Two pea plants heterozygous for the characters of pod color and pod shape are crossed. Draw a Pu

Two pea plants heterozygous for the characters of pod color...

Key Concepts

Punnett Square

A Punnett square is a graphic tool used to predict the outcome of genetic crosses. It displays all potential genotype combinations from the alleles provided by the parents, helping determine the probability of offspring exhibiting particular traits.

Heterozygosity

Heterozygosity refers to having two different alleles for a specific gene. In the context of the problem, each pea plant carries one dominant and one recessive allele for both traits, which sets the stage for a dihybrid cross.

Dihybrid Cross

A dihybrid cross involves the simultaneous inheritance of two different traits, each determined by two alleles. This type of cross illustrates how alleles of different genes assort independently, following Mendel's laws.

Phenotypic Ratios

Phenotypic ratios quantify the observable traits in the progeny resulting from a cross. When dealing with a dihybrid cross between heterozygous individuals, the traits typically segregate into a 9:3:3:1 ratio, assuming independent assortment.

Transcript

00:01 This question, we're asked to find the phenotypic ratio of offspring of two pea plants that are heterozygous for pod color and pod shape.

00:12 So i'm going to choose some symbols for pod color.

00:20 So for color, i'm going to choose g because green is the dominant genotype or the dominant allele and little g will indicate yellow.

00:34 And then for pod shape, i'm going to choose i because inflated is the dominant allele.

00:50 And little i is constricted, and that is the recessive allele.

00:59 And we're told that we're crossing the turkey plants that are heterozygous for both traits.

01:04 So the parent generation will be heterozygous.

01:11 So that means they both have a dominant allele and a recessive allele.

01:18 And it's for both the male and the female.

01:25 Okay, so they're crossed.

01:26 And so now let's set up a punnet square.

01:30 Punant square, in this case, we have to find all the gametes possible.

01:36 So across the top, we're going to do the male gametes.

01:41 That's just convention.

01:42 The male gametes go across the top.

01:44 And i like to start off with the dominant combinations.

01:54 So you can have green and green with constricted at your seed pods.

02:04 You can have or with inflated seed pods.

02:06 You can have green with constricted seed pods.

02:08 You can have yellow with inflated seed pods or yellow with constricted seed pods.

02:20 So that's for the male gametes.

02:23 And then for the female gametes, it would be the same because they have the same genotype.

02:28 So you can have green with inflated, green with restricted, yellow with inflated, yellow with inflated, or yellow with constricted.

02:44 All right, so now we're going to make our punnets square.

02:57 So this is a large punnit square.

03:01 It's a 4 by 4.

03:05 Let me see if i can squeeze all these gannets in to the gritting that i've given or allowed myself.

03:15 Okay, so here we just go across the top.

03:18 We see here that it's 2 g's and 2 i's.

03:25 There is two capital gs, one capital i, and two eyes.

03:37 And i really should be calling the alleles.

03:40 So one green olele, a little allele, inflated, and a this is right.

03:48 Okay, so that's the first line for all the offspring.

03:54 And so we just continue that all the way through to complete our punnets flare.

04:18 And now we're going down to the next line.

04:20 So we go ahead with the green and yellow.

04:23 And we both have inserted.

04:43 You're almost through.

04:45 So just the last line.

04:53 Hopefully it's clear that what i'm doing is first, first i write down the dominant allele, or the allele from one and then the other.

05:11 So that makes g, g, and then i write down the next alleles pair.

05:21 This is simulating what happens when the parental game is neat and the different alleles are passed down to the offspring.

05:36 Okay, so now we have this pun and square.

05:39 We've got all the different possible genotypes.

05:42 This is what allowed us, using this pundit square, allowed us to find all the genotypes that are possible from all the gamete combinations of the females.

05:53 This is typically the female and the male...

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