Black(B) rabbit coat colors are dominant to white(b) coat colors. Long hair (H) is dominant to short hair (h). A breeder crosses a rabbit homozygous for white, short hair with a homozygous black rabbit with long hair. The F1 is backcrossed to the rabbit with white, short hair and the following progeny are produced. Use the chi-square test to answer the following questions. What are the expected offspring numbers if the two genes are not linked, and therefore assort independently?

Okay. So this question is a big long word problem, which you're going to see often in genetics questions. So let's just walk through individually and figure out what's important. So it says, black rabbit coat colors are dominant to white, and long hair is dominant to short hair. So that's good to know here. Says, a breeder crosses a rabbit homozygous for white short hair. So that rabbit is going to look like this, with a homozygous black rabbit with long hair. Okay? So if we were to do this Punnett Square and create the f one generation, which is you're totally welcome to do if you want the practice, go ahead and pause it right out the Punnett Square. What we would get is all of our f one generation is going to look like this. Then it says, the f one generation, so this genotype here is backcrossed, meaning what? Meaning that it's crossed with one of its parents And the parent that it's back crossed to is the white short haired rabbit. So this cross is made and the following progeny are produced. Using the Chi Square Test, answer the following questions. So, the first question says, what are the expected offspring ratios if the 2 genes are not linked and therefore, assort independently? So the first thing we need to do is let's write out all the different genotypes that would create these, phenotypes because I think that's going to be helpful. Now you can do this by doing, writing out a full Punnett square. But what you're going to see is that the Punnett square can be shortened because all the genotypes that can be made, through these combinations is just all gonna be the same. Right? Whereas this one, we take the first b, the first h, the first b, the second h, the second b, the first h, and the second b, the second h. So the genotypes that can be made are these, and I keep writing my b's like h's. I'm sorry if that's confusing. I'm gonna try to fix it. Oh, whoops. This is why you should always go slow on your Punnett squares. So that you can, catch your errors if you make them. B b h h, b h h. Okay. So this one is gonna be the black, long. This one is gonna be the black, short. This one is gonna be the white, long. And the white, short. There's our genotypes from our Punnett Square. Now it says, what are the expected offspring numbers if 2 genes are not linked? So if the genes are not linked, that means they completely store independently. And if they store independently, that means our recombination frequency would be what? They're not linked. Do you know? So we know that recombination frequencies can't be greater than 50%. Right? So if, genes are not linked, then the highest recombination frequency is what we would expect. So if the genes are not linked, no linkage, then what we would expect is a 50% recombination frequency. Anything lower than that is going to suggest some kind of linkage. And so, our numbers are here. Right? And it says, what would be the expected offspring numbers if the two genes are not linked? Meaning, the recombination frequency is 50%. So our total number of offspring is 146. So if 50% of those were parents and 50% of those were, were recombinants, which is what we would see if there was no linkage, then we would expect that, a, we would have 73 parents and 73 at recombinant, and we just do 146 divided by 2, and that equals 73. And that means that 50%, which is our combination frequency of 146 equals 73. So we expect 73 offspring that look like the parents and 73 offspring that look like recombinants. So the, just know that if there are no link there's no linkage, if 2 genes are not linked, then their recombination frequency is going to be 50%, and that means 50% of the offspring are going to look like the parents, and 50% are going to look like the recombinants. So with that, let's move on.

Black(B) rabbit coat colors are dominant to white(b) coat colors....

1. Introduction to Genetics51m

2. Mendel's Laws of Inheritance3h 37m

3. Extensions to Mendelian Inheritance2h 41m

4. Genetic Mapping and Linkage2h 28m

5. Genetics of Bacteria and Viruses1h 21m

6. Chromosomal Variation1h 48m

7. DNA and Chromosome Structure56m

8. DNA Replication1h 10m

9. Mitosis and Meiosis1h 34m

10. Transcription1h 0m

11. Translation58m

12. Gene Regulation in Prokaryotes1h 19m

13. Gene Regulation in Eukaryotes44m

14. Genetic Control of Development44m

15. Genomes and Genomics1h 50m

16. Transposable Elements47m

17. Mutation, Repair, and Recombination1h 6m

18. Molecular Genetic Tools19m

19. Cancer Genetics29m

20. Quantitative Genetics1h 26m

21. Population Genetics50m

22. Evolutionary Genetics29m

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