Nucleic Acids A1.2 SL/HL

IB Biology

DNA

Deoxyribonucleic acid

Double Stranded

Double Helix

Antiparallel

Deoxyribose sugar

• Hereditary information passed to offspring

• Polymer mad eof monomers called nucleotides

RNA

Ribonucleic acid

Single-stranded

Ribose Sugar

(is used by some viruses instead of DNA, but viruses are not living organisms)

Components of nucleotides

• pentose sugar (5 sided)

• Phosphate group

• nitrogenous base

Bases in DNA

Adenine

Thymine

Cytosine

Guanine

Bases in RNA

Adenine

Uracil

Cytosine

Guanine

Purines (double rings)

Adenine

Guanine

Pyrimidines (single rings)

Cytosine

Uracil

Thymine

Condensation Reaction

Removal of water to create a bond

Complimentary Base Pairing

A→ T

G → C

(Hydrogen Bonds between them)

DNA Replication is…

Semiconservative

Each resulting copy is made of one parent strand and one new strand

• Parent strands are used as templates to make the new strands

• Follows the rules of complimentary base pairing

Gene Expression

using the codes in DNA to synthesize a protein

Protein synthesis happens in steps….

DNA → RNA → Protein

Diversity of DNA sequences

• DNA molecules can vary in length

• Many possibilities for unique sequences

Universal genetic code

• all life arose from a common ancestor

• the same codons on RNA code for the same amino acids in almost every organism

Directionality of RNA and DNA

Carbons are numbered

5’ and 3’ ends

Antiparallel

New nucleotides can only be added to the 3’ end

Each complementary pair has…

one purine and one pyrimidine

All pairs are the same length

this increases stability of DNA molecule

Nucleosome

DNA wrapped twice around a core of 8 histone proteins

Hershey-Chase Experiment

Trying to figuire out whether DNA or Proteins were reaponsible for transmitting genetic information

(Protein adherance) Sulfur → virus was in the supernatant

(incorporated into DNA) Phosphorous → virus was in the pellet

Bacteriophages

Centrifuges (separates things based on weight)

Pellet (stuff that sinks to the bottom)

Supernatant (Virus Particles)

Realized that DNA IS THE GENETIC MATERIAL

Chargaffs experiement

Looking for data on the relative amounts of pyrimidine and purine bases across diverse life forms

Tetranucleotide hypothesis: DNA consisted of a repeating sequence of 4 nucleotides in equal amounts and proyteins were the genetic material

Chargaffs rule of complimentary base pairing

linker DNA

What makes up a nucleosome?

DNA and histone proteins

What provides the strongest evidence for universal common ancestry amongst living species?

highly conserved sequences of DNA amongst living organisms

Reactions

• Photosynthesis: Plants convert light energy into chemical energy in the form of glucose, producing oxygen as a byproduct. 

• Cellular respiration: Cells break down glucose to produce energy, releasing carbon dioxide and water. 

• Anabolism: The synthesis of complex molecules from simpler ones, such as proteins and nucleic acids. 

• Catabolism: The breakdown of complex molecules into simpler ones, releasing energy. 

• Condensation reactions, also known as dehydration synthesis, build larger molecules from smaller ones by removing water,

• Hydrolysis reactions break down large molecules into smaller ones by adding water. 

Types of bonds

• Covalent Bonds:

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  These strong bonds are formed when atoms share electrons, allowing them to achieve a stable electron configuration. They are common in biomolecules like proteins, carbohydrates, and lipids. 

• Ionic Bonds:

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  These bonds occur when one atom donates electrons to another, resulting in oppositely charged ions that attract each other. They are important in maintaining the structure and function of biomolecules like proteins. 

• Hydrogen Bonds:

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  These weak interactions occur when a hydrogen atom is attracted to an electronegative atom (like oxygen, nitrogen, or fluorine) in another molecule. They play a crucial role in the structure of proteins, DNA, and water.