lecture 4

Question 1

how are genes inherited from one gen to next

Answer 1

in form of chromosomes

Question 2

are the number of chromosomes related to complexity, explain with examples

Answer 2

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

Question 3

describe mendels pea plant

Answer 3

7 pairs of chromosomes

Question 4

describe how mendel demonstrated independent assortment

Answer 4

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

Question 5

where are genes for seed colour and shape for pea plant

Answer 5

seed colour = chromosome 1
seed shape = chromosome 7
each on diff chromosome so can be independently assorted

Question 6

describe chromosome segregation of dihybrid during meiosis

Answer 6

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

Question 7

describe independent assortment in humans

Answer 7

only one chromosome will be transmitted

Question 8

during meiosis what is the probability that the paternal chromosome 1 and 2 are transmitted to a single gamete in human

Answer 8

1/4 ignore rest since independently assorting

Question 9

how many diff genotypes of a gamete can a human produce during meiosis during independent assortment alone

Answer 9

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

Question 10

explain dihybrid cross - pea plant experiment

Answer 10

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

Question 11

describe another way to think of dihybrid cross

Answer 11

think of independent assortment and how each has chances then put over common denominator

Question 12

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?

Answer 12

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

Question 13

what does dihybrid test cross lead to

Answer 13

produces equal number of parental and recombinant types

Question 14

what is testcross

Answer 14

easy way to determine genotypes of gametes that a testee can produce

Question 15

why do we get equal parental and recombinant for dihybrid test cross - gen

Answer 15

due to indep ass = equal number of parental and recombo types are observed in progeny of a dihybrid

Question 16

why do we get equal parental and recombinant for dihybrid test cross - explain more

Answer 16

fully recessive tester = so phenotype determines unknown one
gametes produce results
equal parent and recombo
recombinant = traits used to make F1

Question 17

what happens if a and b are on same chromosome, also what would be the ratio between parental and recombinant

Answer 17

almost impossible to get recombinant type since nothing will happen
would have to break chromosome

Question 18

describe what morgan thought

Answer 18

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

Question 19

describe morgans findings

Answer 19

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

Question 20

when are recombinants produced

Answer 20

during meiosis
due to cross over during meiosis

Question 21

in real life setting what ratio do we get and why

Answer 21

doesn’t fit expected ration exactly

Question 22

how to say if pr and vg are not independently assorted

Answer 22

use chi2 test

Question 23

describe chi-squared test

Answer 23

way of determining if observed values is significantly diff from expected values
confidence level

Question 24

what is formula for chi squared test

Answer 24

X^2 = Σ (O-E)^2 / E
O = observed
E = expected

Question 25

what does chi squared test help us determine

Answer 25

determine degree of deviation from expected value
in science = like 95% confidence level

Question 26

are pr and vg independently assorted

Answer 26

do chi2 formula for all 4 phenotypes and then sum them = 33

Question 27

what is critical value

Answer 27

used to determine confidence level

Question 28

what happens if p=0.05 or if p=<0.05

Answer 28

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

Question 29

explain if hypothesis is rejected or accepted and why - for chi squared independent assortment of pr and vg - in own words

Answer 29

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

Question 30

what is degree of freedom

Answer 30

number of independent values -1