Lecture notes
FIRST CLASS Lecture notes Genetics
- Module
- Genetics
- Institution
- University Of Bath (UoB)
Mendel lecture notes
[Show more]
Seller
Follow
Content preview
MendelGregor mendel discovered the basic principles of
heredity
Mid 19th century there was much confusion about how traits were
inherited: conventional wisdom thought that inheritance was
“blending”
Whether by accident/intent, Mendel’s discovery was reliant on his
choice of organism (peas): they give plenty of progeny & there were
plenty of pure breeding varieties available to him. Peas are not a
model species now as they only give 1 generation per year (slow by
standards of today’s “model” species) – but Mendel had time.
And, crucially, his choice of traits: Mendel picked 7 traits that
showed discontinuous variation (no “medium”) – seed colour, seed
shape, seed coat colour, pod colour, pod shape, flower position &
stem length.
Monohybrid crosses reveal the principle of
segregation and the concept of dominance
Monohybrid cross = cross between 2 parents that differ in a single
characteristic (cross looking at 1 trait, crossing between lines that
wouldn’t normally be crossed)
- Conclusion 1: one character is encoded by 2 genetic factors
- Conclusion 2: 2 genetic factors (alleles) separate when gametes are
formed
, - Conclusion 3: the concept of dominant & recessive traits
- Conclusion 4: two alleles separate with equal probability into the
gametes
What Mendel did: he took pea plants that were true breeding (peas
usually are self-fertilising) – we now know these to be homozygotes
for the short stem allele. He forced plants different in 1 of his 7 traits
(but the same otherwise) to mate by artificially transferring pollen.
He then let the F1 self-
fertilise. This 2nd generation
of progeny is the F2
He noticed something odd:
for each of the 7 traits about
¾ of the progeny resembled
one of the original parents,
¼ resembling the other
This is now the classic
“Mendelian” proportions of
3:1
Mendel knows nothing about
meiosis, DNA or mutation,
but works out that:
a) Inheritance is not blending – there was no medium type
b) The pattern of inheritance supports the idea that inheritance is
“particulate”, not blending
c) Because the F2 has types resembling both parents, the F1 must
still contain the information for both, even though only 1 phenotype
is seen
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller jessicabrown-11. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £7.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
52355 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now