processes to learn - DNA

Question 1

mention the proteins involved

What do are the steps of DNA replication?

Answer 1

1. The double helix is untwisted by DNA gyrase
2. DNA helicase breaks the hydrogen bonds, unzipping the double strand
3. The bases are exposed and primers of RNA create a latching on point
4. DNA polymerase creates a new DNA strand, builds the phosphate sugar backbone using free complementary nucleotides
5. DNA polymerase builds 5’ to 3’. One strand is continuous following behind the helicase (leading strand). Lagging strand is made in fragments called okazaki fragments
6. DNA ligase bonds the fragments to create a continuous DNA strand
7. DNA replication occurs simultaneously in multiple places
8. Semi conservative replication occurs and the new double helix is half old, half new

Question 2

What is the process of transcription?

Answer 2

1. Gene unwinds and unzips
2. Hydrogen bonds between complementary nucleotides break
3. RNA polymerase catalyses the formation of temporary hydrogen bonds bewteen temporay nucleotides and the complementary unpaired bases. This DNA strand is called the template strand
4. A length of RNA that is complementary to the template strand of the gene is produced. It is therefore a copy of the other DNA strand - the coding strand
5. The mRNA now passes out of the nucleus through the nuclear envelope and attaches to a ribosome

Question 3

What is the process of Translation?

Answer 3

Once the modified mRNA has left the nucleus it attaches to the small subunit of the ribosome at the start codon.
1. The tRNA molecule with the complementary anticodon to the start codon aligns opposite the mRNA, held in place by the ribosome. The ribosome can hold 2 tRNA molecules at a time
2. The two amino acids that have been delivered by the tRNA molecule have joined together by a peptide bond that is catalysed by an enzyme using ATP
3. The ribosome will move along the mRNA molecule to the next codon and another complementary tRNA will attach to the next codon on the mRNA
4. The continues until the ribosome reaches the stop codon at the end of the mRNA molecule causing the ribosome to detach and end translation
5. The polypeptide chain is now created and will enter the golgi body for folding and modification

Question 4

DNA precipitation

Answer 4

1. Homonogenise the cell with detergent. This will break open the cells and cell membranes to release their contents
2. Filter to remove large debris
3. Add salt to break hydrogen bonds between the DNA and water molecules
4. Add protease to digest the proteins associated with the DNA
5. Add ice-cold ethanol to precipitate out the DNA from the solution. The DNA appears as white strands