Chapter 13- RNA and Protein Synthesis BIG IDEA: How does info. flow from DNA to RNA to direct the synthesis of proteins.

13.1 RNA How is RNA different from DNA? -Ribonucleic acid, RNA is a nucleic acid consisting of a large chain of nucleotides 3 Important diff. between DNA and RNA: sugar is ribose, NOT deoxyribose RNA is generally single-stranded instead of double-stranded RNA contains uracil in place of thymine

Functions of RNA: Messenger RNA (mRNA)- carry info. from DNA to other parts of cell Ribosomal RNA (rRNA)- subunits that make up proteins Transfer RNA (tRNA)- transfers each amino acid to the ribosome as specified by the messages in mRNA

How does the cell make RNA? In transcription, segments of DNA serve as templates to produce complementary RNA molecules. RNA complements base sequences of DNA RNA polymerase binds DNA to complementary strand

Introns- pieces of RNA that are cut out and discarded Promoter- a specific base sequence that tells RNA polymerase where to start and stop RNA synthesis RNA Editing Introns- pieces of RNA that are cut out and discarded Exons- The remaining pieces of RNA that are spliced (put) back together to form the final RNA introns and exons may play a major role in evolution. , small changes in DNA and RNA can create big changes on how genes affect cellular functions

13.2 Ribosomes and Protein Synthesis What is the genetic code and how is it read? Bases (in the case of RNA)- A,U, C, and G form the genetic code. Code is read 3 letters @ a time. Each “word” is 3 bases long, and corresponds to an amino acid Each 3 letter “word”= codon

4 different bases in RNA= 64 different possible 3-base codons Most amino acids can be specified by more than 1 codon. Can be read using genetic code table

GAC AAG TCC ACA ATC From left to right, write the sequence of mRNA transcribed. Use codon table to translate into amino acids Repeat step 1 using complementary strand as new base

What role does the ribosome play in assembling proteins? Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains Translation is the decoding of mRNA→ protein

Steps in Translation Begins @ start codon (AUG). Ribosome attaches to mRNA “EPA” assembly line Continues until ribosome reaches “stop” codon.

Central Dogma of Molecular Biolgy Information is transferred from DNA → RNA → protein Gene expression= the in which DNA, RNA, and proteins put genetic info. into action in living cells.

13.3 Mutations Mutations are heritable changes in the genetic information

Point mutations -Changes in 1 or a few nucleotides that occur @ a single point *Substitution- 1 base (A/U/C/G) is changed into a different base. Usually affect 1 amino acid and may have no affect *Insertion/Deletion (frameshift mutation)- 1 base is inserted or deleted from DNA sequence. Can change every amino acid following the mutation.

Chromosomal mutations: 1) deletion: loss of part or all of chromosome 2) duplication: extra copy of all or parts of chromosome 3) inversion: reversing the direction of parts 4) translocation: part of chromosome breaks off and reattaches to diff. chromosome mutaTIONS ARE PRODUCED BY ERRORS in the genetic process. genetic material can be altered naturally or by artificial means. small changes may have little to no effect, but over time the changes gradually accumulate

What type of mutation? milk → mile fast → fats beast → best lot → lost substitution, deletion, insertion, inversion

Some mutations are caused by physical agents in the environment, called mutagens The effects of mutations can have little/no effect, or can negatively disrupt gene function

Harmful mutations vs. Helpful mutations Change protein structure or gene activity Some cancers Diseases New or altered functions in proteins that can be useful to organisms in changing environments. Genetic diversity Disease resistance

13.4 Gene Regulation and Expression To conserve energy prokaryotes transcribe certain genes @ a time. -Regulated by DNA-binding proteins Operon= group of genes that are regulated together

lac (lactose) operon is on when lactose is present , bacteria knows when it needs nutrients Promoter=where RNA-polymerase binds to start transcription Operator= region that controls rate of transcription

Eukaryotic gene regulation: transcription factors control the expression of genes Some open up chromatin to start transcription, some attract RNA polymerase, etc. Cell specialization (nerve cells, epithelial,cardiac, etc.) RNA interface (RNAi) turns genes on and off, plays a role in growth/development

Cell differentiation = cells become specialization in structure and function Master control genes (homeotic genes) regulate where specific organs grow in the body Homeotic genes are like switches that trigger certain patterns of development and differentiation in cells and tissues.