19.1 Mutations And Variations Flashcards
What is a mutation
A mutation is a change in the sequence of bases in DNA
What is the change in sequence caused by
Substitution, deletion or insertion of one or more nucleotides within a gene
What is substitution
A substitution mutation is when one nucleotide is replaced with another in a sequence changing that particular codon
What decides the function and structure of the protein
Position and involvement of amino acid in r group interaction within protein determines impact of new amino acids on function of protein
What is deletion mutation
Deletion mutation is when one nucleotide is randomly deleted causes every following colon to change it is a frame shift mutation
What is a insertion mutation
Where one nucleotide is randomly inserted into DNA sequence
Changes amino acid as it creates new different triplet of base
It has a knock on effect by changing the triplets further on in dna sequence known as frameshift
Describe how a sequence of dna forms a specific protein
- Helicase enzyme unwinds and unzips dna
- RNA nucleotides bind to complementary dna bases on template strand
- RNA polymerase joins together the se rna nucleotide with phosphodiester bonds
- The mRNA formed detaches and leaves nucleus
- The mRNA attaches to a ribosomes
- A tRNA molecule with a complementary anticodon to the mRNA codon joins to the mRNA strand and carries a specific amino acid
- Each codon on the mRNA is read and the tRNA molecules bring the specific amino acid and they are joined by peptodyl transferase
- Once the stop codon is reached the polypeptide chain can then fold into its secondary and tertiary structures
effect of mutations - silent mutation
Does not alter the amino acid sequence of polypeptides this is because certain codons can code for the same amino acid as the genetic code is degenerate
Effects of mutations - nonsense mutation
Premature stop codon is formed
Resulting in shortened amd often non functioning polypeptides
Effect of mutation - missense
Alters a single amino acids in the polypeptides chain
Cannot become start and stop codon to be
Changes primary’s thruster and 50/50 chance if changing secondary tertiary and quaternary does not chnage
Gene mutations can be placed into one of three categories
Beneficial
Harmful
Neutral
Beneficial mutations
Sometimes mutation can alter polypeptides itch a different shape sometimes it can result in altered characteristics which are useful in organisms and causes beneficial effects for organisms
Harmefu mutations
Phenotype in a organisms is affected in a negative way because proteins are no longer syntheised or protein synthesis are non functional
This can interfere with essential processes
Neutral mutations
There is no effect on the phenotype of an organism because normally functioning proteins are still synthesised
How do mutations occur
They can occur spontaneously often during dna replication but the rate of mutation is increased my mutagens
What is a mutagen
A mutagen is a chemical, physical or biological agent which causes mutations
What are some physical mutagens and what they do
Ionisizing radiations such as x rays
- they break one or both strands some breaks can be repaired but mutations can occur in the process
What are chemical mutagens and what they do
Chemically alter bases in dna such as converting cytosine to uracil in dna changing the base sequence
What are some Biological agents and what they do
Alkylating agents - methy or ethyl groups are attached to bases resulting in the incorrect pairing of baes during replication
Base analogs - incorporated into dna in place of the usual base during replication changing base sequence
Viruses - viral dna may inset itself into a genome changing the base sequence
What is sickle cell anaemia
Is a blood disorder caused by a mutation in the gene coding for haemoglobin
Thymine replace Adeline making the sixth amino acid valine instead of glutamic acid
Changes in chromosome strucutre include?
Deletion - section of chromosome breaks off and is lost within cell
Duplication - sections of chromosome gets duplicated
Translocation - section of chromosomes breaks off and joins another non homologous chromosome
Inversion - section breaks off and joins in reverse
