Gene Expression: from DNA to protein to phenotype

• How is DNA transcribed to RNA?• How is mRNA translated to protein?• How do alterations in DNA lead to

alterations in phenotype?

Q: This figure shows gene expression in what type of cell? (polyribosome = complex of ribosomes + mRNA + polypeptide chains being synthesized)A) Prokaryotic cell

B) Eukaryotic cell

C) Could be either prokaryotic or eukaryotic

A) left to right B) right to left C) not enough information to determine

Q: What is the direction of transcription in this figure?

Q: The sequence below is a portion of the template strand of DNA. What is the RNA sequence transcribed from this template?

5’-AAGCTGAGCGAT-3’

A) 5’-AAGCUGAGCGAU-3’

B) 5’-TTCGACTCGCTA-3’

C) 5’-AUCGCUCAGCUU-3’

D) 5’-UUCGACUCGCUA-3’

E) 5’-ATCGCTCAGCTT-3’

Q: The sequence below is the 5’ end of an mRNA; what are the first four amino acids of the polypeptide that will be translated from it?

5’-UACGAGUAUGCCAGGUCAG….

A) N-TyrGluTyrAla….

B) N-AspTrpThrVal….

C) N-MetProGlyGln….

D) C-MetProGlyGln….

E) N-TyrThrArgGlu….

Q: The sequence below is the 5’ end of an mRNA; what are the first three amino acids of the polypeptide that will be translated from it?

5’-AUAUGAGUAUGCCAGGUC….

A) C-MetSerMet….

B) N-MetSerMet….

C) N-MetProGly….

D) N-IleTyrMet….

E) N-Ile(Stop)….

Q: The sickle cell mutation changes a glutamic acid (glu) to valine (val). What is the specific base change in the DNA?

A) A→T

B) A→U

C) A→G

D) G→A

E) G→C

Which type of mutation is most likely to render a protein non-functional?

A. A mis-sense mutation B. A nonsense mutation near the 3’ end of

the coding region C. A single nucleotide deletion near the 5’

end of the coding regionD. A single nucleotide insertion near the 3’

end of the coding regionE. A 3-nucleotide deletion in the middle of

the coding sequence.

Questions for discussion:

• What is a mutation?• Do healthy people have “mutations” in their

DNA?• Do all “mutations” have bad consequences?

Genomics is now, and it’s personal!• Resnick TED talk• 23 and Me SNP (single nucleotide

polymorphism) profiling

http://www.mun.ca/biology/scarr/DNA_Chips.html

Breast cancer (BRCA1,2)

What do these 3 SNPs: 185delAG, 5382insC, and 6174delT have in common?

Lactose intolerance

Based on this information, what is the mode of inheritance of lactose intolerance?

Which of these should concern me most?

Closer look at prostate cancer

European ancestry: 15.3%Average risk: 17.8%

Asian ancestry: 16.4%Average risk: 11.2%

Overall heritability estimate: 42-57%