Chapter 15 Flashcards
mutation
a change in the nucleotide sequence of DNA that can be passed on ot the next generation
somatic mustations
occur in somatic (body) cells. Passed to daughter cells in mitosis but not to sexually
germ line mutations
occur in germ line cells that give rise to gametes. A gamete passes these mutations on at fertilization
loss of fun mutations
gene may not be expressed at all, or protein doesn’t functions (non-functional protein)
-tumor suppression gene
gain of fun mutation
leads to a protein with altered function
- dominant
- common in cancer
point mutation
change in a single nucleotide (alters mPNA sequence, and may not result in a change in the protein)
- transition
- transversion
transition
substitution of one purine for the other, or one pyrimidine for the other
transversion
substitution of a purine for a pyrimidine of vice versa
silent mutation
usually don’t affect protein function
- might be in non-coding region/code for same amino acid as original
- common: a result in genetic diversity that isn’t expressed
missense mutation
may have no effect on protein function (or the protein functional efficiency may be reduced, but not commonly inactivated, eg. Sickle Cell anemia)
nonsense mutation
a base substitution causes a stop codon to form somewhere in the mRNA (if its near the 3’ end, usually no effect)- results in a shortened protein that in typically non-functional
frameshift mutation
insertions or deletions of bases
-alter reading-frame for 3 base codons during translation (nonfunctional proteins produced)
chromosomal mutations
result in extensive changes in DNA
- break and rejoin
- can be caused by damage to chromosomes by mutagens/errors in chromosome replication
deletions
chromosomes may break in two places and rejoin, leaving out a large part of DNA
duplications
can occur with deletions when homologous chromosomes break at different places
inversions
chromosome breaks and rejoins, with one segment flipped
translocations
segment of DNA breaks off and attaches to another chromosome; can cause duplication and deletion (uneven exchange of genetic material)
spontaneous mutations
occur with no outside influence and are permanent (imperfect cellular processes)
- errors in replication by DNA polymerase
- most errors are repaired by proofreading fn, but some become permanent
- imperfect meiosis: nondisjunction and random breaking and rejoining of chromosomes
induced mutations
are due to outside agents or mutagens such as chemicals or radiation or retroviruses
- chemicals can alter bases (some chemicals add other groups to bases)
- radiation damages DNA: ionizing radiation (x-rays/gamma rays/radiation from unstable isotopes) creates highly reactive free radicals
genetic screening
tests to determine if a person has a genetic disease, is predisposed, or is a carrier
prenatal screening
to detect changes in a fetus’s genes or chromosomes before birth (eg. down syndrome)
screening of newborns
used just after birth to identify genetic disorders that can be treated early in life (eg. PKU)
carrier testing
identify ppl who carry one copy of a gene mutation that when present in two copies can cause a genetic disorde
DNA testing
direct analysis of DNA for mutations-the most accurate way of detecting abnormal alleles
