Chapter 15: Gene Mutation and DNA Repair 1OO% GRADE A+ GUARANTEED

Chapter 15: Gene Mutation and DNA
Repair 1OO% GRADE A+ GUARANTEED
mutation
Any permanent change in an organism's DNA.--> changes in dna sequence

creates of new alleles

origin of genetic variation within populations

(Cell death, genetic disease, cancer)

provide basis for genetic analysis

genetic markers

any base change of at least one base pair

Classified by type of molecular change, phenotypic effects, location
of mutation
mutations are classified by:
Classified by type of molecular change, phenotypic effects, location
of mutation
genotype
The gene or set of alleles (forms of genes) that give rise to a
polypeptide, cellular feature (enzyme, signaling molecule, organelle,
etc.), and/or organismal feature (like size, color, etc.).
genetic variation
The variety of different types of genes in a species or population.--
->Differences among individuals in the composition of their genes or
other DNA segments


Genetic variation means that biological systems - individuals and
populations - are different over space. Each gene pool includes
various alleles of genes. The variation occurs both within and among
populations, supported by individual carriers of the variant genes

The variation occurs both within and among populations, supported by
individual carriers of the variant genes.

,Genetic variation is brought about, fundamentally, by mutation, which
is a permanent change in the chemical structure of chromosomes.
Genetic recombination also produces changes within alleles.
w/o genetic variation that arises from changes in DNA sequence---->
no phenotypic variability
no adaptation (environment)
NO EVOLUTION
genetic variant
Difference in the DNA sequence compared with a reference sequence
(prod by mutation)

A single-nucleotide polymorphism (SNP), in case it is a common
genetic variant
A mutation, in a case where it is a rare genetic variant
A copy-number variation
See also
Polymorphism (biology), the effect of genetic variants: a range of
phenotypes.
Polymorphism
(biology) the existence of two or more forms of individuals within
the same animal species (independent of sex differences)

The coexistence of two or more distinct forms in the same population.
phenotype
Observable feature of an organism that results from a genotype
(polypeptide, cellular feature, and/or organismal feature).
Importance of New Mutations
Characteristic of DNA (along with ability to carry genetic
information, self-replicating, and able to express genetic
information)

Source of variation (new alleles)

Raw material for evolution

Basis of most genetic analyses (we don't know whether a gene exists
until we see the effect of a mutation)
gene mutation
An alteration in DNA sequence

Any base-pair change in sequence
Single base pair substitution
Deletion or insertion of base pairs

,Major alteration in chromosomal structure
May occur in somatic or germ cells
May occur in coding or noncoding regions
somatic
relating to or affecting the body, corporeal
germ line
The lineage of reproductive cells that contributes to the formation
of a new generation of organisms, as distinct from somatic cells,
which form the body and leave no descendants in the next generation.
Types of mutations
insertion, deletion, substitution
Classification based on Type of Molecular Change:
point mut//base sub

missense // nonsense // silent

transition//transversion

frameshift
Classification Based on Phenotypic Effects
loss of function mutation//null mutation

recessive mutation

dominant mut

haploinsufficiency

dominant gain of function

visible mutations

nutritional mutation

biochemical mutations

behavioral mutations

regulatory mutations

lethal mutations

conditional mutations

, temp sensitive mutations

neutral mutation
Classification Based on Location of Mutation
Somatic Mutations

autosomal mutations

X/Y Linked mutations
point mutation
gene mutation in which a single base pair in DNA has been changed

change of one letter
frameshift mutation
mutation that shifts the "reading" frame of the genetic message by
inserting or deleting a nucleotide

loss of one letter
Base substitutions
replacement of one nucleotide with another
- effect depends on whether there is an amino acid change that alters
the function of the protein

gain of one letter

Transitions versus Transversions

can result in missense, nonsense, or silent mutations
transitions vs transversions
Transitions - Within same family of nitrogenous base (Purine ->
Purine , Pyrimidine -> pyrimidine)
MORE LIKELY

Transversions - Between different families of nitrogenous base
(Purine -> Pyrimidine , Pyrimidine -> Purine)
transition mutation
a base substitution that occurs within the same family of nitrogenous
base (Purine -> Purine , Pyrimidine -> pyrimidine)
Transversions mutations
a base substitution mutation Between different families of
nitrogenous base (Purine -> Pyrimidine , Pyrimidine -> Purine)
Phenotypic Effects of Mutations
Forward mutation versus reverse mutation