1. (3) Gene Expression Gene Expression (A) What is Gene Expression?
(E) Splicing and post-translational modification
(B) Structure and Functions of RNA
(D) Translation
(C) Transcription

2. Gene Expression (C) State where transcription occurs
Name the enzyme involved in transcription
State the role of this enzyme
Describe the stages of transcription
State what introns and exons are
State what RNA splicing is
Explain the difference between the primary and mature RNA strands

3. Re-cap on the cell ultrastructure
Nat 5s - you should know these!

4. Animal Cell Ultra structure
Plasma membrane

5. Animal Cell Ultra structure
Mitochondrion
Produces ATP by aerobic respiration

6. Animal Cell Ultra structure
Cytoplasm

7. Animal Cell Ultra structure
Nuclear membrane

8. Animal Cell Ultra structure
Nuclear Pore

9. Animal Cell Ultra structure
Nucleolus Synthesis of RNA and ribosomes

10. Animal Cell Ultra structure
Rough Endoplasmic Reticulum Synthesis and transport of proteins for export

11. Animal Cell Ultra structure
Ribosomes Site of protein synthesis

12. Animal Cell Ultra structure
Golgi Body Packages complex molecules for secretion

13. Animal Cell Ultra structure
Golgi Vesicle Encloses and transports molecules

14. Animal Cell Ultra structure
Lysosome Contains digestive enzymes

15. Animal Cell Ultra structure
Smooth Endoplasmic Reticulum Synthesis and transport of lipids

16. Animal Cell Ultra structure
Small vacuole

17. Animal Cell Ultra structure
Centriole Involved in the formation of spindle fibres

18. Animal Cell Ultra structure
Fluid filled pinocytic vesicle

19. Re-cap – cell ultrastructure
Cell membrane
Fluid filled vesicle
Cytoplasm
Mitochondria
Nuclear membrane
Centrioles
Nuclear pore
Small vacuole
Nucleus
Nucleolus
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
ribosomes
Golgi Body
Lysosome
Golgi Vesicle

20. Pathway to making a protein
DNA
(containing all the genetic material / coding)
“The middle man”
Protein
messengerRNA

21. Pathway to making a protein
DNA
RNA
Protein
a mRNA molecule is made (transcribed) from a portion of DNA and then carried to the cytoplasm
transcription
translation
occurs when the sequence of bases of mRNA DIRECTS the sequence of amino acids in a protein
RIBOSOME – site of protein synthesis

22. Where does transcription occur?
Where do you find the DNA?
Where is protein made?
DNA never leaves the nucleus just incase it becomes damaged!
Therefore the DNA is transcribed (copied) into mRNA inside the nucleus
Education Scotland - TRANSCRIPTION ANIMATION

23. Notice Uracil Cytoplasm Nucleus PORE IN THE NUCLEAR MEMBRANEG A T C G A T C
PORE IN THE NUCLEAR MEMBRANE
SECTION OF DNA UNWOUND C A G U
SECTION OF DNA UNWOUND AND UNZIPPED
mRNA MOLECULE FORMING C A G U
mRNA transcript PASSING THROUGH THE POREIN NUCLEUS
Notice
Uracil

24. transcription
Step 1: Transcription can only take place if the enzyme RNA polymerase is present
RNA polymerase is built at the promoter region of DNA (region where transcription is initiated)

25. transcription
Step 2: RNA polymerase moves along the DNA, unwinding and unzipping the double helix by breaking the weak hydrogen bonds between the complementary base pairs

26. transcription
Step 3: RNA polymerase joins RNA nucleotides together and synthesises a primary mRNA transcript by complementary base pairing
Only 1 DNA strand is used as template for transcription. The DNA strand is read from the 3’ to 5’ direction
Free RNA nucleotides join on to the 3’ end of the growing mRNA strand. Hydrogen bonds form between complementary base pairs.

27. transcription
Step 4: mRNA continues to grow until a terminator sequence on the DNA strand is reached.
The mRNA and RNA polymerase become separated from the DNA strand.
This mRNA strand is called the primary transcript.
The DNA strands wind back up to form the double helix.

29. transcription Step 5: Splicing of the mRNA strand takes place.
Genes have introns (non-coding regions of genes) and exons (coding regions of genes).
The introns are removed in RNA splicing.
The exons are joined together to form mature transcript. This process is called RNA splicing.

31. transcription
Step 6: The mature mRNA transcript leaves the nucleus through the nuclear pores and enters the cytoplasm

32. Transcription of DNA into primary and mature RNA transcripts in the nucleus
ribosome

33. Codons A triplet of bases on the mRNA template codes for 1 amino acid.
This triplet of bases is called a CODON. A U G C
mRNA
start
codon
codon 2
codon 3
codon 4
codon 5
codon 6
codon 7
codon 1

34. Codons DNA strand: A-T-C – T-G-C – A-G-T mRNA strand:
A triplet of bases on the mRNA strand codes for 1 amino acid.
This triplet of bases is called a CODON.
U-A-G
A-C-G
U-C-A
codon 2
codon 3
codon 1

35. Notice Uracil Codon 2 Codon 1 Cytoplasm NucleusG A T C G A T C
PORE IN THE NUCLEAR MEMBRANE
SECTION OF DNA UNWOUND C A G U
SECTION OF DNA UNWOUND AND UNZIPPED
mRNA MOLECULE FORMING C A G U
mRNA transcript PASSING THROUGH THE POREIN NUCLEUS
Notice
Uracil
RNA Splicing
Codon 2
Codon 1 U C A G
Splicing RNA attaches to ribosome

36. TASK Collect a diagram and tick it into your jotter
Describe what is happening at each step (1-8)

37. Questions A gene has coding sections – what are these called?
A gene also has non-coding sections – what are these called?
Which of these is removed from the primary transcript of mRNA? By what process?
During transcription, all of the genetic information in a gene is initially copied into an RNA molecule - What is this called?
What enzyme is responsible for transcription?
The initial RNA molecule is ‘spliced’ – Explain what this means and why the cell does this.
What name is given to the final mRNA which moves out of the nucleus into the cytoplasm?
Draw a diagram of the mRNA strand that would be transcribed from section X of the DNA molecule below:
Section X
A T C G G G C C A A T
T A G C C C G G T T A

38. Gene Expression (C) State where transcription occurs
Name the enzyme involved in transcription
State the role of this enzyme
Describe the stages of transcription
State what introns and exons are
State what RNA splicing is
Explain the difference between the primary and mature RNA strands