AQA AS Biology Unit 2 - 1 June 2015

Hi could someone please help me with this question.
Last two questions. I don't understand how many combinations of gametes you could make. Answer is 8 btw.
But I don't understand why.
Also drawing the gamete how do you know that they'll be three of them.

Please could someone explain the thought process. Thanks

Reply 181

kandykissesxox

21

Original post by Kadak

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Alright.One of the reasons the science papers were harder this year was because we're memorising the mark schemes and getting good grades.

but isn't memorising the MS a good idea?

Reply 182

ozzie2

12

Original post by Kadak

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Alright.One of the reasons the science papers were harder this year was because we're memorising the mark schemes and getting good grades.

I don't memorise the mark schemes anyway, and I dunno where you got that from based on me simply saying mark schemes will allow asexual reproduction. I guess it could be implied by what I said, but very loosely.

Reply 183

Serine Soul

18

Original post by Amara123

Hi could someone please help me with this question.
Last two questions. I don't understand how many combinations of gametes you could make. Answer is 8 btw.
But I don't understand why.
Also drawing the gamete how do you know that they'll be three of them.

Please could someone explain the thought process. Thanks

Okay, so the general principle of meiosis is that it produces four genetically unique haploid cells.

The cell in question is a diploid cell as it contains two sets of chromosomes for each shape (1 is maternal, 1 is paternal).
Meiosis produces haploid cells as gametes, so half the number of chromsomes in the diploid cell. This means that the gamete will have three chromosomes, 1 of each shape :smile:

To find the number of combinations of gametes, the general formula is 2^n, where 'n' is the number of the different types of chromosomes in the diploid cell.
So for instance, in this diploid cell, there are three types of chromosomes, therefore
2^3 = 8

Hope this helps :smile:

Reply 184

username1533709

5

Original post by ozzie2

I don't memorise the mark schemes anyway, and I dunno where you got that from based on me simply saying mark schemes will allow asexual reproduction. I guess it could be implied by what I said, but very loosely.

Posted from TSR Mobile

I meant it in general, it wasn't aimed at you.

define heamoglobin

Original post by cilla_e

define heamoglobin

its a protein that has a quaternary structure, found in red blood cells and carries oxygen to where its needed in the body.

Reply 187

Amara123

Original post by enaayrah

Okay, so the general principle of meiosis is that it produces four genetically unique haploid cells

The cell in question is a diploid cell as it contains two sets of chromosomes for each shape (1 is maternal, 1 is paternal).
Meiosis produces haploid cells as gametes, so half the number of chromsomes in the diploid cell. This means that the gamete will have three chromosomes, 1 of each shape

To find the number of combinations of gametes, the general formula is 2^n, where 'n' is the number of the different types of chromosomes in the diploid cell.
So for instance, in this diploid cell, there are three types of chromosomes, therefore
2^3 = 8

Hope this helps :smile:

Yes it did thank you so much. That was pretty simple. Feel kinda stupid now. Thanks again.

Reply 188

cilla_e

3

define what is meant by partial pressure of oxygen

Reply 189

username1426305

2

Original post by cilla_e

define what is meant by partial pressure of oxygen

the concentration of oxygen in an area i.e in the lungs, there is high partial pressure because you're breathing in air saturated with oxygen.

Reply 190

username1533709

5

Posted from TSR Mobile
Six marker on tissue fluid? How would I describe it and the process?

Reply 191

Serine Soul

18

Original post by Amara123

Yes it did thank you so much. That was pretty simple. Feel kinda stupid now. Thanks again.

Don't be harsh on yourself, I make awful mistakes too :tongue:

I'm glad I could be of help

Reply 192

username1426305

2

Original post by Kadak

Posted from TSR Mobile
Six marker on tissue fluid? How would I describe it and the process?

At the arteriole end you have high hydrostatic pressure, which forces the fluid out through the fenestrations of the capillary, you're left with larger proteins in the capillary because they can't get passed the fenestrations, as you go along the capillary the hydrostatic pressure decreases, the pressure inside falls because of friction and loss of fluid, so because theres high hydrostatic pressure outside than inside, water returns, also it returns because of the plasma proteins, which lower the water potential causing water to re-enter via osmosis, any excess fluid is dumped back using lymph vessels.

Reply 193

elkie

What are the key points of the structure of the Xylem? :smile:

Reply 194

kandykissesxox

21

Guys help, should i go onto past papers now like have I left it too late? Is there any point of going over content like will the past papers cover it all

Reply 195

username1533709

5

Original post by kandykissesxox

Guys help, should i go onto past papers now like have I left it too late? Is there any point of going over content like will the past papers cover it all