AQA BIOL2 Biology Unit 2 Exam - 26th May 2011

Reply 380

ChessMister

12

Original post by V.I.P

Can somebody please explain the answer to question 3d) in the Jan 2010 paper.

can somebody link the paper?

Reply 381

Reminisce

11

Original post by V.I.P

Can somebody please explain the answer to question 3d) in the Jan 2010 paper.

Just look at the pattern of the base sequence and see how many are repeated and how many times. For example, after the first Gln which is GTT, we have two TAC and no more after so we then look at the list of amino acids and there are two Met present so TAC codes for Met, etc. etc. etc.

Reply 382

V.I.P

Original post by Reminisce

Just look at the pattern of the base sequence and see how many are repeated and how many times. For example, after the first Gln which is GTT, we have two TAC and no more after so we then look at the list of amino acids and there are two Met present so TAC codes for Met, etc. etc. etc.

Oh I get it thanks! :biggrin:

+ve rep.

Also why i the last one Asn and not Gln?

Reply 383

jessplease

When DNA replicates in Interphase do the chromosomes replicate as well? I don't understand june 09 4a?

Reply 384

Introverted moron

2

Original post by therapist_1

Probably just stick to what I have said about viruses, and RBC = Red Blood Cells.

Could you please tell me where have you found this question on antibiotics. :eek:

It was on a test that we did in class last year. The exact question was:

3a) Antibiotics are used to treat bacterial infections but have no effect on viruses.

ii) Suggest an explanation why antibiotics may sometimes usefully be given to patients suffering from a viral disease.

b) Many antibiotics are produced by bacteria or fungi. Suggest an advantage to these organisms of producing antibiotics.

I don't get this one either. Why do bacteria produce substances that could kill them? :confused:

Reply 385

TlanTlan

6

DNA replicates forming two chromatids, and during prophase these condense to form double armed chromosones, which consist of 2 identical chromatids joined by a centromere.

Reply 386

Jay_Kay_72

I prefer biology unit 1, I thought it was far more interesting. I enjoyed learning how the diseases affected the body and how the molecules are built up. In Bio 2 though, I find some bits really interesting, like dna replication and genetic diversity but I can't stand the plant section.

Reply 387

should be revising

This is going to sound stupid because it's something I should obviously know, but I still dont fully understand the relationship between cells, chromosomes, chromatids, genes, DNA etc...

I was told a good analogy a few years ago but I can't remember it too well. It was something like:

Imagine the cell as a library, the chromosomes are the shelfs, the genes are the books, the dna are the words etc...

Is that right??

Reply 388

RG1994

Original post by should be revising

This is going to sound stupid because it's something I should obviously know, but I still dont fully understand the relationship between cells, chromosomes, chromatids, genes, DNA etc...

I was told a good analogy a few years ago but I can't remember it too well. It was something like:

Imagine the cell as a library, the chromosomes are the shelfs, the genes are the books, the dna are the words etc...

Is that right??

no genes are sections of dna that code for sequence of amino acids so dna would be the book and gene the words

Reply 389

ChessMister

12

A gene is a section of DNA that codes for a single polypeptide

Reply 390

therapist_1

Original post by Introverted moron

It was on a test that we did in class last year. The exact question was:

3a) Antibiotics are used to treat bacterial infections but have no effect on viruses.

ii) Suggest an explanation why antibiotics may sometimes usefully be given to patients suffering from a viral disease.

b) Many antibiotics are produced by bacteria or fungi. Suggest an advantage to these organisms of producing antibiotics.

I don't get this one either. Why do bacteria produce substances that could kill them? :confused:

This is blowing my mind. :frown:

just 4gt it, it just should not come in the paper...

Reply 391

??????????????????

8

Original post by Introverted moron

It was on a test that we did in class last year. The exact question was:

3a) Antibiotics are used to treat bacterial infections but have no effect on viruses.

ii) Suggest an explanation why antibiotics may sometimes usefully be given to patients suffering from a viral disease.

b) Many antibiotics are produced by bacteria or fungi. Suggest an advantage to these organisms of producing antibiotics.

I don't get this one either. Why do bacteria produce substances that could kill them? :confused:

Original post by therapist_1

This is blowing my mind. :frown:

just 4gt it, it just should not come in the paper...

ai) I think antibodies inhibit the enzyme that makes the cell wall so it becomes weaker so it bursts from osmotic lysis. Viruses are strands of DNA so antibiotics won't work as it has no wall.
aii)The virus may infect a cell so the infected cell must be destroyed to erradicate the virus?
b)They reproduce rapidly to higher yield?

The bacteria don't produce substance that could kill them. Scientists genetically engineer them by putting the strand that codes for it in the plasmid. When it replicates, the daughter cells contain the gene to code for it too.

(edited 12 years ago)

Reply 392

lolo-x

Ribonuclease is an enzyme. It is 127 amino acids long. What is the minimum number of DNA bases needed to code for ribonuclease?

I multiplied 127 by 3 to get 381 but the mark scheme says that the answer can be 381, 384 or 387. Why?

Reply 393

SittingOnCornflakes

Original post by Introverted moron

It was on a test that we did in class last year. The exact question was:

3a) Antibiotics are used to treat bacterial infections but have no effect on viruses.

ii) Suggest an explanation why antibiotics may sometimes usefully be given to patients suffering from a viral disease.

b) Many antibiotics are produced by bacteria or fungi. Suggest an advantage to these organisms of producing antibiotics.

I don't get this one either. Why do bacteria produce substances that could kill them? :confused:

Hmmm, in regards to 3a) ii), on page 224 of the Nelson Thornes textbook it says:

"Antibiotics are sometimes used to treat viral diseases because although they are ineffective against viruses, they may help to prevent the development of secondary bacterial infections to which patients may be vulnerable."

I hope that's all they want you to say otherwise I have no idea. :biggrin:

Reply 394

therapist_1

Original post by SittingOnCornflakes

Hmmm, in regards to 3a) ii), on page 224 of the Nelson Thornes textbook it says:

"Antibiotics are sometimes used to treat viral diseases because although they are ineffective against viruses, they may help to prevent the development of secondary bacterial infections to which patients may be vulnerable."

I hope that's all they want you to say otherwise I have no idea. :biggrin:

That should be it :biggrin:

thanks

Reply 395

xkate1019x

Dreading this exam :frown:

Reply 396

Patchey1000

2

Original post by lolo-x

Ribonuclease is an enzyme. It is 127 amino acids long. What is the minimum number of DNA bases needed to code for ribonuclease?

I multiplied 127 by 3 to get 381 but the mark scheme says that the answer can be 381, 384 or 387. Why?

start and a stop code

Reply 397

TlanTlan

6

Original post by lolo-x

Ribonuclease is an enzyme. It is 127 amino acids long. What is the minimum number of DNA bases needed to code for ribonuclease?

I multiplied 127 by 3 to get 381 but the mark scheme says that the answer can be 381, 384 or 387. Why?

Inclusion of start and stop codons in the DNA base sequence. As a gene is [Start Codon][Gene][Stop Codon]

Reply 398

spoinkytheduck

12

Silly question (I know) but I need to be sure...

We dont have to learn what MRSA stands for do we?
Just the example of the whole antibacterial resistance thingy, right?