Part IV: Investigation the Law of Independent Assortment by...

Part IV: Investigation the Law of Independent Assortment by Phenotyping a Dihybrid Cross in Wisconsin Fast Plants The Law of Independent Assortment states that genes located on different chromosomes assort independently from one another. To see the effects of this law, you must examine two different genes that are carried on two different chromosomes. We can investigate this phenomenon by looking at two traits, color and height, in WFP. Independent Assortment predicts that the F2 generation will show a mixture of green/short, green/tall, purple/short, and purple/tall. If Independent Assortment is not happening, you would expect F1 and F2 to only resemble the original parents. Procedure 2: For this experiment, use the provided data to complete the following. Trait: Stem color and stem height (purple and tall are dominant, green and short are recessive) Parents: Green/Tall (ppTT) x Purple/Dwarf (PPtt) 1. F1: Complete a Punnett square predicting the F1 generation in your Lab Notebook. Record the predicted phenotypic and genotypic ratios and percentages. 2. F2: Complete a Punnett square predicting the F2 generation in your Lab Notebook. Record the predicted phenotypic and genotypic ratios and percentages. - Use the following data in Part VI o # Green/Tall 183 o # Green/Short 55 o # Purple/Tall 570 o # Purple/Short 192 o Total 1000

Transcript

00:01 So for this experiment, you're using the data to complete the following cross.

00:08 You have two traits of a plant, stem color and stem height.

00:12 Purple and tall are dominant, so capital p stands for purple, capital t stands for dominant.

00:18 And then you have stem height, the grain color is lower p and short is lower t, recessive.

00:31 So now you have two parents, one is gray and tall, so which has a genotype of lower p homozygous and capital t homozygous.

00:40 And then the other parent is purple and wolf, so the genotype is capital p homozygous and lower t homozygous.

00:50 F1, complete the component square predicting the f1 generation.

00:54 Record the predicted phenotype and genotype and percentage.

00:58 So let's say we have the parent, you have homozygous lower p and homozygous capital t.

01:08 So that means that the two alleles are the same, so you'll only have one type of gametes, lower p and capital t.

01:18 And all the gametes has the same genotype.

01:22 And for the other parents, the purple and the wolf, again, it's a homozygous parent, so the two alleles are the same.

01:31 So as you can see, there's only one type of gamete produced from this parent, which is capital p versus lower t.

01:39 So now you put the two gametes together, all f1 plant will have the same genotype.

01:46 It pick up one allele from each of the parents, so capital p, lower p from each of the parents, and then capital t and lower t from each of the parents.

01:57 So you have a heterozygous f1 plant for both genes.

02:04 Now, as you can see, since this is 100%, every single one has a heterozygous p and heterozygous t.

02:19 And the phenotype, obviously, is dominant purple and tall.

02:29 Again, it's 100 % because one parent produces only one type of gametes, and the other parents produce, again, only one gamete.

02:39 So 100 % will give you the same genotype and phenotype.

02:46 Now, let's take a look at f2.

02:50 So for f2, it's a lot more complicated.

02:52 So you have this cross right here, heterozygous f1 parents intercross.

03:05 So now this time, the gamete formation will be a lot more complicated.

03:09 So the parent generation homozygous, there's only one type of gamete coming out of each of the parents.

03:16 But since now you have heterozygous for both genes, now you have separation of the alleles and also the independent assortment of the two genes.

03:27 So you can see the two alleles of the same gene separate, capital p and lower p.

03:34 The same idea with t and p, lower t and capital t.

03:38 So capital t and lower t also separate during meiosis i.

03:44 And then independent assortment, capital p can sort with capital t.

03:50 This is called independent assortment.

03:53 And then capital p can sort with lower t.

03:58 Lower p can sort with lower t and lower p with lower t.

04:08 So you have four different gametes, capital p and t, capital p, lower t, lower p, capital t, and lower p, lower t.

04:18 And it's the same for the other parents.

04:20 So now we have a more complicated punnett square.

05:00 Okay, so now we put all the gametes on top and the side of the punnett square.

05:10 So you have four type of gametes on top and the same four type of gametes on the side.

05:19 Then the next step, we put the two alleles back together.

05:22 Remember, you put p and p together, you put t and t together.

05:27 So the first one is p homozygous, t homozygous, capital.

05:32 So dominant p, dominant t homozygous.

05:37 The next one, homozygous, capital p, and then heterozygous t...

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