DNA Deoxyribose Nucleic Acid
Biomolecules Remember 1. Carbohydrates 2. Lipids 3. Nucleic acids hold genetic information; code for proteins 4. Proteins
History of DNA
Who Discovered DNA Rosalind Franklin Took X-ray diffraction images In 1953 James Watson & Francis Crick Used Franklin s image Developed the 1 st accurate model of DNA
Nucleic Acids Overall Importance to Organisms Stores and transmits genetic hereditary information Codes for proteins Gene- specific segment of DNA
Nucleic Acids DNA double stranded genetic molecule RNA single stranded genetic molecule
Basic Building Block- Nucleotide
Sugar part of Nucleic Acids DNA RNA
Base pairs in DNA: A T and G C Hydrogen bonds
Held together by H bonds
DNA Double Helix Twisted Ladder Rungs of ladder are Nitrogenous base pairs held together by weak Hydrogen bonds Adenine with Thymine Guanine with Cytosine Side of ladder Alternating Sugar and phosphate backbone
DNA is Antiparallel
5 5 5 3 3 3 3 5 Parallel Strands Antiparallel Strands
Nucleosome
DNA histones nucleosomes chromosomes Organization of DNA In chromosomes, DNA is wound around histones A nucleosomes is a cluster of 8 histones
Reason for Packaging DNA must be tightly wound in order to fit inside the nucleus or nucleoid region of a cell Uncoiled human DNA is about 6 feet long!
Summary of DNA Structure 1. DNA is made of nucleotides as building blocks Nucleotides consist of deoxyribose (sugar), phosphate and a base 2. DNA has a antiparallel double helix shape 3. DNA is held together by hydrogen bonds 4. DNA consists of two strands joined by complementary base pairs Adenine and Thymine (A-T) Guanine and Cytosine (G-C) 5. A segment of DNA is called a gene, which codes for proteins
DNA Replication
Replication Replication copying DNA for new daughter cell Occurs during S phase of cell cycle S for DNA Synthesis
Replication copying DNA Replication copying DNA to supply new cells with DNA copy DNA instructions to make proteins and specialized cells
Base sequence The sequence of bases codes for proteins Ex. The strand you see now is ACAGGACGAC which may be the gene for the protein, keratin, in your fingernails That sequence of DNA would be the gene for keratin
Human DNA (As Chromosomes) 23 pairs of chromosomes 25, 000 genes
Replication is used to provide new cells with copy of DNA when new cells divide for Healing Replacement Growth increase # of cells
Cancer uncontrollable growth of cells Defect in their DNA that tells them to keep growing and dividing
Cancer Cells under Microscope
DNA Replication What do you see?
Terms of Replication Helicase enzyme that unwinds DNA DNA Polymerase enzyme that adds nucleotides to DNA Parent strand original DNA double helix Daughter DNA DNA copies with one side from parent strand and one new side Replication fork where DNA is unwound and separated into 2 single strands
Steps of DNA Replication S phase 1. Helicase carefully unwinds double helix of DNA, revealing replication fork 2. DNA Polymerase adds complimentary nucleotides to the two original strands of unwound DNA 3. Hydrogen bonds hold Adenine to Thymine, and Cytosine to Guanine 4. Two new strands of DNA are formed, one for original cell, and one for new cell
Can you label the parts?
Helpful Videos http://sites.fas.harvard.edu/~biotext/animations/r eplication1.swf Flash DNA Replication 3D animation https://www.dnalc.org/resources/3d/04- mechanism-of-replication-advanced.html Overview of DNA structure and replication https://www.youtube.com/watch?v=27txkofu2nw
Mutations Mistakes made during replication Most mutations have no affect! Types of Mutations Point Mutations Deletions Substitutions Frame Shift
Mutations on Chromosomes