Pretest: Genetics
Chapter 4 (Monohybrid Crosses and Sex Chromosome Linked Genes in Drosophilla sp.) and
Chapter 5 (Imitation of Appearance and Modification of Phenotype Ratios)
1. Why is Drosophila melanogaster used in genetic research?
2. Name and explain the life cycle of Drosophila!
3. Write the differences between male and female Drosophila !
4. Explain what a sex comb is!
5. How does temperature affect the life cycle of Drosophila ?
6. What are the F1 and F2 results of crossing wild-type female Drosophilla and white-eyed
male Drosophilla ?
7. How do young and adult flies change?
8. How to determine sex in Drosophila ?
9. What is meant by pseudo-deviation of Mendel's laws?
10. Mention the types of phenotypic ratio deviations!
11. Mention events with different cross results using Mendelian comparisons!
12. Which method is suitable for calculating Mendel's ratio ratio? Explain!
13. In chapter 4, what tools and materials are needed in the practicum?
14. What tools and materials are needed for practicum chapter 5?
15. Mention examples of ratio comparisons of 16 types of genotype combinations!
Answer:
1. Drosophila melanogaster is often used because it is easy to obtain, maintain and breed,
its life cycle is short (around 2 weeks), it has 8 chromosomes so it is easy to observe.
2. Drosophila life cycle starts from zygote, embryo, egg, larva and develops into an imago
or adult fly. Spermatozoa fertilize eggs through small holes called microphylls. Fertilized
egg cells can be released immediately by the mother fly or remain in the uterus during the
early embryonic stages. The larval stage of the embryo is divided into 3 stages, namely
instars 1, 2, and 3. In instar 3, the larvae reach approximately 4.5 mm in length. At this
stage the larvae are very active and eat a lot. After that the larvae turn into pupae and
move to a dry place. After undergoing changes, fruit flies emerge from pupae and
become adult flies.
