Revision is going well people! Lets quiz up and stuff! What enzyme is responsible for free nucleotide addition to the template strand on DNA in transcription.. and where do these free nucleotides come from within the cell?

Reply 5

koyyj127

9

Original post by SAS18

Yup im doing this exam. But having to teach myself all of the by5 as ive hardly learnt anything in lessons

Same :P I ended up learning the subject by reading the textbook >_>

Reply 6

Beatbox22

OP

' What enzyme is responsible for free nucleotide addition to the template strand on DNA in transcription.. and where do these free nucleotides come from within the cell?'

Reply 7

some student

Hey guys! My school have decided that we should do wjec biology even though we're in London... apparently we're one of 6 schools who do it in the whole of England :tongue:

I'm feeling quite happy about unit 4, but there's waaayyyy too many details to learn in unit 5 and I'm having to self learn it all because of a bad teacher.

How's everyone's revision going? :smile:

Posted from TSR Mobile

Reply 8

some student

Original post by Beatbox22

' What enzyme is responsible for free nucleotide addition to the template strand on DNA in transcription.. and where do these free nucleotides come from within the cell?'

RNA polymerase? And I have no idea where the nucleotides come from, we were never taught this :/ I'm guessing they're synthesised in the nucleus somewhere? I really don't know :frown:

Posted from TSR Mobile

Reply 9

Nita.Jordan

i'm doing this exam too! we've only just finished learning the BY5 unit content, there's so much environmental stuff in this unit i so prefer BY4

Reply 10

Beatbox22

OP

Original post by some student

RNA polymerase? And I have no idea where the nucleotides come from, we were never taught this :/ I'm guessing they're synthesised in the nucleus somewhere? I really don't know :frown:

Posted from TSR Mobile

Well done that is the enzyme.. the free nucleotides are actually from the NUCLEOPLASM.. it actually was asked in a old paper :smile:

Your turn to ask now :smile:

Reply 11

some student

Original post by Beatbox22

Well done that is the enzyme.. the free nucleotides are actually from the NUCLEOPLASM.. it actually was asked in a old paper :smile:

Your turn to ask now :smile:

Could you tell me more about the nucleoplasm thing? :smile:

QUESTION: describe a backcross (or test cross) and explain why it is useful

Posted from TSR Mobile

Reply 12

Beatbox22

OP

Original post by some student

Could you tell me more about the nucleoplasm thing? :smile:

QUESTION: describe a backcross (or test cross) and explain why it is useful

Posted from TSR Mobile

well there isn't much to know about the nucleoplasm.. just think of it as like ... so.. (the cytoplasm for the whole cell) and (the nuceloplasm is just for the nucleus)

I actually have no clue?! Maybe I know it as a different name... sorry please tell me what is a backcross? and why it is useful :P

Reply 13

Nita.Jordan

Original post by Beatbox22

well there isn't much to know about the nucleoplasm.. just think of it as like ... so.. (the cytoplasm for the whole cell) and (the nuceloplasm is just for the nucleus)

I actually have no clue?! Maybe I know it as a different name... sorry please tell me what is a backcross? and why it is useful :P

Isn't a backcross used to establish whether you have a purebreed/homozygous dominant, or heterozygous organism?

Reply 14

some student

Original post by Beatbox22

well there isn't much to know about the nucleoplasm.. just think of it as like ... so.. (the cytoplasm for the whole cell) and (the nuceloplasm is just for the nucleus)

I actually have no clue?! Maybe I know it as a different name... sorry please tell me what is a backcross? and why it is useful :P

It's for determining whether an individual with dominant characteristics is heterozygous or homozygous dominant. You breed it with an individual with homozygous recessive characteristics, and look at the offspring's characteristics to work out the parents genotype

Eg a bull with black coat could be homozygous dominant black BB or heterozygous black Bb. You breed it with a white coated cow bb, and look at the coat colours of the offspring. If all of them have a black coat, your original bull was homozygous BB, but if there's a mix of white and black coated offspring then your original bull was heterozygous Bb. It's useful because now you know the genotype of that inducidual when you didn't before.

It's called a back cross because you're looking at a previous generation, and a test cross because you're testing the genotype :smile:

but obviously you need to have lots of offspring produced in order to be sure of your results... which might not work in real life :tongue:

Your turn to ask something!

(edited 9 years ago)

Reply 15

some student

Original post by Nita.Jordan

Isn't a backcross used to establish whether you have a purebreed/homozygous dominant, or heterozygous organism?

Yup!

hi there!

Reply 16

Beatbox22

OP

Original post by some student

It's for determining whether an individual with dominant characteristics is heterozygous or homozygous dominant. You breed it with an individual with homozygous recessive characteristics, and look at the offspring's characteristics to work out the parents genotype

Eg a bull with black coat could be homozygous dominant black BB or heterozygous black Bb. You breed it with a white coated cow bb, and look at the coat colours of the offspring. If all of them have a black coat, your original bull was homozygous BB, but if there's a mix of white and black coated offspring then your original bull was heterozygous Bb. It's useful because now you know the genotype of that inducidual when you didn't before.

It's called a back cross because you're looking at a previous generation, and a test cross because you're testing the genotype :smile:

but obviously you need to have lots of offspring produced in order to be sure of your results... which might not work in real life :tongue:

Your turn to ask something!

Im being so stupid - i knew that already :frown:

but just forgot that was the term! Thank you so much for such a brilliant response.

rated!

What stage does crossing over (synapsis/chiasma crossover) occur in Meiosis.. and where else in the Meiotic division (other than the aforementioned stage) does variation occur... and why is variation seen as an advantage to offspring created (5 marks)

Reply 17

some student

Original post by Beatbox22

Im being so stupid - i knew that already :frown:

but just forgot that was the term! Thank you so much for such a brilliant response.

rated!

What stage does crossing over (synapsis/chiasma crossover) occur in Meiosis.. and where else in the Meiotic division (other than the aforementioned stage) does variation occur... and why is variation seen as an advantage to offspring created (5 marks)

Aww thanks! You didn't have to :colondollar:

it's fine, everyone forgets silly things. At least you know it now rather than trying to remember it in the exam.

Crossing over during metaphase I, variation also comes from independent assortment also in metaphase I, from random gamete fusion (I think that's the term) and from mutations. Variations are good in a population as they allow natural selection to occur and so the species is likely to become fitter as a whole? (I know what I'm trying to say but can't think of the right words)

Question for you... in photosynthesis describe how the products of the light dependent stage are used in the light independent stage.

Posted from TSR Mobile

Reply 18

some student

Original post by Electrode

Actually, crossing over occurs during prophase 1 of meiosis :tongue:

Also variation allows natural selection and evolution but generally it helps a species be more likely to survive changing environmental conditions since more organisms within the population are likely to have some beneficial alleles that may confer a selective advantage depending on the selection pressure etc I've waffled a bit but I could probably keep going on :biggrin:

Then ATP from cyclic and non cyclic photophosrylation and nadph2 from non cyclic is used to convert g3p to gripes phosphate. Atp also used in regeneration of rubp by phosphorylating rp
Posted from TSR Mobile

Oh yeah, oops. Thanks for pointing that out :smile:

Please keep going with that explanation - you're saying the things that I was trying to but couldn't find the right words! Your explanation is really helping me out :biggrin:

Yup that sounds about right! You could also mention that the whole thing is called the Calvin Cycle, that the nadph2 is used in the reduction stage only whereas ATP is used in reduction and the regeneration of rubp (which you basically did say but I'm nitpicking). Also, what's gripes phosphate? I thought that molecule was called TP...