1. Gene Expression, RNA, Transcription and Translation
Higher Human Biology
Gene Expression, RNA, Transcription and Translation

2. Learning Intention:
To learn about gene expression
Success Criteria:
By the end of the lesson I should be able to
State that Phenotype is determined by the proteins produced as the result of gene expression.
State that only a fraction of the genes in a cell are expressed.
State that gene expression is influenced by intra- and extra-cellular environmental factors.
State that gene expression is controlled by the regulation of both transcription and translation.

3. A cell’s genotype is determined by the sequence of DNA bases in its genes
Phenotype is determined by the proteins produced as the result of gene expression

4. Although a specialised cell has a complete set of the organism's genes, only those needed for its specialised functions are switched on. All other genes are switched off.
So only a fraction of genes in a cell are expressed

5. The process of differentiation proceeds in a stepwise fashion and involves changes in gene expression. 
Gene expression is the activation of a gene that results in the formation of a protein.
Gene expression is influenced by intra- and extra- cellular environmental factors.

6. Gene activity in different specialised cells
Cell type
Activity of genes coding for production of:
antibodies
lysosome enzymes
enzymes for synthesis of urea
pepsin
phagocyte
off on
liver
stomach lining
lymphocyte
A good example of the mechanism by which genes can be switched on and off in response to various environmental signals is found in bacteria.

7. Gene expression - Summary
Phenotype is determined by the proteins produced as the result of gene expression.
Only a fraction of the genes in a cell are expressed.
Gene expression is influenced by intra- and extra-cellular environmental factors.
Gene expression is controlled by the regulation of both transcription and translation.

8. Learning Intention:
To learn about RNA
Success Criteria:
By the end of the lesson I should be able to
State that RNA is single stranded
State that RNA contains uracil instead of thymine RNA contains ribose instead of deoxyribose sugar.
State that mRNA carries a copy of the DNA code from the nucleus to the ribosome.
State that ribosomal RNA (rRNA) and proteins form the ribosome.
State that each transfer RNA (tRNA) carries a specific amino acid.

9. Structure of RNA Single Strand Uracil base pairs with adenine
It’s a ribose Sugar

10. Types of RNA
Messenger RNA (mRNA) – carries the genetic information from the nucleus to the cytoplasm for protein synthesis. (codon)
Transfer RNA (tRNA) – Carries amino acids on the anti-codon to the appropriate codon to form a polypeptide.

11. RIBONUCLEIC ACID DNA carries the code (“recipe”) for making proteins
The “equipment” for protein synthesis is in the cytoplasm
mRNA acts as a go-between molecule, carrying the “recipe” to the “equipment”.

12. RNA - Summary RNA is single stranded
RNA contains uracil instead of thymine RNA contains ribose instead of deoxyribose sugar.
mRNA carries a copy of the DNA code from the nucleus to the ribosome.
Ribosomal RNA (rRNA) and proteins form the ribosome.
Each transfer RNA (tRNA) carries a specific amino acid.

13. Learning Intention:
To learn about transcription
Success Criteria:
By the end of the lesson I should be able to
Describe the transcription of DNA into primary and mature RNA transcripts and include the role of RNA polymerase and complementary base pairing.
State that the introns of the primary transcript of mRNA are non-coding and are removed in RNA splicing.
State that the exons are coding regions and are joined together to form mature transcript. This process is called RNA splicing.

14. mRNA mRNA is transcribed from DNA in the nucleus.
When mRNA is formed, it has triplets of bases along it. These are called codons
A G C U U A C G G A U G
CODON

15. DNA to Protein

16. TRANSCRIPTION
The process of making mRNA from the template provided on DNA
DNA to act as template
Free RNA nucleotides
Enzymes including RNA polymerase
ATP for energy

17. TRANSCRIPTION

18. Energy is required from ATP
Transcription copies the information in DNA into an RNA molecule. This occurs in the nucleus. RNA polymerase enzyme binds to the promoter region of the DNA and moves along the DNA, unwinding the double helix and breaking the hydrogen bonds holding the base pairs together.
Energy is required from ATP
Free RNA nucleotides bond with their complementary base pairs on the DNA. RNA uracil pairs with DNA adenine, RNA adenine pairs with DNA thymine and cytosine pairs with guanine
The RNA nucleotides are held in place by hydrogen bonding, while strong covalent bonds form between the phosphate of one and the ribose sugar of the adjacent nucleotide.
When transcription is complete the RNA polymerase enzyme is released. The RNA that has been produced at this stage is known as the primary transcript.
The primary transcript now undergoes splicing 18

19. TRANSCRIPTION Hydrogen bonds between DNA bases re- form
DNA coils up into double helix

20. Splicing - Exercise
JUHTHEHFGBOYHSKYRSATANDLETHJDFKETHEJKFICA TUFNAPDFGFORSDSTHEDAY
Copy the letters above onto a scrap piece of paper – it contains a sentence interspersed with letters.
Cut the nonsense sections out and stick together the words to make a sentence.

21. It should read:-
THE BOY SAT AND LET THE CAT NAP FOR THE DAY
But you may also have come up with:-
THE BOY SAT FOR THE DAY
THE BOY LET THE CAT NAP
THE BOY LET THE CAT NAP FOR THE DAY

22. Introns and exons
The primary transcript of RNA is composed of introns and exons.
The introns are non-coding regions of genes and so do not appear in the mRNA in eukaryotic cells. The exons are coding regions of genes and so do appear in the mRNA.
The introns of the primary transcript of mRNA are removed in RNA splicing. 22 22

23. RNA splicing
In RNA splicing the primary transcript is cut at the boundaries between the introns and exons.
The introns are removed and the exons are joined together.
The mRNA can then leave the nucleus via a nuclear pore and enter the cytoplasm.

24. Transcription - Summary
How to describe the transcription of DNA into primary and mature RNA transcripts and include the role of RNA polymerase and complementary base pairing.
That the introns of the primary transcript of mRNA are non- coding and are removed in RNA splicing.
The exons are coding regions and are joined together to form mature transcript. This process is called RNA splicing.

25. Learning Intention:
To learn about translation
Success Criteria:
By the end of the lesson I should be able to
Describe the translation of mRNA into a polypeptide by tRNA at the ribosome.
State that tRNA folds due to base pairing to form a triplet anticodon site and an attachment site for a specific amino acid.
State that Triplet codons on mRNA and anticodons translate the genetic code into a sequence of amino acids.
State that start and stop codons exist.
State that codon recognition of incoming tRNA, peptide bond formation and exit of tRNA from the ribosome as a polypeptide is formed.

26. TRANSLATION Changing the code on mRNA into a sequence of amino acids.
Occurs in the cytoplasm
Involves ribosomes

27. The ribosome
The ribosomes are found in the cytoplasm either floating freely or attached to the rough endoplasmic reticulum. Ribosomes floating freely are used to synthesise proteins for use within the cell; those attached to the endoplasmic reticulum synthesise proteins for export or inclusion in the membrane.
Ribosomes are formed from proteins and a third type of RNA known as ribosomal RNA (rRNA).
During translation they allow the mRNA and tRNA to come together.
David S. Goodsell RCSB PDB 27

28. tRNA
Amino acid attachment site
Complementary base pairing occurs between nucleotides within the strand of tRNA, producing tRNA’s distinctive structure. This structure exposes a triplet anticodon site and attachment site for a specific amino acid.
The triplet anticodon site is complementary to the triplet codon site on the mRNA.
Triplet anticodon 28

29. TRANSLATION AMINO ACID tRNA ANTI-CODON RIBOSOME CODON mRNA U C G A G C

30. TRANSLATION U A U C G A G C U

31. TRANSLATION
PEPTIDE BOND U C G U A A G C U

32. TRANSLATION U C G U A U C G A G C U

33. TRANSLATION U C G G A U C G U A A G C U

34. TRANSLATION U A U C G A U C G A G C U

35. TRANSLATION U C G U C G U C G A A G C U

36. TRANSLATION
POLYPEPTIDE CHAIN G A U C A G C U

37. Summary - translation
During translation the mRNA passes through the ribosome.
The ribosome binds to the mRNA so that the start codon is in position
The codons are recognised by tRNA, each carrying a particular amino acid.
The appropriate tRNA brings its amino acid to the ribosome as it moves along the mRNA.
Adjacent amino acids then join with a peptide bond.
The tRNA then leaves the ribosome.
This process continues until a stop codon is reached and the polypeptide is released.

38. DNA – mRNA – tRNA - Protein
Complete the sequences of mRNA and tRNA then using Torrance pg 39 find out the names of the amino acids.
DNA - TTACGGCAATGCGGTACCGTTGGGGGCAG
mRNA -
Codons (set of 3 bases)
tRNA -
Anti-codons (set of 3 matching bases)
Protein -

39. DNA – mRNA – tRNA - Protein
DNA - TTACGGCAATGCGGTACCGTTGGGGGCAG
mRNA - AAUGCCGUUACGCCAUGGCAACCCCCGUC
Codons (set of 3 bases)
tRNA - UUACGGCAAUGCGGUACCGUUGGGGGCAG
Anti-codons (set of 3 matching bases)
Protein - aspn– ala – val – thr – pro – try – glu – pro - pro

40. Overview

41. Fate of Protein
The protein is carried in a vesicle from the RER to the Golgi where it is processed and packaged into a vesicle which fuses with the cell membrane.

42. Translation –Summary
The process of translation of mRNA into a polypeptide by tRNA at the ribosome.
tRNA folds due to base pairing to form a triplet anticodon site and an attachment site for a specific amino acid.
Triplet codons on mRNA and anticodons translate the genetic code into a sequence of amino acids.
Start and stop codons exist.
Codon recognition of incoming tRNA, peptide bond formation and exit of tRNA from the ribosome as a polypeptide is formed.

43. Protein synthesis storyboard
You are going to produce a storyboard showing the process of protein synthesis in a number of steps.
For each step you should draw a diagram and give a short description of what is happening.
Use as many boxes as you require to describe the full process.
The steps should be displayed in the correct order, with all the main molecules mentioned.

44. Protein synthesis storyboard44

45. Learning Intention:
To learn about One gene, many Proteins
Success Criteria:
By the end of the lesson I should be able to
State that one gene, many proteins as a result of RNA splicing and post translational modification.
State that different mRNA molecules are produced from the same primary transcript depending on which RNA segments are treated as exons and introns.
Explain post translation protein structure modification by cutting and combining polypeptide chains or by adding phosphate or carbohydrate groups to the protein.

46. One gene many proteins
It is thought that at least 70% of the approximately 25,000 genes in the human genome undergo alternative splicing and that, on average, a given gene gives rise to 4 alternatively spliced variants - encoding a total of ,000 proteins which differ in their sequence and therefore, in their activities.

47. A gene is first transcribed into a pre-messenger RNA (pre-mRNA), a copy of the genomic DNA containing both introns (destined to be removed during pre-mRNA processing) and exons (destined to be retained within the mRNA in order to code the protein sequence).

48. During RNA splicing, exons are either retained in the mRNA or targeted for removal in different combinations to create a diverse array of mRNAs from a single pre-mRNA.  This process is known as alternative RNA splicing.
RNA splicing is specifically deregulated in disease conditions

49. Alternative splicing

50. Post-translational modification
Once translation is complete, further modification may be required to enable a protein to perform its specific function

51. Post-translational modification
Post-translational modifications (PTMs) are known to be essential mechanisms used by eukaryotic cells to diversify their protein functions and dynamically coordinate their signalling networks.
Defects in PTMs have been linked to numerous developmental disorders and human diseases,

52. Cleavage Cleavage is a method of post-translational modification
a protease cleaves one or more bonds in a target protein to modify its activity. (proteolytic processing)
This processing may lead to activation, inhibition or destruction of the protein's activity.
The protease may remove a peptide segment from either end of the target protein, but it may also cleave internal bonds in the protein that lead to major changes in the structure and function of the protein.
Many proteins are synthesized as inactive precursors in one tissue or organ, transported to another tissue or organ and activated there by proteolytic processing.

53. Insulin and post-translational modification
Insulin starts as a single polypeptide chain
To become active it requires its central section to be cut out by protease enzymes
This results in in two polypeptide chains held together by sulphur bridges

54. Post-translational modification of insulin
The hormone insulin, which increases the uptake of glucose by cells, consists of two polypeptide chains that originate as one chain. Disulphide bridges form between cysteine residues in the original polypeptide chain, known as pro-insulin. A protease enzyme (an enzyme which cuts protein at a peptide bond) cuts the polypeptide chain in two places. The middle section of the protein is then removed.

55. Modification by the addition of a phosphate
Phosphorylation is one of the most intensely studied post– translational modifications.
This PTM plays critical roles in the regulation of many cellular processes including: cell cycle, growth, apoptosis and differentiation.

56. Phosphorylation of p53
Regulatory protein p53 requires the addition of a phosphate by phosphorylation to become activated in order to repair DNA

57. Modification by the addition of a carbohydrate
Mucus adheres to many epithelial surfaces, where it serves as a diffusion barrier against contact with noxious substances and as a lubricant
Mucus is a glycoprotein consisting of protein and an added carbohydrate

58. One gene many protein -Summary
One gene, many proteins as a result of RNA splicing and post translational modification.
Different mRNA molecules are produced from the same primary transcript depending on which RNA segments are treated as exons and introns.
Post translation protein structure modification by cutting and combining polypeptide chains or by adding phosphate or carbohydrate groups to the protein.