1 10 pts normal hedgehogs have straight fur and long...

1) (10 pts) Normal hedgehogs have straight fur and long whiskers. Mutant hedgehogs have been isolated with either kinked fur or short whiskers. The genes for each of these characters are on different chromosomes. You capture some hedgehogs and mate them and get the following data. Number of progeny mating genotypes straight fur and long whiskers straight fur and short whiskers kinked fur and long whiskers kinked fur and short whiskers Straight, short X Straight, short 30 90 10 30 Kinked, long X 40 40 Straight, short 40 40 Kinked, short X straight, short 40 120 0 0 A a) (2 pts) For each mutation, indicate whether it is dominant or recessive by filling in the blanks below with the word dominant or recessive. The allele for kinked fur is to the allele for straight fur. The allele for short whiskers is to the allele for long whiskers. b) (2 pts) Define genes and alleles for each trait (using A/a for fur type and B/b for whisker type).

Transcript

00:01 Okay so here you have a question of genetics.

00:03 You have a six crosses, you have the female parent, the male parent and the offspring.

00:08 And they're asking you which is the dominant and which is the recessive allele and just define your answer with the aid of a cross shown in the table.

00:15 So let's suppose that this is the straight allele and this is the curved allele.

00:20 We're just going to represent that like this.

00:23 For example here from this cross as you can see here you have zero females with a straight tail and you have zero males with curved tail.

00:36 And you have kind of the same here.

00:38 So what about here? for example you have a straight and a straight and you're getting only a straight and a straight.

00:45 You're getting zero curved.

00:46 So in this case for example this may be that both parents are homozygous.

00:50 Now the same is going to happen maybe here which is the opposite.

00:54 You have curved and you're getting offspring with curved tail only.

00:59 So these two parents are also homozygous.

01:02 Now what about in this case? in this case here you're crossing two curved parents and you're getting some offspring with curved tails and some offspring with straight tails.

01:15 So you're getting a straight tail when you cross two curved parents.

01:21 So it means that in this case the straight allele was hidden in at least one of these parents.

01:29 So in this case you're going to have that the straight is actually recessive.

01:39 We're not going to use this anymore.

01:41 It's recessive and curved is dominant.

01:46 So these are your alleles.

01:48 Now if you want to check it out then let's check.

01:51 So the curved and the curved.

01:53 Supposing that the curved is dominant first.

01:56 So this case the curved is heterozygous and the second parent is also heterozygous.

02:01 So in this case you can produce offspring with homozygous dominant, heterozygous and also homozygous recessive if each of these parents donates the recessive allele and you're going to produce this.

02:10 Okay so you can get curved offspring and also offspring with straight tails...

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