Module 2, section 3: Nucleotides and nucleic acids.

What atoms are nucleotides made of, and describe the structure of both RNA and DNA

Comprised of oxygen, carbon, hydrogen, nitrogen and phosphorus.

Their structure comprises of a sugar-phosphate backbone and a variable base. DNA features deoxyribose, whilst RNA features ribose.

How many nitrogen-carbon rings do pyrimidines have, and what about purines?

Pyrimidines have one ring, whilst purines have two.

Think (pure= pure bricks of cocaine, meaning big. So, purines are bigger, thus have two rings)

Describe the process to purify DNA.

1. Break up cells using a mortar and pestle, to break down cell walls.

2. Add cells to washing-up liquid/salt solution.

3. Add to water bath at around 60 degrees celcius to denature enzymes that break down DNA, allowing washing-up liquid to destroy cell membranes and salt clumping up DNA

4. Cool down solution using ice bath, and filter through coffee filter.

5. Add protease enzymes, that break down proteins.

6. Add ice-cold ethanol, that precipitates the DNA onto the surface of of the solution, and pull the dna using a hook-like instrument.

Describe the process of DNA replication?

DNA helicase splits the hydrogen bonds between complementary bases.

Free floating nitrogenous bases attach to the free bases.

DNA polymerase then forms hydrogen bonds between these bases, and forms the sugar-phosphate backbone.

This form of copying is called semi-conservative replication, because half of the DNA is conserved, and a singular DNA strand can make two.

Describe the accuracy of DNA replication and what might happen if it isn’t accurate.

DNA replication is highly conserved, meaning it undergoes very little changes.

However, it can be changed through mutations, which change the genetic code. This can alter the proteins coded for.

How are RNA polynucleotides different to DNA polynucleotides?

RNA polynucleotides are single stranded, use ribose instead of deoxyribose and use uracil instead of thymine as a nitrogenous base.

What are the functions of the three RNA types in cells, and where can they be found?

Messenger RNA is a molecule that copies genetic code that can then be used for protein synthesis. It is found and made in the nucleus.

Transfer RNA has a complimentary anti-codon to the mRNA triplet, and releases its amino acid when it binds. It’s found in the cytoplasm, and moves into the ribosome for protein synthesis.

Ribosomal DNA forms peptide bonds between the deposited amino acids, forming a protein chain. It is found in the ribosomes.

How is tRNA kept in the clover shape?

It is held together by hydrogen bonds between its nitrogenous bases.

Why is the degenerate nature of the genetic code important?

It means that multiple triplets can code for the same amino acid, thus reducing the effect of genetic mutations.

Describe the stages of transcription.

RNA polymerase attaches to a DNA double helix, using it as a template. Free bases in the nucleus attach to it.

RNA polymerase moves down the DNA strand, assembling the mRNA molecule as it goes. Hydrogen bonds reform as the polymerase goes down.

When RNA polymerase reaches a stop-codon it detaches and leaves the nucleus, and goes to a ribosome.

Describe the steps of translation.

mRNA attaches to the ribosome, and tRNAs with complementary anti codons deposit amino acids.

rRNA then forms peptide bonds between amino acids, forming a polypeptide. The tRNA detaches, and this cycle then repeats until a stop codon is reached.