In honeybees the system of sex determination is based on a...

In honeybees, the system of sex determination is based on a mechanism called haplodiploidy, in which the sex of an individual is determined by the ploidy of their genome: females are diploid and males are haploid. Male offspring result from the development of unfertilized eggs, while female offspring result from fertilized eggs. 1. An autosomal recessive mutation leads to white eyes. Wild-type eyes are brown. What offspring would result from a mating between a white-eyed female and a browneyed male? Include the genotypes and phenotypes of both fertilized and unfertilized eggs. 2. What offspring would result from a mating between the F1 from part 1? Include the genotypes and phenotypes of both fertilized and unfertilized eggs.

Transcript

00:02 So we're talking about the genetics of bees, and there's something in particular that is pretty unique when we do genetics, and that is the determination of sex based on polypoidy.

00:14 So males are going to be from unfertilized eggs, so therefore they only have one set of chromosomes.

00:21 So they might only have one, they'll have one set of all the chromosomes, including the sex chromosome.

00:28 And females are diploids, meaning they have two sets, meaning it's a fertilized egg.

00:32 So they will have two sets of all their chromosomes, including the sex chromosome.

00:38 So now that we have that information, we can look at the certain circumstance that we're given, the certain scenario, where we're told that we have a female parent who has a recessive trait.

00:49 That's sex -linked, meaning on her x chromosome, on both of her x chromosomes, she has a recessive allele.

00:55 But the male has the dominant allele on his only x -cromosome.

01:01 So then what would we expect for their offspring? and we are meant to find out what we would expect for their offspring given male and female.

01:14 So if the offspring are female, that means that they get an x from mom and they get an x from dad.

01:21 Well, dad only has one to give, so that one's easy.

01:23 It will be one with the dominant allele.

01:26 But mom has two to give.

01:28 So it could be this one or it could be that one.

01:31 But in this case, they both have the same alleles.

01:33 They both have a recessive allele.

01:34 So again, it really doesn't matter because in either case, they're getting a recessive allele on their x chromosome.

01:40 So we know that all the females will be heterozygous and will be carriers for this certain recessive trait.

01:48 The males, on the other hand, won't get an x from dad...

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