DNA and Protein Synthesis DNA • DNA stands for deoxyribose nucleic acid. • This chemical substance is found in the nucleus of all cells in all living organisms • DNA controls all the chemical changes which take place in cells • The kind of cell which is formed, (muscle, blood, nerve etc) is controlled by DNA Ribose is a sugar, like glucose, but with only five carbon atoms in its molecule. Deoxyribose is almost the same but lacks one oxygen atom. The nitrogen bases are:

o ADENINE (A)

o THYMINE (T)

o CYTOSINE (C)

o GUANINE (G)

Nucleotides • A molecule of DNA is formed by millions of nucleotides joined together in a long chain. • DNA is a very large molecule made up of a long chain of sub-units. • The sub-units are called nucleotides. • Each nucleotide is made up of a sugar called deoxyribose, a phosphate group -PO4 and an organic (Nitrogen) base: A, T, C, G BASE PAIRING RULE amount of C= amount of G AND amount of A= amount of T • Adenine always pairs with thymine, and guanine always pairs with cytosine.

DNA STRUCTURE • The nucleotide bases will point to the inside of the DNA molecule while the outside (backbone) of the DNA molecule will be made of the sugar and phosphate molecules. • When complete the DNA molecule forms a double helix (two spiral sides wrapped together). • The paired strands are coiled into a spiral called A DOUBLE HELIX. Genes • Each chromosome contains hundreds of genes. • Most of your characteristics: hair color, height, how things taste to a person, are determined by the kinds of proteins cells make (gene). • Proteins are made of chains of hundreds or thousands of amino acids. • The instructions for making a specific protein are found in a gene which is a section of DNA on a chromosome. • The gene determines the order of amino acids in a protein. • Changing the order of the amino acids makes a different protein. • REMEMBER: One gene makes one protein! DNA REPLICATION • Why do we replicate DNA? • When chromosomes are duplicated before mitosis or meiosis, the amount of DNA in the nucleus is doubled. STEPS OF DNA REPLICATION 1. DNA replicates (duplicates) itself in the nucleus when prepare to divide during mitosis 2. DNA molecule separates into two strands (unzips) 3. Each new strand will match up with free nucleotides present in the nucleus until two new IDENTICAL strands of DNA are formed 4. Each new DNA molecules carries the same base code as the original strand

PROTEIN SYNTHESIS • It is the process by which GENOTYPE (genetic makeup) is translated into PHENOTYPE (physical traits) • Process by which DNA code is translated into proteins. • Genes are found in the nucleus, but proteins are made on ribosomes in cytoplasm. • The codes for making proteins are carried from the nucleus to the ribosomes by another type of nucleic acid called ribonucleic acid, or RNA. • COMPARING DNA AND RNA RNA DNA *Single stranded *Double stranded *Base pairs: *Base pairs: C-G, A-U C-G, A-T *Ribose sugar *Deoxyribose sugar

• The three main kinds of RNA made from DNA in a cell’s nucleus are messenger RNA (mRNA), ribosomal (rRNA), and transfer RNA (tRNA). Part 1: TRANSCRIPTION Protein production begins when mRNA moves into the cytoplasm. Step 1: An enzyme “unzips” a section of DNA Step 2: messenger RNA (mRna) Step 3: RNA bases match up to their complimentary base on the DNA strand. The bases continue to match- up until it reaches a stop code. At the END of TRANSCRIPTION: We get a mRNA strand ready for translation– each triplet code on the MRNA strand is called a CODON. TRANSCRIPTION PART 2:TRANSLATION Step 1:mRNA made in transcription attaches to a ribosome Step 2: tRNA creates a complementary strand to the codon. A tRNA carries a set of 3 bases called an ANTICODON  the tRNA carries a specific amino acid that matches the anti-codon

CODON- 3 base section on the mRNA Step 3: The tRNA matches up with a 3 base section (codon) on the mRNA. For Example: CODON- UGG (mRNA) ANTICODON-ACC (tRNA) Step 4:As each anticodon matches up with it complimentary codon it leaves behind its amino acid creating a chain. How do genes know when to “turn on” or “turn off” protein making? Some codons code for START and others for STOP.

What did we get from TRANSLATION?  Genetic information from the mRNA is translated into a PROTEIN!

Complete the example on the following example using the Genetic Code chart.

DNA STRAND: ATT CCG GTA CTG ATT GUG CGT TGA CCA

MRNA –CODON: ______

TRNA-ANTICODON: ______

RRNA-(AA) _____-______-______-______- ______-______-______-______- ______

TRANSLATION

Mutations • If DNA is not copied exactly, the proteins made from the instructions might not be made correctly. • These mistakes, called mutations, are any permanent change in the DNA sequence of a gene or chromosome of a cell. • Outside factors such as X rays, sunlight, and some chemicals have been known to cause mutations. • All mutations are not bad! • Most mutations have little or no effect on the organism’s function. • Mutations are a source of variation in a population (crossover) • Only mutations found in sex cells can be inherited by the offspring in sexually reproducing organisms.

Mutagen- a factor in the environment that can cause DNA mutations. Ex: radiation, nuclear chemicals

Carcinogen- an agent that causes or tends to cause cancer. Ex: tar in cigarettes, certain viruses, certain drugs, UV rays

Impact of the Environment • Although genes determine many of your traits, you might be able to influence their expression by the decisions you make. • For instance, if some people at risk for skin cancer limit their exposure to the Sun and take care of their skin, they might never develop cancer. • Every organism has a specific number of chromosomes. • However, mistakes in the process of meiosis can result in a new organism with more or fewer chromosomes than normal. • If three copies of chromosome 21 are produced in the fertilized human egg, Down’s syndrome results. MUTATION TYPE: ADDITION

Genetic Engineering • Through genetic engineering, scientists are experimenting with biological and chemical methods to change the arrangement of DNA that makes up a gene. • Genetic engineering already is used to help produce large volumes of medicine.

Recombinant DNA • Recombinant DNA is made by inserting a useful segment of DNA from one organism into a bacterium. • Recombinant DNA is made by inserting a useful segment of DNA from one organism into a bacterium. • This method is used to produce human insulin, human growth hormone, and other chemicals by bacteria.

Genetically Engineered Plants • Genetic engineering can produce improvements in crop plants, such as corn, wheat, and rice. • One type of genetic engineering involves finding the genes that produce desired traits in one plant and then inserting those genes into a different plant.