Watermelon genotypic and phenotypic ratio practice read the...

Watermelon Genotypic and Phenotypic Ratio Practice Read the information below. Determine the ratios for phenotype and genotype of each Punnett Square. A genetic engineer is going to cross two watermelon plants to produce seeds for spring planting. He is breeding for size and wants to have as many watermelons with the phenotype for long shape as possible. In watermelons, the allele for short shape (S) is dominant to the allele for long shape. Determine the Genotypic ratios and phenotypic ratios for each Punnett square. Which cross would yield the highest number of long watermelons? 1. SS x SS 2. SS x ss 3. SS x Ss 4. Ss x ss 5. Ss x ss 6. Ss x Ss

Transcript

00:02 A genetic engineer is going to cross two watermelon plants to produce seeds for spring planting.

00:09 So he's breeding for size and wants to have many watermelons with the phenotype of long shape as possible.

00:16 So in watermelons, alleles for short shape is capital s, which is dominant over the allele for long shape lower s.

00:24 So there are six different crosses and determine the genotype ratio and phenotype ratio of each planet square and the size.

00:32 Which cross will yield the highest number of long shape watermelon.

00:38 So on the board, i show you two alleles, capital s stands for short shape and lower s, stand for long shape.

00:44 The short is dominant over long, so we're selecting for recessive allele, which is long.

00:50 So let's take a look at each of the crossing.

00:52 The first one is between homozygars capital s.

00:56 So as you can see, for each parent, it produced two alleles, but they see since both alleles are capital s.

01:05 So as you can see on punny square, i put capital s on top and side of the punning square.

01:11 So all for offspring will be capital s homozygers, and they all will have short phenotype.

01:20 Now the second cross is between homozygars, capital s, and homozygars lower s.

01:26 So the parents of homozygars, capital s produced two to alleles, capital s.

01:35 And the homozygars, recessive, l .s will produce two lower s alleles.

01:42 So when we put the pettin square together, all four offspring will be heterozygars, capital s, lower s, so 100 % heterozygars.

01:51 Since it has a dominant allele, all four offspring will be a short shape, your type.

01:58 The third cross is between the heterozygars.

02:02 Zyghers, kaptos and lower s and the homozegers keptu s.

02:07 So you can see the parents on the left side produce two same alleles, kaptal s and kaptos.

02:15 The one on the right side, the heteralzygers produce two possible alleles.

02:20 One is kepta s, the other is lower s.

02:22 Each has 50 % of chance to be passed down to gametes.

02:26 So when we put the penny square together, as you can see, half of the offspring will be heterozygars and half of the offspring will be homozygars capital s...

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