AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011

Reply 1700

NRican

Original post by Cyanohydrin

wouldn't it actually be AGC ?

No, its from the 2nd tube with C terminator nucl. so it stops at C. Original was TGG... so AC

Reply 1701

Flux_Pav

guys
in DNA fingerprinting, different probes are needed to bind to different core repetitive sequences in the DNA.
does this mean that DNA sequencing is needed prior to this to find the base sequence of the core repeated sequences?

Reply 1702

username554371

I have got from now to 9am tomorrow to learn everything on the spec again (I just had all my other exams!). This isn't going to go well, but I'm going to work through the CGP book with the Nelson Thornes one & my class notes to check & pad it out. I can catch up on my sleep over the holiday...

Reply 1703

Tericon

8

Original post by Flux_Pav

guys
in DNA fingerprinting, different probes are needed to bind to different core repetitive sequences in the DNA.
does this mean that DNA sequencing is needed prior to this to find the base sequence of the core repeated sequences?

Yes, to make probes, you need to sequence the target gene, to find out what bases the probe needs to have to contain to be complementary and so bind.

Reply 1704

Ramin Gorji

1

Original post by Flux_Pav

guys
in DNA fingerprinting, different probes are needed to bind to different core repetitive sequences in the DNA.
does this mean that DNA sequencing is needed prior to this to find the base sequence of the core repeated sequences?

Yes that is true. You need to use a primer that is complementary to the base of the dna and you can only find out by sequencing before hand.

Reply 1705

Sparkly-Star

OP

13

I'm so confused!! What's the difference between insulin and glucagon? :frown:

Reply 1706

Cyanohydrin

13

Original post by NRican

No, its from the 2nd tube with C terminator nucl. so it stops at C. Original was TGG... so AC

ah of course..!

Reply 1707

claire4095

Little bit off subject, sorry :/
but have i got a gender sign next to my name? if not how do i get one?
xx

Reply 1708

Cyanohydrin

13

Original post by Sparkly-Star

I'm so confused!! What's the difference between insulin and glucagon? :frown:

Insulin = released by beta cells and lowers glucose levels

Glucagon = released by alpha cells and works increase glucose levels

Reply 1709

User12399

5

Original post by Sparkly-Star

I'm so confused!! What's the difference between insulin and glucagon? :frown:

insulin converts glucose to glycogen, glycagon converts glycogen to glucose. Insulin decreases glucoce conc, where as glucagon increases it.

Reply 1710

Cyanohydrin

13

Original post by Tericon

Yes, to make probes, you need to sequence the target gene, to find out what bases the probe needs to have to contain to be complementary and so bind.

How would sequencing actually tell you that?

Reply 1711

Tericon

8

Original post by Sparkly-Star

I'm so confused!! What's the difference between insulin and glucagon? :frown:

Both secreted by the Islets of Langerhans in the pancreas, both hormones.

Insulin secreted by beta cells in Islets, Glucagon by alpha cells in Islets.

Insulin is secreted when blood glucose concentration is too high.

Functions:

Activates enzymes for glycogenesis = converts glucose into glycogen.

Increases rate of respiration of glucose in cells

Makes cells more permeable to glucose.

Glucagon, secreted when blood glucose concentration is too low

Functions:

Activates enzymes for glycolysis = conversion of glycogen into glucose

Decreases rate of respiration of glucose

Stimulates gluconeogenesis = production of glucose from non-carbohydrates, such as amino acids for example.

Reply 1712

aj2010

I REALLY don't unterstand sanger method and restriction mapping. can someone explain pleasseeeee; :smile:

and also what's the difference between adenovirus and retrovirus

Reply 1713

appleschnapps

Original post by *QueenBeee

can someone please please help me on:
stem cells!
majorrrrrrrrrr rep!

Stem cells aw yeah.

They are unspecialised (which means you can bring them into an essay on specialised cells for contrast), they are constantly replacing themselves, and embryonic stem cells are totipotent. (This means they can mature into any type of body cell.) Adult stem cells, which are found in bone marrow, are multipotent - this means they can only mature into a few types of cells, and thus narrows their usage.

How they become specialised: certain genes are expressed, others are switched off, which means when transcription occurs only the mRNA from the expressed genes is transcribed, so only those selected proteins are produced - these proteins determine the cell's structure and its processes which make it suited for its function.

In plants, totipotent stem cells can be taken from the root or the shoot (hurray rhyming!), and will produce a genetically identical plant if the stem cell is placed in growth medium that contains growth factors and necessary nutrients, and kept in the right conditions (e.g. not too hot).

Stem cells can treat disease as they can be used to replace diseased or damaged cells, and has already been used to treat lymphoma and leukaemia. However, this is an application-y area as you need to consider the ethical viewpoints surrounding stem cell treatment.

+ Can save lives.
+ Improve quality of life.
+ embryos produced for IVF would otherwise be destroyed.
- Does an embryo have a right to life?
- Shouldn't use humans as a means to an end.
- Respect for human life - will human cloning etc. follow if we allow stem cell research?

Adult stem cells don't get as much criticism, but can't develop into as many types of cell as embryonic.

Reply 1714

oloyeded020

do we need to know about water potential control with ADH etc

anyone?

Reply 1715

Carpet21

12

The book doesn't really tell us much about troponin does it?

Reply 1716

Tericon

8

Original post by Cyanohydrin

How would sequencing actually tell you that?

You need to sequence the target gene that you want to make probes for.

Sequencing allows you to work out the base sequence of a piece of DNA via the chain termination method, (CTM) (addition of modified labelled nucleotides).

Synopsis of CTM

Single stranded DNA template, DNA polymerase, DNA primers, free nucleotides and fluorescently labelled modifed nucleotides are added to each of four tubes.

When a modified nucleotide is added to a DNA strand, it halts the addition of any more bases, and so 'terminates' the hybirdisation.

Tubes undergo PCR, produces many strands of different length, (each terminates at different point, depending on where modified nucleotide added).

DNA fragments in each tube undergo electrophoresis are are visualised under UV (modified nucleotdies fluroescently labelled).

Complementary base sequence can be read from the gel, smallest nucleotide (one base) at bottom of gel, each band after this represents on more base added, by reading bands from bottom of the gel to the top, you can determine the DNA base sequence.

Once you have the sequence of your target gene, you can then know the base sequence required for a complementary probe.

So if base sequence is: ATGTTCG

and you want a probe of four nucleotides long, it would be: TACA, as T is complementary to A (first nucelotide in DNA sequence).

Hope that helped :biggrin:

Reply 1717

.Hayley.

Original post by beckydanks

Helloooooo

I've got a list of past essay questions, and I'm making plans for each of them, then trying to remember the information i write down. Hopefully you can make what you know fit the title. you need to include info from 3 kingdoms, e.g. humans plants bacteria fungi etc. or from 3 different units e.g. unit 4 unit 5 unit 1. to get full breadth marks and I read that its important to be specifically biological in everything you say. For example if you got a question about hormones and you wanted to write about insulin production. rather than saying: 'insulin is released into the blood to remove glucose', you would say: 'insulin is released from the Beta cells of the islets of langerhans in the pancreas, where it is released into the blood to reduce glucose by...etcetcetc.' just adding contant detail where it's not really relavant shows you know alot of biology and thats all they want about synopicity really.

hope thats helpful!

Yeah thats great thanks :smile:

where did you find the past essay questions? :smile:

Reply 1718

Stratos

15

Original post by appleschnapps

Stem cells aw yeah.

They are unspecialised (which means you can bring them into an essay on specialised cells for contrast), they are constantly replacing themselves, and embryonic stem cells are totipotent. (This means they can mature into any type of body cell.) Adult stem cells, which are found in bone marrow, are multipotent - this means they can only mature into a few types of cells, and thus narrows their usage.

How they become specialised: certain genes are expressed, others are switched off, which means when transcription occurs only the mRNA from the expressed genes is transcribed, so only those selected proteins are produced - these proteins determine the cell's structure and its processes which make it suited for its function.

In plants, totipotent stem cells can be taken from the root or the shoot (hurray rhyming!), and will produce a genetically identical plant if the stem cell is placed in growth medium that contains growth factors and necessary nutrients, and kept in the right conditions (e.g. not too hot).

Stem cells can treat disease as they can be used to replace diseased or damaged cells, and has already been used to treat lymphoma and leukaemia. However, this is an application-y area as you need to consider the ethical viewpoints surrounding stem cell treatment.

+ Can save lives.
+ Improve quality of life.
+ embryos produced for IVF would otherwise be destroyed.
- Does an embryo have a right to life?
- Shouldn't use humans as a means to an end.
- Respect for human life - will human cloning etc. follow if we allow stem cell research?

Adult stem cells don't get as much criticism, but can't develop into as many types of cell as embryonic.

Nice summary of stem cells considering my teacher didn't cover that at all and with my GCSE knowledge it doesn't seem to be changed much.

Anyway what could they ask about in the synoptic question?

I'm prepared for things to do with neurones, proteins, water and co2