Year 12s: what will be the first way you research your future options? >>

BIOL4 Biology Unit 4 Exam - 13th June 2011

Scroll to see replies

Does anyone know how to prove an allele is not on the x chromosome? This is in reference to the Jan 2011 paper :\

2 is Rhesus negative, and since the allele for Rhesus negative is r, then 2 must be homozygous recessive. This means that 3 (who is Rhesus positive) will not get the Rhesus positive allele from his mother (2). 1 (the father) is Rhesus positive, so he must have the R allele, which he passes to his son (3). Since the son gets the Rhesus positive allele from his father, it cannot be on the X chromosome, as sons will only ever get the Y chromosome from their father. So it cannot be on the X chromosome if the father gives it to him. Therefore Rhesus is not a sex-linked disease.

Reply 601

xbabycakes

Original post by Abby :)

What are all your revision plans for tonight? You going to stay up late tonight to revise...? or Wake up early tomorrow to get a few hours of revision in? Im interested to see what others do. xD

I'm going to go to bed early, wake up early, do a 3 hour philosophy exam and then spend around 30 minutes panicking like f***! I think you can safetly say, I'm screwed.

Reply 602

xbabycakes

Original post by 04bellot

Does anyone know how to prove an allele is not on the x chromosome? This is in reference to the Jan 2011 paper :\

Alternatively you could look at 3 and 4's daughters. If it was on the X chromosome, you'd expect all girls to be positive, as they could only get the X from the positive father (and because it's dominant they'll be affected ectect). But number 9 isn't, she's rhesus negative, so therefore not carried on the X chromosome.

Reply 603

Rickesh

Advantages & Disadvantages of biological control

Reply 604

tehsponge

I'm confused as to what overlapping standard deviations tell you?

Reply 605

hanaleechan123

Original post by Stratos

1. Identify the pests and their population density at which they cause economic harm – the economic
threshold. Only take action against the pest if its population is above the threshold.
2. Use suitable cultural methods to prevent pests reaching their threshold.
3. If the pest population starts to exceed threshold the use biological control to bring it down.
4. If biological control doesn’t work then use chemical pesticides, but at low and carefully controlled dose,
and at the best time of year to minimise damage to other organisms while maximising effect on pest.
5. At each stage the effect of that treatment is evaluated before deciding to proceed to the next stage.

Thank you!

Reply 606

tehsponge

Original post by Rickesh

Advantages & Disadvantages of biological control

Advantages:
Specific to the pest
Does not bioaccumulate like chemical pesticides
Pest cannot become resistant
Doesn't need to be reapplied

Disadvantages:
Species used can sometimes become a pest itself
They do not act as quickly

Reply 607

Lozzah8

Original post by tehsponge

I'm confused as to what overlapping standard deviations tell you?

That the data is not reliable, thats as far as I've ever been taught regarding that :/

Reply 608

xbabycakes

Original post by tehsponge

I'm confused as to what overlapping standard deviations tell you?

That the data isn't statistically significant, because if your values fell in the extremes of both the ranges then they could technically be the same, making the data unreliable.

It'd be probably more helpful if I knew what the data was in relation to. Sorry if this doesn't help!

Reply 609

Rickesh

Can someone ask me a question lol?

Reply 610

tehsponge

Original post by xbabycakes

And if P<0.05 that means the data is statistically significant, and there is a high probability the results aren't due to chance, so the null hypothesis can be rejected, right?

Reply 611

Stratos

Original post by Rickesh

Can someone ask me a question lol?

Why did the human population start to rapidly increase from the 18th century?

Reply 612

Rickesh

Original post by Stratos

Why did the human population start to rapidly increase from the 18th century?

More food available, better medical care, higher birth rate than death rate?

Reply 613

tehsponge

Original post by Stratos

Why did the human population start to rapidly increase from the 18th century?

Industrial revolution and improved agricultural technologies and techniques.

Reply 614

04bellot

Original post by Abby :)

I was also having trouble with this...

I think its to do with that males can only get there Y chromosome from the father... and they HAVE to get the X chromosome from the mother. If the mother has the disease and is homozygous then the child would HAVE to have it... but in the question in Jan '11 the child dosnt... showing it isnt on the x chromosome.

Hope that makes sense... Thats what the mark scheme said anyways.

Yeah its very confusing but hopefully since it was in the jan paper, it wont be in tommorows :smile:

Reply 615

xbabycakes

Original post by tehsponge

And if P<0.05 that means the data is statistically significant, and there is a high probability the results aren't due to chance, so the null hypothesis can be rejected, right?

not just a high probability, but a 95% probability that the results are not due to chance :smile:

but yes.

Reply 616

usmana

what can be the synoptic element from units 1 and 2

Reply 617

04bellot

Original post by Rickesh

What does the Jan 11 paper say? I dont remmeber seeing that question lol ?

It was question 2....

Reply 618

Stratos

Original post by usmana

what can be the synoptic element from units 1 and 2

Having done the two as retakes I'm almost sure it will be something to do with respiration and the lung, and from unit two probably something to do with meiosis and genetics.

Reply 619

tehsponge

Original post by Stratos

Having done the two as retakes I'm almost sure it will be something to do with respiration and the lung, and from unit two probably something to do with meiosis and genetics.