Review 1

Base Pairing Rule Watson and Crick showed that DNA is a double helixWatson and Crick showed that DNA is a double helix A (adenine) pairs with T (thymine)A (adenine) pairs with T (thymine) C (cytosine) pairs with G (guanine)C (cytosine) pairs with G (guanine) 2

DNA Replication 3

Steps in DNA Replication Occurs when chromosomes duplicate (make copies) Occurs when chromosomes duplicate (make copies) The enzyme DNA polymerase adds new nucleotides Each old strand of nucleotides serves as a template for each new strand Each old strand of nucleotides serves as a template for each new strand 4

Another View of Replication 5

RNA 6

RNA Differs from DNA 1.RNA has a sugar ribose 2.RNA contains the base uracil (U) 3.RNA molecule is single-stranded 7

Structure of RNA 8

Three Types of RNA Messenger RNA (mRNA) carries genetic information to the ribosomesMessenger RNA (mRNA) carries genetic information to the ribosomes Transfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesizedTransfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesized Ribosomal RNA (rRNA), along with protein, makes up the ribosomesRibosomal RNA (rRNA), along with protein, makes up the ribosomes 9.

RNA RNA – Ribonucleic Acid Single stranded nucleotide chain –Single stranded helix DNA’s Thymine is REPLACED by Uracil –A & T “break up” because of the new guy: U –But C & G are still 4-eva

mRNA - messenger RNA –Used for protein synthesis –Codes for amino acid sequence –made from DNA –travels Nucleus  Cytoplasm  Ribosomes DNA:GACCATAGC mRNA: Codon: group of 3 bases “GAC” or “CAT” CUGGUAUCG

tRNA – transfer RNA –Brings specific amino acid to the growing amino acid chain –“fetching puppy” Anticodon “ACC” mRNA codon “UGG” Corresponding Amino Acid

The Genetic Code Use mRNA codons with chart!!!!

DNA = AAT CCG GGG ATC ATG CCG mRNA 14

Ribosomal RNA (rRNA) rRNA is a single strandrRNA is a single strand Globular in shapeGlobular in shape Site of protein SynthesisSite of protein Synthesis “docking station”“docking station”

Transfer RNA (tRNA) Clover-leaf shape Single stranded molecule folded like a “t” attachment site at one end for an amino acid Opposite end has three nucleotide bases called the anticodon

Transfer RNA anticodon

Making a Protein 18

Argenine – Leucine – Aspartic Acid Proteins = polypeptide = amino acid chain Peptide Bonds – amino acids are connected together through peptide bonds

Transcription Transcription – stage of protein synthesis where instructions for making a protein are transferred to an RNA molecule –DNA  mRNA : transcription Translation – stage of protein synthesis when the information in mRNA is used to make proteins –mRNA  amino acid chain

Genes & Proteins  Proteins are made of amino acids linked together by peptide bonds  20 different amino acids exist  Amino acids chains are called polypeptides  Segment of DNA that codes for the amino acid sequence in a protein are called genes 21

Two Parts of Protein Synthesis  Transcription makes an RNA molecule complementary to a portion of DNA  Translation occurs when the sequence of bases of mRNA DIRECTS the sequence of amino acids in a polypeptide 22

Genetic Code  DNA contains a triplet code  Every three bases on DNA codes for ONE amino acid  Each three-letter unit on mRNA is called a codon  Most amino acids have more than one codon!  There are 20 amino acids with a possible 64 different triplets  The code is nearly universal among living organisms 23

Always…use mRNA to decode!!!

Name the Amino Acids Use the code by reading from the center to the outside GGG? UCA? CAU? GCA? AAA?

Remember the Complementary Bases On DNA: A-T C-G On RNA: A-U C-G

Codons and Anticodons The 3 bases of an anticodon are complementary to the 3 bases of a codon Example: Codon ACU Anticodon UGA UGA ACU

29 Transcription Translation

PROTEIN SYNTHESIS 30

Protein Synthesis  The production (synthesis) of polypeptide chains (proteins)  Two phases: Transcription & Translation  mRNA must be processed before it leaves the nucleus of eukaryotic cells 31

DNA  RNA  Protein 32 Nuclear membrane Transcription RNA Processing Translation DNA Pre-mRNA mRNA Ribosome Protein Eukaryotic Cell

Pathway to Making a Protein DNAmRNA tRNA (ribosomes) Protein 33