This discussion is now closed.

Check out other Related discussions

AQA BIOL2~3rd June 2013~AS Biology (Now Closed)

Can someone explain to me if at prophase the number of chromosomes is 26 and the mass of the dna is 60 units, why at telophase the number of chromosomes is also 26 with a mass of 30 units? I thought at telophase 2 nuclei are formed so wouldnt it have twice the number of chromosomes? And even if it does have 26 chromosomes why is the mass of the Dna halved? Thanks.

The DNA replication happened during the s phase of interphase.

The mass of DNA halved because of cytokines.

At least, I think xD
Can someone confirm this?

Posted from TSR Mobile

Reply 981

Linked

6

Original post by x-Sophie-x

The DNA replication happened during the s phase of interphase.

The mass of DNA halved because of cytokines.

At least, I think xD
Can someone confirm this?

Posted from TSR Mobile

yes that is correct :smile:

Reply 982

propagation

14

Is there anyone here like me that is retaking and has literally done nothing because of other exams and are hoping that their previous knowledge and A2 exam techniques would be enough to get them through this exam??? :/

Reply 983

Jimmy20002012

4

Original post by ImAz

When classifying DNA- using the comparison of proteins.

I don't understand it.
You create one precipitate which is from the original proteins mixed with the antibodies formed.
And then you get another separate protein from a different species and see how much precipitate is formed.

So are you comparing the closeness of the two species of how close they're related to the rabbit?

Posted from TSR Mobile

I think is what you do is:

1. Inject serum/protein into one species, where there is an immune response as the body sees it as a no self, so antibodies are produced, you then obtain these antibodies from the species.

2. Now you add the serum/protein into another species where you will get antibodies produced, and one agin you obtain them.

3. You now mix the antibodies of the different species together and the amount of precipitate produced drew mines how closely related the two species tested are. :smile:

Posted from TSR Mobile

Reply 984

FutureMedic1009

2

140ums on June 09 wooo!

Posted from TSR Mobile

Reply 985

Paulineuh

Original post by Jay95

Trying to get my head around loading, unloading and partial pressure of oxygen, can someone please explain that heamoglobin chapter please?

thank u!

Posted from TSR Mobile

I'll try my best explaining!
But basically at high partial pressure of O2 (high concentration) haemoglobin loads O2: the 1st O2 is hard to obtain but once there, it can quickly load the other 3 O2. It has a high affinity for O2. This is normally the lungs in humans.

When the haemoglobin reaches the respiring issues, there's a low partial pressure of O2 and high concentrations of CO2. The Bohr effect occurs - the haemoglobin changes shape so that it can unload the O2 more easily (it has a low affinity for O2) due to the presence of CO2 which is acidic and its low pH is what causes the haemoglobin to change shape.

However when it reaches the lungs again, there is a low concentration of CO2 (so a higher pH) so it changes shape again to load O2 easily. And then it gets back to the tissues and the CO2 changes it shape again etc. :yes:

Hope that helped!

Posted from TSR Mobile

(edited 10 years ago)

Reply 986

123jess

Original post by homefind

No we don't

Posted from TSR Mobile

Thanks!

Reply 987

Secret.

14

Original post by JackTheNerd

Is a chromatid one half of the chromosome, but a sister chromatid is half a chromatid?

Noo! A chromatid is one half of a chromosome, a sister chromatid is the other half that is genetically identical

Reply 988

Secret.

14

Original post by Jimmy20002012

I think is what you do is:

1. Inject serum/protein into one species, where there is an immune response as the body sees it as a no self, so antibodies are produced, you then obtain these antibodies from the species.

2. Now you add the serum/protein into another species where you will get antibodies produced, and one agin you obtain them.

3. You now mix the antibodies of the different species together and the amount of precipitate produced drew mines how closely related the two species tested are. :smile:

Posted from TSR Mobile

No mixing antibodies won't give a precipitate, the precipitate comes from the antigen-antibody complex. I think your step 2 and 3 are wrong

Reply 989

dooobie_

What topics do people think will come up?

Reply 990

chickychock

This is my first post, so hope it ends up in the right place!
Can anyone help explain question 9d on unit 2 January 2010 aqa paper.
i know it's probably really easy,but I just can't get to the answer
9d. The scientists concluded that taxol......

Thanks

Reply 991

Secret.

14

Original post by chickychock

This is my first post, so hope it ends up in the right place!
Can anyone help explain question 9d on unit 2 January 2010 aqa paper.
i know it's probably really easy,but I just can't get to the answer
9d. The scientists concluded that taxol......

Thanks

They've calculated growth per unit time, unit of time being days.

For the control, the mass increased by 371 over 50 days = 371/50 = 7.42

the same can be done with the taxol group.

Percentage decrease: change/original

so (372-87)/372 x 100 = 76.6

Reply 992

chickychock

Original post by Secret.

They've calculated growth per unit time, unit of time being days.

For the control, the mass increased by 371 over 50 days = 371/50 = 7.42

the same can be done with the taxol group.

Percentage decrease: change/original

so (372-87)/372 x 100 = 76.6

Thanks so much - I can see it now!!!

Reply 993

neelam123h

does anyone have a list of all the 6 mark questions that can come up?

Also can someone please help me with the 6 mark question on the specimen paper on insects? Thanks :smile:

Reply 994

homefind

Original post by neelam123h

does anyone have a list of all the 6 mark questions that can come up?

Also can someone please help me with the 6 mark question on the specimen paper on insects? Thanks :smile:

Just describe the system in insects for gaseous exchange and in terms of preventing water loss talk about how they have a large SA:Vol ratio and therefore water loss is reduced, they have a waxy coating and spiracles can close to prevent water loss.

Reply 995

SophieL1996

2

can anyone help me with 1c and 3b? thanks http://filestore.aqa.org.uk/subjects/AQA-BIOL2-QP-JAN12.PDF

(edited 10 years ago)

Reply 996

Jimmy20002012

4

Original post by homefind

Just describe the system in insects for gaseous exchange and in terms of preventing water loss talk about how they have a large SA:Vol ratio and therefore water loss is reduced, they have a waxy coating and spiracles can close to prevent water loss.

Why does a large surface area:volume ratio reduce water loss?

Posted from TSR Mobile

Reply 997

elliewoodheadx

Original post by propagation

Is there anyone here like me that is retaking and has literally done nothing because of other exams and are hoping that their previous knowledge and A2 exam techniques would be enough to get them through this exam??? :/

Yup! Sounds like me..

Reply 998

homefind

Original post by SophieL1996

can anyone help me with 1c and 3b? thanks http://filestore.aqa.org.uk/subjects/AQA-BIOL2-QP-JAN12.PDF

1c) measure the length of the chloroplast then times that by 1000 to get it into um, then divide that by the magnification.

3b) 5, count how many different genus there are (which is the generic name i.e the genus for Synodontis batensoda is Synodontis

Reply 999

PeaceLovePink

11

Original post by SophieL1996

can anyone help me with 1c and 3b? thanks http://filestore.aqa.org.uk/subjects/AQA-BIOL2-QP-JAN12.PDF

you measure the chloroplast from one end to the other (the long way) in mm, which should give you 76mm. times that by 1000 to get it into um. and then divide 76000 by the magnification which is 30000 to get your answer which should be 2.53.

The equation for this is Image length= magnification x original/actual length or you can use a triangle with I (image length) on the top and M (magnification) and O (original/actual length) at the bottom

AQA BIOL2~3rd June 2013~AS Biology (Now Closed)

Related discussions

Latest

Trending

Trending

Articles for you