Okay so I have a test next week on logarithms.

My teacher said this would be the hardest kind of question on the test, and I sort of understood where he went with in class, but now at home I don't understand wtf he did.

He's a very fast teacher and it pisses me off because he's so fast most of the class has very bad grades xD

FUCKING HATE MATH

Anyway...

2^(x+1) = 5^(1-2x)

So he said we should take the natural logarithm of both sides.

so ln (2^(x+1)) = ln (5^(1-2x))

Well we can remove those exponents to the outside, so...

(x+1) ln (2) = (1-2x) ln (5)

Now I don't understand wtf he did.

He wrote on the board:

ln (2) x + ln (2) = ln (5) - 2 ln (5) x

I figured maybe he switched the terms around:

ln (2) (x+1) = ln (5) (1-2x)

And then got:

ln 2x + 2 = ln 5 -10x

But....wtf how did he get 2 ln (5) x??

Karen and Steve each have a sibling with sickle-cell disease. Neither Karen, Steve, nor any of their parents has the disease, and none of them has been tested to reveal sickle-cell trait. Based on this incomplete information, calculate the probability that if this couple should have another child, the child will have sickle-cell anemia.

Pedigree charts and Punnet Squares

Basically, sickle-cell is a recessive trait, correct?

So we can either have

Homozygous dominant = No sickle cell

Heterozygous dominant = No sickle cell (carrier of the disease)

Homozygous recessive = Has sickle cell disease

Let's call a healthy allele "S", and an allele for sickle cell "s".

So you have:

SS = No sickle cell

Ss = No sickle cell (but carries the recessive allele for the disease)

ss = Has sickle cell disease (carries both recessive alleles)

Let's look at Karen and Steve's parents first.

Since the case is the same for both families (two children, one with sickle cell, one healthy child, and two healthy parents), we'll just refer to one.

These are all possible genotype combinations for two parents, right?

SS - SS

SS - Ss

SS - ss

Ss - ss

ss - ss

Ss - Ss

Let's look at each option.

SS - SS <- Wrong. This is not possible because neither parent has the sickle cell allele, so it would make it impossible for their children to have sickle cell. One of them does.

SS - Ss <- Wrong. This is not possible. Although one parent has a sickle-cell allele, all offspring combinations would lead to "SS" or "Ss", where no children would contract sickle cell. One of the children has the disease.

SS - ss <- Wrong. This is not possible. None of the parents contracted the disease, so neither of them can have "ss". This would also lead to children that do not have the disease, and one of them does.

Ss - ss <- Wrong. This is not possible. Although the offspring could end up having or not having the disease to match the problem, none of the parents contracted the disease, so neither of them can have "ss".

ss - ss <- Wrong. This is not possible. Both parents and offspring would in this case all have sickle cell disease, and that's not the case.

**Ss - Ss <- Correct. This fits perfectly. Both parents are carriers for the disease, yet they do not have it themselves. They pass sickle cell on to one of their children, but not on to Karen (or in the other family's case, Steve).**
So we can safely assume that the parents of both families are Ss and Ss.

This means there's a:

25% chance of their offspring being healthy homozygous dominant (SS)

50% chance of their offspring being healthy heterozygous dominant carrier for sickle cell disease (Ss)

**25% chance of their offspring having sickle cell disease (ss)**

And its also important to know wether its a sex-linked gene or not, in this case, sickle-cell disease is a sex-linked gene meaning you use the X and Y.

It's sex-linked? Are you sure? Hmm....

That screws up my work XD