Chapter 14 Flashcards
Mutation
Small change in the sequence of bases in a gene or in the addition of removal of a base pair
Point mutation Examples Base substitution Silent mutations Missense mutations example of this Nonsense mutation Frameshift
One pair is changed, added or subtracted
When a base isn’t added or removed but is substituted for another one
Occur in the Third base of codons w/o changing the type of amino acid that’s coded
Base substitution that changes one amino acid in a polypeptide sequence. Depending how different the new one is it may or may not change the protein function. Sickle cell is an example
Change from abnormal codon to a stop/termination codon, making translation end too early
Addition or removal of nucleotides NOT in multiples of 3. Because codons read in groups of 3 this change shifts the reading frame causing a complexity different amino acid sequence which is likely to inhibit protein function
Sickle cell
A missense mutation that involves changing the sixth amino acid to valine instead of glutamic acid. Valine, the new one, is hysrophobic, the old one is Philic
Germ line cells mutation
Somatic cells mutation
Mosaic
If a mutant gamete participates in fertilization all the cells of the resulting offspring will contain the mutation. Half of the gametes from this organism carry the mutation
All other body cells besides sperm or egg, can occur early or late in development . None of the gametes from this organism carry the mutation
An individual with somatic regions that are genetically different from each other
Spontaneous mutations
Induced mutations
Mutagens
Chemical ones, example for
Physical ones
From abnormalities in biological processes.. exp normal metabolic processes can produce free radicals which react with DNA and change its structure
One mutation per one million genes per division 10 to the 6th
Causes by environmental agents. Occur more frequently
Chemical or physical agents that alter DNA
Chemical ones act by covalently modifying the structure of nucleotides or disrupting nucleotide pairing by alkylating bases
Nitrogen mustard is an exp
Physical. Radiation of short wave length with high energy called ionizing radiation alters DNA structure. This includes X-rays and gamma rays they penetrate deep
Non ionizing like I’ve had less energy so it penetrates only the surface, skin
Benzopyreno
Found in cigarettes it’s a chemical mutagen.
Types of repair to DNA
Direct repair: a repair enzyme recognizes an incorrect structure in the DNA and directly converts it back
Nucleotide excision repair: portion of DNA strand containing an abnormal nucleotide is removed and replaced
Methyl directed mismatch repair: a base pair mismatch is detected and a strand of surrounding DNA is removed and replaced
Nucleotide excision repair
_____ DNA repair system
Uses U damaged strand as ____
NER was discovered in humans from genetic diseases that affect DNA repair such as
What’s a common characteristic in all three syndromes
Most common
A template for resynthesis of a normal complementary strand
XerodermA pigmentosum
Cockaynes syndrome
PIBIDS
Photosensitivity because of an inability to repair UUC induced lesions
Cancer definition
Characterized by
How
Many Americans diagnosed a year? How many die?
What percent of cancers give you a higher predisposition to develop the disease as an inherited trait
What percent do not involve heridity
Disease of multicellular organisms Characterized by uncontrolled cell division 1.5 mil .5 mil 10% 90%
What percent of cancers are related to carcinogens
80%
Tumor
They can be ____\ or ____
May become
Invasive
Metastic
An overgrowth of cells with no useful purpose
Benign or pre cancerous
Malignant(cancerous)
Can invade healthy tissue
Can migrate to other parts of the body
Oncogene
A mutation causes gene to be over active causing uncontrolled cell growth. Can promote cancer by keeping the cell division signaling pathway in a permanent on position
Four common genetic changes that can change a proto oncogene into an oncogene
Misense- changes a single amino acid in a protein( chemical mutagens usually responsible)
Gene amplifications-abnormal increase in the number of otherwise normal genes. Which results in too much protein. Amplication of myc found in leukemia
Chromosomal translocations- one part of a chromosome gets attached to another chromosome
Retorviral insertions- virus integrates into the chromosome, where vital regulatory elements enhance the expression of a nearby proto oncogene, converting it into an oncogene. Exp, hep c, Epstein Barr, job
Tumor suppressor gene Their normal role Typical functions Checkpoint proteins P53 Apoptosis
Prevent cancerous growth
Monitor/ repair DNA damage and halt cell division when needed.
Checkpoint proteins check the integrity of the genome and prevent a cell from processing past a certain point in the cell cycle by controlling the proteins ‘cyclin’ and ‘cyclin dependent kinases’ which are responsible for advancing the cell through the 4 phases of cell cycle
P53 is a checkpoint protein that stops cell from progressing from g1 to S phase until damage is repaired. If damage is too severe p53 will activate other genes that promote programmed cell death
It’s involved in 50% of all human cancers
Caspases
Nicknamed the executioners, they function as professes that digest selected cellular proteins causing the cell to breakdown
