Studied by 65 PeopleTags & Description
autosomal dominant pedigree characteristics
no generation skipping, each affected individual must have 1 affected parent, 2 unaffected parents cannot produce affected individual
autosomal recessive pedigree characteristcs
generation skipping, 2 affected parents cause all offspring to be affected
x-linked dominant pedigree characteristics
one copy of gene is enough to affect females, affected male causes all daughters affected, no sons affected (if female is unaffected), affected female transmits gene equally
x-linked recessive pedigree characteristics
need 2 copies to affect female, more males than females affected, affected male causes all unaffected, affected female causes all affected
what happens in G1 stage of cell cycle?
cell grows and metabolizes, cells have normal number of chromatids
what happens in S stage of cell cycle?
dna replication occurs
what happens in G2 stage of cell cycle
cell checks for errors in replication, gets ready for mitosis or meiosis. at this point cells have twice as many chromatids as a g1 cell
what is the order of phases of mitosis?
prophase, metaphase, anaphase, telophase
what is the order of phases of meiosis
prophase metaphase anaphase telophase I, prophase metaphase anaphase telophase II
when does the cell go from 2n to n?
in meiosis I, the cell is 2n, once the first telophase happens, the cell is now haploid (n).
which part of meiosis is most similar to mitosis? why?
meiosis II, ploidy stays the same and no crossing over
what is mendels law of segregation?
each parent with 2 copies of a gene will have equal likelihood of passing on one of those genes
what does it mean TO complement?
the wild type phenotype is shown
what does it mean TO fail to complement?
the mutant phenotype is shown
what does it mean THAT genes complement?
the mutant alleles occur on 2 different genes
what does it mean THAT genes fail to complement?
the mutant alleles occur on the same gene
why does complementation test work?
one phenotype has 2 strains of mutation that can cause the phenotype
how to find the number of different possibilities with just the ploidy and the number of homozygous and number of heterozygous gene pairs?
2^n where n=number of pairs that are heterozygous
what does it mean for a gene mutation to be leaky?
it does not cause full loss of function
what constitutes a complementation group? what is it?
groups of mutations that do not complement each other, a gene
which phase of meiosis most clearly shows mendel's law of segregation?
anaphase 1
which phase of meiosis most clearly shows mendels law of independent assortment?
metaphase 1
which cut on a Holliday junction does give recombination?
N-S cut
which cut on a holliday junction does NOT give recombination?
E-W cut
how do we know if there are too many genes for a phage to take in?
there will be 0
what are the two mechanisms for chromosomal mutations?
breakage and rejoining, and crossing over between repetitive dna
what is haplosufficiency? what does it mean?
one WT allele is enough to show WT phenotype. mutant is recessive
what is haploinsufficiency? what does it mean?
one WT allele is NOT enough to show WT phenotype. mutant is dominant
what is penetrance? what does it measure?
the percentage of individuals that show the phenotype. whether they have the trait at all
what is incomplete or variable penetrance?
some individuals that have the mutation do not show the phenotype
what is expressivity? example?
differing levels of how the phenotype is expressed. eye colour
what is variable expressivity? example?
some individuals show varying levels of the phenotype. shade of eye colour (light/dark)
what do we assume about new individuals coming into pedigrees?
they are homozygous not heterozygous
what are the 4 types of chromosomal mutations?
deletion, translocation, duplication, inversion
what can be caused by deletion chromosomal mutation? what is it?
pseudo-dominance. when a recessive phenotype is "revived" because the WT allele was in the part of the chromosomal that was deleted
what is a deletion loop caused by?
the fact that only homologous regions can recombinate, so the chromosome with the remaining genes will bulge outwards because there is no corresponding gene for that region
how does deletion chromosomal mutation affect map distances?
they are inaccurate
what is duplication chromosomal mutation?
a part of the chromosome is duplicated and placed somewhere on the chromosome
what are the types of duplication chromosomal mutations? what are their subgroups?
tandem and non-tandem. same order and reverse order
what are the two ways inversion chromosomal mutation can physically affect the chromosome?
paracentric and pericentric
what is pericentric inversion?
when the inversion includes the centromere
what is paracentric inversion?
when the inversion does NOT include the centromere
which inversion –paracentric or pericentric– is more damaging to the chromosome? why?
paracentric, because 2 of the recombinant chromosomes will be completely non-functional
how can multigene families form? what does the event remove?
from a duplication event that causes a slightly different enzyme/protein/etc that does not affect the function of the original gene. this removes selective pressure on that duplicated gene and allows it to mutate
what is translocation chromosomal mutation? (specifically reciprocal translocation)
two chromosomes have a breakage and fragments get exchanged
how might abnormal phenotypes be caused in a reciprocal translocation
if the breakage point disrupts a gene
summarize the messelsohn-wiegle experiment
2 genotypes, heavy and light, because recombination happened, there were more than just the 2 lines in the centrifuge tube
summarize the beadle and tatum experiment?
took mutated spores and grew them in different tubes with complete medium, transferred to minimal media, took the ones that didn't grow and tested on all 20 amino acids seperately and one with vitamins. whichever ones grew in the amino acid tube meant that it was an auxotroph for that amino acid
what did beadle and tatum learn from their experiment?
each mutation behaved as a single gene, and some mutations were int eh same pathway and therefore an arginine auxotroph could be created in multiple ways, by not having enzyme x, y or z, not just z.
how to read the "compound tested vs mutant number" table? what's another way of thinking of it?
the first compound tested is the one with the least +'s, the first mutant blocked is the one with the most +'s. the more mutants supported by a compound, the later it is in the pathway
how to figure out epistasis and complementary gene action ratios?
total will ALWAYS be 16, and must be made from the regular 9:3:3:1 ratio
how to use the "best" branching diagram method?
treat the two genes in the dihybrid as separated and calculate the ratio of phenotypes, then set up a cross multiplication and multiply across. for a heterozygous dihybrid cross you should get 9:3:3:1
how to use the product rule?
treat each gene as an individual cross and calculate probability of getting "desired genotype", then multiply all those probabilities together, similar to pedigree probability
what is the simplified formula to get 95% guarantee of desired genotype? What must you do with that number?
log(0.05)/log(probability of FAILURE)=n. round up always, even if decimal is below 5.
what is the purpose of a dihybrid test cross?
to find which genotype is dominant and recessive
why is the maximum recombination frequency 50%?
in crossing over, only 2 out of 4 homologous chromosomes undergo recombination, so at least 50% of the genes will stay parental, it can't be more because with independent assortment, 50% of genes will stay together and 50% will be separated by crossing over