quiz #1 Flashcards
(82 cards)
Reasons for Mendel’s success
- most people at the time studied complex traits –> complex results
- he studied simple individual traits
Mendel conclussions
- interpreted his quantitavely based on probability
- alleles of unlinked genes sort independently (genes on teh same chromosome often exhibit various degrees of linkage depending on how close they are together –> chromosome mapping)
Advantages of peas for mendel’s work
- many variants available from commercial sources
- normally self-fertilizing (true breeding lines like homozygous)
- easy to cross
- crosses not easily contaminated with other pollen
- relatively fast life cycle
simple dominant vs recessive alleles
dominant- often produce a functional gene product
recessive- often do NOT produce funcitonal gene product because most recessive genes are missing something (this is why most disease genes are recessive –> from mutations that eliminate gene function)
haplosufficient
one copy is enough for normal function in heterozygotes
types of loss of function mutations
null/amorphic: no functional gene product
leaky/hypomorphic: small amount of wt product or function
conditional: only manifest under a particular condition
**dominant negative **
dominant negative mutation
function of protein complex is altered by mutant gene product that interacts abnormally with its usual partners –> malformed protein complex
types of gain of function mutations
hypermorphic: more activity per allele than usual; often due to increase in gene copy number, higher transcription/allele or loss of inhibitors
neomorphic: mutants acquire novel gene activities that are not found in wild type; usually dominant
incomplete dominance
full contributions from both parents are required for full phenotypic expression
one copy works, but 2 copies work better
co-dominant expression
each allele produces a unique product which does not mask expression of the other
all alleles identified directly from DNA sequence data are always co-dominant (also applies to simple sequence repeats)
pleiotropy
the production, by one particular mutant gene, of unrelated multiple effects at the phenotypic level
multigenic trait
more than 1 gene specifying a given phenotype
positive genetic interaction example
suppression:
one allele is a suppressor for another mutant allele. Second mutation effectively “reverses” the effect of a mutation of another gene –> WT
negative interaction example
synthtic lethality
synergistic phenotype= contribution of 2 or more genes to a ……. exceeds the expectations from sum of their individual effects
WT: fully binding; fully functional
Mutant A: partial binding; functional
Mutant B: partial binding; functional
double mutant: binding impossible; nonfunctional
what does synthetic lethality suggest about molecular mechanisms?
share a common function (if cut off both, youre not going anywhere)
when does recombination happen?
prophase 1
why is recombination needed?
allows unfavorable alleles to be eliminated and favorable alleles to accumulate
forward vs functional genetics
forward: phenotye –> genotype
reverse: genotype –? phenotype
model organisms considerations
relevance and tractability
genetic and biochemical perspective
commonly used model organisms
e coli, budding yeast, round worm, fruit fly
zebra fish, mouse, thale cress plant
how are polynucleotide chains conneted in DNA and RNA?
phosphodiester bonds
DNA’s relation to:
2’ -OH
3’ -OH
2’ : DNA lacks
3’: where things are added on to
why use DNA for long-term storage of genetic info?
because DNA is not rapidly hydrolyzed under basic conditions, unlike
RNA because of the 2’ -OH
RNA sense vs antisense
RNA: top strand, same as sequence message
antisense: bottom/coding stand, complementary to message
often only top/sense strand is written
