypeptide)