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

Reply 1960

Sorry I know this has been asked so many times but can someone link me to the 2013 paper and markscheme or tell me what page it's on PLEASE

This also please

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Reply 1961

Suzanna5678

Original post by Katy1704

The most recent paper? What did the markscheme say for the most recent paper?

Think it said the surface area and distance moved by air bubble. Kind of confused though cause I thought an air bubble was trying to be prevented?! But the markscheme says its needed to measure the water uptake ?!

Reply 1962

bad8oy

14

Original post by Suzanna5678

Sorry I know this has been asked so many times but can someone link me to the 2013 paper and markscheme or tell me what page it's on PLEASE

Found it page 22 23 or 24
Scienceisgood posted it look for it around there

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Reply 1963

Suzanna5678

Original post by bad8oy

Found it page 22 23 or 24
Scienceisgood posted it look for it around there

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Thank you !

Reply 1964

BarryIsMyName

Original post by Suzanna5678

Think it said the surface area and distance moved by air bubble. Kind of confused though cause I thought an air bubble was trying to be prevented?! But the markscheme says its needed to measure the water uptake ?!

The amount the bubble moves across the calibrated tube tells us how much water has been taken up the plant.

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Reply 1965

Suzanna5678

Does a tissue consist of different cells or similar cells?!

Reply 1966

alice.o123

when are chromosomes visible in the cell cycle?

Reply 1967

Simran Mars Foster

12

Thinking about it we made so many predictions for Unit 1 but hardly any of them came up! Gah.

Reply 1968

jemo9

Original post by Suzanna5678

Serum A is obtained from Species 1
its then put into Species 2 and serum B is obtained (from species 2)
Serum B is put into species 3. If similar it will produce antibodies to the antigens of species 1. The more precipitate the more closely related

I've read so many responses on immunology and only just understood it after reading this response, so, thank you!

Reply 1969

homefind

Original post by alice.o123

when are chromosomes visible in the cell cycle?

After interphase, the chromosome condense to become shorter and fatter in prophase

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Reply 1970

jemo9

Original post by alice.o123

when are chromosomes visible in the cell cycle?

Chromosome condense and become visible in Prophase

Reply 1971

eilish1903

17

Original post by alice.o123

when are chromosomes visible in the cell cycle?

They aren't visable in interphase.
They condense and become visable in prophase, when the nuclear envelope and nucleus disintegrate.
They are also visable in metaphase through to teleophase.
In Telophase they uncondense and the nuclear envelope/nucleus is reformed and the chromosomes become invisable again as daughter cells are produced
(They can be seen in nuclear division but less in cell division)

Let me know if that help!! :biggrin:

Reply 1972

Locutus73

2

Can someone please tell me what page the long post with the long questions and answers is on please? Thank you!

Reply 1973

Suzanna5678

Original post by Simran Mars Foster

Thinking about it we made so many predictions for Unit 1 but hardly any of them came up! Gah.

That's true ! Everyone seems to think the paper will be dominated with plant stuff but a lot of the jan 13 paper has plant stuff sooo

Reply 1974

ImAz

6

Original post by alice.o123

when are chromosomes visible in the cell cycle?

Prophase- the DNA in the nucleus condenses into chromosomes so the can move apart without being tangled

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Reply 1975

jemo9

Original post by Suzanna5678

What are people doing for revision today? Is everyone just looking over notes ?

Doing past papers, marking them, then looking at the examiner's report which I find to be very helpful and recommend it if you haven't already :smile:

Reply 1976

Suzanna5678

I never seem to know whether to talk about horizontal or vertical gene transmission? For example looking at jan 2013 and the question says.... Using isoniazid to treat diseases caused by other species of bacteria could increase the chance of the bacterium that causes tuberculosis becoming resistant to isoniazid. Use your knowledge of gene transmission to explain how.

Reply 1977

alice.o123

Original post by eilish1903

They aren't visable in interphase.
They condense and become visable in prophase, when the nuclear envelope and nucleus disintegrate.
They are also visable in metaphase through to teleophase.
In Telophase they uncondense and the nuclear envelope/nucleus is reformed and the chromosomes become invisable again as daughter cells are produced
(They can be seen in nuclear division but less in cell division)

Let me know if that help!! :biggrin:

ahhh thank you that did help :biggrin:

also when so the sister chromatids get pulled apart, is it in anaphase?

Reply 1978

JackTheNerd

7

Original post by homefind

Okay if you understand mitosis then just think about it being the whole cycle of mitosis however with two divisions

interphase - DNA is unravelled and replicates itself so there are two copies of chromatids

PROPHASE I - DNA condenses into double armed chromosomes made from two sister chromatids. (You also have nuclear envelope breaking down and centrioles move to opposite poles and produce spindle fibres) CROSSING OVER OCCURS HERE

METOPHASE I - Chromosomes arrange themselves into HOMOLOGOUS PAIRS (similar sized chromosomes, however one may have a gene for blue eyes and the other may have a dominant allele for brown eyes) they line up at the equator and are joined to the spindle fibres by their centromere. INDEPENDENT SEGREGATION OCCURS HERE

ANAPHASE I - Spindle fibres contract and pull each chromosome from the homologous pair to opposite poles of the cell (NOTE- THEY ARE STILL 'X' SHAPED, I.e each double armed chromosomes with two sister chromatids are pulled to opposite poles)

TELOPHASE I - nuclear envelope develops and cytoplasm divides, there are now TWO NUCLEI with two pairs of sister chromatids in each

PROPHASE II - this step isn't significant they just condense.

METOPHASE II - PAIRS OF SISTER CHROMATIDS LINE UP AT THE EQUATOR ATTACHED TO SPINDLE FIBRES BY CENTROMERE ETC...

ANAPHASE II - the pairs of chromatids that make up each chromosome are separated (contraction of spindle fibres)

TELOPHASE II - FOUR HAPLOID CELLS THAT ARE GENETICALLY DIFFERENT FROM EACH OTHER ARE PRODUCED (nuclear envelope forms and cytoplasm divides)

THERE ISN'T A INTERPHASE II!!!

At the start of mitosis is there enough DNA replicated to have twice as many chromosones as there usually is, so it can produce identical cells?