REVISION : F215 Biology OCR- 11th June 2013 - Control, Genomes and Environment

Hi all,
this thread is for those doing the exam and want to revise.

There are four modules to this unit.

1. cellular control
2. biotechnology
3. ecosystems
4.responding to the environment

Hello


you know on page 106 about ribosomes i dont understand that part where it says that the two subunits can groove?

question for you :-

How is apoptosis controlled (3)

Hello


you know on page 106 about ribosomes i dont understand that part where it says that the two subunits can groove?

question for you :-

How is apoptosis controlled (3)

I think it means the two subunits make up a ribosome and there is a groove and the space in the groove is where the mRNA can move into

apoptosis is controlled by cell signals, both inside and outside the cell for example cytokines made by cells of the immune system and hormones and nitric oxide.
nitric oxide can cause apoptosis by making the mitochondrial membrane more permeable to protons and this disrupts the proton gradient.
Proteins which are released into the cytoplasm bind to complementary apoptosis inhibitors and allow the process to occur as the reaction is triggered once the proten-inhibitor complex is formed.


what is a genetic code (2 marks)

what is a homeobox gene (1 mark)

explain the significance of meiosis (4 marks)

I just noticed how many red reps you have
but you're always so helpful! ^_^

thanks thats nice of you

I dont know what ever you say here people neg for no reason

but what is groove ? is it not a dance move to groove lol


that is correct! well done you know your stuff


1) genetic code is the entire sequence of DNA of a (multicellular) organism. Also, the sequence of nucleotide bases(genes) codes for a particular (one or more) polypeptide chain and as a result this constructs the protein molecule/polymer of polypeptide chains.

2) Homeobox gene- is the control of the development of the body plan of an organism such as the drosophila including its polarity and positioning of organs.

3) meiosis is a type of sexual reproduction in which the daughter cells are genetically different from each other and from parent cell. This as a result leads to genetic variation and the varation of the organism increases due to different alleles present and the different genes that codes for a different polypeptide chain results in different proteins being made and will result in a particualr change such as blood type? Furtehrmore, this variation must happen for evoluation or natural selection to occur in order to out compete other organisms as they have a beneifical trait. Also, this happens due to crossing over that occurs in prophase 1 and random mutation of chromosomes or reassortment of the number of chromoes, random mutation which alters the DNA and sequence of polypeptide and results in different individuals

I just noticed how many red reps you have
but you're always so helpful! ^_^

really! did i get the significance of meiosis right?


Give 3 diseases that can be caused as a result of mutation (3)

it makes sense to me and its in the book

erm cystic fibrosis, sickle cell anemia and huntingtons diease



name a stop codon (1 mark)
what is geneotype
what is phenotype


ps : i'm logging off for abit, so thatll be why if I'm slow to reply

have not yet reached till the definitions


the stop codon is usually , we are given this in the exam so there is no need for us to memrozie but i think its UAC?

ahh nvm!
oh yes we do actually good to know one just incase :P but UAC is right

also, the bit on ecosystems are dynamic in module 3- do you know what they mean? I thought its when the increase and decrase are at the same rate ?

oh my god have u reached till ecosystem
I only covered up to significance of meiosis!

I want to finish chapter 1 this week

LOL no no I havent I've done up to meiosis and am going over it this week until its solid in my head
but with our other teacher we've done ecosystems haha so I'm going over the first few pages of that until its also well understood then moving on :P

I want to do it in order chapter 1 then 2 then 3 then 4.


I imagine it means that ecosystems are constant so same rate

ah good idea! this is a resit exam right, so youve done all the learning previously? or are you self studying the entire unit (poor you!)?
yeah I thought so but it only mentions if the no. of predators increase, the no. of prey decrease which would contradict dynamic? unless its ocr mistakes again :l

I am doing this again, sadly I got B for bio but not good enough

ok

Describe transcription (5)

well done I know the feeling, although a B in A-level biology is good, its not good enough when you need an A or when you havent reached your potential My teacher says that all the time, a B can be a fail, if its not what you are capable of.


transcription - the DNA acts as a template to produce mRNA a copy in the nucleus which leaves via the nuclear pore on the nuclear evelope into the cytoplasm to the RER where ribosomes are present for the second stage - translation

1. the DNA helix untwists and unzips and hydrogen bonds are broken
2. bases become exposed and free nucleotides in the nucleoplasm bind to the complementary bases and hydrogen bonds are formed for example, C binds with G
3. ATP is used to produce these bonds, as two phospate groups are released

the mRNA produced is complementary to the strand of template DNA strand


is this right?


three differences between meiosis and mitosis

what does it mean by degenerate code?

where are chismata found?

what do beta galactosidase and lactose permease do?

I know

Correct, but you could be more specific. But this would get you the majority of marks

1) mitosis= number of cell division is one , product= 2 cells produced and both are genetically identical daughter cells and are same as their parents. Meiosis= bivalent is formed, 4 cells produced and the daugther cells are genetically different to each other, number of cell division is 2. Also, in meiosis there are is crossing over.

2) degenrate code= is a coding of one or more amino aicd triplet bases
3) chiasmata= is it when the chromatids overlap?
4) lactose permerase is an enzyme that causes lactose to be uptaken by the e.coil for aerobic respiration to provide energy.
B galattocisidase breaksdown the lactose into glucsoe and galactose and is an eznyme

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