Question

Q:           WHICH OF THE phases of mitosis did you see the most and fewest examples of in your microscopic examination of onion root tips?

Q:           WHAT CONCLUSIONS CAN you draw about the relative length of each of the stages of mitosis from your examination of onion root tips?

Q:           WHAT ONION CELLS would you have to look at to examine meiosis as well as mitosis?

Q:           BASED ON YOUR examination of polytene chromosomes in fruit flies, what is the normal number of chromosomes present in most fruit fly cells?

Q:           HOW DIFFICULT WAS it to distinguish between two stretches of polytene chromosome by looking at differences in their banding patterns?

Q:           WOULD YOU HAVE to look at more or less asci to observe the same number of recombination events between the gene for ascospore color and the centromere if you used a gene that was closer to the centromere?

Answer 1

1. Interphase, Prophase, Metaphase, Anaphase, Telophase.

2. The examination of onion root tips reveals that it takes most of the time in interphase. i.e about to 90%. The longest phase Prophase and the shotest phase is Anaphase. Metaphase and Telophases are in between the two Phases.

3. Generally meristematic cells possess active cell divisions. So Mitosis Cell divisions occur in meristematic region of root tip in onion cell experiment. Where meiosis cell division occur in reproductive cells. So to observe the meiosis we need to exmine the flower buds i.e anther tissue for gametes and ovules for the egg.

4. The normal diploid number of chromosomes in Drosophila melanogaster (fruit fly) is Egiht (8)

5. The streches of Polytene chromosomes shows two type of banding pattern light and dark. It the dark bands are regions of inactive chromatin where light bands are with higher transcriptional activity. This banding pattern distinguish the polytene chromosomes from normal chromatin structure.

6. If the gene closer to the centromere the number of recomination is less frequent. Hence there is same number of recombination events between the genes for ascospore colour and centromere.