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Outline the work done by Morgan that has led to our understanding of sex linkage. - HSC - SSCE Biology - Question 22 - 2013 - Paper 1
Question 22
Outline the work done by Morgan that has led to our understanding of sex linkage.
Worked Solution & Example Answer:Outline the work done by Morgan that has led to our understanding of sex linkage. - HSC - SSCE Biology - Question 22 - 2013 - Paper 1
Step 1
Sketches in general terms the sex-linked inheritance experiments conducted by Morgan
Answer
Thomas Hunt Morgan conducted pivotal experiments with fruit flies (Drosophila melanogaster) in the early 20th century that laid the groundwork for our understanding of sex linkage. He focused on the inheritance patterns of traits and discovered that certain traits were linked to the sex chromosomes. His most famous experiments involved observing the inheritance of eye color in these flies, particularly the white-eyed mutation. Morgan observed that the white-eyed trait only appeared in male offspring when crossed with red-eyed females, demonstrating a link between sex and genetic traits.
Step 2
Notes the different frequencies of occurrence of the sex-linked trait in males and females
Answer
Morgan's work showed that sex-linked traits occur at different frequencies in males and females due to the presence of sex chromosomes. In his studies, traits located on the X chromosome would exhibit different expression ratios; for instance, in the case of the white-eyed mutation, all male offspring displayed the trait, while female offspring required two copies of the allele to express it. This evidence contributed significantly to the understanding of why certain genetic traits are more likely to appear in one sex over the other.
Step 3
Indicates some of the features of Morgan’s work with fruit fly
Answer
Morgan's experiments utilized the unique reproductive capabilities and short life cycles of fruit flies to analyze genetic inheritance patterns. He noted clear phenotypic ratios that deviated from Mendelian inheritance, which provided insights into linked genes. Furthermore, his meticulous breeding experiments allowed him to establish the concept of gene mapping based on the recombination frequencies observed among traits, which are foundational to modern genetics.