IB Biology HL- Nucleic acids

Nucleic acids

large molecules contained in the nucleus of cells

2 types of nucleic acids

Deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)

DNA

the genetic material of all living organisms

Viruses use _______ as their genetic material, but they are not considered ___________.

RNA; living

Role of Nucleic acids

Storage and transfer of genetic information to make proteins

Nucleic Acid components(CHOPN)

C- Carbon
H- Hydrogen
O- Oxygen
P- Phosphorous
N- Nitrogen

Component of nucleotides

Phosphate group(circle) - Pentose sugar(pentagon)- Nitrogenous base(rectangle)

Nucleotides

Monomers of nucleic acids, form the basis of DNA and RNA

Sugar-phosphate bonding as back bone

Makes a continuous chain of covalently bonded atoms in each strand of nucleotide, forms a strong "backbone"

Nitrogenous bases

A- Adenine
T- Thymine
C- Cytosine
G- Guanine

RNA

A long polynucleotide strand formed by condensation of nucleotide monomers

Condensation reaction in RNA

Forms a Phosphodiester bond

Phosphodiester bond

Linkage of the 5' phosphate group of one nucleotide and the 3' hydroxyl (OH) group of the adjacent nucleotide's pentose sugar molecule

5' to 3' linkage in replication and transcription

The only direction that polymerase can synthesize DNA/RNA
it does so by adding nucleotides to the 3' end of a DNA strand.

Structure of single nucleotides

5' to 3' linkage role

Ensures the accuracy of the order of DNA/RNA/amino acids to form protein

5' to 3' linkage in translation

Ribosomes read the mRNA and synthesize the polypeptide chain in a 5' to 3' direction

Structure of RNA polymers

DNA structure

- Double helix
- Two antiparallel strands of nucleotides
- Linked by hydrogen bond between complementary base pair

Complementary base pairing

A-T(DNA)/U(RNA), C-G

A and G

Purine

U, T and C

Pyrimidine

Purine Pyrimidine bonding

- same lengths for AT and CG➡️same three-dimensional structure➡️maintain the stable, twisted structure of DNA double helix

Differences between DNA and RNA

1. Strands: RNA 1, DNA 2
2. Bases: RNA U, DNA T
3. Pentose sugar: RNA ribose, DNA deoxyribose

Difference between ribose and deoxyribose

ribose has a 2'-OH group and deoxyribose has a 2'-H

Role of complementary base pairing

- accurate DNA replication, Transcription, Translation

Complementary base pairing is based on _____________________________.

Hydrogen bonding

Any vertical sequence of nitrogenous bases is possible

Phosphodiester bond will form any way as long as phosphate group and pentose sugar present

DNA can be any length

increasing the number of possibilities of base sequences, enormous capacity in a limited amount of space

Possibilities of potential base sequences with n bases

4^n

Structure of a nucleosome

Core DNA wrapped around histone octamer
Held together an additional H1 histone protein attached to the linker DNA

Nucleosomes allow DNA to ____________.

Supercoil

Hershey-Chase experiment conclusion

DNA is the genetic material, instead of protein

Hershey-Chase experiment design

Used bacteriohages(virus) that infect bacterial cell by injecting genetic information for bacterial ribosomes to build new phages causing burst of the cell, thus further infect other bacterial cells
1. Add phages to grow in E.Coli radioactive medium (S35 phage coat labelled, P32 phage DNA labelled)
2. Put radioactive T2 phages with bacteria for infection and the injection of genetic material
3. Centrifugation to separate "ghost" phage(protein) from bacterial cell

Hershey-Chase experiment result

Radioactivity in supernatant for S35(phage coat), Radioactivity in pellet for P32(bacteria), supporting the conclusion that protein is not not the genetic material ,DNA is

Hershey-Chase experiment NOS: technological developments

Radioisotopes were made available to scientists as research tools, their experiment became possible.

Chargaff's data conclusion

- The amounts of the nitrogenous bases (A, T, C, and G) were not found in equal quantities.
- Instead amount of A = amount of T, amount of C = amount of G

Chargaff's data design

DNA was extracted from the given species, hydrolyzed to break apart the nucleotides, and then analyzed chemically.

Chargaff's data NOS: certainty of falsification

Chargaff's data falsified the tetranucleotide hypothesis that there was a repeating sequence of the four bases in DNA.