Nucleic Acids

What is the role of DNA?

Contains the genetic code which dictates all the inherited characteristics of an organism. DNA does this by controlling the proteins that are made in organism.

Define ‘gene’:

Specific sequence of DNA bases that code for a specific sequence of amino acids in a polypeptide

Define ‘chromosome’:

Large lengths of DNA that contain many genes

Why is every single organism different?

Due to the differences they have in their DNA and in the number and type of proteins that it produces

→ Organisms of different species show greater differences in their DNA and proteins than organisms of the same species

Describe the structure of DNA

DNA is a long chain polymer made of many subunits called nucleotides or mononucleotides

What are the 3 components of a DNA nucleotide/ mononucleotide?

• Phosphate

• Deoxyribose (pentose sugar)

• Nitrogenous base

Explain the bonding between DNA nucleotides/ mononucleotides:

A phosphodiester bond forms between the phosphate group of one mononucleotide and the deoxyribose sugar of the other mononucleotide

Hydrogen bonds form between the nitrogenous bases

Name the 4 bases that could be found on a DNA nucleotide:

• Adenine

• Thymine

• Cytosine

• Guanine

Describe the complementary base rules:

• A pairs with T → 2 hydrogen bonds

• C pairs with G → 3 hydrogen bonds

Identify what type of reaction takes place when two DNA mononucleotides join together to make a strand of DNA

Undergoes condensation reaction as water is produces a a by- product

Explain how to create a double helix from two DNA polymers

1. DNA mononucleotides are composed of a phosphate group a deoxyribose sugar and a base

2. The phosphate group of one mononucleotides joins with a deoxyribose sugar of an adjacent mononucleotides

3. A phosphodiester bond is created in a condensation reaction

4. This continues to happen until a signle strand of DNA is formed

5. Two DNA strands align and are joined by hydrogen bonds between complementary base pairs

6. Adenine forms 2 hydrogen bonds with thymine

7. Cytosine forms 3 hydrogen bonds with guanine

8. This forms a double stranded DNA molecule (double helix)

What do mRNA and tRNA both have in common?

They both have a nitrogenous base

What is the role of mRNA and tRNA?

DNA contains the genetic code to make proteins.

→ In order to translate the genetic code into a protein, mRNA and tRNA are needed

Describe the molecule DNA:

This molecule contains the genetic code e.g., the base sequence that determines the amino acid sequence in a polypeptide. The antisense strand acts as a template during transcription.

Describe the molecule mRNA:

This molecule is made during transcription in the nucleus and is copy of the DNA antisense strand. It is made up of codons (triplet of bases), which code for particular amino acids. It is free to leave the nucleus and attaches to the ribosome.

Describe the molecule tRNA:

This molecule attaches to specific amino acids and carries them into the ribosome. Two of these molecules can enter the ribosome at one time. They have anticodons which complementary base pair with mRNA codons allowing them to hold the amino acids in place when condensation reactions occur to form peptide bonds.

How are RNA molecules stranded?

Singularly

What is RNA made up of?

RNA mono nucleotides

What does the RNA mono nucleotide consist of?

Phosphate group, ribose sugar and nitrogenous bases

What are the 4 bases in RNA?

• Adenine

• Uracil

• Cytosine

• Guanine

What are the 3 components of a RNA nucleotide?

1. Phosphate

2. Ribose

3. Nitrogenous base