BIOL4 Biology Unit 4 Exam - 13th June 2011

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Reply 620

Stratos

Original post by tehsponge

Fffuuu- I hate meiosis. Quick recap of it for me please? :tongue:

I literally completely forgot about it, I don't think I got a question about it on Unit 2 :ahee:

Reply 621

*Rainbow*

Original post by tehsponge

Fffuuu- I hate meiosis. Quick recap of it for me please? :tongue:

Eeeeerm what i can remember?

diploid number of gametes (so double of mitosis)
random fusion of gametes increases genetic diversity
also independent segregation and crossing over

that's all i can remember :frown:

Reply 622

sakha1

Original post by *Rainbow*

Does anyone get question 2c in Jan 2011? The hardy weinberg? Dont really get why they got 48% I got like 27% :s-smilie:

I'm still confuzzled as to how this answer is worked out?
Could someone show the working out how to get the answer ... i'm using p2 + 2pq +r2 to work it out.

Reply 623

*Rainbow*

Original post by sakha1

I'm still confuzzled as to how this answer is worked out?
Could someone show the working out how to get the answer ... i'm using p2 + 2pq +r2 to work it out.

Finally worked this out..

you have to square the p and then do 1-q try that and let me know if u get it

(edited 12 years ago)

Reply 624

Shoorooz

16% 0.16
square root of 0.16=0.4=q

p+q=1
if q=0.4 then p=0.6

2pq=% that is hetorzygous

so you do 2x0.6x0.4=0.48

Reply 625

Jing_jing

Original post by sakha1

I'm still confuzzled as to how this answer is worked out?
Could someone show the working out how to get the answer ... i'm using p2 + 2pq +r2 to work it out.

The question tells us that 16% of the population is Rhesus negative, therefore

q^2 = 0.16

. (Rhesus negative is recessive, therefore to be rhesus negative you must be homozygous recessive).

If you square root 0.16 you get the value of q, i.e. 0.4
1-0.4 = p as p+q=1
So p=0.6

The % of the population that is hetrozygous is 2pq = 2x0.6x0.4=0.48

Therefore 48%

Reply 626

tehsponge

Original post by sakha1

I'm still confuzzled as to how this answer is worked out?
Could someone show the working out how to get the answer ... i'm using p2 + 2pq +r2 to work it out.

Weird, I just did that question.
Here's my working out:
16% = rr
0.16 = rr
so q^2=0.16
so q=0.4

p+q=1.0
so p=0.6

Then I just put those values into p^2+2pq+q^2=1.0 and got 0.48

Reply 627

sakha1

Original post by *Rainbow*

Finally worked this out..

you have to square the p and then do 1-p try that and let me know if u get it

I still don't get it:
This is what i've got so far and i know it's wrong ...
16% = r2
0.16
r=0.4
p2 +2pq + r2 = 1
2pq=0.2=1
2pq=0.8
pq=0.4

I don't even know what i'm doing now :frown:

could you show me the full working out please?

Reply 628

sakha1

Original post by tehsponge

Weird, I just did that question.
Here's my working out:
16% = rr
0.16 = rr
so q^2=0.16
so q=0.4

p+q=1.0
so p=0.6

Then I just put those values into p^2+2pq+q^2=1.0 and got 0.48

Oh, that makes sense ... thank you. Why didn't i just plug the values in :colondollar:

Thanks all :smile:

Original post by sakha1

I still don't get it:
This is what i've got so far and i know it's wrong ...
16% = r2
0.16
r=0.4
p2 +2pq + r2 = 1
2pq=0.2=1
2pq=0.8
pq=0.4

I don't even know what i'm doing now :frown:

could you show me the full working out please?

There's lots of people above me who've done a far better job of explaining than me! hehe :colondollar:

Reply 631

NRican

For the Hardy Weinberg, if it gives you a % you have to square root but otherwise you don't right ? What if they give you frequency?

Reply 632

tehsponge

Original post by NRican

For the Hardy Weinberg, if it gives you a % you have to square root but otherwise you don't right ? What if they give you frequency?

Well that depends if they gave you the frequency of the allele or the frequency of a genotype. If it was just the frequency of an allele then there would be no need to square root it.

Reply 633

*Rainbow*

Original post by tehsponge

Well that depends if they gave you the frequency of the allele or the frequency of a genotype. If it was just the frequency of an allele then there would be no need to square root it.

Do you have any examples of this :s

Reply 634

Tericon

Can someone please help me with this?

Question 1cii Jan 11

How do you get to the answer?

Reply 635

Jing_jing

Original post by *Rainbow*

Do you have any examples of this :s

Well say you had a question that went something along the lines of:

In London there are short haired mice and long haired mice. The allele for short haired mice H is dominant to the allele for long haired mice, h.

If the question went on to say: the allele frequency of long hair is 0.4 then you know that q=0.4.

However if it said something like, the frequency of long haired mice in the population is 0.4 then

q^2=0.4

. Because you're given the genotype frequency and not the allele frequency, you must square root it.

Reply 636

Jing_jing

Original post by Tericon

Can someone please help me with this?

Question 1cii Jan 11

How do you get to the answer?

Total population in 2007 is 107,000,000

Death rate is 5 per 1000 people. Divide the total population by 1000 and multiply by 5 to work out how many people died in 2007. ie. 535000

Birth rate is 20/1000. Divide total population by 1000 and multiply by 20 to work out how many births there were in 2007. ie. 2140000

Population of 2008 is: Total population in 2007 + total number of births in 2007 - total number of deaths.