As biology unit 1 21/5/2014 panic thread

Reply 100

Lorri97

guys whats the new pad link ?

Reply 101

ybadri

3

please could someone explain to me how dna replication occurs?

Reply 102

Alnassenigzig

OP

Original post by ybadri

please could someone explain to me how dna replication occurs?

Semiconservative replication:
-involved in making more DNA
-when DNA replicates, the two strands unwind and hydrogen bonds between bases using an enzyme called DNA helicase.
-the strands act as a template for the new DNA strands.
-exposed bases attract free DNA nucleotides and new hydrogen bonds form
-The strands join to form DNA using enzymes DNA ligase and DNA polymerase
-Each new DNA molecules contains one new strand and one original strand
-New DNA is identical to the original DNA

Reply 103

trialbyc0mbat

if 30% of the DNA in a cell consists of guanine, why does it contain 20% adenine?

Reply 104

Fattyma97

2

Original post by trialbyc0mbat

if 30% of the DNA in a cell consists of guanine, why does it contain 20% adenine?

Since guanine and cytosine pair up together as bases, we know that the percentage of cytosine is equal to that of guanine. Therefore that makes it 30+30=60. We know that adenine pairs with thymine, therefore they must contain same amount. So subtract 60 from 100 and you get 40 then divide by 2 and you will get 20%.

Hope you understood :smile:

Posted from TSR Mobile

Reply 105

aliali8

Original post by trialbyc0mbat

if 30% of the DNA in a cell consists of guanine, why does it contain 20% adenine?

Because there will be 30% cytosine. This means there will be 40% left so you do 40%/2 = 20%

Reply 106

mr osaka

4

Original post by trialbyc0mbat

if 30% of the DNA in a cell consists of guanine, why does it contain 20% adenine?

this is because of chargaff's rule.
chargaff's rule states that A=T and C=G

so if guanine is 30%, then cytosine is 30%

adenine and guanine r from the same family,, so they make up 50% (as there r 4 bases in total, so 2/4 =50%)

50%-30% = 20% of adenine

hope that makes sense :smile:

Reply 107

trialbyc0mbat

wow 3 fast replies. got it now. thanks! :smile:

Reply 108

The Assassin

18

http://www.mediafire.com/download/mrrgmqgkhbqidi5/WBI01_01_que_20140108.pdf

If anyone wants the Jan 2014 IAL paper (not sure if posted)

Reply 109

Vanners

http://www.scribd.com/doc/54621588/Edexcel-Biology-AS-Revision-Notes here's a pretty good summary for Unit 1. Goodluck everyone ^_^

Reply 110

Fattyma97

2

Has anyone finished studying and solving papers, I've only begun solving now :s-smilie:

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Reply 111

trialbyc0mbat

Original post by mr osaka

this is because of chargaff's rule.
chargaff's rule states that A=T and C=G

so if guanine is 30%, then cytosine is 30%

adenine and guanine r from the same family,, so they make up 50% (as there r 4 bases in total, so 2/4 =50%)

50%-30% = 20% of adenine

hope that makes sense :smile:

actually what do you mean by adenine and guanine are from the same family? A=T and C=G are base pairs right?
so what is the relationship between AG and CT?

Reply 112

Alnassenigzig

OP

Original post by trialbyc0mbat

actually what do you mean by adenine and guanine are from the same family? A=T and C=G are base pairs right?
so what is the relationship between AG and CT?

there isn't a direct relationship between A and G as far as i know ._. dont worry man its not in our specification.All we need to know is that A=T and C=G and U replaces T in RNA ....as far as percentages are concerned ,its all simply reasoning like the others mentioned above

Edit:corrected my silly mistake after a few aggressive members of TSR tore my noble-good hearted post apart

(edited 9 years ago)

Reply 113

crazzysashgirl

Original post by trialbyc0mbat

actually what do you mean by adenine and guanine are from the same family? A=T and C=G are base pairs right?
so what is the relationship between AG and CT?

there are 2 types of nitrgenous bases,,
1. Purine - 2 ring molecule
2.adenine - 1 ring molecule

Adenine and Guanine are purine bases
Cytosine, thymine and uracil are pyramidine bases

Reply 114

ybadri

3

guys for anyone who sat for C12 paper on 19th may ial n would want to discuss follow this link:http://www.thestudentroom.co.uk/showthread.php?t=2686829

Reply 115

Katiekatie1

Hey guys, what is DNA polymerase used for? Is it the same as DNA helicase?

Reply 116

Husain J.

Original post by Alnassenigzig

there isn't a direct relationship between A and G as far as i know ._. dont worry man its not in our specification.All we need to know is that A=T and C=G and U replaces G in RNA ....as far as percentages are concerned ,its all simply reasoning like the others mentioned above

Uracil replaces Thymine mate, not Guanine

Reply 117

mr osaka

4

Original post by trialbyc0mbat

actually what do you mean by adenine and guanine are from the same family? A=T and C=G are base pairs right?
so what is the relationship between AG and CT?

dont worry about that , its just my teacher told us that Cytosin and Thymine r from a group called "Pyrimidine" (as both have 'Y' in their names) and guanine and adenine is from a group called "purine".
but dont worry this wont come , i didnt c it in any past paper , i dont know y my teacher said it in the first place :biggrin:

anyways just understand how to do those percentages and ull be fine :smile:

sorry if i confused u , i shouldnt mentioned "same family" :colondollar:

Reply 118

trialbyc0mbat

Original post by Alnassenigzig

there isn't a direct relationship between A and G as far as i know ._. dont worry man its not in our specification.All we need to know is that A=T and C=G and U replaces G in RNA ....as far as percentages are concerned ,its all simply reasoning like the others mentioned above

dont you mean U replaces T? :confused:

Reply 119

trialbyc0mbat

Original post by mr osaka

dont worry about that , its just my teacher told us that Cytosin and Thymine r from a group called "Pyrimidine" (as both have 'Y' in their names) and guanine and adenine is from a group called "purine".
but dont worry this wont come , i didnt c it in any past paper , i dont know y my teacher said it in the first place :biggrin:

anyways just understand how to do those percentages and ull be fine :smile:

sorry if i confused u , i shouldnt mentioned "same family" :colondollar:

yeah got it now, thanks!

As biology unit 1 21/5/2014 panic thread

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