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Lecture 13

BIOL 151 Lecture Notes - Lecture 13: Homologous Chromosome, Gene Duplication, Deoxyribose


Department
Biology
Course Code
BIOL 151
Professor
Josephbattistelli
Lecture
13

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BIOL 151 – Chapter 14
14.1 The Rate and Nature of Mutations
Spontaneous: occurrence by chance in the absence of any assignable cause
For individual nucleotides, mutation is a rare event
oThe highest rates of mutation per nucleotide per replication are found among
RNA viruses and retroviruses
oCertain nucleotides are especially prone to mutation and can exhibit rates of
mutation that are greater than the average by a factor of 10 or more
Sites in the genome that are especially mutable are called Hotspots
oIn some multicellular organisms, the rates of mutation differ between the sexes
oIn mammals, the rate of mutation per nucleotide per replication is greater in
somatic cells (cells other than the reproductive cells) than in germ cells
(reproductive cells and cells that give rise to them)
Across the genome as a whole, mutation is common
oSome genomes are much larger than others, and across a genome as a whole,
there will be a greater number of mutations per genome in large genomes than in
small ones
oFor RNA viruses and retroviruses, the average number of new mutations per
genome reflects the high rate of mutation per nucleotide
oLarge numbers of new mutations, as the ones in the human genome would be
intolerable in organisms with a high density of protein-coding genes
Only germ-line mutations are transmitted to progeny
oGerm-line Mutations: mutations that occur in eggs and sperms and the cells that
give rise to those reproductive cells
oSomatic Mutations: mutations that occur in the cells that are nonreproductive
oMost cancers result from mutations in somatic cells
oGenetic Risk Factor: any mutation that increases the risk of disease in an
individual
14.2 Small-Scale Mutations
Point mutations are changes in a single nucleotide
oMost DNA damage or errors in replication are immediately removed or corrected
by specialize enzymes in the cell
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