Chapter 4 Section 3 DNA

DNA deoxyribonucleic acid The code of life. Contains the code for information for an organisms growth and function When a cell divides, DNA code is copied and passed to new cells. This is how the new cells receive identical coded information that was in the original cell.

DNA Franklin Watson Crick Three scientists credited with the discovery of DNA Watson & Crick – developed the model of what DNA looked like

DNA Double helix – twisted ladder Made up of three parts Nitrogen base : ladder rungs Sugar called deoxyribose: side of the ladder Phosphate: side of the ladder

DNA – Nitrogen bases Adenine Thymine Guanine Cytosine These bases are always paired Adenine to Thymine Guanine to Cytosine

DNA Bases 30% Adenine = 30 % Thymine 5% Cytosine = 5% Guanine The paired amounts must be equal Each base will only bond with its correct partner. 30% Adenine = 30 % Thymine 5% Cytosine = 5% Guanine

Copying DNA Occurs BEFORE mitosis or meiosis Occurs in INTERPHASE Original DNA Enzyme separates DNA sides New bases pair with bases on original DNA Pair with correct partner ( A-T / C-G) Two new identical DNA molecules produced

GENES Gene – section of a DNA on a chromosome Genes – have the instructions for the making of your proteins Each chromosome can have thousands of genes Amino acids – building blocks for proteins Genes – determine to order of the amino acids

Making proteins Chromosome made up of a long molecule of DNA DNA is made up of thousands of genes Gene is made up of nucleotides ( three parts – sugar/base/phosphate) Nucleotide determines the type of amino acid Order of amino acids – determines the type of protein.

Making of Proteins DNA – stores the code for the protein DNA – locked in the nucleus Proteins are made by ribosomes Ribosomes are outside the nucleus So the code from the DNA must get out of the nucleus and to a ribosome How does that happen?

Making Proteins Nucleic acid – RNA ( ribose nucleic acid) RNA will get the code from the nucleus to a ribosome and then find an amino acid and build the protein.

Types of RNA 3 types of RNA Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)

RNA RNA – also made of 3 parts (nucleotide) Sugar ( ribose) Phosphate Nitrogen base RNA – singled stranded/ not twisted like a ladder that has all its rungs sawed in half

RNA bases Adenine Uracil Cytosine Guanine Notice they are the same as DNA EXCEPT RNA makes uracil inplace of thymine

Messenger RNA Messenger RNA – made in the nucleus Messenger RNA carries the DNA code From the nucleus to a ribosome in the cytoplasm So messenger RNA is how the code gets out of the nucleus. This code will direct the order in which amino acids will bond. There by directing the code for a protein

Ribosomal RNA Ribosomal RNA – this is the material that makes a ribosome They allow the messenger RNA carrying the code to attach.

Transfer RNA Transfer RNA are molecules of RNA found in the cytoplasm with certain amino acids attached. Transfer RNA brings these amino acids to the ribosome.

Controlling genes Cells must be able to control genes by turning some on and some off. Sometimes mistakes are made when DNA is being copied. Mutation – any permanent change in the DNA sequence of a gene or chromosome If DNA is not copied exactly, proteins made from the instructions might not be made correctly.

Code Copying DNA: AAT GGG CGG TAT DNA : TTA CCC GCC ATA mRNA using DNA the top strand UUA CCC GCC UAU tRNA – AAU GGG CGG AUA Notice that tRNA is almost a perfect match for the original DNA ( thymine was replaced by uracil)