Question

Fruit flies have a diploid number of 8. How many homologous pairs of chromosomes do the somatic cells of an individual fruit fly have?

2, 4, 6, 8

Answer 1

There two chromatids for each chromosome, fruit flies have 16 chromatids in metaphase plate during mitosis.

4 pairs of homologous chromosomes

In eukaryotes, a chromosome is sometimes aligned and associated with its homologue over part or all of its length. Although this chromosome alignment is prominent in meiosis (Roeder, 1995), for some organisms such as Dipteran insects, this association, termed homologous chromosome pairing, is observed to be a normal part of nuclear organization (Metz, 1916). Pairing of homologous chromosomes can also influence gene regulation. In Drosophila melanogaster, gene expression can be modulated by physical pairing of homologous loci in what are termed transvection and trans-sensing effects. Drosophila melanogaster offers a unique system in which to study homologous pairing. Drosophila chromosomes are thought to be homologously associated in the early stages of development in addition to their association observed during meiosis. For instance, the giant polytene chromosomes found in larval tissue exhibit a close synapsis of homologues along their entire lengths. Observations of a side-by-side juxtaposition of metaphase chromosomes in squashed neuroblast preparations lend further support that homologues pair early in development in this organism (Metz, 1916).