RNA structure and function

What is RNA?

A polymer of a nucleotide formed of a ribose sugar, a nitrogenous base and a phosphate group

What are the 4 possible nitrogenous bases in RNA?

Adenine

Guanine

Cytosine

Uracil

What is the general function of RNA?

• Copy and transfer the genetic code

• From DNA to the nucleus

• In the ribosomes

What are ribosomes formed from?

RNA combined with proteins

Name the 3 types of RNA

mRNA

tRNA

rRNA (ribosomal)

What is mRNA?

It is a copy of a gene from DNA.

Where is mRNA created?

nucleus

What is the function of mRNA?

• It leaves the nucleus

• to carry the copy of one gene’s genetic code

• to a ribosome in the cytoplasm

Why is mRNA needed to carry a copy of the genetic code instead of DNA going directly to the ribosome?

• DNA is too large to leave the nucleus

• Thus it would be at risk of being damaged by enzymes

• Destroying the genetic code permanently

Why is mRNA able to leave the nucleus (but DNA is not)?

mRNA is much shorter (only the length of one gene)

mRNA is short lived. Why is this?

• Only needed temporarily to help create a protein

• By the time enzymes break it down it has already carried out its function

mRNA is ______ stranded.

Single

What are codons in mRNA?

3 bases in the sequence that codes for a specific amino acid

Where is tRNA found?

Cytoplasm

Describe the shape of the tRNA.

• Single stranded

• Folded to create a cloverleaf shape, held in place by hydrogen bonds.

Describe the function of tRNA

• Attach to one of 20 amino acids

• Transfer this amino acid to ribosome to create polypeptide chain

How do specific mRNA molecules attach to specific tRNA molecules?

The 3 bases found on tRNA’s anti-codon are complementary and attach to the 3 bases found on mRNA

Why are the 3 bases found on t-RNA referred to as the anti-codon?

Because they are complementary to the codon on mRNA

Define ribosomal RNA

It is the type of RNA that makes up the bulk of ribosomes

Compare RNA as a biological molecule to DNA (polymer wise)

• DNA is larger because it contains the entire genome; RNA shorter because it only contains one gene

• DNA is double stranded; RNA is single stranded

Compare RNA as a biological molecule to DNA (monomer wise)

• DNA contains base Thymine; RNA contains base Uracil

• DNA contains pentose sugar deoxyribose; RNA contains pentose sugar ribose