CH 14 Mutation and DNA Repair Reading Guide Flashcards
Does a new mutation occur every time a cell
divides?
No there is a 10^(-10) percent chance
Do you think that any new mutations have accumulated in the cells within your body since the time your were first conceived
Yes
How can the human genome tolerate ~30 new mutations in every generation?
Because many of the sections of DNA subject to mutation are non functioning section so they play no important role
What’s the difference between somatic cells and germ-line cells?
Somatic cells are all other cells of the body that are not associated with reproduction
Germ cells are the reproductive cells
Give examples of genes that when mutated in somatic cells might give rise to cancer
APC, Ras and p53 genes can give rise to malignant colon cancer
Why
do you think cancer is a lot more common in old people than in young?
Because they have undergone much more cell replications increasing their likely hood for gene to be mutated
Which type (somatic or germ line mutations) can change the course of evolution?
Germ line mutations as they are passed down through generations
What two hypothesis were proposed by the Lederbergs?
Mutations occur randomly with respect to the needs of an organism
The environment induces mutation (in this case antibiotic resistance)
In what sense is a growth medium that contains an antibiotic agent ‘selective’? In what
sense is a growth medium that contains only nutrients, nothing toxic, ‘nonselective’?
Because it allows for only antibiotic resistant bacteria to survive (selects them)
Allows for all type of bacteria to survive
Did the selection on medium containing an antibiotic produce / trigger mutations in
bacteria that allowed the cells to survive in the presence of the antibiotic? Explain.
Yes.
Mutations (antibiotic resistance) can arise in the absence of antibiotic.
Does the environment direct the formation of specific mutations that allow cells to
survive better? Explain?
No
Mutations are random and not directed by the environment
Does DNA polymerase ever make mistakes
during DNA replication? If so, does it have the ability to detect and repair its own
mistakes? Is DNA polymerase 100% reliable?
Yes
Yes it has a proof reading function
Not 100% reliable
Define synonymous mutation
Changes in the base pairs that do not result in a change to the amino acid sequence
Define non synonymous mutation
Point mutation that causes an amino acid replacement
Mutation of which human gene give rise to sickle cell anemia disease? Is this disease
caused by a synonymous or nonsynonymous mutation?
Beta globin gene
Considered a non synonymous mutation. Changes what should be a Glu to a Val amino acid
Define a nonsense mutation
A nonsense mutation changes an amino acid to a stop codon therefore ending translation resulting in a shortened unstable protein
would a nonsense mutation have a more severe effect if it occurred
near the middle of a coding sequence, or close to the end of the last exon?
Yes more severe closer to the middle of the coding sequence
How is a frameshift mutation different from an insertion/deletion of three nucleotides
within a reading frame?
It usually involves the insertion of a single nucleotide that evokes a major shift in the reading frame. Making an entire sequence illegible
What is the normal ‘dosage’ of any given gene (residing on an autosome) in the
genome? How does duplications and deletions result in deviations from normal gene
dosage?
Normal dosage refers to the number of copies of each gene. Every organisms is sensitive to changes in dosage
Duplications makes repeated segments on the chromosome while deletions remove segments
Why are small duplications/deletions better tolerated than large ones?
Large duplications and deletions are not compatible with life
What type of damage can X-rays do to DNA?
Break the sugar-phosphate backbone of DNA
What type of damage can UV radiation do to DNA?
Causes cross-links between adjacent pyrimidine bases, especially thymine, resulting in thymine dimers
Spontaneous hydrolysis of a purine base from carbon 1 of the deoxyribose sugar: is this
a common occurrence?
Yes.
13,000 purines lost per human cell per day
Chemical modification of a base, e.g. replacing an -NH2 group with a double bonded
oxygen: what is the consequence?
Spontaneous damage to the bases
Addition of a bulky side group to a base (e.g. by compounds in tobacco smoke),
consequence?
Hinder proper base pairing and cause deletion and insertions of nucleotides
