DNA, RNA, and Proteins By Liz LaRosa www.middleschoolscience.com 2011

DNA and Protein Synthesis DNA contains the genetic information to make amino acids Amino acids combine to make proteins These proteins determine the physical traits of an organism and control cellular functions. Proteins do everything, and DNA gets all the credit! Think of them as tiny minions who do all the work

DNA and Protein Synthesis

DNA and Protein Synthesis Codon: three bases code for a specific protein: ex: AAA = Lysine The codons code for 20 amino acids Just like the alphabet has 26 letters to make all the words we know, the 20 amino acids make all the different proteins found in living organisms The codons are the template for protein synthesis, which takes place on the ribosomes (rRNA) in the cytoplasm

Name the Amino Acid: UAU CCG AGU Tyrosine GCA Proline Serine Alanine DNA and Protein Synthesis – Codons and amino acids Name the Amino Acid: UAU CCG AGU GCA Tyrosine Proline Serine Alanine

But… How does the information get from the DNA to the cytoplasm? DNA and Protein Synthesis But… How does the information get from the DNA to the cytoplasm? mRNA

DNA and Protein Synthesis - Transcription 1) DNA unzips 2) mRNA (messenger ribonucleic acid) copies info from DNA using base pairings RNA is different from DNA Single stranded, not double stranded Instead of deoxyribose, it has ribose instead of Thymine, it uses Uracil 3) Carries the genetic code from the nucleus to the ribosome in the cytoplasm

DNA and Protein Synthesis - Translation rRNA (ribosomal RNA) attaches to mRNA and starts reading the codons tRNA (transfer RNA) – carries amino acids and attaches them to the growing protein chain When protein production is complete, the ribosome releases the protein chain

DNA and Protein Synthesis - Summary

DNA G A T T A C A C U A A U G U mRNA DNA and Protein Synthesis Practice making mRNA using the DNA template DNA G A T T A C A C U A A U G U mRNA

mRNA CUA AUG UGC DNA and Protein Synthesis Amino acids are linked together in the same order as the codons , creating a protein chain Just like linking letters to make words, linking amino acids makes proteins mRNA CUA AUG UGC Leucine methionine Amino Acid Amino Acid Amino Acid

Mutations are any changes that take place in DNA: DNA and Mutations Mutations are any changes that take place in DNA: Can be spontaneous or caused by mutagens ex: Chemicals, high temperatures, UV light, radiation Can change the genetic code, and be replicated when forming new body cells. In sex cells, can be passed on to offspring. Mutations can be neutral, beneficial, or harmful ex: Blue eyes – a mutation that occurred 6-10,000 years ago, can be traced back to one ancestor what kind of mutation is that?

DNA and Mutations – Let’s look at different mutations THE DOG BIT THE CAT

Substitution - Replace just one letter: THE DOG BIT THE CAR DNA and Mutations - Substitution THE DOG BIT THE CAT Substitution - Replace just one letter: THE DOG BIT THE CAR

Deletion: Delete just one letter (T): THE DOG BIT HEC AT DNA and Mutations - Deletion THE DOG BIT THE CAT Deletion: Delete just one letter (T): THE DOG BIT HEC AT

Insertion - Add just one letter (E): THE DOE GBI TTH ECA T DNA and Mutations-Insertions THE DOG BIT THE CAT Insertion - Add just one letter (E): THE DOE GBI TTH ECA T Cells have “proof reading” proteins that constantly check the DNA and fix errors, so most are corrected

Protein Synthesis- you try it! http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html

DNA transcription and translation- you try it! http://learn.genetics.utah.edu/content/begin/dna/transcribe/

Genes! A string of codons codes for several amino acids to form a gene A gene can be as short as 50 nucleotides and as long as 250 million. Humans have over 3 billion nucleotides or 1 billion codons Each gene codes for a certain trait.

Every gene is paired by the gene of the opposite sex Gene pairing Every gene is paired by the gene of the opposite sex Dominant or recessive (R) or (r) Heterozygous - carrier (different) - Rr Homozygous (same) – rr or RR Dominant gene is expressed as phenotype Punnett Square