Exam 3 Flashcards
what kind of cells cannot pass down mutations?
somatic cells
first disease phenotype correlated with genotype
alkaptonuria
phenylketonuria
buildup of phenylpyruvic acid in brain causing permanent affects
albinism
inability to produce melanin in skin (recessive)
one gene makes one enzyme
beadle and tatum
one gene makes one enzyme changed to
one gene makes one polypeptide
loss of function in protein is
recessive
gain of function in protein is
dominant
point mutation
substitution of one base for another
transition
purine to purine or pyrimidine to pyrimidine
transversion
purine to pyrimidine and backwards
transition letters
A -> G or T -> C
transversion letters
A -> C / A -> G
G -> C / G -> T
missense (anonymous)
changes amino acid (may change function)
nonsense
changes codon to a stop codon
silent
codes for same amino acid
readthrough
changers stop to something else resulting in longer chain
depurination
removes bond at either G or A base
- results in apurinic site
deamination of cytosine
results in uracil
- causes GC to AT transition
wobble base pairing
mispairing due to flexibility in helix
oxidizing agents — DNA
damage
causes frameshift mutations
- strand slippage (delete)
- unequal crossing over (both)
- repeat regions (“insert”)
fragile X symptom
- repeat CGG on X chromosome
- long face and jaw bones and loose joints
x-rays cause chromosome breakage leading to
thymine dimers
dimers
distort the helix and inhibit replication
xeroderma pigmentosum
repair mechanism is defective
- tumors on skin surface
transposable genetic elements
jumping genes
Activator (AC)
complete transposable element with functional transposase and repeats
dissociation (DS)
lacking functional transposase gene (deletion) so it requires the AC transposase to move
transposons
- ability to move regulatory sequences affecting the gene expression
- mutations in drosophila are due to this
Direct repair of mutations
corrects structure of abnormal nucleotide without replacing the nucleotide
methyltransferase job in direct repair of mutations
restores correct form to incorrectly methylated guanine base
translesion DNA polymerases
can bypass lesions on the DNA during replication
- often make errors
termination deletion
produces acentric fragment which is lost during cell division
interstitial deletion
requires 2 breaks
acentric fragments
segments that do not contain a centromere
haploinsufficiency
single copy of gene is not enough to allow the wild-type phenotype to occur
pseudodominance
expression of normally recessive phenotype because there is no homologous allele due to deletion
tandem duplication
direct duplication
- AB.CDEFDEFGH
reverse tandem
reverse duplication
- AB.CDEFFEDGH
displaced (homobrachial)
- AB.CDEFGHDEF
displaced (heterobrachial)
- DEFAB.CDEFGH
paracentric inversion
does not include centromere
- ABCDE.FGH
- ADCBE.FGH
pericentric inversion
includes centromere
- ABCDE.FGH
- ABCF.EDGH
inversions lead to speciation because
cross over products in heterozygotes are not viable while in homozygotes they are
reciprocal translocations
2 nonhomologous chromosomes exchange arms
non-reciprocal translocation
a segment from one chromosome is moved to a nonhomologous chromosome
- AB.CDEFG JK.LM
- AB.CFG JK.LDEM
robertsonian translocation
2 telocentric chromosomes combine to make one large one
- small amount of DNA lost
familial down syndrome due to
robertsonian translocation or isochromosome
isochromosome
2 chromosome 21s join together
which repair mechanisms involve the removal of a single nucleotide
proofreading and base excision repair
wildtype
will grow on minimal media since it is capable of synthesizing arginine
mutant
requires supplemental arginine for growth
Which repair mechanisms involve the removal of several nucleotides?
nucleotide excision repair and mismatch repair
