Lab Practical 5

Question 1

3 ways flies are distinguished between male and female:

Answer 1

1. Sex comb: Males have sex combs while females do not. Tiny black spot under microscope.
2. Abdominal region: banding pattern on tip of fly - males have two bands while females have five.
3. Genital region: male genital organs are surrounded by dark genital arches while female genitals are covered by a plate.

Question 2

Life cycle of fly

Answer 2

1. Egg: egg is laid by female shortly after fertilization and hatched a day later. Produced small white larvae still in development.
2. Larva: larvae feed upon food and grow rapidly, undergoing stages of moly and instar. The larva becomes dry enough to become a pupa after the third instar.
3. Pupa: pupation takes about three days, where the larva undergoes metamorphosis and transforms into adult.
4. Adult: adult fly will break out of its pupal case and quickly matured as an adult, ready to reproduce.

Question 3

How to determine map distance

Answer 3

1. Determine the linkage phase of parental alleles
2. Determine the recombinant allele in comparison to the parental type.
3. Use formula to determine map units: # of recombinant offspring/# total offspring x 100

Question 4

Probabilities

Answer 4

Independent events (and) are multiples
Mutually exclusive events (or) are added

Question 5

Types of errors

Answer 5

1. Sampling error: error that occurred during statistical analysis
2. Type 1/2 error: either rejecting the null hypothesis when it is actually true or accepting the null hypothesis when it is false.
3. Experimental error: an error made throughout process or designing or performing experiment (human error)

Question 6

What is a test cross?

Answer 6

A test cross is used to determine the genotype of a dominant phenotype by crossing with a recessive.

Question 7

Chi square steps

Answer 7

1. Make hypothesis (null hypothesis)
2. Calculate expected results from experimental design. Use formula e=np where e is expected number, n is total number of trials, and p is the probability of the event occurring.
3. Calculate chi squared value (x^2) by using formula x^2=summation of (observed-expected)^2/expected
4. Convert to p-value using degrees of freedom and x^2 value. Df=n-1
5. If p value is less than or equal to 0.5, reject.

Conclusion: We fail to reject our null hypothesis since our p-value is greater than the critical threshold p-value, 0.22 > 0.05 meaning that our observed data does not significantly differ from our expected data.

Question 8

Independent assortment cross

Answer 8

P) wt x recessive (w+w+m+m+) x (wwmm)
F1) wt x recessive (w+wm+m) x (wwmm)
F2)
w+wm+m = wt
w+wm = wt, recessive
wwm+m = recessive, wt
wwmm = recessive, recessive

Question 9

Sex-linked cross

Answer 9

P) XmwXmw x Xm+v+Y
F1) Xm+w+Xmw x XmvY
F2)
Xm+w+xmw, Xm+v+Y (1/2 wt)
XmvXmv, XmvY (1/2 mutant)