2. Genes and Chromosomes Flashcards
Define gene.
A sequence of DNA bases that codes for either a polypeptide or functional RNA.
What does the sequence of amino acids in a polypeptide form?
The primary structure of a protein.
What do different polypeptides have?
Different number and order of amino acids.
What determines the order of amino acids in a particular polypeptide?
The order of the bases in a gene.
How is each amino acid coded for?
By a sequence of 3 bases in a gene called a tripler or codon
What is the first stage of protein synthesis that makes a polypeptide?
DNA copied into a messenger RNA.
What do genes code for that don’t code for a particular polypeptide?
They code for functional RNA.
What is functional RNA?
They’re RNA molecules other than mRNA, which preform special tasks during protein synthesis.
eg tRNA and rRNA which forms part of ribosomes.
Genome.
Complete set of genes.
Proteome.
Full range of proteins that the cell is able to produce.
What is nuclear DNA?
DNA stored in the nucleus.
In eukaryotes what does a lot of the nuclear DNA code for?
Polypeptides.
BUT.
Some genes don’t code for polypeptides at all ( they code for function RNA)
Define intron.
A section of DNA within a gene that does not code for amino acids.
There can be several introns within a gene - purpose isn’t known for sure.
What happens to the introns in eukaroyotes and prokaryotes?
In eukaryotes hey’re removed during protein synthesis - so they don’t affect amino acid order.
Prokaryotes don’t have introns.
Define exon.
A section of DNA within a gene that codes for amino acids.
What is non-coding DNA?
Regions of multiple repeats outside of the genes that don’t code for amino acids.
Define allele.
An alternative from of gene.
What are the bases like in alleles?
The order of the bases is slightly different in each allele, so they code for slightly different versions of the same polypeptide.
EXAMPLE.
The gene that codes for blood.
Exists as one of three alleles.
One type = O
Another type = A
Other type = B.
Define homologous pair.
A pair of matching chromosomes - each chromosome contains the same genes but could have different alleles.
In a eukaryotic cell what is DNA stored as?
Chromosomes.
What are pairs of matching chromsomes called?
Homologous chromosomes.
In a homologous pair, alleles coding for the same characteristic will be found where?
Fixed in the same position on each chromosome.
Define locus.
Position on a chromosome where a particular allele is found.
