History of DNA Friederich Miescher discovers "nuclein" (DNA) in the cells from pus in open wounds -- cells composed mostly of nuclear material. (1869) Fredrick Griffith – a factor in heat killed, disease causing bacteria can “transform” harmless bacteria into ones that cause disease. (1928) Fredrick Griffith Sydney Brenner – Shows the existence of messenger RNA.

Rosalind Franklin – Studied DNA using X-ray diffraction. Shows twisting of DNA. (1952) Watson and Crick determine that deoxyribonucleic acid (DNA) is a double-strand helix of nucleotides. (1953) – won nobel prize in 1962 Craig Venter – Mapped the Human Genome (2000)

DNA and Chromosomes The Nucleus contains chromosomes which are made of DNA and a segment of DNA is a gene. The DNA is wrapped around proteins called Histones. Chromosome Supercoils Coils Nucleosome Histones DNA double helix

What does DNA do? DNA contains the genetic code. The code is the information needed to make proteins.

DNA Structure DNA is a double stranded polymer made of individual nucleotides. NUCLEOTIDES: 1. Phosphate group 2. Deoxyribose sugar 3. Nitrogen base

Nitrogenous Bases Bases come in two types 1. pyrimidines – cytosine (C) – thymine (T) – Uracil (U) found in RNA only 2. purines – guanine (G) – adenine (A)

The Backbone Sugar and phosphate group makes up the backbone of the DNA molecule The sides of the ladder

Nitrogenous Bases Adenine always pairs with Thymine Guanine always pairs with Cytosine Always meet in the middle with a weak hydrogen bond.

Polarity of DNA The polarity of a DNA molecule is opposite; the 5' end of one strand matches up to the 3' end of the other strand. Thus, the strands are said to be "antiparallel."

OK, now let’s try to make a human DNA Polymer Directions: obtain a nitrogenous base from your instructor and build a strand of DNA. DID YOU KNOW: you have about 9 million kilometer of DNA in your body. That’s enough to reach to the moon and back 13 times.

DNA SONG (to the tune of Row, Row, Row your Boat) (author unknown) We love DNA made of nucleotides. Sugar, phosphate and a base bonded down one side. Adenine and thymine make a lovely pair, cytosine without guanaine would feel very bare. O-O-Oh, de-oxy-ribo-nucleic acid RNA is ribo-nucleic acid.

Replication Copying of DNA Occurs in many locations and in both directions The Procedure 1. Hilacase unzips the DNA 2. DNA Polymerase – joins individual nucleotides to produce a new strand. 3. DNA is “proofread” by DNA Polymerase for mistakes.

DNA Replication Growth Replication fork DNA polymerase New strand Original strand DNA polymerase Nitrogenous bases Replication fork Original strand New strand

How are Proteins Synthesized from DNA? 1. DNA is transcribed into mRNA (messenger RNA) 2. mRNA leaves the nucleus and travels to the cytoplasm 3. Ribosomes in the cytoplasm use the code on mRNA to translate it into amino acids 4. Amino acids form a chain - a protein

Transcription RNA is very similar to DNA with the following exceptions: it is single stranded it has uracil instead of thymine it has the sugar ribose, instead of deoxyribose

Transcription Transcribe the following DNA strand to RNA: T G C A T C A G A A C G U A G U C U RNA DNA RNA polymerase Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) DNA Transcription

Translation 1. The mRNA travels through the cytoplasm to the ribosome. 2. The ribosome looks for the "start" codon - AUG, this is where the chain beginscodon 3. Transfer RNA (tRNA), has an anticodon at one end and an amino acid at the other, it binds to a complementary codon. Transfer RNA

Translation Translate the following mRNA to tRNA: A C G U A G U C U U G C A U C A G A Now, what is the amino acid sequence?

A C G U A G U C U = Codon U G C A U C A G A = Anticodon Threonine ---Stop ---Serine (not added on the chain)

Protein Synthesis

DNA SONG (to the tune of Row, Row, Row your Boat) (author unknown) We love DNA made of nucleotides. Sugar, phosphate and a base bonded down one side. Adenine and thymine make a lovely pair, cytosine without guanaine would feel very bare. O-O-Oh, de-oxy-ribo-nucleic acid RNA is ribo-nucleic acid.

Mutations 1. Point mutations- a change (Substitution) in one or a few nucleotides.

Frameshift Mutation The grouping of codons change because of an addition or deletion of a nucleotide. THE FAT CAT ATE THE RAT Delete the “H” in the word THE TEF ATC ATA TET HER

Chromosomal Mutations Involve changes in the number or structure of a chromosome. Deletion Duplication Inversion Translocation

The Significance of Mutations Most mutations are neutral Mutations causes genetic diversity Cancer causing Cause genetic disorders