Mutation and its effect on phenotype

Missense Mutations

-A base substitution that results in a different amino acids in the protein

Insertions and deletions

-Addition or removal of one or more nucleotide pairs -Much more frequent than base pair substitutions -Leads to frameshift mutations

Germ line mutations

-Arises in cells that ultimately produce gametes -Mutation in multicellular organisms -can be passed to future generations and produces individuals that carry the mutation in somatic and germ line cells

Types of gene mutations

-Base substitution -Insertions and deletions

Frameshift mutations

-Insertions and deletions within sequences that encode proteins -changes in the reading frame of the genes -alters all amino acids encoded by nucleotides following the mutation -Drastic effects of the phenotype

Expanding nucleotide repeats

-Mutations in the number of copies of a set of nucleotides increase in number -

Gene mutations

-Mutations that affect a single gene -Can be observed only by studying their phenotypic effect -Used for a relatively small DNA lesions that affect a single gene

Phenotypic mutations

-Reverse mutations -Forward mutations

Mutations

-Source of genetic variation -Source of disease and disorders

Base substitution

-The simplest type -The alteration of a single nucleotide in DNA -Transition and Transversion -Number of possible transversions is twice the number of possible transitions

Chromosome mutations

-They affect the number and structure of chromosomes -They can be observed directly -Large scale genetic alterations that affects chromosome structure or the number of chromosomes

Somatic mutation

-They occur in somatic tissue which do not produce gametes -Soamtic cells within a mutation divides (mitosis) and make more -The earlier in development, the larger the cells that will contain the mutation in clone cells -many have no obvious effect on the phenotype

Insertions/deletions

-Those consiting of multiple of three nucleotides will leave the reading frame intact -Addition or removal of one or more nucleotides will affect the phenotype

Mutation on protein structure

-misense -nonsense -silent mutations

Transition

A purine is replaced by a different purine or a pyrimidine is replaced by a different pyrimidine -They arise more frequently

Reverse mutations

Changes mutant phenotype back to its wild type

Nonsense mutations

It changes a sense codon into a nonsense codon (stop codon that terminates translation) -If mutation occurs at an early stage in mRNA sequence, protein will be greatly shortened and will usually be nonfunctional

Forward mutations

Mutations that alters the wildtype

Transversion

Purine is replaced by pyrimidine or vice versa

Silent mutation

Some different codons specfiy the same amino acids because of the redundancy of the genetic code

Indels

Variations in genome arising from insertion or deletion of base pairs

Point mutations

gene mutations that involve changes in one or a few nucleotides

Reading frame

how the mRNA is read in set of three, consecutive, non-overlapping nucleotides

Neutral mutation

it is a missense mutation that alters the amino acid sequence of the protein but does not change its function