SAC 1

Question 1

Describe initiation in transcription

Answer 1

-occurs in nucleus
-RNA polymerasebinds to the promoter,which unbinds/unzips the double helix structure and signal for weak hygrogen bonds between the two starnds.Then the RNA polymerase starts transcription

Question 2

Describe elongation in transcription

Answer 2

RNA polymerase moves alond the template strand(3’ to 5’) reading te nucloetide sequence and then producing s pre-mRNA molecule using complementary base pairing.

mRNA is similar to the coding strand of the DNA, expect there is uracil insteand of thymine.

Question 3

Decscribe termination in transcription

Answer 3

1. RNA polymerase reaches the gene termination sequence and RNA detached relasing pre-mRNA molecule
   2.The hydrogen bond come together and zips the double helix structure

Question 4

Describe RNA processing

Answer 4

1.Splicing of the exons occurs via a complex moecule known as spliceosome,which removes the introns (non-coding region of DNA) and splices the exons togehter.

2.Adding of the METHYL-G CAP, which is added to the 5’end
3.Adding of the Poly-A tail to the 3’ end

Question 5

What is the function of the methyl cap and poly A tail?

Answer 5

Helps in stabalising the mRNA.Prevents from the disintergration of the molecule and allowing it to bind to the ribosome

Question 6

What is alternative splicing?

Answer 6

exons from the same gene are joined in different combinations, leading to different, but related, mRNA transcripts.
These mRNAs can be translated to produce different proteins with distinct structures and functions WHICH ARE all from a single gene.

Question 7

Describe initiation in translation

Answer 7

mRNA exits the nucleus.The 5’ end of mRNA binds to the ribosome and it is read until the start codon (AUG).The tRNA with compementary anticon (UAC),binds to the ribosome delivering the amino acid (methione),which signal commencement.

Question 8

Decribe elongation is translation

Answer 8

mRNA molecule is feed through the ribosome so the following codons can be matched to its complementary tRNA anticodon. The tRNA bring the corresponding amino acid from the cytosol and bond it with the adjecent amino acid though condenation reaction which forms a poptide bond.Condensation reaction breaks of the carboxylic group and hydrogen group of the adjacent amino acid to add another one.It eventually forms a polypeptide chain as more amino acids are joined together using peptide bond.

Question 9

Decribe the Termination in translation process

Answer 9

Making of the polypeptide chain continues until it reaches the stop codon.The polypeptide chain is either released into the cystosol or sent to the golgi apparatus for further packaging to send in the extracellular environment.
The free floating ribosome usually just produce polypeptide chain that are just required in the cell.

Question 10

tRNA

Answer 10

Brings specific amino acid,corresponding to the anticodon its carrying,from the cytosal.

Question 11

mRNA

Answer 11

Carries the genetic intruction from the DNA to outside nucleus and gets translated into polypeptides in the ribosome.

Question 12

rRNA

Answer 12

Ribosome are made of proteins and ribosomal RNA.

Question 13

describe attenuation when there is high tyrptophan

Answer 13

During attenuation of the trp operon,
transcription and translation occur
simultaneously.
When the RNA polymerase reaches the leader
region it begins transcribing and a ribosome
attaches to the mRNA and begins translating.
 Two trp codons are formed in the mRNA in the
attenuator region. Two trp-bound tRNA molecules
quickly bring trp amino acids to the ribosome and
polypeptide due to the abundance of trp in the
cell.
As a result, a terminator hairpin loop forms. This
causes the mRNA strand and RNA polymerase to
detach from the operon before the 5 structural
genes can be transcribed and translated.
 Therefore trp amino acid is not formed.

Question 14

What is experimental group?

Answer 14

An experimental control is the experimental group which does not receive the treatment or experience the influence of the independent variable .This allows for the presence of a comparison group and can highlight the effects of uncontrolled variables on the dependent variable.

Question 15

Difference between structural genes and regulatory genes

Answer 15

Structural genes are responsible for producing proteins involved in the function or structure of the cell where as regulatory genes control the gene expression of one or more genes.

Question 16

What is gene regulation and its purpose

Answer 16

Refers to the ability of cells to control the expression of their genes.
genes are activated/transcribed only when required
* required genes are expressed, which can save energy

Question 17

Summary of transcription (3marks)

Answer 17

RNA polymerase is involved in copying of the DNA template strand.
Pre-mRNA is produced which undergoes futher modification such as romoval of introns
mRNa is produced which then leaves the nucleus.

Question 18

Process of translation

Answer 18

Ribosome will read the mRNA code
tRNA anticodonattach to the mRNA codons
tRNA beings the specific amino acid from the cytosol to the ribsome
A polypeptide chain is produced.

Question 19

Primary structure

Answer 19

the primary structure of a protein is the sequence of amino acids in the pilypeptide chain of which protein is made.

Question 20

Secondary Structure

Answer 20

a-helices structur forms as groups repel each other which causes the spiriling of the polypeptide and is held together by HYDROGEN BONDS.
Another common motif of secondary is b-pleated sheets.B pleated sheets temd to have alternating hydrophobic and hydrophilic bonds and are also held together by HYDROGEN BONDS.

Question 21

Tetiary structure

Answer 21

The teriary structure of a protein is the overall thee dimensional shape of the protein.
It is the shape that is presented to other molcules.
Dont fold spontaneuosly, folded into 3-d shaped with the help of chaperons.
REMEBER:Most of proteins would have hydrophobic side in the inside and a hydrophilic on the outside, this helps proteins stay suspended in the cell rather sink down.

Question 22

Quternary structure

Answer 22

More than one polypeptide chain with its own secandary and teriary structure.

Question 23

enzyme

Answer 23

 An organic molecule,
typically a protein, that catalyses
(speeds up) specific reactions

Question 24

What is hormone

Answer 24

Hormones are cell signalling molecules that can be used to transmit signals from one part of the body to another

Question 25

sugar-phosphate backbone 

Answer 25

a strong covalently linked chain of five-carbon sugar molecules and
phosphate groups in nucleic acid .

Question 26

outline the secretery pathway

Answer 26

After production, protein will be transported from the rough endoplasmic reticulum, which is where it is made and folded.to the Golgi apparatus, which is where it is packaged into secretory vesicles.From there, it will be exported from the cell through the process of exocytosis, which involves the fusion of the secretory vesicle with the plasma membrane and the release of protien into the extracellular environment

Question 27

what does DNA being universal mean

Answer 27

e universal nature of the genetic code, which involves nearly all organisms using the same set of rules in the production of proteins.

Question 28

Reaction when two amino acids are joined

Answer 28

Descriptions may include:
* The chemical reaction is a condensation reaction.
* Water is an output of the reaction.
* Energy is an input of the reaction.

Question 29

Explain how the expression of a single gene can lead to the production of different proteins.

Answer 29

Explanations may include:
* different post-transcriptional modification or modifications of the pre-mRNA
* different exons joined or alternative splicing
* different nucleotide sequences/mRNA sequences code for a different protein
* post-translational changes to the protein, such as alternative folding

Question 30

Polymerise

Answer 30

joining

Question 31

contrast between proteome to genome

Answer 31

The proteome is an expression of an organism’s genome. However, in contrast with the genome, which is characterized by its stability, the proteome actively changes in response to various factors, including the organism’s developmental stage and both internal and external conditions.