Heredity - MT3 - Part 3 Flashcards
Who was William Bateson?
He was a lifelong defender of Mendel’s approach to the study of heredity
Bateson’s story of how he agreed with Mendel (5)
- Took a train ride to deliver a talk in London
- On the train he read Mendel’s paper
- He experienced an immediate conversion to Mendelism
- He threw away his original talk and delivered a lecture on Mendel’s work instead
- Wrote about about Mendel’s theory “Mendel’s Principle of Hereditary: A defence”
What is gen brief of?
Origin
Who was one critic to Mendelism?
Thomas Hunt Morgan
What were Morgans objectives to Medelism? (4)
- Mendel’s law could not be demonstrated in all organisms, particularly animals
- hard to find the same clean paired traits in animals that you can see in plants - The dominance/recessive relationship could not explain the 1:1 sex ratio
- Often, progeny are intermediate in appearance, rather than resembling one of the parents or grandparents
- Mendel’s principles could not explain this - No physical basis for Mendel’s hereditary determinants had yet been found
What did Mendel’s work imply?
That embryonic offspring are miniature versions of thier parents from the very earliest stages of development, thus supporting the discredited preformationist therapy of hereditary
What did people not know the difference between?
Genotype and phenotype
Genotype
Is the genetic makeup of an organism
Phenotype
Set of observable characteristics that interact with its genotype and the environment
What did Walkter Sutton Observe?
That chromosomes in meiosis behave in the same way that Mendel’s hereditary determinants do
What did Mendel and Mendelists never observe?
That there must be more genes than chromosomes and if genes are one chromosome, some genes should segregate together and wind up in the same sex cells
What does it mean if you have more genes than chromosomes?
That the genes moved together
Co-segregation
The transmission, together, of 2 or more genes on the same chromosome, as a result of their being in very close physical proximity to one another
What did William Bateson discover?
Co-segregation of genes in breeding experiments with plants
- if the gens are close enough together they can move together
- they are physically linked
What is there strong evidence for?
That genes were on chromosomes
Where was the most productive genetics lab in the 20th century?
The lab of Thomas Hunt Morgan
What did Morgan start to breed?
Drosophila fruit flies
What did Morgan think biology should be?
More experimental
What did Herman discover?
That x-rays and radiation cause mutation
What did Morgan want to study?
Evolution
How did Morgan think evolution worked?
In jumps
- new species can be produced in a single generation
What are 4 advantages to studying fruit flies?
- They are model organisms
- They have short generation time
- They are small and dont take up a lot of space
- They have lots of features on their surface that are susceptible to genetic variation
What was Morgans lab achievements? (6)
- Sex linkage
- Genetic maps
- Genetic information is one-dimensional, at the level of gene arrangement
- Creation of mutants as a way to discover new genes
- Related chromosomal aberrations to mutant phenotypes
- Anticipated population genetics as a way of relating Mendelian genetics to evolutionary theory
What did Morgan not find?
Jumps
What did Morgan discover in fruit flies?
Fruit flies with white eyes
- when they normally had dull red eyes
How do white eye alleles travel?
On the X chromosome
- sex chromosome
Where are white eyes only produced?
In white eyed males
What did Morgan discover with genetic maps?
Co-inheritance of certain specific alleles
- implied genetic distances between difference genes (can tell their order and how far apart they were)
What can population genetics bridge? (2)
Bridge genetics with evolution
