TRANSCRIPTION

Question 1

What is a gene

Answer 1

a lenth of DNA that codes for one or more polypeptide chain

Question 2

define the term genome

Answer 2

is the entire DNA sequence of that organism.

Consist of about 3 billion nucleotide base pairs

Question 3

genes code for polypeptides such as what?

Answer 3

• haemoglobin
• collagen
• antibodies
• actin and myosin in muscel cells
• channel proteins
• electron carriers
• enzymes

Question 4

what is the genetic code

Answer 4

sequence of nucleotide bases that code for the construction of proteins e..g.haemoglobin

Question 5

name 4 characteristics of the genetic code

Answer 5

1. Its a triplet codes,20 amino acids code for proteins sythesis,4^{3 =}64 codes this is more than enough,a double or single code wont be enough
2. Its a degenerate code,all amino acids have more than one code expect for methionine
3. Some codes indicate a stop e.g. methionine,which means the end of a polypeptide chain
4. Genetic code is widespread but not universal

Question 6

why is it useful that the genetic code is widespread

Answer 6

Can be used in genetic engeenering,as we can tranfare a gene from one organism into another and it will produce the same protein e.g. insulin can be produced im large quantities by bacteria

Question 7

outline the mechanism of transciption

Answer 7

1. Hydrogen bonds between base pairs are broken by DNA helicase,this caused the section to be trasciped to unwind
2. Free activated nucleotides bind with hydrogen bonds to their complementary bases e.g. U-A, G-C, T-A,this is catalysed by RNA polymerase using energy from extra phosphates on nucleotides
3. mRNA is released from the DNA and passes out of the nucleus through nuclear pores in the nuclear envelop and it then attaches to a ribosome in the cytoplasm

Question 8

what is the role of RNA Polymerase

Answer 8

1. Catalyses the condensation reaction that occur between adjacent RNA nucleotides
2. Checks that the bases have paired up correctly