Life and

Genetic Material

Defining Life

• Even in science there isn’t one single definition of Life

• Scientists try to make all living things fit into their definition so the one we will use in this class is:

1. All life must be built of complex parts

2. All life evolves by natural selection

3. All life reproduces by passing on genetic material

This definition should fit life even if it isn’t from Earth

1 - Complex Parts• The complex parts that all life is made of on Earth are

called Cells

• Cells are the building blocks of all LIVING THINGS• Don’t get this confused with ATOMS!!!

• There are 2 types of cells1. Prokaryotic – evolved early, simple life. Includes all

types of bacteria

2. Eukaryotic – evolved ‘later’, more complex. What all living things other than bacteria are made of.

2 – All Living Things Evolve• All living things evolve

• Evolution is the end result of natural selection• Natural Selection is when certain living things have traits

that help them survive.• If a living thing is more likely to survive, it is more likely to

have offspring (children)• Those children will likely gain the traits that help them

survive from their parents• Those children will likely survive, reproduce, and pass

down the traits• This continues over many, many generations until the living

thing changes.

3 – Living things have Genetic Material

• The important part that we are going to look at is that all life reproduces by passing on genetic material

• Genetic Material is a set of biological information storage

• This information is passed down from a parent to an offspring during reproduction

DNA as Genetic Material• On Earth, all living things have DNA as their genetic

material

• DNA is a molecule.

• This means it is made of many atoms hooked together.

• DNA stands for Deoxyribonucleic Acid.

DNA

• So what is DNA?

• DNA stores all of an individuals genetic information

• DNA is found in the nucleus of eukarotic cells

• It is made of repeating parts called nucleotides

Nucleotides

• A nucleotide has 3 parts1) A Phosphate Molecule (has

Phosphorus atoms)

2) A Pentose Sugar – (has 5 Carbon atoms)

3) A Nitrogenous Base (contains nitrogen atoms)

• This is the basic, repeating unit

of DNA

• Nucleotides hook together over and over and over to make strands

Nucleotides – Nitrogenous Bases

• DNA has 4 nitrogenous bases. • Thymine (T)• Cytosine (C)• Adenine (A)• Guanine (G)

Nucleotides

• Nucleotides hook together to make strands

• The phosphates always connect to the sugars

Nucleotide Strands• DNA molecules are actually made of

2 strands connected together

• The 2 strands are connected in the middle by the nitrogenous bases

• The bases always match up the same way• A on one strand always connects to

T on the other strand• C on one strand always connects to

G on the other strand

Nucleotide Strands• What would be the matching nucleotide sequence for the

following DNA strand?

AATCGCTCATC

• Circle the mistakes in the following DNA molecule.

A C G U T C C T T A C G G C

T C C A A G G T C T G C C U

DNA 3D Structure

• DNA forms a complex, 3D structure

• DNA is connected like a ladder.

• This DNA ‘ladder’ is twisted AND coiled to create a shaped known as a double helix

DNA Sequence

• DNA stores information by its sequence

• The sequence is the order the nitrogenous bases are attached

• This sequence determines how the cell will function.

DNA Sequence

• How does the DNA sequence determine the function of your cells?

• This sequence is used to make proteins

• Proteins are working molecules in the cell that carry out all the functions needed for a cell to survive

• Proteins are made of basic units called amino acids. There are 20 amino acids that make up a nearly infinite amount of proteins

How DNA Makes Proteins

• Every 3 nucleotides tells the cell what amino acid to use

• These amino acids hook to each other

• Eventually, the DNA tells the cell to stop adding amino acids

• The section of DNA that makes 1 protein is called a gene

The Genetic Code

• The Genetic Code is what amino acid goes with each 3 nucleotide sequence

• Which amino acid does the code CAA pick?

• What protein would be made from the DNA sequence AACGATGACTCAGGC?

DNA Replication

• DNA is self-replicating. This means it can make a copy of itself

• DNA copies itself when a cell needs to make a copy of itself (when a cell divides)

DNA Replication

• Because DNA always keeps one original strand, it is called Semi-conservative