5. Chapter 4: Genetics, Neo-Darwinism & Modern Synthesis

Question 1

What were the pre-Mendelian perspectives on transmission of traits?

MIDTERM 1

Answer 1

1. Preformism
2. The theory of blending inheritance
3. Darwin’s pangenesis
4. August weismann’s theory

Question 2

What was the theory of preformism and was is the accepted theory today?

MIDTERM 1

Answer 2

Preformism is the preformist theory on the development of (small) individuals called homoncules. The accepted theory today is epigenesis where organs appear progressively and development goes from fairly simple to more complex.

Question 3

What is the theory of blending inheritance?

MIDTERM 1

Answer 3

The theory of blending inheritance is the belief that both parents participate equally in the genetic makeup of offspring, meaning that a child would show a blend/intermediate value between the traits of its parents. However, (its more complex) based on that reasoning all individuals would be identical or similar which is not consistent with what we observe because progeny do not always look like blend of parents.

Question 4

What is Darwin’s theory on pangenesis?

MIDTERM 1

Answer 4

Darwin’s theory of gemmules (also known as hereditary particles) which are produced by each part of the body. The idea is that when an organ is used, it grows, containing more gemmules, and vice versa. The gemmules are transported from all parts of the body in the bloodstream and assembled in the gametes when they are formed. Gemmules would be the particles associated with the transmission of heredity. Darwin’s hypothesis was later refuted by Francis Galton’s experiment.

Question 5

What is August Weinsmann’s Theory? Provide an example.

MIDTERM 1

Answer 5

Weismann theorized that only the sex cells were responsible for heredity, whereas the rest of the organism(body) was only a structure subject to disappear with the death of the individual. Weismann stated that living beings are divide into two parts which is the germline also known as gametes and the soma which is known as the rest of the body. The germline is unaffected to environmental influences and heredity is simply the continuity of the germline. Thus, the germline and the environment can influence the phenotype but the soma and the environment have no influence on the genotype. The only mechanism that can eventually modify the germline of a population is natural selection. It goes without saying that therefore a chicken is the method by which an egg makes another egg. A perfect example that shows that the soma is first and foremost the receptacle of the germline (the soma of the male monkfish will eventually disappear sole purpose is to latch on to female reproductive systems).