2D: changes in DNA sequences and spontaneous mutations Flashcards
what are mutations?
changes to nucleic acid sequences (DNA or RNA) that may be heritable (germline) or not (somatic) and can be small (gene level) or large (chromosomal)
what is a germline mutation?
a mutation of the DNA/RNA of gametes (spem/egg cells). heritable
what is a somatic mutation?
a mutation of the DNA/RNA of the cells of the body (NOT germ cells). not inherited by offspring
what are chromosomal mutations?
any change from the normal structure or number of chromosomes in a cell
what are 4 type of chromosomal mutations?
➝ deletion
➝ duplication
➝ translocation
➝ inversion
define deletion mutation (chromosomal)
when a segment breaks off of a chromosome and is lost
define duplication mutation (chromosomal)
when a segment is broken off of one chromosome and inserted into its homologue (identical twin chromosome). in the receiving homologue, the alleles are added to the ones that are already there
define translocation mutation (chromosomal)
when a segment broken off of one chromosome attaches to a different, non-homologous chromosome
define inversion mutation (chromosomal)
when a segment breaks off a chromosome and reattaches to the same chromosome from which it was lost but in reversed orientation
what is the impact of a deletion mutation? (chromosomal)
may cause severe issues if the deleted genes were essential for normal development or cellular functions
what is the impact of a duplication mutation? (chromosomal)
increases gene expression of duplicated genes. may be harmful or beneficial, depending on what gene is duplicated. some have been important sources of evolutionary change
how can chromosomal duplication mutations have been a source of evolutionary change?
since there is now more than one copy of the gene, one form of the gene can mutate into new forms without seriously affecting the function of the organism
what is the impact of a translocation mutation? (chromosomal)
genes may be broken internally, and therefore not be functional, or may be transferred to a new location, where the effect can range from beneficial to harmful. many cancers have chromosomal mutations, and the most common one is translocation
what is the impact of a inversion mutation? (chromosomal)
essentially the same effects as translocations: genes may be broken internally by the inversion, with loss of function, or they may be transferred intact to a new location within the same chromosome, producing effects that range from beneficial to harmful.
define mutations at the gene level
changes in the double-stranded sequence of bases in genetic material
define missense mutation
a sense codon is changed to a different sense codon that specified a different amino acid. also called nonsynonymous mutation
define nonsense mutation
a sense codoon is changed to a nonsense codon (stop codon). also called premature stop mutation
define silent mutation
a sense codon is changed to a different sense codon, but the codon specifies the same amino acid as the original (no change)
define frameshift mutation
a single base-pair deletion or insersion in the coding region of a gene alters the reading frame, resulting in all of the codons following the insertion/deletion being affected
define base substitution mutation
single nucleotide base change as a result of point mutations
define insertion mutation
one or more base pairs added in sequence during DNA replication
define deletion mutation
one or more base pairs skipped during DNA replication
do all deletion/insertion mutations result in a shifted reading frame?
no. if multiples of 3 are inserted/deleted, the reading frame remains the same
define transition
purine-to-purine or pyrimidine-to-pyrimidine changes