Homework Assignment for Ch 4 – Extensions of Mendelian Genetics
Thomas H Morgan
The relation of genetics to physiology and medicine
Nobel Lecture, June 4, 1934
Read the pdf article of Thomas H. Morgan’s Nobel Lecture and answer the following questions and post completed assignment to your Box folder as “Morgan Reading.”
1) I had a high school teacher once tell me that Mendel’s principles were no longer valid and had been refuted by the very extensions we have just discussed. In his Nobel Lecture, Morgan addresses this very issue in his talk. What did Morgan say about Mendel and his postulates?
Morgan said that Mendel’s postulates were the basis for the discovery of the exceptions. The discovery of the chromosomes and their actions supported the separation method in which Mendel’s laws postulated. The exceptions were the result of new discoveries via new methods available. Mendel had only his reasoning to form these postulates. Cytological evidence now available supports his postulates, plus gives explanations for linkage, crossing-over, and sex-linked inheritance.
2) In the section “What are genes?” Morgan discusses the nature of the gene. What are the problems he discusses when trying to address this issue at this time in history?
The issue that is disregarded at this time is whether a gene is a hypothetical unit or a material particle. The problems Morgan discusses are about genes dividing. He wanted to know how they “grow”, which means make more for division. He is also trying to understand mutations, and translocations.
3) If you had went back in time to hear Morgan’s lecture, what could you have told him to clear up the issues he discusses from question 2 above?
The semi-conservative method of replication, along with the molecular structure of the DNA, which was discovered later by Watson and Crick, and all others would answer his questions.
4) In the section “The physiological properties of the genes” Morgan speculates about how specialization takes place. Did he put forth a explanation that proved to be true?
Morgan spoke of different protoplasms, sequence of genes being turned on, and different regions of the egg. His speculations about how this specialization takes place have proved true with knowledge of cell determinants and/or maternal determinants acting as transcription factors to turn genes on at different times or not at all, therefore leading to differentiation.
5) Morgan refers to “man as a poor breeder.” This seems like a funny thing to say. Why is this a problem for a geneticist?
Morgan referring to “man as a poor breeder” seems to have been referring to the lack of quality and quantity of information available in human histories for pedigrees. This could be due to the long generation time necessary for humans. The only genetic histories at this time had to due with those phenotypes were obvious, such as malformations and psychopathic disorders.
6) What role does Morgan expect genetics to play in the future of medicine? Did this happen?
His first expectation was that the greater the knowledge obtained would increase the intellect and disprove the myths of genetics. He discussed the future as one with genetic information being used as treatment for defects. He also discussed its importance in prenatal counseling, the prevention of defects, and it’s use in resistance. All of these topics are being utilized or being researched at this time.