Why is there no recombination in Drosophila males?
Unlike most sexually reproduced organisms, Drosophila is peculiar since males are achiasmatic–that is, recombination does not occur during male meiosis. Therefore, autosomes that become fused to the ancestral Y chromosome (so-called neo-Y chromosomes) will be transmitted through males only.
Does X chromosome undergo recombination?
The paternal X-chromosome they receive does not suffer recombination (except in the PARs) and is transmitted directly to the daughters. The maternal X-chromosome contains combined information from the two X-chromosomes present in the mother. Figure 2.
Does recombination occur in male fruit flies?
Formation of chiasmata, the physical link between homologous chromosomes during meiosis, is a requisite for recombination. Geneticists for several decades knew that meiotic crossover and recombination is absent in Drosophila males and some female lepidopterans, a condition termed achiasmy.
How many X chromosomes do Drosophila have?
In Drosophila, sex determination is achieved by a balance of female determinants on the X chromosome and male determinants on the autosomes. Normally, flies have either one or two X chromosomes and two sets of autosomes.
How many homologous chromosomes are present in male Drosophila?
– Drosophila just has four homologous pairs of chromosomes in which three are autosomes and one pair of sex chromosomes.
When chromosomes do not segregate correctly during meiosis This is referred to as?
If chromosomes fail to segregate completely, it’s called nondisjunction and can result in the formation of gametes that have missing or extra chromosomes, according to “Molecular Biology of the Cell, 4th edition.” When gametes with abnormal chromosome numbers fertilize, most of the resulting embryos don’t survive.
How many homologous chromosomes do female fruit flies have?
Females contain two X chromosomes, which are homologous, as in the case of the autosomes. By contrast, males are identified as having one X chromosome and one (much smaller) Y chromosome.
Where does meiosis occur in a male fruit fly?
Near the apical end of the testis, are the cells that undergo Meiosis I, the spermatocytes. The Prophase I stage in Drosophila males show non-conventional phenotypes as the chromosomes of male fruit flies are indistinguishable from G2 phase and lack structural features of a traditional Prophase I.
How many chromosomes are in Drosophila ovum?
With the exception of sex cells (eggs and sperm), there will be the same number of chromosomes in all cells of the body. If fruit fly skin cells have eight chromosomes then wing cells will also have eight chromosomes. These body (somatic) cells undergo mitosis. Fruit fly somatic cells have eight chromosomes.
Where are the Drosophila chromosomes located?
These chromosomes are found in several cell types, the function of which is principally secretory. In Drosophila, the most useful are found in the larval salivary glands.
How many pairs of chromosomes are present in Drosophila fly?
Drosophila Chromosomes: In Drosophila melanogaster there are 4 homologous pairs of chromosomes: 2 pairs of large autosomes, ( one slightly smaller than the other pair), 1 pair of very small autosomes, and a pair of sex chromosomes. Females normally have two X chromosomes; males have one X and one tiny Y chromosome.
What is strange about the chromosomes of Drosophila compared to most other eukaryotic chromosomes?
Drosophila telomeres use arrays of retrotransposons to maintain chromosome length, while nearly all other eukaryotes rely on telomerase-generated short repeats. Regardless of the DNA sequence, several end-binding proteins are evolutionarily conserved.