Chapter 4 Section 3

1. Chapter 4Section 3 DNA

2. DNAdeoxyribonucleic 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.

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

4. 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

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

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

7. 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

8. 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

9. 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.

10. 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?

11. 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.

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

13. 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

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

15. 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

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

17. 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.

18. 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.

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