Chapter 10 – Gene Expression & Regulation

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. messenger Transcription – making a portable RNA copy of a gene

5. RNA vs. DNA

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

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

8. Transcription: RNA polymerase stops transcribing at the end of a gene Termination sequence

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. Translation utilizes specific codon sequences to begin and end protein synthesis Template strand Start and stop codons CFTR gene sequence

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

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. 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. A A T A tryptophan

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? • MP and the 5alpha-reductase-2 (SRD5A2) gene

28. How do mutations in DNA affect protein? • 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

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 • The fat cat ate the rat… • Hef atc ata tet her at… • Example TAC GCG GAT CGA… TAC GCG ATC GAn… Transcribe: AUG CGC UAG

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