lecture 4 Flashcards
how are genes inherited from one gen to next
in form of chromosomes
are the number of chromosomes related to complexity, explain with examples
nooooooo
Adder’s-tongue fern is estimated to have 1440 chromosomes (720 pairs)
Atlas blue butterfly, 448–452 chromosomes (i.e. 224–26 pairs)
humans = 46 chromosomes
only important for diff trait passed onto next gen
describe mendels pea plant
7 pairs of chromosomes
describe how mendel demonstrated independent assortment
7 traits that mendel used to demonstrate independent assortment = all monogenic traits
round or wrinkled
yellow or green seed interiors
green or yellow unripe pods
purple or white petals
inflated or pinched ripe pods
axial or terminal flowers
long or short stems
where are genes for seed colour and shape for pea plant
seed colour = chromosome 1
seed shape = chromosome 7
each on diff chromosome so can be independently assorted
describe chromosome segregation of dihybrid during meiosis
one chromosome doesnt affect assortment of other
independent assortment resulting in equal ratio of 4 diff genotypes of gametes AB, Ab, aB, ab
key step = homologous chromosomes come together in metaphase and then anaphase = way tgey are pulled helps indep ass
describe independent assortment in humans
only one chromosome will be transmitted
during meiosis what is the probability that the paternal chromosome 1 and 2 are transmitted to a single gamete in human
1/4 ignore rest since independently assorting
how many diff genotypes of a gamete can a human produce during meiosis during independent assortment alone
only considering independent assortment and not like crossover or anything
can create 2 diff gametes/chromosomes
2^23 = 8.3 Million
reason why siblings look different than you
explain dihybrid cross - pea plant experiment
4 x 4 = 16 diff combos of fertilization patterns, F1 cross - mendel, phenotypically dom but hetero geno
some produce progeny with same genotype while others result in unique genotype
phenotype = 9:3:3:1 ratio
describe another way to think of dihybrid cross
think of independent assortment and how each has chances then put over common denominator
Assume that we have two plants of genotypes
A/a;b/b;C/c;D/d;E/e
& A/a;B/b;C/c;d/d;E/e
From a cross between these plants, we want to recover a progeny plant of genotype a/a; b/b; c/c; d/d; e/e. What proportion of the progeny should we expect to be of that genotype?
A/a= 1/4 chance
b/b = 1/2 chance
C/c = 1/4 chance
D/d = 1/2 chance
E/e = 1/4 chance
multiply all together = 1/256
what does dihybrid test cross lead to
produces equal number of parental and recombinant types
what is testcross
easy way to determine genotypes of gametes that a testee can produce
why do we get equal parental and recombinant for dihybrid test cross - gen
due to indep ass = equal number of parental and recombo types are observed in progeny of a dihybrid
why do we get equal parental and recombinant for dihybrid test cross - explain more
fully recessive tester = so phenotype determines unknown one
gametes produce results
equal parent and recombo
recombinant = traits used to make F1
what happens if a and b are on same chromosome, also what would be the ratio between parental and recombinant
almost impossible to get recombinant type since nothing will happen
would have to break chromosome
describe what morgan thought
genes are organized in a long row inside chromosomes and how traits related to each other correspond to genes that lie close to one another on the chromosomes. He also discovered the crossover phenomenon, in which parts of different chromosomes can trade places with one another
can happen = cross over during meiosis
describe morgans findings
mutants cross wild type = hetero F1 dihybrid
do test cross = did not get 1/4 for each
means on same chromosome, indicates proximity of genes, could eventually map out, don’t segregate based on mendels
when are recombinants produced
during meiosis
due to cross over during meiosis
in real life setting what ratio do we get and why
doesn’t fit expected ration exactly
how to say if pr and vg are not independently assorted
use chi2 test
describe chi-squared test
way of determining if observed values is significantly diff from expected values
confidence level
what is formula for chi squared test
X^2 = Σ (O-E)^2 / E
O = observed
E = expected
what does chi squared test help us determine
determine degree of deviation from expected value
in science = like 95% confidence level
are pr and vg independently assorted
do chi2 formula for all 4 phenotypes and then sum them = 33
what is critical value
used to determine confidence level
what happens if p=0.05 or if p=<0.05
if p=0.05 means you have 5% chance that rejecting the hypothesis, indep ass is wrong
if p=<0.05 = can reject hypothesis with confidence level of 95% or greater
explain if hypothesis is rejected or accepted and why - for chi squared independent assortment of pr and vg - in own words
use table
determine degree of freedom = 4-1 = 3, look at 3 row
and when p=0.05, value = 7
but 33 is way greater than 7 = reject hypothesis
what is degree of freedom
number of independent values -1
