Heredity Flashcards
Which ancient idea about inheritance was attributed to Hippocrates?
Pangenesis - the idea that characteristics can be improved and one’s life experiences is embedded into one’s body and it is sent to their reproductive organs to be passed on to offspring
Who in more recent times agreed with Pangenesis as a means of inheritance?
Charles Darwin but called the particulates ‘gemmules’
What ancient idea about inheritance came from Aristotle?
form + potentiality = actuality
semen + menstrual fluid = embryo/offspring
What ancient idea about inheritance came from the Bible?
maternal impression - the story of Jacob from Genesis in which he showed striped and spotted patterns carved into sticks to sheep and goats and their offspring were striped and spotted
Give a famous example of maternal impression from the 19th century
The Elephant Man, Joseph Merrick, developed disfigurements throughout his life and this was attributed to his mother being scared by an elephant during her pregnancy
What did weird hybridizations of different animals produce?
offspring species that are intermediate
ex. mules are a cross between a donkey and a horse and that’s exactly what they look like (but they are infertile)
there was no fixed idea of what species were at this point - ex. giraffes are a result of leopards + camels
What remained a widely accepted understanding of inheritance into the 19th century?
acquired inheritance
What is genetic purity? where did it get its origins?
concept originating from essentialism
the concept that hereditary factors are a unitary fluid or essence which can be impurified (especially in combination with acquired inheritance)
What has resulted historically from the idea of genetic purity in combo with essentialism and acquired inheritance?
some hereditary factors or lineages are more pure than others = prejudices, racism, genocide, and other horrific injustices including eugenics
eugenics: the study of creating and controlling form (modifying gene expression to produce a desired result)
What is the debate between preformationism vs. epigenetics?
preformationism was the argument that a pre-existing form is transmitted between generations
v.
epigenetics was the idea that form can be created from formlessness
What is blending inheritance? Which organism was studied that give these some credence?
it was an idea that was widely accepted and argued that hereditary factors BLEND to produce an intermediate offspring
snapdragon flowers showed this
Describe Gregor Mendel’s (1822-1884) life before his experiments
from a poor peasant family in what is now the Czech Republic
Studied at University of Brno until he ran out of money and joined the community of scholars at the Augustinian order as a monk
Worked as a tutor while he was a monk (substitute teacher in elementary schools)
he tried to become a certified teacher but had severe test anxiety and failed twice
What prevented Mendel from becoming a certified school teacher?
his test anxiety
he failed the oral exam twice
Who imprinted on Mendel the significance of quantifying results and of numbers in science?
Christian Doppler (Doppler effect) at a lecture in Vienna
Explain Mendel’s work
He performed pea hybridization experiments in which he focused on quantitative results and gathered a LOT of data
Why was Mendel’s scientific career short?
he published his results from his pea studies but gained little traction - it was hard to read and he didn’t make any claims about the significance or relevance of his work, he just reported what he did
his supervisor at the time also encouraged him to repeat his work (good advice) but with a plant that was unbeknownst to them, extremely difficult to work with (hawkweed)
What 3 reasons allowed Mendel’s success?
- Mendel’s ideas and results were not novel, but he was the first to construct a model to explain his results
- garden peas were a good choice - easy to work with, easy to grow, easy to observe phenotypic differences
- he asked narrow, answerable questions and built a testable, repeatable model AND he was quantitative
What were the major results from Mendel’s pea hybridizations?
- segregation of traits: (uniform parents could produce different progeny) - this had been observed before, but Mendel proposed a model to explain it
= he counted the offspring and created a ratio (3:1) - particulate inheritance: hereditary factors were transmitted as discrete, indivisible entities and not as continuous fluids or essences = dispelled blending inheritance
- independent assortment (he didn’t name it this) - he observed that different genes can be inherited independently and there are different patterns of inheritance
What were Mendel’s limitations to his model?
while he was quantitative, his model was based on a lot of hypotheticals and structures that he didn’t understand or know about
while his model was testable, he wasn’t able to repeat it with another plant species when he tried hawkweed
Why couldn’t Mendel repeat his experiment with hawkweed?
Hawkweed is apomictic - it flowers but it reproduces asexually
Compare and contrast Charles Darwin’s life and scientific career to Mendel’s
Darwin:
- born rich, stayed rich
- completed a university degree
- worldly and well travelled
- long career in biology
- famous
- aware of the significance of his work
- good paper record of his life because he was famous when he died
Mendel:
- born poor, stayed poor
- dropped out of university for financial reasons and became a monk
- not well travelled
- short career in science
- not famous, few people even knew he was a scientist
- unclear whether he knew the significance of his work because
- poor paper trail of his life - he wasn’t famous when he died, so all his personal papers were burned
Compare and contrast Darwin’s genetics to Mendel’s genetics
Both Darwin and Mendel’s genetics were particulate models of inheritance
but
Darwin’s model included acquired inheritance, whereas Mendel’s heritable factors could persist and not be diluted but maybe could be silenced
also Darwin’s model was based on Hippocrates’ Pangenesis idea and Mendel’s was more quantitative
