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Species of the fruit fly Drosophila generally have four pairs of homologous chromosomes - VCE - SSCE Biology - Question 4 - 2011 - Paper 1
Question 4
Species of the fruit fly Drosophila generally have four pairs of homologous chromosomes. a. What is meant by the term 'homologous chromosomes'? The number of chrom... show full transcript
Worked Solution & Example Answer:Species of the fruit fly Drosophila generally have four pairs of homologous chromosomes - VCE - SSCE Biology - Question 4 - 2011 - Paper 1
Step 1
a. What is meant by the term 'homologous chromosomes'?
Answer
Homologous chromosomes are pairs of chromosomes that have the same structure and carry genes for the same traits, although the alleles for these traits may differ. Each chromosome in a pair is inherited from one parent, resulting in two copies of each chromosome that align during cell division.
Step 2
b. Describe an event that could have caused the chromosome differences between D. nasuta and D. nasuta subspecies albomicans.
Answer
An event such as a chromosomal mutation, which could include inversions, duplications, or deletions, could have caused the differences in chromosome number or structure between D. nasuta and its subspecies albomicans. Such mutations can lead to differences in genetic content, affecting the overall function and behavior of the organisms.
Step 3
c. What would be the diploid number of these hybrid flies?
Answer
The diploid number of the hybrid flies would be the sum of the chromosome sets from both parents. Assuming D. nasuta has a diploid number of 8 chromosomes (4 pairs) and D. nasuta subspecies albomicans has a different diploid number due to chromosomal differences, the hybrid flies would typically have an intermediate diploid number depending on the specific arrangement and compatibility of parental chromosomes.
Step 4
d. Explain how chromosome differences between Drosophila nasuta and Drosophila nasuta subspecies albomicans could result in their reproductive isolation and speciation.
Answer
Chromosome differences can lead to reproductive isolation by preventing successful meiosis during gamete formation in hybrids, resulting in infertile offspring. This isolation can occur due to incompatibility in chromosome pairing, leading to improper segregation of chromosomes. Over time, this reproductive barrier can promote speciation as the diverging populations accumulate genetic differences and adapt to distinct ecological niches.