Mendel's experiments with pea plants.

In summary: is correct, in the picture there is a mix of smooshes and wrinkles, this was done to demonstrate a principle.
  • #1
wasteofo2
478
2
In my bio class, we're learning about genetics currently and watched a video demonstrating mendel's experiments with pea plants. Something in the video didn't seem right to me, and my biology teacher is horrible and couldn't understand my question.

In the part of the video in question, it shows a plant which had been bred from one parent which was pure bred so that it's peas were smoothe, and one parent which was pure bred so that it's peas were wrinkly. In the F1 generation, the peas were all smoothe. To demonstrate that the recessive wrinkly pea gene hadn't dissapeared, they showed a plant which had been bred from 2 plants which were swinkly/smoothe hybrids. This plant had 3 smoothe peas and 1 wrinkly pea in the same pod. This was to demonstrate the 3 to 1 ratio that smoothe peas had to winkly peas when bred from 2 hybrid parents.

However, the thing that confused me was the fact that there were 2 different types of peas in the same pod. I understand how if you beed 2 hybrids that you have a 75% chance of getting the dominant factor, but I didn't think that the dominant and recessive factors would show up partially in the same organism. To me, having 3 smoothe and 1 wrinkly pea in the same pod seemed like someone having 25% red hair and 75% black hair.

So, is it possible to have wrinkley and smoothe peas in the same pod, or was that specifically planned that way to demonstrate a principle?
 
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  • #2
I remember seeing that same picture. My understanding was it was only to demonstrate the 3 to 1 ratio.

Nautica
 
  • #3
Yeah, you've got to remember that those peas are now the F3 generation. The F2 plant is heterozygous for the smooth an wrinkly gene, it's descendants (i.e. it's peas) will be 1/4 wrinkly.
 
  • #4
But that means that 1 out of every 4 plants will be totally wrinkly, and 3 out of every 4 will be totally smoothe, and none will be partially wrinkly and partially smoothe (assuming no sort of mutation), right?
 
  • #5
right.
 
  • #6
Thanks nautica and Chemicalsuperfreak!
 
  • #7
Ok, I am not an expert on pea plant fertilization.. but peas in a pod are seeds that have been fertilized. If you have an 'Aa' heterozygotic plant crossed with an 'Aa' heterozygotic plants you get the following.. 'eggs': A and a's, and the following 'sperms': A and a's.

So basically in the undeveloped pod there is a mixture of A's and a's, that get fertilized by a plant with a mixture of A's and a's.

So: NO, there is no such thing as 1 out of four plants totally wrinkled and 3 out of 4 totally smooth. The peas of the single plant will have 1/4 wrinkeled and 3/4 smooth peas.
 
  • #8
So, you and nautica seem to be in disagreement, now I'm confused.
 
  • #9
Peas are seeds that grow from eggs fertilized by pollen, they grow from two 'parents' (actually: in the pea plant, self-fertilization occurs mostly).

I found the following website which explains the same thing as I understand it too:
http://www.fathom.com/feature/122612/

He found that the hybrid plants, grown from yellow seed, did not breed true. Out of 8,023 peas in this second generation, 6,022 were yellow and 2,001 green--a ratio very close to three yellow to one green.
 
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  • #10
Originally posted by wasteofo2
So, you and nautica seem to be in disagreement, now I'm confused.

I was going off memory of the picture. I will have to go with monique on this one, since it looks like she took the time to look it up.

nautica
 

Related to Mendel's experiments with pea plants.

What were Mendel's experiments with pea plants?

Mendel's experiments with pea plants, also known as his hybridization experiments, were conducted in the mid-1800s and involved breeding different varieties of pea plants to observe the inheritance of traits from one generation to the next.

What did Mendel discover through his experiments with pea plants?

Mendel discovered the basic principles of inheritance, which he called the "laws of segregation" and "independent assortment". He also found that traits are inherited in discrete units, now known as genes, and that some traits are dominant over others.

What were some key factors that made pea plants ideal for Mendel's experiments?

Pea plants have a short generation time, produce large numbers of offspring, and have easily observable traits that can be controlled and manipulated through cross-breeding. These factors allowed Mendel to conduct controlled experiments and accurately record and analyze his results.

What were some limitations of Mendel's experiments with pea plants?

Mendel's experiments were limited by the fact that he only studied a small number of pea plant traits and did not account for the effects of genetic linkage or multiple genes influencing a single trait. He also did not have knowledge of DNA or modern genetic techniques, which could have provided more detailed insights into inheritance.

How did Mendel's experiments with pea plants contribute to our understanding of genetics?

Mendel's experiments laid the foundation for modern genetics and provided evidence for the existence of discrete units of inheritance. His discoveries helped to explain patterns of inheritance and paved the way for future research on genetics and heredity.

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