AQA BIOL2 Biology Unit 2 Exam - 26th May 2011

By cell differentiation, so only certain genes are switched "on". Not sure how much detail we need to know about that?

A tissue is a group of similar cells working together to perform a specific function.
An organ is a combination of tissues co-ordinated to perform a variety of functions however they often have one predominant function

Explain how gas is exchanged in insects.

Thanks, how has it doubled btw? Just after DNA Replication?

But the only issue is that the slight difference in the polypeptide chain could for instance cause a change in shape of an enzymes active site, which would mean the substrate of complementary shape can no longer bind and therefore the enzyme would be disfunctional..

the actualy dna doubles at the interphase along with protein synthesis, not prophase, prophase is where the chromosomes widen and the nuclear envelope disappears , i think.

During S phase of interphase, when the DNA replicates (doubles)

But the only issue is that the slight difference in the polypeptide chain could for instance cause a change in shape of an enzymes active site, which would mean the substrate of complementary shape can no longer bind and therefore the enzyme would be disfunctional..

-Air enters through spiracles
-Diffuses down a concentration gradient down trachea and then tracheoles
-Many tracheoles, large surface area
-Respiration maintains conc. gradient
-Tracheles carry air close to every cell in the insect - short diffusion pathway

Name the blood vessels entering and leaving the liver and kidneys.

Wow, I've never seen a question like that, we need to know specific names of vessels?

Thank's so much, so whenever it's referring to mass of DNA think about replication?

I'm assuming mass of DNA halves in Telophase because of the cell splitting into two

yh that is true, but then how would you suggest alleles are part of the same gene because alleles have slightly different polypeptide chains, yet they are part of the same gene, this must mean that the change that creates the allele will give that allele abiltiy to product a different colour yet it would still be the same gene

overall would it be easier to say the defintion of a gene is that it codes for a particular charcetristic to prevent confusion?

The spec says "Names are required only of the cronary arteries and of blood vessels entering and leaving the heart, liver and kidneys."

It was the first Q on one of the previous papers?

Liver - Hepatic Vein/Artery and Hepatic Portal Vein

Kidneys - Renal Vein / Artery

Yes that is correct, for example the gene that codes for you eye colour, an allele of this gene that codes for you eye colour will give another colour. So in essence the coded information is very much similar however a gene that codes for brown eyes may have an allele that codes for blue eyes.

The simplest definition for a gene and allele I would learn is that, a gene is a section of DNA that contains the coded information for making polypeptides. And for allele, an allele is an alternative form of a gene.

Hope that helps

Oh wow, must have missed that one, i'll be sure to remember them for tomorrow

Can anyone summarise all they know about oxygen dissociation curves. It covers like 1 page in my textbook but there have been Qs on it every exam paper

Explain how bacteria may become resistant to more than 1 antibiotic.

The resistance gene may be passed along from one species of bacteria to another species via horizontal gene transmission. The plasmid may also be passed down from one generation to the next via vertical gene transmission.

Explain ways in which variation may occur as a result of meiosis?

What do people think the 6 mark question will be on?