A1.2 Nucleic Acids

Nucleic Acids

A1.2.1. universal genetic material

dna; genes instruct the body of performing actions (construct proteins) and pass information between generations. DNA; DioxyRibonucleicAcid. All living organisms use DNA, some viruses use RNA but non-living as not all functions of life.

A1.2.2. Nucleotides

Building blocks of DNA/RNA are nucleic acids; Phospahte group (PO4)-Pentose Sugar ((de-)oxyribose) - Nitrogenous base

A1.2.3. Sugar backbone

Sugar–phosphate bonding makes a continuous chain of covalently bonded atoms in each strand of DNA or RNA nucleotides, which forms a strong “backbone” in the molecule. Occurs between C3 and C5 (phosphate), builds onto 3’ end. Condensation reactions polymerize

A1.2.4. Nitrogenous bases

5 different bases. 3 common for RNA and DNA, 2 different. Sequence of these basis of genetic code to store info.

A1.2.4. The nitrogenous bases

Uracil, Cytosine, Thymine (Pyrimidine-1ring)
Adenine, Guanine (Purine-2ring)
DNA: AT-CG, RNA: AU-CG

A1.2.5. Forming of RNA

RNA: ribose, single stand of covalently bonded sugar-phosphate bonds; GUAC, grows on 3’ end (3rd carbon), condensation (produce H2O) - polymerization of monomers

A1.2.6. DNA

DNA: double strand; linked by hydrogen bonds, A-T (2H) and C-G (3H), complementary base pairs. Antiparalel strands. Wound together into double helix. Both have sugar backbone w bases in centre. Always build 5’ to 3’

A1.2.7. RNA vs. DNA - differences

1. Ribose vs Deoxyribose (C2 OH vs H bottom)

2. Uracil vs Thymine (bonds with Adenine)

3. Single vs Double stranded

4. Used in protein synthesis vs used for conserving hereditary information

Both are nucleic acids formed by nucleotides, used in cells.

A1.2.8. Complementary base pairs roles

Weak hydrogen bonds holding together strands.

Roles:

1. DNA replication: accurate copies using template

2. Transcription: mRNA also matches to carry code

3. Translation: use sequence on tRNA and mRNA to place the right a.a. codon

A1.2.9. DNA sequences

4ⁿ options of sequences, and n is the nr of nucleotides in the nucleid acid, so very many….even 10 bases has 1.048.576 options. DNA can store infinite amount of information in its code

A1.2.10. Conservation of genetic code

Because all cells use the same genetic code, we know all life evolved from the same original ancestor. Genetic code is how that the 4³=64 different codons (3 bases) code for 20 different amino acids

A1.2.11. 3’ and 5’ ends

3’: the 3rd carbon, where theres a spot for the phosphate to bind - the OH here + the H on the phosphate bind into H2O during condensation

5’: the phosphate group attached to the 5th carbon, where the 3’ end attaches to.

New nucleotides add onto the 3’ end, of the growing strand with their 5’end; 5’→3’ growth. Because in DNA the strands run antiparallel; 5’ and 3’ end

A1.2.12. Purine bond with pyrimidines

Purine: 2, Pyrimidine: 1 ring. Each purine (AG) bonds with a pyrimidine (CTU) - equal distance bonds for complementary; keep DNA stable and allow any sequence of bases.

A1.2.13. Nucleosomes

disc like; package DNA into condensed chromosomes. Has 8 histones (2×H2a, 2×H2b, 2×H3, 2×H4) in a square with DNA rapped around it (double loop), H1 histones help secure structure. Linker DNA is between adjacent nucleosomes to form chromatin: chain of nucleosomes.

A1.2.14. Hershey-Chase

E-coli viruses labelled with radioactive S protein coat and P DNA, let the virus infect bacteria, then centrifuged, and end up with Sulfur outside of the cell, and Phosphorus still inside the cell; proof for DNA as genetic material

A1.2.15. Chargaff’s data

Evidence for complementary base pairs:
Purine always bonds to pyrimidine; AT, CG
Chargaff showed no matter what the percentages of nucleotides were, but A=T and C=G, A+G=T+C=50%