4.1: DNA, genes and chromosomes Flashcards
Topic 4
Define gene
A section of DNA that codes for making a polypeptide and functional RNA.
Locus
Location of a particular gene on a chromosome
Allele
One of a number of alternative forms of genes
What is a homologous pair?
A homologous pair of chromosomes have the same genes but may have different alleles
Describe DNA in eukaryotic cells (5)
1) DNA stored as chromosomes inside the nucleus
2) Linear
3) Associated with histones
4) Contains introns and exons
5) longer
Describe DNA in prokaryotic cells (5)
1) Circular
2) Not associated with histones
3) Only contains exons
4) No nucleus
5) shorter
How is the DNA in mitochondria and ribosomes similar to prokaryotic cells?
1) DNA shorter
2) DNA is circular
3) DNA not associated with histones
What are the three features of the genetic code?
1) Degenerate
2) Non-Overlapping
3) Universal
Definition of degenerate
More than one triplet codes for each amino acid
Advantage of degenerate
If mutation occurs could still possible code for the same amino acid
Definition of universal
Same triplet of bases codes for the same amino acid in all organisms
Advantage of universal
Genetic engineering
Definition of non-overlapping
Each base is only part of one triplet
What are introns
Sections of DNA that don’t code for amino acids
Exons?
sections of DNA that code for amino acids
