Mendel's experiments with garden peas highlight that humans are poor genetic model organisms due to long generation times, ethical concerns in controlled crosses, and the inability to manipulate human genetics effectively. In contrast, Drosophila melanogaster (fruit flies) are better suited for genetic studies because they have a short reproductive cycle, a high genetic similarity to humans, and are easy to maintain in the lab. Additionally, the inheritance of ABO blood types in humans illustrates concepts of universal donors and acceptors, while the nature vs. nurture debate examines the influences on genetic traits.

1. Menders experiments were conducted using garden peas. Why would humans be an awful
choice for an experimental organism (give at least 3 reasons)? Give an example of an animal that
would be better sorted for genetics experiments. In Mendel's experiments, a plant with purple
flowers was crossed with a plant having white flowers. Explain why white flowers disappeared
in the F_1 generation and reappeared in the F_2. Your pet rabbit has curly fur. After seeking
advice from a rabbit breeder, you learn that curly fur is a dominant trait, but you want to know
the precise genotype of your pet. Describe how you could find out. Describe the inheritance of
ABO blood types in humans and explain why individuals with type O are universal donors while
individuals with type AB are universal acceptors. Describe the nature vs. nurture debate. In your
explanation, give an example of a trait that is controlled entirely by nature and one that is heavily
influenced by both nature and nurture.
Solution
Answer:
1. Studying human genetics is unlike studying the genetics of any other organism. In many ways,
humans are very poor model organisms for genetics. Long generation times make for slow
progress when doing genetic crosses, which brings us to another problem with human genetics:
The inability to make controlled crosses.
So, any human geneticist that tried to make controlled human crosses would most likely be
considered a very disturbed criminal and not a brilliant scientist. Besides, humans usually only
have one child at a time, which makes it really difficult to generate numbers of offspring that can
achieve statistical significance. On top of all this, there's the issue of genetic manipulation. Key
genetic techniques, like mutation screening and transgenics, are completely off-limits to human
geneticists.
Drosophila melanogaster (Fruit fly) would be better suited as a model organism for genetics
experiments.
1. The relationship between fruit fly and human genes is so close that often the sequences of
newly discovered human genes, including disease genes, can be matched with equivalent genes
in the fly.
2. 75 per cent of the genes that cause disease in humans are also found in the fruit fly.
3. Drosophila have a short, simple reproduction cycle. It is normally about 8-14 days, depending
on the environmental temperature. This means that several generations can be observed in a
matter of months.
4. Fruit fly are small (3 mm long) but not so small that they can’t be seen without a microscope.
This allows scientists to keep millions of them in the laboratory at a time.

2. 5. They are inexpensive to maintain in the laboratory.
6. They require a simple diet consisting of simple sources of carbohydrates (cornmeal) and
proteins (yeast extract).
7. The only care they need is having their food changed regularly (every 10-14 days at 25C or 5-
6 weeks at 18C).
8. Drosophila have ‘polytene’ chromosomes, which means that they are oversized and have
barcode-like banding patterns of light and dark. During early Drosophila research scientists
could therefore easily identify chromosomal rearrangements and deletions under the microscope.
9. It is relatively straightforward to mutate (disrupt or alter) fruit fly genes.
10. The fruit fly provides a simple means of creating transgenic animals that express certain
proteins, such as the green fluorescent protein of jellyfish.
11. The long and distinguished history of research devoted to the study of the fruit fly means that
a remarkable amount is now known about its biology.