Topic 5-1 Flashcards
what are the two basic classes of mutations in multicellular organisms?
- somatic mutations
- germ-line mutations
any alteration at the cellular level in somatic tissues occuring after fertilization
somatic mutation
congenial genetic mutations in gametes, these genetic mutations are heritable and can be passed down to offspring
germ-line mutations
true or false: somatic mutations can be passed onto offspring
false
what are the two major categories of germ-line mutations?
gene mutations and chromosomal mutations
- mutations that usually affect a single gene
- base substitutions
- insertions and deletions
- expanding nucleotide repeats
these are characteristics of:
gene mutations
mutations affection chromosome structure or number
chromosomal mutations
what are the two main types of base mutations?
transition and transversion
substitiuting a purine with a purine or a pyrimidine with a pyrimidine
transition mutation
substituting a puring with a pyrimidine or a pyrimidine with a purine
transversion
which is more common, transitions or transversions?
transitions
what are the three main causes of base substitutions?
- spontaneous replication errors
- spontaneous chemical changes
- mutagens
what are tautomers?
structural isomers of nucleotide bases
nonstandard base pairs can occur as a result of:
flexibility in the DNA structure
true or false: insertions and deletions are more common than base substitutions
true
loss of a purine
depurination
loss of an amino acid
deamination
the loss of a purine base from a nucleotide may lead to a:
base substitution
what are the two main types of deamination?
cytosine –> uracil
5-methylcytosine –> thymine
occurs when one of the DNA strands forms a small loop
strand slipping
a spontaneous nucleotide insertion occurs due to strand slippage on the:
newly synthesized DNA strand
a spontaneous nucleotide deletion occurs due to strand slippage on the:
template DNA strand
in addition to strand slippage, DNA insertion or deletion can also be caused by:
unequal crossing over
occurs when a set of nucleotides is increased in copy number beyond what they should
expanding set of nucleotide repeats
epanding set of nucleotide repeats are associated with how many human diseases?
~30
Fragile-X syndrome, Huntington disease, and amyotropic lateral sclerosis (Lou Gehrig disease) are all caused by
expanding nucleotide repeats
how do expanding nucleotide repeats occur?
the formation of a secondary structure on the newly synthesized DNA strand
true or false: with the exception of thymine being replaced by uracil, the mRNA strand is the same as the DNA coding strand
true
each codon codes for one a.a. with the exception of:
stop codons
the protein code is:
degenerate
when reading the mRNA codes, which position is not read very carefully
wobble position
base substitutions can cause what kinds of mutations
- missense
- nonsense
- silent mutations
a type of base substitution mutation where the new codon encodes a different amino acid; causing a change in the amino acid sequence
missense mutation
a type of base substitution mutation where the new codon is a stop codon; causing a premature termination of translation
nonsense mutation
a type of base substitution mutation where the new codon encodes for the same amino acid as the original; therefore there is no change to the amino acid sequence
silent mutation
insertions or deletions can cause what type of mutations?
- frameshift mutations
- in-frame mutations (if in multiples of 3)
what is a loss of funtction mutation?
partial or complete abscense of gene product function, usually recessive
what is a gain of function mutation?
the gene product has a new function, usually dominant
what is a conditional mutation?
the phenotype (expression) of this mutation occurs only under certain conditions
