UNIT 7 NOTES RNA, Protein Synthesis, Mutations, & Gene Expression Unit 7 Quiz: December 4, 2015 (Friday) Unit 7 Test: December 9/10, 2015 (Block day)

RNA I.RNA – Venn (pp. 336) Your Foldable DNA contains specific sequences of nucleotides known as ___________. The instructions they contain are carried out through the making of _______________. Protein synthesis occurs at the ____________ which are located in the ____________, but DNA is found in the ____________. DNA cannot leave the nucleus because it is_____________, so another molecule is required to take the genetic code from the _______________ to the ________________ so protein synthesis can take place. This molecule is __________. genes proteins ribosomes cytosolnucleus a double helix nucleus cytoplasm RNA

The Central Dogma The reading & expressing genes from DNA to RNA to proteins occurs in all living things from bacteria to humans and is refer to by scientists as the central dogma of biology.

II. PROTEIN SYNTHESIS (pp ) In protein synthesis, the instructions contained in _______ are carried out through the making of a protein. Protein synthesis takes place in two steps: DNA

Transcription A. Transcription takes place in the _____________ and allows the _______________ of DNA to be carried out to the ________________. 1. First, the enzyme ___________________________, unzips part of the DNA molecule. 2. RNA nucleotides are moved in according to base pairing rules and ________________ is synthesized. There are 3 important ways that transcription differs from replication: a. Only _______________ of the DNA molecule is copied in transcription. b. In RNA, the nucleotide that pairs with adenine is ______. The nitrogen base, _______, is not found in RNA. c. Only the portion of __________________________________________ is “unzipped” and transcribed. nucleus instructions ribosome RNA Polymerase mRNA one side uracil thymine DNA representing a gene

Transcription 3.When the mRNA is first transcribed, there are long sequences of _____________ that are not required for the synthesis of the protein called _________. The DNA sequences that code for the protein are known as _____________. Introns are edited out (cut out) of the mRNA before it leaves the nucleus and the remaining _____________ are spliced together to form the final mRNA. nucleotides introns exons

4. Before mRNA is ready to leave the nucleus a ____________ cap is added to the 5’ end called the ________________ and a long string of ___________ nucleotides called the ____________ to the 3’ end. So far scientist have determined the GTP cap helps in ________________ recognition but have yet to learn the significance of the poly A tail. protective 5’ GTP Cap adenine poly A tail ribosome

Transcription 5. mRNA leaves the ___________ through the _______________ and travels to the _________________, the site of protein synthesis. When mRNA arrives at the ribosome, the two parts of the ribosome, (small and large ribosomal subunits) come together and form a functioning ribosome. nucleus nuclear pores ribosomes

Translation B. Translation takes place at the ______________. The message in ________ is read by the ribosome, _______ brings the corresponding ____________ to make the final product – a polypeptide chain  ____________. Ribosomes a) Synthesized in the _____________________ of eukaryotic cells b) Composed of _______________ and ___________________ c) Composed of two _________________ that come together when translation begins  Two locations for eukaryotic ribosomes o Bound Attached to ___________________ Synthesize proteins _________________________________________ – Free Found in ________________ Synthesize Proteins_______________________ ribosome mRNA tRNA amino acid protein nucleolus rRNA protein subunits rough ER Destined for export out of cell cytosol Remain in the cell

Codons 1. Codons – A Mechanism to “Read” mRNA The ______________ of proteins are _______________. There are ____ amino acids used in building the proteins essential for life. The mRNA message is read by the ribosome in groups of three __________________ called __________. Each codon codes for a specific amino acid. A codon can be made up of any combination of the 4 nucleotides; in other words, there are 4 X 4 X 4, or ____ possibilities for codons. Since there are only 20 amino acids, many different codons represent the same amino acid. There are codons that are _________( AUG _) and ________ signals for the amino acid chain. The genetic code is ___________; that is, the same ____________ codes for the same____________ in all organisms. monomersamino acids 20 nucleotidescodons 64 start stop universal codon amino acid

Codon Charts Ex: CCC

Using Codons For the following codons, identify the corresponding amino acid: a. UAC - ______________________________ b. AGA - ______________________________ c. GCA - ______________________________ d. CCU - ______________________________ For the following amino acids, give all possible codons: a. arginine - ______________________________________________ b. glycine - _______________________________________________ Tyrosine Arginine Alanine Proline CGU, CGC, CGA, CGG, AGA, AGG GGU, GGC, GGA, GGG

tRNA 2. tRNA –transfer RNA The function of tRNA is to transfer the _____________ specified by the _____________ to the ____________ for protein synthesis. The __________ of the cell is stocked with all 20 amino acids required for protein synthesis. The tRNA molecule carries an __________ at one end and at the other end, it has a group of ___ nucleotides known as an _______________. The anticodon binds to the mRNA codon according to base pairing rules and insures that the proper amino acid is brought to the ribosome. amino acid mRNA codon ribosome cytosol amino acid 3 anticodon

t RNA When the__________________________________ comes to the ribosome to begin initiation, its anticodon attaches to the codon of the mRNA that is located in the _________ of the ribosome. The next t RNA enters and its anticodon attaches to the mRNA codon in the ___________ of the ribosome. The two amino acids form a ______________________ (with the aid of the enzyme peptidyl transferase & rRNA). The initiator tRNA is bumped off, but it leaves its amino acid behind as a part of the growing polypeptide chain first tRNA (initiator RNA) P site A site peptide bond

3. Building a Protein The ________ slides through the ribosome (translocates) so that the next codon is in the A site. As the codon is read, the t RNA with the corresponding _anticodon_ (according to base-pairing rules) comes to the ribosome carrying its amino acid. That amino acid forms a peptide bond to the last amino acid in the polypeptide chain. This whole process is known as elongation, and will continue until a stop codon on the mRNA is reached. This begins termination. Then the ribosome releases the amino acid chain, which coils & folds to form a _protein; the t RNA, mRNA, and ribosomal subunits disassemble. mRNA

Building a Protein

Mutations (pg 345) A mutation is a change in the DNA sequence. The mutation may be classified as: chromosomal or gene mutations. Most mutations are harmful, but a few are beneficial. A. Chromosomal Mutation - Chromosomal mutations involve the number or structure of the entire chromosome. It affects all genes on that chromosome! - These errors generally occur during meiosis or mitosis. - May result in a number disorder (extra chromosome or deleted chromosome), or insertion, deletion, or translocation of a piece of chromosome and the corresponding genetic information.

Mutations B. Gene Mutation - Gene mutations affect only one gene on an individual chromosome. This may result in a change to only one nucleotide or many nucleotides. - There are 2 types of gene mutations. 1. Point Mutation Point mutation is a change at one point in the DNA sequence. Ex: one base change: substitution, or insertion, or deletion. - This might have no effect or change on an amino acid sequence. Therefore, the resulting protein may or may not be altered. The incidence of these mutations is relatively low due to the action of enzymes that proofread the DNA sequence after replication.

Mutations 2. Frameshift Mutations Frameshift mutations involve the insertion or deletion of a nucleotide. - An insertion or deletion of a nucleotide causes a shift in the reading of the remainder of the codons; therefore, the translation of the remainder of the mRNA is altered. This will usually result in tremendous changes in the polypeptide chain and completed protein.

Only a ________________in a cell are expressed at any given time. An expressed gene is a gene transcribed into RNA. ??? How does the cell decide which will be turned on and which will stay “silent”? You already know about _____________ regions that show RNA polymerase where to start. There are other ______________________ that control whether a gene is ON or OFF. PROMOTER REGULATORY SITES fraction of genes Gene Expression (pg. 344)

Regulatory sites Promoter (RNA polymerase binding site) Start transcription DNA strand Stop transcription Section 12-5 Typical Gene Structure

Gene Regulation Cells turn genes ___________as needed Many genes are regulated by ___________ proteins that keep them turned off until needed. Others use proteins that _________ translation or _______ protein synthesis repressor speed up affect ON & OFF

Eukaryote gene regulation is more COMPLEX than Prokaryote regulation Gene regulation is also important in _________ way organisms________. _______________ must occur Cells differentiate by turning _________________ on and off. How does a zygote Become a multicellular organism? How does it know what kind of cell to be? shaping develop different genes Differentiation

In the 1980s, researchers discovered a series of genes in fruit flies called ____________. These genes control the differentiation of the developing embryo and tell parts where to grow and when._____________________. EX: Mutations to Hox genes can cause a ____ to grow where an _________ should sprout. Hox genes Controls basic body plan leg antenna

Since that time, Hox genes with ____________ _________ have been found in a variety of organisms Including ______ because of common ancestry. © Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved almost identical sequences humans

FYI Similar genes controlling the eyes of insects and our own eyes have also been discovered. Our version of the gene can be inserted in a fly and still trigger the building of an insect eye!