Cells use information in genes to build several thousands of different proteins, each with a unique function. But not all proteins are required by the cell at any one time. By regulating gene expression, cells are able to control when each protein is made. CHAPTER 11: GENE EXPRESSION

Role of Gene Expression -activation, or “turning on” of a gene that results in transcription and production of mRNA

Somewhat similar to DNA replication Strands must separate Enzymes and energy are required Also quite different from DNA replication Only one gene on one strand is transcribed Different enzyme is used RNA Polymerase (RNAP) What Occurs During Transcription?

Initiation – Proteins called transcription factors attach to the beginning of the gene Called the promoter region Signal where RNAP should bind What Occurs During Transcription? cont.

2. Eukaryotic DNA can be divided into two main parts 3. Introns – sequences of DNA that do not become proteins 4. Introns interrupt genes 4. Can be between genes or within one gene 3. Exons – sequences of DNA that become proteins 4. Exons are expressed 1. What Happens During RNA Processing?

Only ____ % of your DNA actually codes for protein! We used to think the other ____% was “junk DNA” We now think that most of that DNA plays a role in regulating gene expression Only ____% is now thought to be non-coding DNA FUN FACTS!

2. Both introns and exons are transcribed 3. Only exons are used to make proteins 4. Introns must be spliced (cut) out 5. Different proteins can be made depending on the order in which exons are put back together (alternative splicing) 1. What Happens During RNA Processing?

2. Extra nucleotides are added to both ends of the RNA 3. Forms a cap and tail 4. Keeps RNA stable as it “swims” out of nucleus and into cytoplasm 5. Single-strand RNA is less stable than double-strand DNA 1. What Happens … RNA Processing? cont.

There is no RNA processing in prokaryotes. RNA is translated immediately after it is transcribed.

RNA processing only happens in eukaryotes Click Here!

1. Piece of mRNA immediately after transcription 2. Parent DNA strand that the mRNA came from 3. Gene that produced the mRNA 4. Piece of mRNA immediately prior to translation 5. Daughter strand of DNA produced during replication 6. One exon in the gene PUT THE FOLLOWING IN ORDER FROM LARGEST TO SMALLEST…

A B C D E F G H A – polypeptide chain B – amino acid C – tRNA D – mRNA E – small ribosomal subunit F – large ribosomal subunit G – anticodon H - codon

2. RNA message is used to construct protein 2. Occurs in three main steps 3. Initiation – beginning of the process 4. Small ribosomal subunit attaches 4. Initiator tRNA binds to start codon 5. Anticodon of tRNA matches codon of mRNA 4. Large ribosomal subunit attaches 1. What Happens During Translation?

3. Elongation – constructing a polypeptide 4. Incoming tRNA binds to A site of ribosome 4. Polypeptide leaves tRNA of P site and attaches to new amino acid on tRNA of A site 4. Old tRNA leaves 5. mRNA and new tRNA shift left which makes room for next tRNA to bind 1. What Happens During Translation? cont.

3. Termination – the end of protein synthesis 4. Stop codon enters A site of ribosome 5. Signals end of translation 4. Polypeptide is released 4. Ribosomal subunits break apart 1. What Happens During Translation? cont. See? I tahld yoo I’d bee bahck!

TRANSLATION & YOU!

3-D Computer AnimationMolecular Data Animation

1. What is the difference between introns and exons? 2. What is RNA processing? What happens during this process? 3. What are two reasons why RNA must be processed in eukaryotes? 4. What happens during translation? 5. What role do the following play in translation: mRNA, tRNA, amino acids, small ribosomal subunit, large ribosomal subunit, A site, P site? Check Those Concepts

2. Mutations can involve changes to a single gene or to an entire chromosome 2. Can be beneficial or harmful 3. Beneficial mutations lead to genetic diversity 4. Genetically diverse populations have a greater chance of survival 4. May lead to evolution 1. What Causes Mutations?

2. Gene mutations (three types) 3. Substitution – one nitrogenous base is changed to another 4. May have no effect due to redundancy in code 1. What Causes Mutations? cont.

3. Insertion – new nucleotide is added to existing sequence 3. Deletion – nucleotide is removed 3. Both insertion and deletion mutations result in frameshifts 4. RNA “downstream” of the mutation is read differently 5. Creates a “domino effect” 5. Almost always create non-functioning protein 1. What Causes Mutations? cont.

Frameshift

Example: | THE | FAT | CAT | ATE | THE | RAT | If the letter “e” in THE is deleted, the letters shift and the entire sentence now has a different meaning FRAMESHIFTS & YOU…OR YOUR CAT | THF | ATC | ATA | TET | HER | AT | I’m not overweight, I’m under-tall!

3 DNA nucleotides + 3 RNA nucleotides (codon) = 1 amino acid GGACCUProline IT’S TIME FOR MATH WITH MR. J.!

1. What are the two main types of mutations? 2. What are the three different types of gene mutations? What is the difference between them? 3. Which type of gene mutation is more serious? Why? 4. Mutagens cause mutations. What are some mutagens? Are Those Concepts? Let’s Check!

3. Chromosomal mutations (four types) 4. Deletion – portion of chromosome is lost 4. Duplication – chromosome receives a new piece 1. What Causes Mutations? cont.

4. Inversion – portion of chromosome breaks away and is attached in reverse order 4. Translocation – portion of chromosome breaks away and reattaches to a different chromosome 1. What Causes Mutations? cont.