3 ways flies are distinguished between male and female:
- Sex comb: Males have sex combs while females do not. Tiny black spot under microscope.
- Abdominal region: banding pattern on tip of fly - males have two bands while females have five.
- Genital region: male genital organs are surrounded by dark genital arches while female genitals are covered by a plate.
Life cycle of fly
- Egg: egg is laid by female shortly after fertilization and hatched a day later. Produced small white larvae still in development.
- 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.
- Pupa: pupation takes about three days, where the larva undergoes metamorphosis and transforms into adult.
- Adult: adult fly will break out of its pupal case and quickly matured as an adult, ready to reproduce.
How to determine map distance
- Determine the linkage phase of parental alleles
- Determine the recombinant allele in comparison to the parental type.
- Use formula to determine map units: # of recombinant offspring/# total offspring x 100
Probabilities
Independent events (and) are multiples
Mutually exclusive events (or) are added
Types of errors
- Sampling error: error that occurred during statistical analysis
- Type 1/2 error: either rejecting the null hypothesis when it is actually true or accepting the null hypothesis when it is false.
- Experimental error: an error made throughout process or designing or performing experiment (human error)
What is a test cross?
A test cross is used to determine the genotype of a dominant phenotype by crossing with a recessive.
Chi square steps
- Make hypothesis (null hypothesis)
- 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.
- Calculate chi squared value (x^2) by using formula x^2=summation of (observed-expected)^2/expected
- Convert to p-value using degrees of freedom and x^2 value. Df=n-1
- 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.
Independent assortment cross
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
Sex-linked cross
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)
