Nucleic Acids

Nucleic acids Connects all life together; it has the same structure in all organisms

Nucleic Acids There are 2 types of nucleic acids DNA (Deoxyribonucleic acid) RNA (Ribonucleic acid)

Nucleic acids Location DNA RNA In the nucleus ONLY In the nucleus and the cytosol

Nucleic Acids Purpose or Responsibility To store and transmit genetic information

Nucleic acids Purpose or Responsibility Codes for proteins Proteins are responsible for giving you all of your heritable characteristics and for all cellular activity DNA --> RNA --> Protein

Nucleic acids Nucleic acids are macromolecules Large molecules

Nucleic acids Macromolecules are made up of monomers - small repeating subunit A bunch of bricks makes a brick house.

Nucleic acids Nucleic acids are macromolecules that are made up of monomers called nucleotides A bunch of nucleotides make a DNA or an RNA molecule

What is a nucleotide? A nucleotide has three parts A sugar A phosphate A nitrogen base

Differences between DNA and RNA Sugar: Ribose Nitrogen bases A - Adenine U - Uracil C - Cytosine G - Guanine DNA Sugar: Deoxyribose Nitrogen bases A - Adenine T - Thymine C - Cytosine G - Guanine

Differences between DNA and RNA Shape: Double helix, like a twisted ladder RNA Shape: Single chain; like a strand of hair

The shape of DNA! Rungs - steps on the ladder = the nitrogen bases: (A, T, C, G) Rails - what you hold on to = the sugar / phosphate backbone

DNA and RNA bonding When nitrogen bases bond together, they can only bond to one type of base. Bases that bond are called complementary bases.

Complementary base pairing rules DNA A:T G:C (AT, Good Cat) RNA A:U G:C

Who Discovered the Shape of DNA? James Watson Francis Crick Rosalind Franklin Maurice Wilkins 1953

DNA Replication

DNA Replication DNA replication is the process of copying DNA

DNA replication Step 1 Enzymes called helicases help separate the two chains

DNA Replication Once the two chains are separated, each chain acts as a template for a new chain A template is a pattern or a guide used to make something accurately

DNA replication Step 2: An enzyme called DNA polymerase binds to the separated chains of DNA and makes new strands of DNA that are complementary to the old strands of DNA

DNA replication

DNA replication

DNA replication DNA replication is semi-conservative because when two identical DNA strands are made, half of the strand is new and half of the strand is old

Complementary nature Write the complementary DNA strand A C T G

Complementary nature Write the complementary DNA strand A - T C - G G - C

Accuracy and Repair A mutation is a change in the nucleotide sequence Original sequence A - T T - A C - G G - C Mutated sequence A - T T - A C - A G - C An error occurs during replication and A bonds to C instead of G. This is called a mutation.

Accuracy and Repair During replication, there is about one error per 1 billion nucleotides There are few errors because cells constantly proofread and repair damage

What causes mutations? Mutagens: substances that cause mutations Certain chemicals UV radiation X-rays

What happens when mutations occur? Usually nothing, mutations are mostly neutral Sometimes mutations are harmful and can cause disease, cancer, and death

What happens when mutations occur? Sometimes mutations are beneficial and improve an individual’s chance of survival

How fast does DNA replicate? In humans about 3 hours Bacteria about 10 - 20 minutes