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AS Biology Edexcel IAL Unit 1 & 2 2015

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Reply 140

A84

Original post by PlayerBB

I'm gonna start solving p.p tmw, u?

hey
same here... omg they r like literally empty but if ive made a good schedule and ill finish by 30th

Reply 141

Polpi

Original post by AJC1997

yeah, I was also thinking about maybe mentioning prenatal testing BUT the question already said that both parents
were carriers - as they were heterozygous, meaning testing and amniocentesis would have no benefit as they already knew that they were at risk of giving birth to a sufferer.

Yes true,you have a point....So it's alright if I mentioned about 25% risk and drew the punnet box and yeah that's it I guess for that question.
Also what did you write for the risk associated with the use of heparin,is liver damage alright?

Reply 142

PlayerBB

Original post by A84

hey
same here... omg they r like literally empty but if ive made a good schedule and ill finish by 30th

Hahahahah same

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Reply 143

AJC1997

Original post by Polpi

I just said excessive bleeding if they get injured + liver damage is right too :smile:

Reply 144

Mushi123

Original post by AJC1997

Well it's reassuring to here I didn't write complete rubbish for this question, I'm happy with 3+ marks for it haha :smile:

Most of the pounts match except for the fact that i wrote that the potatoes to be cooked in a range of temperatures for the same amount of time since it was asked "the effect of cooking" not time or any temperature in particular..

Reply 145

AvWOW

Original post by Lama1847

what did u write for why galactose and glucose are monosaccharides

both have a general formula of C6H12O6 and are the simplest molecules that have not undergone a condensation reaction :/ Not so sure if it's right

Reply 146

Mushi123

Original post by AvWOW

both have a general formula of C6H12O6 and are the simplest molecules that have not undergone a condensation reaction :/ Not so sure if it's right

I wrote since both of them are composed of single units and are made of carbohydrates or reducing sugar ..hence the term monosachharides

Reply 147

AvWOW

Original post by Mushi123

I wrote since both of them are composed of single units and are made of carbohydrates or reducing sugar ..hence the term monosachharides

really not sure about that. In retrospect I kinda think It wasn't as easy as I initially though. Still want to scrape an A.

Reply 148

Mushi123

I guess they wanted us to justify the two parts of the term .."mono" and "sachharide" hence the explanation..it was of 2 marks...should get 1 at least

Reply 149

PlayerBB

I wrote because they consist of one sugar unit and both don't contain glycosidic bonds

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Reply 150

A84

I also wrote the single unit and more unit point, and I mentioned the sweet taste in mono but no sweet taste in poly..

Reply 151

hm1234

hello

could someone please give me a good description of how crossing over and independent assortment result in genetic variation?

Reply 152

PinkRhinos

Original post by hm1234

hello

could someone please give me a good description of how crossing over and independent assortment result in genetic variation?

Hey

-Both are features of meiosis
-Meiosis is important as it reduces chromosome number in gametes from 46 to 23 , so from diploid to haploid and creates genetic variation.

Independent/random assortment
-Means the number of chromosomes (out of 23) that a gamete receives that are from the paternal (male) or maternal (female) side is determined by chance (randomly).
-This leads to genetic variation in gametes because the estimated number of paternal-maternal chromosome combinations is over 8'000'000!

Crossing over/Recombination
-Large multi-enzyme complexes 'cut' and 'stitch' parts of paternal and maternal chromatids together.
(Homologous pair of chromosomes next to each other 'cross over' their chromatids making an X shape called chiasma, chromatids break and recombine.The location at which the chromatids break is called chiasmata).
-This leads to genetic variation because chromatids have exchanged genetic information and because errors in the process can lead to mutations which will introduce new combinations

(edited 8 years ago)

Reply 153

Lama1847

Original post by AvWOW

both have a general formula of C6H12O6 and are the simplest molecules that have not undergone a condensation reaction :/ Not so sure if it's right

same

Reply 154

PinkRhinos

Can anyone explain X chromosome inactivation, please?
EDIT: do we even have to know about it?

(edited 8 years ago)

Reply 155

PlayerBB

Original post by PinkRhinos

Can anyone explain X chromosome inactivation, please?
EDIT: do we even have to know about it?

This only occurs in females because they contain 2x-chromosome so double the genetic material in which one x chromosome in inactivate in the nuclues during embryo development and passed to embryonic cells. It is inactivated by supercoiling of chromosome forming a mass known as Barr body

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