Question

In gardena peas,the allele for yellow peas is dominant to the allele for green pears.Suppose you have a plant that produces yellow peas,but you dont know whether it is homozygous dominant or heterozygous. What experiment could you do to find out? Draw a punnet square to help you

Answer 1

Do you know what a genotype is?

Answer 2

Rr ,rr,RR

Answer 3

Yes, those are genotypes. Each genotype has 2 alleles.

Here's the problem:

We have yellow peas.

But we don't know the genotype of the yellow peas.

Since yellow is a dominant phenotype,
what are the two possible genotypes, of yellow peas?

Answer 4

umm i dont know...

Answer 5

I'm not a 100% but I believe RR and Rr

Answer 6

^ Right.

DOMINANT alleles are CAPITAL letters.
RECESSIVE alleles are LOWERCASE letters.

So let's pretend this:

A -- Yellow

a -- Green

We know that a genotype has 2 alleles.

Here's a BIG RULE:
In a genotype, the Capital letters matter more than the lowercase letters.

So, if a pea has the genotype (A a),
it's YELLOW.
Because there's a Capital A in there.

If a pea has the genotype (A A),
it's YELLOW.
Because there's a Capital A in there.

But...if a pea has the genotype (a a),
then it's GREEN.
Because there are no Capital A's.
Just lowercase ( a ).

Do you get it so far?

Answer 7

yea

Answer 8

Do you know how to make a Punnett Square?

Answer 9

not really

Answer 10

You wanna learn?

Answer 11

yea

Answer 12

Punnett Squares show us what happens when two parents, each with their own genotypes, get together and breed. Make babies.

Answer 13

So before we make a Punnett Square, we need the genotypes of two different parents.

Can you give me two different genotypes?
One GREEN pea plant,
and one YELLOW pea plant.

Answer 14

rr.RR?

Answer 15

Right.

( r r) would be green.

(R R) would be yellow.

Answer 16

Okay, so here's what the Punnett Square would look like:



The FIRST parent (R R) is on TOP.
The SECOND parent (r r) is on the LEFT side.