UNDERSTANDING YOURSELF: GENETIC MAKE-UP and GENE FUNCTIONS

DNA

Double Helix structure Discovered by James Watson

and Francis Crick Composed of nucleotides 2 nucleotide chains running

together in opposite directions Antiparallel orientation

What is DNA made of?

Three main components Phosphate Deoxyribose sugar Four nitrogenous bases

Purines Adenine Guanine

Pyrimidines Cytosine Thymine

NUCLEOTIDES• Each consisting of phosphate, deoxyribose sugar, and one

of four nitrogenous bases

• Nucleotides run along each of the two strands of DNA, bonding together

• Nitrogenous bases of each nucleotide bond to the base of another nucleotide by hydrogen bonds– Adenine of one strand bonds with

Thymine of the other

– Guanine of one strand bonds with Cytosine of the other

Double Helix Bonding

Each strand has a backbone of a repeating phosphate sugar polymer: phosphodiester bonds are what bond each polymer together

ACTIVITY BREAK

• Use the colored wooden pieces provided to make a mini-double helix

• Red pieces: adenine

• Green pieces: guanine

• Blue pieces: Cytosine

• Orange pieces: Thymine

• Use the purple beads to create hydrogen bonds

• Use the yellow beads to create phosphodiester bonds—your phosphate backbone will be made out of the large black pieces

How is DNA organized in you?

One unique set of DNA is called a genome

A genome composed of chromosomes Composed of one DNA molecule carrying many

genes This one DNA molecule is extremely coiled and

super coiled Chromosomes can be located in the mitochondria of

a human/animal cell and in the chloroplast of a plant cell

WHAT A MESS OUR GENOME IS!

REPLICATION

• Final product: two identical DNA molecules (helixes)

• Each of the two DNA strands separate

• Each DNA strand acts as a template for the synthesis of its complimentary strand– 5’AAGGCTGA3’ acts as a template to make 3’TTCCGACT5’

• DNA Polymerase• Enzyme responsible for building new DNA strands• Matches up each base of the new strand with the

complementary base on the old, template strand

Types of Genomes

Plasmids

Organellar DNA

Viral Genomes

Prokaryotic Genomes

Eukaryotic Nuclear Genomes

PLASMIDS

• Found in bacterial cells

• Small DNA elements that are NOT essential for the basic operation of the bacterial cell

• Cannot survive outside of the cell

• Relatively small

• Can occasionally be found in fungal and plant cells

• Most found in mitochondria and chloroplast organelles, but can be found in nuclei or cytosol

ORGANELLAR DNA

• Organelle-specific DNA

• Individual mitochondria and chloroplasts contain identical multiple copies of their chromosomes

• Organelle chromosomes contain genes specific to the functions of the organelle concerned

• ENDOSYMBIOTIC THEORY:– Mitochondria and chloroplasts were originally prokaryotic

cells that entered another cell and became indispensable to it

VIRAL GENOME

A virus is a nonliving particle that can reproduce itself only by infecting a living cell

In some viruses, the DNA is double-stranded, but can be single-stranded, too

Can contain DNA or RNA, another type of genetic material

PROKARYOTIC GENOME

Can also be referred to as bacterial DNA

Contained within a single chromosome that is a single, circular double helix of DNA

Within each bacterial cell there can be from one to several identical copies of the single chromosome type

DNA arranged in a dense clump called a nucleoid

EUKARYOTIC NUCLEAR GENOME

Genes found in chromosomes of nucleus

Eukaryotic species classified as either diploid or haploid with only one or two chromosome set per cell

Animals and plants are diploid (two chromosomes per cell)

46 chromosomes in a human body cell

RNA

Production of RNA is the first step in the process of transferring information from gene to protein

It’s base sequence must match the base sequence of a segment of one of the two DNA strands

Synthesis of is transcription => RNA is the transcript

PROPERTIES

Single stranded (no double helix here)

Ribose sugar

Nitrogenous bases, just like DNA with one exception Purines: adenine and guanine Pyramidines: cytosine and uracil (not thymine)

DNARNA

mRNA (messenger RNA): Transcript synthesized directly from the DNA

Nucleotides in mRNA are read, not as individual nucleotides, but as a sequence of amino acids in a polypeptide chain through a process called translation

Enzyme RNA polymerase attaches to DNA and moves along it, making a longer and longer RNA molecule

One or more polypeptide chains and fold together to make a protein

ACTIVITY BREAK

Now, instead of bonding together strands of DNA, we’re going to make RNA out of DNA

Brown wooden pieces are uracil

Use one of your DNA strands to make new strands of RNA

Don’t forget your bonds!

PROTEINS

Polymer composed of amino acids

Chain of amino acids referred to as polypeptide chain

-20 amino acids known to occur in proteins-amino acids linked together by covalent bonds called peptide bonds-polypeptide chain always has amino end (NH2) and a carboxyl end (COOH)

STRUCTURE OF

PRIMARY STRUCTURE is the linear sequence of amino acids in a polypeptide chain

SECONDARY STRUCTURE specific shape the polypeptide chain takes on by folding

TERTIARY STRUCTURE produced by folding the secondary structure

QUATERNARY STRUCTURE composed of two or more tertiary structures joined together by weak bonds