Waxy endosperm wx shrunken endosperm sh and yellow seedling...

Waxy endosperm (wx), shrunken endosperm (sh), and yellow seedling (v) are encoded by three recessive genes in corn that are linked on chromosome 5. A corn plant homozygous for all three recessive alleles is crossed with a plant homozygous for all the dominant alleles.

Transcript

00:01 Hello everyone, in this question the waxy endosperm, the shrunken endosperm, the yellow seedling are encoded by three recessive genes and these are linked to chromosome number 5.

00:14 So there is a corn plant that is homozygous for all these recessive alleles, that is this here is the genotype.

00:24 Is crossed with the plant homozygous for all the dominant condition.

00:30 So that means this will be the condition and now it says the resulting f1 are then crossed with the plant homozygous recessive.

00:43 So here the f1 generation will have the heterozygous condition for all the alleles.

00:50 Now this here will be test crossed with the homozygous recessive condition.

00:57 So we have to determine the order of the genes on the chromosome.

01:03 So here let us find out the parental type first that is the highest number that is wx plus sh plus v plus wx sh and v.

01:13 These are 3479 and 3478 in number.

01:20 Then we will find the double cross overs that are wx sh v plus which is 87 in number and wx plus sh plus v that is 94 in number.

01:35 So here we can see wx plus is present here also wx plus is present here sh plus is present here also sh plus is present but this v here is different in these two.

01:49 Similarly we can compare the next one also where we can see this wx wx is same this sh sh is identical but this v here is changed.

01:59 So that means this v should be present in the middle.

02:03 So our gene order will be wx v and sh this here is the gene order.

02:13 Then we have been asked to determine the recombination frequency and the genetic map.

02:19 So basically we have to find the recombination frequency and we can find the single gene order from that.

02:26 So the distance between wx and v is equals to the single cross over that will be between wx and v.

02:41 So here it will be 218 plus 292 plus the heterozygote plus the double cross over that is 87 plus 94 divided by total that will be 10756.

03:00 So this here will be equals to 7 map unit.

03:05 Similarly we can find the distance between the sh and v...

Question

Waxy endosperm (wx), shrunken endosperm (sh), and yellow seedling (v) are encoded by three recessive genes in corn that are linked on chromosome 5. A corn plant homozygous for all three recessive alleles is crossed with a plant homozygous for all the dominant alleles.

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