lecture 3.1 - Pre 20th century understanding of heredity Flashcards
What were Aristotle’s three main ideas?
1) Species have an ‘essence’ that is transmitted from generation to generation that kept them the same.
2) Environment has a large influence on life and offspring (e.g act of sex influences baby’s characteristics - rigorous and energetic = strong, healthy baby and less exciting = girl baby
3) Blending - once blended can’t get original back. -removes variation. (short man and tall woman = middle heighted child
Who was Gregor Mendel, what did he do and what did he disprove?
Gregor Mendel was a Friar who did crossing and counting experiments with peas.
He found that ‘factors’ were passed from generation to generation and that they were sometimes unchanged - meaning characteristics can come out again in (later) offspring.
He published his work in 1865 and
This disproves Aristotle’s ideas about blending.
Who was August Weismann, what did he do and what did he disprove?
August Weismann looked at the germ line and theorised the idea about gemmules.
He suggested that particles called gemmules were made all over the body and then travelled to the gonads to make offspring.
This theory meant that your offspring’s liver was made by your liver gemmules.
He tested this theory with the use of mice. Cutting of their tails for 6 generations to see if offspring would still be born with tails.
Every time the offspring would have a tail and so he disproved the idea of ‘inheritance of acquired characteristic’
What is the germline?
The germline are cells that can pass on their genetic material to their progeny. (i.e egg and sperm cells)
What is the Chromosome theory?
‘Chromo’ meaning coloured, ‘some’ meaning thing.
With the use of telescopes - scientists were starting to see ‘string like things’.
They saw different amount in different species.
Used sea urchin embryos to find out that you needed the right number (and right type) of chromosomes for sea urchins to develop well.
Thus showing chromosomes as the carriers of genetic material.
