14.3 Chromosomal Mutations / 14.4 DNA Damage and Repair
Duplications
>most common chromosome in which a region is present twice instead of once -large duplications can be harmful and quickly eliminated from the population -small duplications including only one or two genes can be maintained over many generations -duplication is less harmful than deletion of the same region
What is the difference between mismatch repair and nucleotide excision repair?
In mismatch repair, one nucleotide is replaced, whereas in nucleotide excision repair several nucleotides are replaced.
centromere
a constriction that physically holds sister chromatids together; the site of the attachment of the spindle fibers that move the chromosome in cell division >rarely deletion or duplicated bc it is usually lost within few cell divisions because it cannot be directed properly into the daughter cells during cell division
deletion
a region of the chromosome is missing >result from an error in replication or from the joining of breaks in a chromosome that occur on either side of the deleted region >some deletions decrease the chance of survival or reproduction of an organism even when homologous chromosome is normal
mutagens
agents that increase the probability of mutation (radiation or chemicals)
DNA ligase
an enzyme that uses the energy of ATP to close a nick in DNA strand, joining 3' hydroxyl of one end to 5' phosphate of the other end
chromosomal mutations can
delete or duplicate regions of a chromosome containing several or many genes, and the resulting change in gene copy number also changes the amount of the products of these genes in the cell
_____ is the process where new genes evolve from duplicates of old ones
duplication and divergence
molecular clock
estimates of the time when different taxa diverged, based on the amount of genetic divergence between them
A chromosomal mutation where a segment breaks off, flips, and then reattaches itself is called a(n)
inversion
Which type of repair is a backup for the DNA polymerase proofreading function?
mismatch repair
In organisms with large genomes, inversions are more likely to be tolerated if the breakpoints occur in:
noncoding DNA
reciprocal translocation
occurs when two different chromosomes undergo an exchange of parts >both chromosomes are broken and the terminal segments are exchanged before the breaks are repaired >large genomes, the breaks are likely to occur in noncoding DNA, so the breaks themselves do not usually disrupt the gene function >change only arrangement of genes and not their number, most reciprocal translocations do not affect organisms survival
Chronic myelogenous leukemia (CML) is caused when a segment of chromosome 9 and a segment of chromosome 22 both break off and switch places. How is this mutation classified?
reciprocal translocation
dosage
the number of copies of each gene in a chromosome
duplication and divergence
the process of creating new genes by duplication followed by change in sequence over evolutionary time
inversion
the reversal of the normal order of a block of genes >typically produced when the region between two breaks in chromosomes is flipped in orientation before the breaks are repaired >small inversion can have almost no affect
A chromosomal segment that breaks off and attaches to another chromosome is what type of mutation?
translocation
A chromosomal mutation in which a segment is missing is called a deletion
true
Mutagens increase the amount of damage to DNA
true
Mismatch repair, base excision repair, and nucleotide excision repair are similar in that each: (Select all that apply.)
uses an undamaged segment of DNA as the template to repair a damaged segment of DNA.
Which of the following causes breaks in one or both of the sugar-phosphate backbones?
x-rays
