# Biology calculations

I am not sure where to put this question in biology or maths forum.But i finally decided to ask here.Somatic cells have two "copies" of each of chromosomes, one inherited from each parent. Each sperm cell, on the other hand, only gets one "copy" of each chromosome (either the one from your mom or your dad). So there are something like 2^23 different possible sperm configurations.Similarly there are four different types of nitrogen bases ,so they can form 4^3 i.e 64 possible combinations of triplets,called codons.
How these calculations are done,i am not getting ,if i will learn this it will make my life way easier. please help.How we can understand that where should we put ( ^)[to the power raised to].......?

jedishrfu
Mentor
It looks like you're mixing and matching different things. On the one hand, you're thinking about chromosomes and all the possible that they can combine. On the other hand, you're thinking about the DNA strands that compose the chromosome and all the possible ways they can be coded.

So what is it you're trying to figure out? Humans have largely the same DNA packaged into the same chromosomes. There is still a large variety of differences but not necessarily from codon to codon. We gain our traits mostly in how the chromosomes are paired from our mother's chromosomes and our fathers chromosomes. You might want to think more at the gene level than at the codon level.

http://en.m.wikipedia.org/wiki/Chromosomes

There's a table inside that shows the number of genes in each chromosome.

It looks like you're mixing and matching different things. On the one hand, you're thinking about chromosomes and all the possible that they can combine. On the other hand, you're thinking about the DNA strands that compose the chromosome and all the possible ways they can be coded.

So what is it you're trying to figure out? Humans have largely the same DNA packaged into the same chromosomes. There is still a large variety of differences but not necessarily from codon to codon. We gain our traits mostly in how the chromosomes are paired from our mother's chromosomes and our fathers chromosomes. You might want to think more at the gene level than at the codon level.

http://en.m.wikipedia.org/wiki/Chromosomes

There's a table inside that shows the number of genes in each chromosome.
I have given jut two examples,actually i want to understand how such( 4^3/ 2^23)calculation is done?

Pythagorean
Gold Member
4^3 means multiply 4 three times. So it would be:

4^3 = 4*4*4 = 16*4 = 64

4^3 means multiply 4 three times. So it would be:

4^3 = 4*4*4 = 16*4 = 64
I know 4^3 = 4*4*4 = 16*4 = 64 .I just want to know how can i understand that here i have to calculate in this way.As in my examples ,there are four nitrogenous bases and i want to figure out how many different combinations i can make if i make pair of three of them i.e codon.If i will sit to write each and every combination it will be very tedious and tough task but in my textbook it is just calculated in this way 4^3 = 4*4*4 = 16*4 = 64 .64 different combinations.That's what i want to learn how to do such calculations.Four different bases .i want to make pair of three so how it comes out to do 4^3 why not 4 multiplied by 3?That's what i want to learn.

Pythagorean
Gold Member
Think of it this way. If you have a switch with an on off state, that's one switch with two states, so: 2^1

If you have two switches with two states each, there are four total states the whole two system switch can be in: 2^2=4

If a widget has 4 states and you have three widgets, the total number of states is 4^3.

You can also count them out. For two switches each with two states, all your states are:

00
01
10
11

Four states, 2^2!

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that's one switcj wotu two states,
I didn't understand this.Is it in this way
one switch with two states.

Pythagorean
Gold Member
I fixed that typo :) sorry, mobile keyboard.

So basically what is general formula to do such calculations?Is it like number of things^their variable states(possible positions) right?

Pythagorean
Gold Member
States^(number of things) right? Because 4^3 was three things with four states each. And bits are always 2^n.

Because 4^3 was three things with four states
AA.............Four things with three states .There were four nitrogenous bases.

States^(number of things) right? Because 4^3 was three things with four states each. And bits are always 2^n.
Now i am getting confused.According to your examples States^(number of things),But according to mine number of things^their variable states.What next?

Pythagorean
Gold Member
Well, let's go to 2^3 - that's 8. If you have three bitz with two states each, you have

000
001
010
011
100
101
110
111

That's 8. Wheres 3^2 would be 9. So which formula is right?

Pythagorean
Gold Member
Also, a codon is three base pairs and the pairs have four possible things they could be: A C G or T, so 4^3 is right!

Edit: actually I think that T should be a U.
edit 2: genes -> base pairs

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Also, a codon is three genes and the genes have four possible things they could be: A C G or T, so 4^3 is right!
But i am taking it in this way there are 4 nitrogenous bases,and they are arranged in codon such that they can be given either of three positions in codon.So things^their variable states.I am taking number of things as number of bases you are taking number of things as number of genes in a codon.So ...........

I am taking number of things as number of bases you are taking number of things as number of genes in a codon.So ...........What actually is number of things?

Pythagorean
Gold Member
Sorry, gene was the wrong word. We are talking about the same thing - the units of genes (base pairs).

Sorry, gene was the wrong word. We are talking about the same thing - the units of genes (base pairs).
So four base pair so four things. How three things^variable states?

Pythagorean
Gold Member
No the value of the base pair is the state, the position is the thing, in this case. So three things (positions) with four possible states (four different things can go in each place).

• gracy
No the value of the base pair is the state, the position is the thing, in this case. So three things (positions) with four possible states (four different things can go in each place).
Now i understood.Thanks a lot.

Ygggdrasil