What is it? When is it done? What is copied? DNA Replication What is it? When is it done? What is copied?

Two New, Identical DNA Strands Result from Replication Replication is called semiconservative because each new double helix is composed of an old (parental) strand and a new (daughter) strand.

PROTEIN SYNTHESIS

Protein Synthesis After replication and cell division, each new cell has its own DNA Now, how do those cells use that DNA to make proteins? How do you go from DNA (nucleic acid) to protein (amino acid)?

Overview of Protein Synthesis Copy (mRNA) is made of gene mRNA sent out of nucleus Ribosomes use mRNA as instructions to make a protein

Protein Synthesis Two phases: DNA Transcription mRNA Translation

Transcription

Transcription In nucleus DNA the template for mRNA RNA polymerase makes the mRNA

Only one DNA strand is used Just a portion of the DNA is copied (one gene) copy is called mRNA

DNA RNA RNA Differs from DNA T (thymine) U (uracil) Deoxyribose sugar Double stranded Single stranded T (thymine) U (uracil)

Question: What would be the complementary RNA strand for the following DNA sequence? DNA 5’-GCGTATG-3’

Answer: DNA 5’-GCGTATG-3’ RNA 3’-CGCAUAC-5’

Translation mRNA protein

Translation mRNA ribosome Ribosome reads the mRNA and makes protein

mRNA leaves nucleus ribosome attaches to mRNA ribosome reads the bases in groups of 3 (codon) AUG CUG codon

The ribosome uses the code to make the protein How The ribosome uses the code to make the protein How? How do you go from nucleic acid to amino acid?

tRNA Carries amino acids to ribosome U A C Amino acid Carries amino acids to ribosome Has anticodons that are complementary to mRNA codons

A A UAC AUG CUG

Genetic Code DNA contains a triplet code Every three bases on DNA stands for ONE amino acid Codon: Each group of 3 bases on mRNA The fact that the genetic code is about universal in living things suggests that the code dates back to the first organisms on earth and that all living things are related.

r http://www.wisc-online.com/objects/index_tj.asp?objid=AP1302

Gene Mutations Chromosome Mutations

What happens when there is a mistake during replication? What could go wrong when the DNA is being replicated? http://www.pbs.org/wgbh/nova/genome/program.html

Gene Mutations Point Mutations A. Substitution Frame shift Mutations Insertion Deletion

Point Mutations – substitution One WRONG BASE is used Original The fat cat ate the wee rat. Mutation The fat hat ate the wee rat

Examples of Point Mutations Sickle Cell Anemia

Examples of Point Mutations Tay Sachs Hemophilia B

Frame Shift Mutations A Insertion AAT AGG CAG GTT Deletion AAT AGG CAG GTT

Frame Shift Mutations A Insertion AAT AGG CAG GTT becomes AAT AAG GCA GGT … Deletion AAT AGG CAG GTT becomes AAA GGC AGG …

Frame Shift Original The fat cat ate the wee rat. Insertion The fat caa tet hew eer at.

Example of Frame Shift Mutation: Huntington’s Disease

Chromosome Mutations 1. Inversions 2. Duplications 3. Deletions 4. Translocations

Incorrect Chromosome Number – from nondisjunction during meiosis Trisomy 21 causes Down’s Syndrome http://learn.genetics.utah.edu/units/disorders/whataregd/down/