practical 4 study

Question 1

what is the law of segregation?

Answer 1

describes how alleles for a gene wll segregate so each gamete only contains 1 allele

Question 2

what is random fertilization

Answer 2

it adds to genetic variation because sperm can only fuse with one ovum

Question 3

what is the law of independent assortment

Answer 3

due to random orientation of homologs during metaphase of meiosis 1, different chromosomes will assort independently of one another into gametes

the assortment of one pair will not affect the other

Question 4

what are the cases in which different genes will be assorted into gametes independently?

Answer 4

when they are on different chromosomes or when they are on the same chromosome but are far enough apart that they recombination frequency is 50%

Question 5

at what phase is the combination of maternal and paternal chromosome for a gamete determined

Answer 5

at metaphase 1

Question 6

what is crossing over? what does it produce

Answer 6

corssing over is when non sister chromosomes synapse and exchange alleles through recombination at prophase 1

this produces recombinant chromosomes

Question 7

when will linked genes not recombine?

Answer 7

when they are very close together they are less likely to be recombined

Question 8

what are pure breeding strains

Answer 8

they are individuals that are homozygous for a trait of interest, they are created by inbreeding for many generations

Question 9

what are tester strains? what are they used for?

Answer 9

testers are homozygous recessive and are used to determine whether genes assort independently or are linked

Question 10

in the case of independent assortment, what are the proportions of the f2 generation when a dihybridheterozygote is crossed with a test strain?

Answer 10

the proportions will be equal for all 4 phenotypes, each will be 1/4

Question 11

how genes are linked, how will the F2 ratios change?

Answer 11

the phenotypes will be the same but will exist in different ratios

Question 12

when genes are linked, what phenotypes will make up the majority/minority of the offspring?

Answer 12

the parental phenotypes will be the majority while the minority will be made up of the recombinant phenotypes

Question 13

if a diheterozygote has 100% linked genes, what will the ratios be for a cross with a tester?

Answer 13

50% wild type and 50% mutant

Question 14

what does it mean when genes are partially linked?

Answer 14

it means they are on the same chromosome but they are far enough apart that some crossing over/recombination occurs

Question 15

what can the proportion of recombinant progeny tell us?

Answer 15

it can be used to determine how far apart the two loci are

Question 16

how do you calculate recombination frequency

Answer 16

of recombinant offspring/ total offspring

Question 17

what is probability?

Answer 17

probability is the fraction of time that a particular event will occur

Question 18

what is the sampling rule? how is it calculated?

Answer 18

it is the probability of any chance event occurring
it is the # of event A/ total # of events

Question 19

what is the product rule? how is it calculated?

Answer 19

it is the probability that two independent chance events will both occur in a defined order

it is calculated by multiplying the probability of A x the probability of B

Question 20

when tossing a coin twice, what is the probability of getting tails the first and second toss?

what rule should be used to calculate this?

Answer 20

the product rule should be used.

=( 1/2 chance of tails) x (1/2 chance of heads) = 1/4 chance of TT

Question 21

what is the sum rule?

Answer 21

it is the probability of either event occurring

it is calculated by the sum of two probabilities
(probability of A) + (probability of B)

Question 22

when tossing a coin, what is the probability of getting heads or tails?

what rule should be used to calculate this

Answer 22

the sum rule should be used

(1/2) + (1/2) = 1

Question 23

in the binomial expansion equation, what is n?

Answer 23

n is the total number of events

Question 24

in the binomial equation, what is x

Answer 24

x is the number of events in one category (ex. 1 tail in a group of 4 tosses)

Question 25

in the binomial expansion equation, what is p

Answer 25

p is the probability of x event occuring (ex. 1/2 chance of tails)

Question 26

in the binomial expansion equation, what is q

Answer 26

q is the probability of the other event occurring

Question 27

how do we determine if there is a significant relationship between observed and expected values?

Answer 27

chi-square test

Question 28

what are the three main reasons for a lack of perfect match between observed and expected values

Answer 28

experimental errors incorrect hypothesis sampling errors

Question 29

what is a sampling error

Answer 29

they are errors where the fraction used is not representative of the entire population

Question 30

what is the null hypothesis?

Answer 30

there is no statistical difference between observed and expected results

Question 31

what is an alternative hypothesis?

Answer 31

there is a statistical difference between observed and expected results

Question 32

how do you calculate the expected values for Chi-sqaure

Answer 32

the fraction of a event expected x the total number of events

Question 33

how do you calculate the degrees of freedom

Answer 33

df=n-1 n is the number of categories

Question 34

what does a p value of 0.05% mean

Answer 34

it means that there is a 5% chance that results are due to chance alone

Question 35

if the calculated X^2 value is less than or equal to the critical X^2 value, what does that say about the null hypothesis

Answer 35

there is no statistically significant difference between the observed and expected values, we fail to reject the null hypothesis

Question 36

if the calculated X^2 value is greater than the critical X^2 value, what does that say about the null hypothesis

Answer 36

we can reject the null hypothesis, there is a statistical difference between the observed and expected results

Question 37

what is X-linked inheritance?

Answer 37

genes that are located on sex chromosomes (X)

Question 38

what is the genome of drosophila

Answer 38

diploids with 4 pairs of chromosomes

Question 39

what is a 100% linked gene?

Answer 39

genes on a chromosome that are so close that they will not cross over/recombine/assort independently

Question 39

what are the phenotypic differences between male and female drosophila

Answer 39

sex combs in males, male external genitalia, and abdominal structure and pigmentation

Question 40

when are genes more likely to recombine/cross over

Answer 40

when there is greater distance between loci

Question 41

if there is no crossing over/recombination, what will the phenotypes be for a diheterozygote test cross

Answer 41

we will only see wild type and double mutants

Question 42

if there is some crossing over,what will the phenotypes be for a diheterozygote test cross

Answer 42

we will see some recombinant flies

Question 43

if genes are completely unlinked, what will the phenotypes be for a diheterozygote test cross

Answer 43

you will see 4 phenotypes in equal proportions