7. (a) A man who is heterozygous for brown eyes marries a...

7. (a) A man who is heterozygous for brown eyes marries a woman who is homozygous for blue eyes and they have four children (F1). Half of the children are brown eyed and another half are blue eyed. Using the B for brown eyed and b for blue eyed, i. Identify the genotype of the parent. [2 marks] ii. If a brown eyed man in F1 marries a woman and produces F2 offspring with the phenotype ratio 3:1, identify the genotype of the woman. [1 mark] iii. Draw a genetic diagram to show this marriage until F2 generation. [3 marks] (b) A woman with group A blood marries man with group B blood. Their child has group O blood. i. What is meant by multiple alleles? [1 mark] ii. State the genotypes for woman, man and child. [3 marks]

Transcript

00:01 So here in this question we have been given that brown eyes allele which is represented by capital b is dominant over blue eyes allele which is represented by small b and is recessive now in first part of this question man with brown eyes is crossed with a female with blue eyes now genotype of them will be man here is heterocylides and the female is homozygous recessive.

00:57 Now cross between a heterozygote and a homozygous recessive.

01:02 Now here we are taking gametes of male on one side in the punnette square and the gametes of female on another side of the punnid square.

01:13 So the genotype of the offspring will be getting are two heterozygotes and two homozygous recessive.

01:24 Here the phenotypic ratio of individual with brown eyes and individual with blue eyes is two ratio two or 50 percent each so the parent's genotype is man is heterozycus and women is homozycus recessive and brown individual or brown man in fn generation.

03:03 Now here this one is our f1 generation and the brown individual will be showing hetrozygous condition.

03:13 Here brown is showing hetrozygous condition and the blue will be showing homozygous recessive.

03:23 So brown man in fn generation will be hetrozygous.

03:28 Is crossed with another female who also has brown eyes and she is also heterozygous.

03:38 Now cross between them.

03:47 Now here we are taking gametes of male on one side and gametes of female on another side.

03:53 So the genotype of the offspring will be getting is one homozygous dominant, two heterozygotes and one homozygous recessive.

04:04 This individual here will be showing blue eyes and the phenotypic ratio here of brown eyes individual and blue eyes individual is 3 ratio 1.

04:35 And therefore the genotype of the female is also hetrozygous with brown eyes.

04:55 In third part of this question let's draw a pedigree.

05:02 Now, in the first generation, a male who is hetrozygous with brown eyes is crossed with a female who is homozygous recessive with blue eyes and produces four offspring with all hetrozygous genotype and brown eyes as, sorry, it produces half heterozygote and half homozygous recertes.

06:05 As we can see in the f1 generation, that homozygous recessive ones will have blue eyes.

06:17 Sorry for the mistake.

06:19 Here, two individuals will be heterozygote and two individuals will be homozygous recessive.

06:25 Now, this male with brown eyes, which means it is hetrozygous with brown eyes, is crossed with a female who also has hetrozygous brown eyes.

06:41 And cross between them will be producing four individuals, three with brown eyes, where one is homozygous dominant, two are heterozygodes, and one is homozygous recessive with blue eyes.

07:12 As we can see in the f2 generation.

07:19 This one is our f2 generation and this one is our f1 generation...

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