Bio 130 CH 14
Card Set Information
Bio 130 CH 14
A heritable change in the genectic material. Essential to continuity of life and a source of variation for natural selection.
New mutations are more likely to be harmful that beneficial so hwat is in place to counter it?
DNA repair systems.
Gene mutations may affecr amino aciud sequences. What are the ways?
Silent mutation, Missense mutation, nonsense mutaion, and frameshift mutation
this mutation does not alter the maino acid sequence amd os due do degeneracu of genetic code.
This mutation Changes a single amino acid in a polypeptide. May not alter function is substituted amino acid is similar in chemistry to original. ex Sickle cell
This mustation is a change from a normal codon to a stop codon. Produces a truncated polypeptide.
This mutation is an addition or deletion of nucleotides and creates a completely different amino acid sequence downstream from mutation.
A mutation may alter the sequence within a promoter and affect the rate of transcription. What will this cause?
It may enhance or inhibit transcription
Mutations may occur in other regulatory elements or operator sites. what does this cause?
May alter DNA sequence of operator so that repressor protein does not bind
What determines the severity and heritability of a mutation?
Time and location
these cells give rise to gametes
These are all cells in the body
in Germ-line cells where does the mutation occur?
In sperm, egg, or in gamete progenitor cells
In somatic cells wher doe sthe mutation occur?
early or late development. gives a genetic mosaic with patches of mutamt tissue
These mutations are From abnormalities in biological processes. Rates vary species to species and gene to gene. Background mutation rate ~1 mutation / million genes
these mutations are caused by environmental agents
chemical or physical agents that alter DNA
How do mutagens work?
They can disrupt base pairing by changing a c to u for ex. dsrupt replication by adding something between bases such has benzoyrene. also radiation causing deletions or gaps
This radiation has high energy and penetrates deeply to create free radicals. X rays and gamma rays. Cause deletions or breaks in one or both DNA strands
This radiation has less energy and can only penetrate the surface. UV rays can cause formation of thymine dimers, causing gaps or incorporation of incorrect bases
Uses Salmonella typhimurium that cannot synthesize histidine due to a point mutation. ? Test monitors rate at which second mutation occurs.
All organisms require the ability to repair DNA. What are the two components?
Detection of damage and repair of damage
What are the types of repair?
Direct repair, nucleotide excision repair, and methy-directed mismatch repair
in this repair A repair enzyme recognizes an incorrect structure in the DNA and directly converts it back.
in this repair portion of DNA strand containing an abnormal nucleotide is removed and replaced.
Nucleotide excision repair. (NER)
in this repair a base pair mismatch is detected and a stran of surrounding DNA is removed and replaced
Methyl-directed mismatch repair
What is the most common repair system?
NER nucleotide excision repair
What where the diseases that led to the discovery of NER?
Xeroderma pigmentosum (XP), Cockaynes syndrome (CS), PIBIDS
90% of cancers are due to exposure. About what percent is from carcinogens?
Can migrate to other parts of the body
An oncogene may promote cancer by keeping the cell division signaling pathway in a permanent
Oncogenic mutations may decrease ability of Ras to hydrolyze GTP or exchange GDP/GTP faster. What does this cause?
Both keep signaling pathways constantly open
What is a proto-oncogene?
A normal gene that, if mutated, can become an oncogene.
What are the four common genetic changes?
Missense mutations, gene amplifications, chromosomal translocations, and retroviral insertions.
this mutation Increase in copy number results in too much protein
In this mutation Two chromosomes break and switch ends. Very specific translocations associated with certain types of tumors. Can create chimeric genes
What are the two ways that viruses cause cancer?
modifying host dna and carry oncogenes
What are the typical functions of tumor-supressor genes
prevent cancerous growth, maintain genome integrity, and ihibitor of cell division
Proteins called cyclins and cyclin-dependent protein kinases (cdks) are responsible for advancing a cell through the four phases of the cell cycle. what are these called?
about 50% of all human cancers are associated with defects in this gene
function as proteases that digest selected cellular proteins causing the cell to break down . It is beneficial for a multicellular organism to kill an occasional cell with cancer causing potential