DNA And PROTEIN SYNTHESIS

Hershey and Chase Virus -made of DNA and protein The experiments a virus with either radioactive DNA or radioactive protein were used to infect bacteria Either the radioactive proteins or radioactive DNA would be transferred to the bacteria Identifying which one is transferred would identify the genetic material. Only the radioactively labeled DNA was transferred.

DNA Structure Composed of nucleotides nitrogen containing base, a five -carbon sugar (deoxyribose), and a phosphate group. Four possible bases: adenine (A), guanine (G), cytosine (C), or thymine (T)

Chargaff’s Rules 1st: The composition of DNA varied from one species to another. This molecular diversity added evidence that DNA could be the genetic material. 2nd: the amount of one base always approximately equals the amount of a particular second base. Example: guanines equals the number of cytosines

Base Pairing Purines- Adenine and guanine two ring structures. Pyrimidines- Thymine and cytosine one ring structure. A purine always combines with a pyrimidine in the DNA double helix!

The double Helix Rosalind Franklin Worked with DNA fibers. Maurice Wilkins, used x-ray diffraction photographic techniques to analyze the structure of DNA. In February 1953, Francis Crick and James D. Watson had started to build a model of DNA. indirectly obtained Franklin's data which had crucial information Crick and Watson then published their double helical model of DNA! (They get most of the credit)

Watson and Crick

RNA DNA Single Stranded Double Stranded Specific Base Uracil Thymine Sugar Ribose Deoxyribose Size Relatively small Big (chromosomes) Location Moves to cytoplasm Stays in Nucleous Types mRNA, tRNA, rRNA

The process is called Protein Synthesis! DNA → RNA → Protein The process is called Protein Synthesis! Making Protein!!!

“DNA → RNA” Transcription When a section of DNA is copied to RNA RNA Polymerase Happens in the nucleus

“RNA → (amino acids) protein” Translation “RNA → (amino acids) protein” The transfer of the instructions in RNA to a protein made of amino acids. Happens in the cytoplasm and interacts with a ribosome.

Amino acids make protein!!! The Genetic Code There are 20 different amino acids It takes 3 letters (A,U,G,C) to code for each amino acid mRNA is divided into three-base segments called codons. A codon is the segment of nucleotides that codes for an amino acid or for a start or stop signal There are 64 codons. Amino acids make protein!!!

Start and Stop Codons AUG codes for the amino acid methionine. “The start codon” which begins every translation of every amino acid chain. There are three stop codons: UAG, UGA, UAA.

DNA → RNA → Protein

Mutations change in the DNA or RNA sequence May result in new alleles Important for evolution Can be beneficial or harmful May be spontaneous (due to mistakes during transcription/translation or mitosis/meiosis) May be environmentally endued! There are also chromosomal mutations, large changes with dramatic effects.

chromosomal alterations Types of Mutations point mutations frameshift mutations (Mutations that disrupt the reading frame by insertions or deletions of a non- multiple of 3 nucleotide bases.) chromosomal alterations

Beneficial Mutations They lead to new versions of proteins that help organisms adapt to changes in their environment. essential for evolution increase an organism’s changes of surviving or reproducing Example: Mutations in many bacteria that allow them to survive in the presence of antibiotic drugs. The mutations lead to antibiotic-resistant strains of bacteria. Wolverine, from X-Men, has a mutation that causes his cells to repair themselves very quickly. This allows him to get up after an injury and continue to do good. It also gives him the appearance that he doesn’t age.

Harmful Mutations When a mutation alters a protein that plays a critical role in the cell it may not function properly, resulting in a medical condition. Harmful mutations may cause genetic disorders or cancer. A genetic disorder is a disease caused by a mutation in one or a few genes. Example: cystic fibrosis. A mutation in a single gene causes the body to produce thick, sticky mucus that clogs the lungs and blocks ducts in digestive organs. Cancer is a disease in which cells grow out of control and form abnormal masses of cells. It is generally caused by mutations in genes that regulate the cell cycle. Because of the mutations, cells with damaged DNA are allowed to divide without limits. Cancer genes can be inherited.

Cancer Mutations Cancer is caused by a series of mutations Cells have developed a number of control mechanisms to overcome mutations A mutation in one proto-oncogene would not cause cancer effects would be masked by mitosis and tumor suppressor genes. Signals for cell growth overwhelm the signals for growth regulation, and the cell quickly spirals out of control (Often, because many of these genes regulate the processes that prevent most damage to the genes themselves, DNA damage accumulates as one ages.) Cancers are caused by a series of mutations. Each mutation alters the behavior of the cell. For example, the first mutation inactivates a tumor suppressor gene, the second mutation inactivates a DNA repair gene, the third mutation creates an oncogene, and a fourth mutation inactivates several more tumor suppressor genes, resulting in cancer.