Unit 2 - Gene expression

Question 1

What is gene expression?

Answer 1

The process by which specific genes are activated to produce a required protein.

Question 2

RNA? (Shape, bases, composition)

Answer 2

Single stranded
Uracil instead of Thymine ( A-U , C-G )
Has sugar called ribose

Question 3

mRNA? (Function, Composition)

Messanger RNA

Answer 3

Carries a copy of DNA code from nucleus to ribosome

Made of a series of base triplets known as codons (which code for a specific amino acid)

Question 4

tRNA? (Function, Composition)

Transfer RNA

Answer 4

Carries a specific amino acid to the ribosome

Folds due to complementary base pairing (cloverleaf shape)

Question 5

rRNA? (Function)

Ribosomal RNA

Answer 5

Forms the ribosome with proteins

Question 6

What is transcription?

Answer 6

Synthesis of mRNA from a section of DNA

Question 7

What occurs in transcription?

Answer 7

1. RNA P moves along DNA strand unwinding and breaking hydrogen bonds between bases adding RNA nucleotides (only to 3 prime end of new mRNA strand)
2. Resultant mRNA breaks off and is primary transcript

Question 8

What is RNA splicing?

Answer 8

new mRNA primary transcript is transformed into a mature mRNA. During splicing, introns are removed and exons are joined together.

Question 9

What is translation? (Function, Location)

Answer 9

The synthesis of a polypeptide from mRNA at the ribosome

Begins at start codon and ends at a stop codon in cytoplasm on a ribosome

Question 10

What occurs in translation?

Answer 10

1. mRNA attaches to ribosome and tRNA transports amino acids to ribosome
2. Ribosome reads start codon to start translation
3. Anticodons and codons match up and form complementary base pairs.
4. Peptide bonds form between the 2 amino acids to form the polypeptide (protein)
5. tRNA molecules detatch from amino acid and leaves to pick up another AA
6. Last codon of mRNA molecule is stop codon = translation stops

Question 11

Alternative RNA splicing?

Answer 11

Different segments of mRNA can be treated as exons and introns. Different exons result in different mature transcripts and produce different proteins

Question 12

How are polypeptides formed

Answer 12

Amino acids are linked by peptide bonds to form polypeptides (which fold to form a 3d shape held by hydrogen bonds and interactions between amino acids)