a. The fruit fly, Drosophila melanogaster, feeds on sugars found in damaged fruits. A fly with normal features is called a wild type. It has a grey striped body and its wings are longer than its abdomen. There are mutant variations such as an ebony-coloured body or vestigial wings. These three types of fly are shown in the diagrams.

Wild-type features are coded for by dominant alleles: A for wild-type body and B for wild-type wings. Explain what is meant by the terms allele and dominant.

b. Two wild-type fruit flies were crossed. Each had alleles A and B and carried alleles for ebony body and vestigial wings.

Draw a genetic diagram to show the possible off spring of this cross.

c. When the two heterozygous flies in b were crossed, 384 eggs hatched and developed into adult flies. A chi-squared (χ2) test was carried out to test the significance of the differences between observed and expected results:

i. Copy and complete the table.

ii. Calculate the value for χ².

The table below relates χ² values to probability values.

As four classes of data were counted, the number of degrees of freedom was 4 − 1 = 3. The table gives values of χ² where there are three degrees of freedom.

iii. Using your value for χ2 and the table above, explain whether or not the observed results were significantly different from the expected results.

Transcribed Image Text:

wild type ebony body vestigial wing