Post by laurcat on Jan 24, 2013 21:43:49 GMT -5
[glow=blue,2,300]This is a more complicated aspect of genetics that I only just learned about this week, so bear with me, and make sure you've got down the basics of lesson one.[/glow]
Remember how alleles determine our traits? Well, what if I told you some traits have even more alleles?
In New Germany, the traits for hair type and color are on the same chromosome. Remember how we used 'S' and 's' for hair type? In New Germany, they have some pretty weird hair colors- black and green. What the hagen? Who's ever heard of black hair? Black hair is dominant to green hair, so black hair is represented as 'B' and green as 'b'. Now say you have straight, black hair, and you are homozygous for both. Your genotype would be 'BBSS'. Whoa, what? Did I just put those together? Yes I did. Now we should try crossing two parents with these crazy genotypes.
Daniellashlieben has black, straight hair. Johnenhagen has green, curly hair. What will their sixteen childrenhagen look like? (They're going to be the talk of the neighborhood soon...)
Mom: BbSs (Heterozygous for both traits)
Dad: bbss (Homozygous recessive for both traits)
Now for the crazy part. This isn't your basic Punnett square. Last year in algebra, I learned how to do the FOIL technique. Turns out it's used in biology, too! Take a look!
F- First
O- Outer
I- Inner
L- Last
See how that works? Now we have four different combinations. That was just the mother, though. But don't worry! The father's genotype is bbss. You can actually tell by looking at it that all four combinations will be the same. If you are homozygous in both traits, there's only one possible combination. You can try it out.
Now, let's fill those combinations in!
Whoa, dude, sixteen squares? Yup. So how do we fill it in now? Well, it's just like the basic Punnett squares, but you combine two different traits at the same time.
Look at the box in the top left hand corner. You are crossing BS with bs. When you cross the 'B' and 'b', you get 'Bb'. When you cross 'S' with 's', you get 'Ss'. Now put them together, and you get 'BbSs'.
Now once you complete the top row, you can stop. See, here's the beauty of the father's lack of variety: See how his genotypes are all the same? You're basically crossing the same genotypes over and over. You're crossing BS, Bs, bS, and bs with bs on every single row, so once you've done the top row, you can just copy the same thing down on the rest of the rows.
Your result should look like this:
Notice the 'genotype' and 'phenotype' counts. When prompted for genotypes and phenotypes, you count up all the different genotypes and phenotypes. Look back at the Punnett square and see if you can determine what the offspring in each box looks like.
Remember, B=black, b=green, S=straight, and s=curly.
Remember how alleles determine our traits? Well, what if I told you some traits have even more alleles?
In New Germany, the traits for hair type and color are on the same chromosome. Remember how we used 'S' and 's' for hair type? In New Germany, they have some pretty weird hair colors- black and green. What the hagen? Who's ever heard of black hair? Black hair is dominant to green hair, so black hair is represented as 'B' and green as 'b'. Now say you have straight, black hair, and you are homozygous for both. Your genotype would be 'BBSS'. Whoa, what? Did I just put those together? Yes I did. Now we should try crossing two parents with these crazy genotypes.
Daniellashlieben has black, straight hair. Johnenhagen has green, curly hair. What will their sixteen childrenhagen look like? (They're going to be the talk of the neighborhood soon...)
Mom: BbSs (Heterozygous for both traits)
Dad: bbss (Homozygous recessive for both traits)
Now for the crazy part. This isn't your basic Punnett square. Last year in algebra, I learned how to do the FOIL technique. Turns out it's used in biology, too! Take a look!
F- First
O- Outer
I- Inner
L- Last
See how that works? Now we have four different combinations. That was just the mother, though. But don't worry! The father's genotype is bbss. You can actually tell by looking at it that all four combinations will be the same. If you are homozygous in both traits, there's only one possible combination. You can try it out.
Now, let's fill those combinations in!
Whoa, dude, sixteen squares? Yup. So how do we fill it in now? Well, it's just like the basic Punnett squares, but you combine two different traits at the same time.
Look at the box in the top left hand corner. You are crossing BS with bs. When you cross the 'B' and 'b', you get 'Bb'. When you cross 'S' with 's', you get 'Ss'. Now put them together, and you get 'BbSs'.
Now once you complete the top row, you can stop. See, here's the beauty of the father's lack of variety: See how his genotypes are all the same? You're basically crossing the same genotypes over and over. You're crossing BS, Bs, bS, and bs with bs on every single row, so once you've done the top row, you can just copy the same thing down on the rest of the rows.
Your result should look like this:
Notice the 'genotype' and 'phenotype' counts. When prompted for genotypes and phenotypes, you count up all the different genotypes and phenotypes. Look back at the Punnett square and see if you can determine what the offspring in each box looks like.
Remember, B=black, b=green, S=straight, and s=curly.
