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Edexcel Biology AS 2016 new spec [Exam discussion thread]

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Okkkkk thanks everyone!!
Another question, i dont really understnd what we are supposed o know about stem cells, as in this part 'Be able to discuss the way society uses scientific knowledge to makedecisions about the use of stem cells in medical therapies'

Like what are the key ideas, its quite vague and i dislkie vagueness

Also do any of you know about the acetabularia experiment? Are we supposed to know it?

(edited 7 years ago)

Reply 41

imogenr

Original post by THESTRESS

Okkkkk thanks everyone!!
Another question, I don't really understand what we are supposed to know about stem cells, as in this part 'Be able to discuss the way society uses scientific knowledge to make decisions about the use of stem cells in medical therapies'

Like what are the key ideas, its quite vague and i dislkie vagueness

Also do any of you know about the acetabularia experiment? Are we supposed to know it?

Ok, my guess is that what you have referred to includes understanding the ethics behind the use of stem cells and how the government controls the study of stem cells (i.e. what regulations have been put in place to control stem cell research).

You probably also should know how pluripotent cells can be used to replace damaged tissue (i.e. the stem cells are stimulated by surrounding cells which activates certain genes leading to transcription and translation etc etc)

Just researched that experiment, yes, it is mentioned in the textbook (Hammerling's experiment) because it helps us understand the role of the nucleus in controlling the development of the inividual cell and the whole multicellular organism's phenotypes because the rhizoid (NOT the hat or stalk) contained the nucleus.

(edited 7 years ago)

Reply 42

THESTRESS

Riiiight Thank You for the the help (and the research).

Soz for so many questions.....but, in methylation/acetylation, is it that one makes the gene inaccessible while the other makes it accessible. The idea i get is that methylation tightens the gene whereas acetyl loosens it?

Reply 43

imogenr

Original post by THESTRESS

Yes, DNA methylation is when methyl groups attach to the cytosine base which means that the DNA can't be transcribed. I didn't think acetyl groups loosened it though...I thought it had the same effect as methyl groups.

Reply 44

THESTRESS

Original post by imogenr

My textbook made it confusing, so i had to do some research and it suggested that dna methylation tightens the dna, and histone modification via acetyl loosens it. The i saw in my CGP revision guide that it does just that. Also if you look at this link on ggogle images it shows it https://www.google.co.uk/search?q=dna+acetylation+epigenetics&espv=2&biw=1366&bih=667&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjhqcXknI7NAhWrJsAKHaxwABIQ_AUIBigB#imgrc=1AVX-w83LUagjM%3A

Reply 45

Alevelz

Hi do we need to know about the frog experiment on early/ late frog blastula?

Reply 46

Alevelz

And do we need to know the exact process for melanin production? Or just how environment can affect it? And do we need to know about transpiration?

Reply 47

THESTRESS

Original post by Alevelz

And do we need to know the exact process for melanin production? Or just how environment can affect it? And do we need to know about transpiration?

I think it is safe to know both of them. I think definitely how melanin is made, they coud ask you to incroporate how the environment effects it, and jst to be safe about the frog bastulla (im thinking this is about the complimentary mrna and dna/mrna hybrid)

And transpirationa quick run through covering the maun principles like cohesion,adhesion, root pressure etcc..