Chapter 15 Flashcards
Mutation
A heritable change in the genetic material
Point mutation affects?
A single base pair.
2 basic alterations
Change base sequence
Add or remove nucleotides
Silent mutation
Doesn’t alter the amino acid sequence
How many codon per amino acid?
More than 1
Missense mutation
Changes a single amino acid in a polypeptide
Nonsense mutation
Change from a normal codon to a stop or termination codon
Frameshift mutation
Addition or deletion of nucleotides that are not multiples of 3
Mutation outside of coding sequences
Mutation may alter DNA operator sequence so that repressor protein doesn’t bind
Germ-line cells mutation
Rise to gametes
Can occur in sperm/egg cells or the cells that gives rise to eggs & sperm
Somatic cell mutation
All other cells
Can occur early/late in development
Spontaneous mutation
Result from abnormalities in biological processes
DNA polymerase adds wrong nucleotide.
How many spontaneous mutation
1 mutation for every 1 million genes.
Induced mutation
Brought on by environmental agents
Mutagens
Chemical/physical agent can alter DNA in various ways.
Disrupt pairing by
Modifying nucleotide structure
Base analogue mutagens similar to particular bases cause errors in replication
Alkylating bases
Interfering with replication
Benzopyrene (auto exhaust) inserts between bases & distort the helix causing errors
Ionizing radiation
Have high energy & short wavelength
X Pay & gamma Rays
What can lonizing radiation do?
Can penetrate deeply into biological materials to create free radicals.
Free radicals
Unstable molecule that can build up in cell & cause damage in other molecule
Why lionizingradation can penetrate biological materials?
Cause base deletions or breaks in 1/both DNA strands
Base deletion
A mutation in which a part of a chromosome or a sequence of DNA is left out during DNA replication
Nonionizing radiation
Has less energy & can only penetrate the surface
Uv Rays
What does Wrays causes
A formation of thymine diner causing gaps or incorporation of incorrect bases
Ames test
Test ability of substance to cause mutation
DNA repair
Living orgs must have the ability to repair changes that occurs in DNA in order to minimize mutation
What requires for DNA repair
DNA damage be detected
Repair of DNA damage
Direct repair
Enzyme removes a modification
Altered DNA strand removed & new sequent synthesized
Nucleotide excursion repair (ner)
Recognizes abnormal base
Region encompassing several nucleotides in the damaged strand is removed from the DNA
Intact undamaged strand is used as a template for resynthesis of a normal complementary strand.
Fixes many mutation.
How ner was discovered in human?
By the analysis of genetic diseases that have defective ner based DNA repair.
Cancer
Multicellular Disease organisms that is characterized by uncontrolled cell division.
Carcinogens
Agents that increase the likelihood of developing cancer
Invasive
Can invade healthy tissue
Metastatic
Can migrate to other parts of the body.
Proto-oncogene
Mutation causes this gene to be overactive
Called an oncogene
Involved in cell growth
Tumor-suppressor gene
Normal y this gene encodes a protein that prevents cancer
Missense mutation
Chemical mutagens have been shown to cause missense mutation leading to cancer.
Gene amplification
Abnormal increase in copy number results in foo much of encoded protein
Chromosomal translocations
2 different chromosome break & the ends of broken chromosome fuse with each other incorrectly.
Retroviral insertion
Viral DNA may insert into a host chromosome in such a way that a viral promoter & response elements are next to a proto- oncogene
Cyclin-dependent protein kinases (CDKS)
Responsible for advancing a cell through the four phases of the cell cycle
3 ways to loss of tumor-suppressor gene
Mutation occurs specifically within a tumor- suppressor gene to inactivate it’s function
Chromosome loss may contribute if the missing chromosome carries 1/more tumor- suppressor genes
Abnormal methylation of CpG islands near promoter regions
