1. Cell Signaling to Transcription and Translation
Biology 160
We started by trying to understand this:

2. Figure 5.11

3. The Role of Membranes in Cell Signaling
Watch Neutrophil explanation:
Watch XVIVO animation:
Want the longer version? Check out:
Click on “Inner Life: Animation”

5. Intro to the Immune System
Switch to Microbe Detectives presentation

6. 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

7. DNA Structure

8. 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.

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

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

11. 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

12. 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

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

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

15. Transcription: From DNA to RNA
In transcription,
Genetic information is transferred from DNA to RNA.
An RNA molecule is transcribed from a DNA template.

16. Transcription of an entire gene

17. 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.

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

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

20. 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

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

22. 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.

23. The Genetic Code

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

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

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

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

28. A fully assembled ribosome holds tRNA and mRNA for use in translation.

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

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

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

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

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

34. Termination
Elongation continues until the ribosome reaches a stop codon.

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

36. 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!