1. Chapter 10 – Gene Expression & Regulation
What is gene expression?
How do mutations in DNA affect proteins?
How is gene expression regulated?

2. What is gene expression?
The process of making proteins from the DNA nucleotide message of genes
Also called protein synthesis

3. Gene expression (protein synthesis) is a two-step process

4. Transcription – making a portable RNA copy of a gene
Biology: Life on Earth (Audesirk)
Transcription – making a portable RNA copy of a gene
messenger
Not all genes are transcribed
Chapter 1

5. RNA vs. DNA

6. Transcription copies the template strand of a gene
DNA: TACGCCACTAAT
mRNA:
AUGCGGUGAUUA
Replication:
ATGCGGTGA TTA

7. Transcription animation
Transcription: RNA polymerase copies a gene’s nucleotide sequence into an mRNA sequence
promoter sequence (example: TATAAT)
Transcription animation
back-up link

8. Transcription: RNA polymerase stops transcribing at the end of a gene
Biology: Life on Earth (Audesirk)
Transcription: RNA polymerase stops transcribing at the end of a gene
Termination sequence
Figure: 10.4ab
Title:
Intiation and elongation of RNA transcription
Caption:
Chapter 1

9. Gene expression (protein synthesis) is a two-step process

10. Translation – synthesizes a polypeptide (protein) according to the nucleotide sequence information of a mRNA molecule
Codons – triplets of mRNA nucleotides, each specifying a particular amino acid
CFTR gene sequence

12. Biology: Life on Earth (Audesirk)
Translation utilizes specific codon sequences to begin and end protein synthesis
Template strand
Start and stop codons
CFTR start codon (TAC) in second line; Stop codon (ATT) in second from bottom line
CFTR gene sequence
Chapter 1

13. Translation is accomplished by ribosomes

14. Translation utilizes transfer RNA molecules to carry specific amino acids to the ribosomes
tRNA anticodon – complementary to an mRNA codon

15. Translation uses complementary base pairing between mRNA codons and tRNA anti-codons
tRNAs
Ribosome
mRNA

16. Biology: Life on Earth (Audesirk)
Figure: 10.7
Title:
Complementary base pairing is critical at each step in decoding genetic information
Caption:
(a) DNA contains two strands: the template strand is used by RNA polymerase to synthesize an RNA molecule; the other strand, which is complementary to the template strand, is needed for DNA replication. (b) Bases in the template strand of DNA are transcribed into a complementary mRNA. Codons are sequences of three bases that specify an amino or a stop during protein synthesis. (c) Unless it is a stop codon, each mRNA codon forms base pairs with the anticodon of a tRNA molecule that carries a specific amino acid. (d) The ribosome links the amino acids together, forming the protein.
Chapter 1

17. Biology: Life on Earth (Audesirk)
Chapter 1

18. The process in which the DNA sequence of a gene is copied into mRNA is called
DNA replication
mRNA replication
RNA polymerase
Translation
Transcription

19. What is the promoter region of a gene?
The location on RNA where RNA polymerase binds and initiates transcription.
It is a component of each type of RNA.
The location where ribosomes bind to the DNA.
The location on the DNA template strand where RNA polymerase binds and initiates transcription.
The location where ribosomes bind to the mRNA.

20. Transcription of the DNA sequence ATCGATA would be
TAGCTAT
AUCGAUA
TUGCTUT
UUGCUUU
UAGCUAU

21. Imagine that the template strand of a gene has the sequence TAC
Imagine that the template strand of a gene has the sequence TAC. What sequence of the anticodon would decode this?
ATG
AUG
UAC
TAC
TUG

23. Ribosomes
Translate mRNA molecules in the nucleus of the cell
Bind to the promoter sequence of a mRNA to initiate translation
Contain anti-codons which match specific mRNA codons
All of these
None of these

24. How do mutations in DNA affect proteins?
Nucleotide substitutions
Nucleotide deletions
Nucleotide insertions

25. Biology: Life on Earth (Audesirk)
Figure: 10.7
Title:
Complementary base pairing is critical at each step in decoding genetic information
Caption:
(a) DNA contains two strands: the template strand is used by RNA polymerase to synthesize an RNA molecule; the other strand, which is complementary to the template strand, is needed for DNA replication. (b) Bases in the template strand of DNA are transcribed into a complementary mRNA. Codons are sequences of three bases that specify an amino or a stop during protein synthesis. (c) Unless it is a stop codon, each mRNA codon forms base pairs with the anticodon of a tRNA molecule that carries a specific amino acid. (d) The ribosome links the amino acids together, forming the protein. A
tryptophan
Chapter 1

26. How do mutations in DNA affect proteins?
A single amino acid substitution at position 269
CAA changed to CCA
Glutamine to proline

27. How do mutations is DNA affect protein?
Biology: Life on Earth (Audesirk)
How do mutations is DNA affect protein?
MP and the 5alpha-reductase-2 (SRD5A2) gene
Chapter 1

28. How do mutations in DNA affect protein?
Biology: Life on Earth (Audesirk)
How do mutations in DNA affect protein?
Read abstract; go to Genbank accession # (in section “Analysis of SRD5A2 gene”) to see gene sequence; copy SRD5A2 into protein search, click on first link to show the amino acid changes
FIG. 1. Mutations of the SRD5A2 gene. A, A heterozygous C78G transversion at exon 1, resulting in Tyr26Stop (Y26X) in case 1. B, A heterozygous G100C transversion at exon 1, leading to Gly34Arg (G34R) in case 2. C, A homozygous G680A transition at exon 4, causing Arg227Gln (R227Q) in case 3.
Link
Chapter 1

29. How do mutations in DNA affect proteins?
Nucleotide insertions and deletions shift the “reading frame” (how mRNA codons are translated)
Also called frameshift mutations

30. Insertions, deletions and frame shifts
Biology: Life on Earth (Audesirk)
Insertions, deletions and frame shifts
The fat cat ate the rat…
Hef atc ata tet her at…
Example
During example, ask how stop codons can appear prematurely, then continue with nucleotide sequence next to “example” link
TAC GCG GAT CGA…
TAC GCG ATC GAn…
Transcribe:
AUG CGC UAG
Chapter 1

31. Mutations and genetic disease
Werner’s syndrome
Cystic fibrosis

32. Myostatin gene mutation
11 bp deletion

33. How is gene expression regulated?
Control can happen at several points in the process
Control to turn on/turn off protein production
Control amount of protein production

34. How is gene expression regulated?
Transcriptional regulation involves regulatory “repressor” and/or “activator” molecules
Transcription factors – molecules required to promote binding of RNA polymerase to a gene promoter

35. How is gene expression regulated?
mRNA is “silenced” by RNA interference (RNAi)
siRNA molecules (small interfering RNAs) are double stranded RNA molecules that when activated, degrade (cut up) specific mRNA molecules, silencing gene expression

36. A frameshift mutation
Occurs when an incorrect nucleotide is substituted for the correct one somewhere in the DNA sequence of a gene
Occurs whenever nucleotides are inserted or deleted from a DNA sequence of a gene
Occurs when any change is made in the nucleotide sequence of a gene

37. A transcription factor
Promotes gene expression by facilitating the binding of RNA polymerase to mRNA
Inhibits gene expression by preventing RNA polymerase from binding to mRNA
Silences mRNA by cutting it up
Prevents mRNA from being transcribed into a protein

38. Which of the following regulate gene expression post-transcriptionally?
Transcription factors
Repressor proteins
RNA interference
All of these