Unit 3 - Mutations Flashcards
Mutation is…
a permanent change in the nucleotide sequence of a cells DNA
Mutation 3 factors
1) typically, neutral or harmful = rarely beneficial
2) allows species to change over time
3) only those who adapt will live
Mutation passes onto
daughter cells
Multicellular organisms have two types of mutations:
1) somatic
2) germ line
Somatic Mutations
passes on during mitosis, but not so subsequent generations
- non heritable
- non germline tissues
Germ Line mutation
occur in cells that give rise to gametes, pass to subsequent generations
- present in egg and sperm
- can be inherited
Mutations can be (3)
a) spontaneous or induced
b) physical or chemical
c) chromosomal or single gene
a) spontaneous
take place naturally as a result of normal mo interactions
ie. DNA replication
a) induced
cause by agents outside the cell
ie. mutagens; an environmental agent increased rate of mutations
Environmental agents directly alters DAN in a cell can be..
physical = x-rays or UV
chemical = gasoline or cigarette smoke
b) physical
- produces highly reactive chemical species called free radicals which can change the base in DNA to unrecognizable forms by DNA polymerase
- can break DNA backbone = chromosomal rearrangment or deletion
Ionizing radiations
x-ray
gamma rays
= induced
UV radiation
is absorbed by T in DNA causing it to form inter-base covalent bonds with adjacent nucleotides called DIMERS = chaos in DNA replication
b) chemical
can enter the cell nucleus and chemically alter the structure of DNA
ie. co2, tobacco smoke
-modify individual nucleotides
-mimicking DNA mol
-insert itself between strands of double helix and alter structure of DNA
Nitrous Acid vs Benzpyrene
1) can turn C in DNA into U = induced
2) A component of cigarette smoke, adds a large chemical group to G making it unavailable for bp = induced
Small scale mutations
include mutations of an individual bp called point mutation or of a small group of bp
substitution
of one base for anotheri
insertion
of a single bp
deletion
of a single bp
inversion
of two adjoining bp
effects of small scale mutations; 4 groups
1) missense mutations
2) nonsense mutations
3) silent mutations
4) frameshift mutations
substitution mutation ie sickle cell anemia (5)
1) point mutation in hemoglobin
2) = misshapen hemoglobin
3) reduces lifespan by 30y
4) cant transport O2 effectively
5) nucleotide 19 sub from A=U
Missense Mutation
occurs when the change of a single base pair or group of bp results in the code of diff aa
- protein sythensized will have a diff sequence and strucure
- may or may not function (protein)
Nonsense Mutation
occurs when a change of a single base pair or group of base pairs results in a premature stop codon
= polypeptide chain is cut short most likely unable to function
Silent Mutations
occurs when the change in one or more base pairs does not affect the functioning of the gene. (may occur within an intron). gene codes fro same aa.
Frameshift Mutations
occurs when one or more nucleotides are inserted into or deleted from a DNA sequence =reading frame of codons to shift in one direction or the other (deleting or inserting 3bp)
Large scale Mutations
also called chromosomal mutations
- large scale mutations can invlive multiple nucleotides or entire gene
-small pieces of a chromosome or chromosomes may be deleted, duplicated, insertion, inverted, or translocated
Deletion
a mutation in which a part of a chromosome or sequence of DNA is deleted and bc “missing”
Duplication
any duplication of a region of DNA that contains a gene
- this duplication can now supply additional material that had the ability to evolve new functions
(Marie-tooth disease type 1)
Insertion
a type of chromosomal abnormality in which a DNA sequence is inserted into a gene, disrupting the normal structure and function of that gene.
Inversion (3) facts
1) reversal of a segment of DNA in chromosome
2) breaking and rejoining
3) effect if break occurs in a gene
Translocation
a fragment of DNA moves from one part of the genome to another = fusion protein ie. leukemia
Leukemia
- cancer of the blood and bone marrow caused by translocation between chrom 9 and 22.
associated to exposure: benzene, x-rays, radiation
negative mutation
renders the individual less fit than other membranes of its group and will be seleced against by nature
Benefical Mutation
lead to new versions or proteins that help organisms adapt to change. As a result experience greater survival and reproductive success
Neutral mutation
changes in DNA sequence that r neither beneficial nor detrimental to the ability of an organism to survive and reproduce
impact of mutation can be beneficial under diff circumstances like
1) mutation causes sickle cell anemia and also gives resistance to malaria
2) mutation that causes lactose tolerance in humans allows us to consume milk from cows
DNA composition: coding region
5% of genome
- 42000 genes
DNA composition: noncoding regions
95% of genome
- repetitive DNA
telomeres
centromeres
VNTRs (microsatellites)
Pseudogens
genes that r no longer expressed in the cell
