Cell Signaling to Transcription and Translation Biology 160 We started by trying to understand this: http://www.youtube.com/watch?v=VAhM9OxZDkU&NR=1

Figure 5.11

The Role of Membranes in Cell Signaling Watch Neutrophil explanation: http://www.youtube.com/watch?v=OWUmXx5V_wE Watch XVIVO animation: http://www.youtube.com/watch?v=Mszlckmc4Hw Want the longer version? Check out: http://multimedia.mcb.harvard.edu/media.html Click on “Inner Life: Animation”

Intro to the Immune System Switch to Microbe Detectives presentation

cause B cells and T cells to grow and divide? So how do microbes cause B cells and T cells to grow and divide? Each cell has a receptor on its cell surface that recognizes a specific part of a microbe. That receptor triggers a Signal transduction pathway. This triggers gene expression (transcription) that… …leads to protein synthesis (translation) that… …allows the cell to grow (duplicate all its proteins that help to duplicate all its organelles) and divide (mitosis). OK, so let’s go into the nucleus and remind ourselves about DNA structure Watch cell signaling video

DNA Structure

DNA vs RNA Structure The four nucleotides found in DNA Differ in their nitrogenous bases. Are thymine (T), cytosine (C), adenine (A), and guanine (G). RNA has uracil (U) in place of thymine.

The model of DNA is like a rope ladder twisted into a spiral.

Detailed representations of DNA Notice that the bases pair in a complementary fashion.

The Flow of Genetic Information from DNA to RNA to Protein DNA functions as the inherited directions for a cell or organism. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

How an Organism’s Genotype Produces Its Phenotype An organism’s genotype, its genetic makeup, is the sequence of nucleotide bases in DNA. The phenotype is the organism’s specific traits (or what it looks like and how it functions), which arise from the actions of a wide variety of proteins. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

The one gene–one polypeptide hypothesis states that the function of an individual gene is to dictate the production of a specific polypeptide.

From Nucleotides to Amino Acids: An Overview Genetic information in DNA is transcribed into RNA and then translated into polypeptides.

Transcription: From DNA to RNA In transcription, Genetic information is transferred from DNA to RNA. An RNA molecule is transcribed from a DNA template. http://www.youtube.com/watch?v=WsofH466lqk

Transcription of an entire gene

Initiation of Transcription The “start transcribing” signal is a nucleotide sequence called a promoter. The first phase of transcription is initiation: RNA polymerase attaches to the promoter. RNA synthesis begins.

RNA Elongation The second phase of transcription is elongation: The RNA grows longer.

Termination of Transcription The third phase of transcription is termination: RNA polymerase reaches a sequence of DNA bases called a terminator.

The Processing of Eukaryotic RNA The eukaryotic cell processes the RNA after transcription. RNA processing includes: Adding a cap and tail Removing introns Splicing exons together

Translation: The Players Is the conversion from the nucleic acid language to the protein language. The Players mRNA tRNA Ribosome

Messenger RNA (mRNA) What are the rules for translating the RNA message into a polypeptide? Triplets of bases Specify all the amino acids. Are called codons.

The Genetic Code

The genetic code is shared by all organisms. A firefly gene expressed in a plant!!!

An mRNA molecule also has a cap and tail that help it bind to the ribosome.

Transfer RNA (tRNA) tRNA Acts as a molecular interpreter. Carries amino acids. Matches amino acids with codons in mRNA using anticodons.

Ribosomes Ribosomes Are organelles that actually make polypeptides. Are made up of two protein subunits. Contain ribosomal RNA (rRNA).

A fully assembled ribosome holds tRNA and mRNA for use in translation. http://www.youtube.com/watch?v=5bLEDd-PSTQ&feature=related http://www.youtube.com/watch?v=41_Ne5mS2ls

Translation: The Process Translation is divided into three phases: Initiation Elongation Termination

Initiation The first phase brings together: The mRNA The first amino acid with its attached tRNA The two subunits of the ribosome

Elongation Step 1, codon recognition The anticodon of an incoming tRNA pairs with the mRNA codon.

Elongation Step 2, peptide bond formation The ribosome catalyzes bond formation between amino acids.

Elongation Step 3, translocation A tRNA leaves the P site of the ribosome. The ribosome moves down the mRNA.

Termination Elongation continues until the ribosome reaches a stop codon.

Review: DNA RNA Protein The flow of genetic information in a cell

cause B cells and T cells to grow and divide? So how do microbes cause B cells and T cells to grow and divide? Each cell has a receptor on its cell surface that recognizes a specific part of a microbe. That receptor triggers a Signal transduction pathway. This triggers gene expression (transcription) that… …leads to protein synthesis (translation) that… …allows the cell to grow (duplicate all its proteins that help to duplicate all its organelles) and divide (mitosis). On to the Cell cycle!