Unit 7 Review DNA, Protein Synthesis, Mutations

Hershey and Chase DNA is the hereditary material

Watson, Crick, Franklin Franklin: X-Ray crystallography Image of DNA Watson and Crick: Built the 3D Model of DNA

Chargaff A-T C-G

DNA vs. RNA DNA Usually double stranded (some viruses have single stranded DNA) 2 strands held together by weak H bonds THYMINE Deoxyribose sugar RNA Single stranded – mRNA – carries instructions for making proteins – tRNA – transfers AA – rRNA – assembles AA URACIL Ribose sugar BOTH are nucleic acids BOTH are built from nucleotides BOTH have A, C, and G

Nucleic Acids Polymers Made of nucleotides – 5-Carbon Sugar – Phosphate Group – Nitrogen Base The bases are the INFORMATIONAL part of DNA!!

Protein Synthesis Anabolic Proteins are built of Amino Acids Genes code for proteins – Transcription (RNA synthesis) – Translation (assembling amino acids into proteins) Are all proteins the same size? Why or why not?

Genetic Code UNIVERSAL Suggests a common ancestor Specific order of nitrogen bases (or nucleotides) determines what proteins are made, and therefore, what traits are expressed.

Codon Chart = Universal

Gene Expression Gene expression is a regulated process Even though ALL of your cells have the same genes, liver cells express different genes than cardiac muscle cells, resulting in cell differentiation

Lac Operon Inducible system Lactase is only produce in the presence of lactose So if no lactose, no lactase produced… Gene regulation results in conservation of cell resources

Genes code for proteins But not ALL of a gene is expressed Only EXONS code for proteins INTRONS are removed by RNA splicing

Mutations Heritable mutations occur in gametes Somatic mutations cannot be passed down

Types of Mutations – mistakes a)Point Mutations – effects a single gene i. Substitution -Missense -Nonsense ii. Frameshift -Insertion -Deletion a)Chromosomal mutations – most drastic, change in structure or # of chromosomes (affects many genes)

The Effects of Point Mutations ► A point mutation is a change in a single base pair in DNA. – A change in a single nitrogenous base can change the entire structure of a protein because a change in a single amino acid can affect the shape of the protein. (SUBSTITUTION) Gene Mutations Normal Point mutation mRNA Protein Stop mRNA Protein Replace G with A

Frameshift Mutations ► What would happen if a single base were lost from a DNA strand? ► A mutation in which a single base is added or deleted from DNA is called a frameshift mutation because it shifts the reading of codons by one base. – As a result, every codon after the deleted base would be different. Gene Mutations mRNA Protein Deletion of U

Mutations can be – Good – Bad – Have no effect (silent) Fixed by enzymes Result in same AA Occur in a non-coding region of DNA (such as an intron) Occur in a gene that is not expressed