© Cengage Learning 2015 What would the DNA code be, to give you the following polypeptide? Met-arg-asp-ala-tyr-thr-val-pro-stop mRNA ___ ___ ___ ___ ___ ___ ___ ___ ___ DNA ___ ___ ___ ___ ___ ___ ___ ___ ___

© Cengage Learning 2015 The Messenger: mRNA 2

© Cengage Learning 2015 Biology Concepts and Applications | 9e Starr | Evers | Starr © Cengage Learning 2015 Chapter 10 Control of Gene Expression

© Cengage Learning What Is Gene Control? A typical cell in your body uses only about 10 percent of its genes at one time –Some genes affect structural features and metabolic pathways and are expressed in many cell types –Others genes are expressed only by certain subsets of cells (e.g., globin in RBCs) –Control over gene expression allows cells to respond to changes in their environment

© Cengage Learning 2015 Gene Expression Control The “switches” that turn a gene on or off are molecules or processes that trigger or inhibit the individual steps of its expression

© Cengage Learning How Do Genes Control Development in Animals? As an animal embryo develops, its cells differentiate and form tissues, organs, and body parts –Driven by cascades of master gene expression The products of master genes affect the expression of many other genes –Final outcome is the completion of an intricate task such as the formation of an eye

© Cengage Learning 2015 What Are Some Outcomes of Gene Control in Prokaryotes? Operon: group of genes together with a promoter–operator DNA sequence that controls their transcription –Although first discovered in bacteria, operons also occur in archaea and eukaryotes

© Cengage Learning 2015 The lac Operon An operon called lac allows E. coli cells to metabolize lactose The lac operon includes three genes and a promoter flanked by two operators

© Cengage Learning 2015 The lac Operon Three genes of the lac operon: –One gene encodes a transport protein that brings lactose across the plasma membrane –Another gene encodes an enzyme that breaks the bond between lactose’s two monosaccharide monomers, glucose, and galactose –A third gene encodes an enzyme whose function is still being investigated

© Cengage Learning 2015 Lactose Intolerance An individual’s ability to digest lactose declines at a species-specific age –In the majority of human worldwide, the switch occurs at about age five, when expression of the gene for lactase shuts off –Results in the condition lactose intolerance

© Cengage Learning 2015 Lactose Intolerance When lactase production slows, lactose passes undigested through the small intestine –The lactose ends up in the large intestine, which hosts huge numbers of E. coli etc. –The E. coli switch on their lac operons, resulting in the production of gaseous products – causing distention and pain –Other metabolic products lead to diarrhea

© Cengage Learning 2015 Lactose Intolerance Not everybody is lactose intolerant –About one-third of human adults carry a mutation that allows them to digest milk –This mutation is more common in some populations than in others

© Cengage Learning 2015 Lactose Intolerance

© Cengage Learning Application: Between You and Eternity A mutated version of BRCA1 and/or BRCA2 genes is often found in breast and ovarian cancer cells The RNA product of the XIST gene does not properly coat one of the two X chromosomes in breast cancer cells

© Cengage Learning 2015 Application: Between You and Eternity Why does the RNA product of an unmutated XIST gene not properly coat an X chromosome in cancer cells? –The BRAC1 protein physically associates with the RNA product of the XIST gene –Researchers restored proper XIST RNA coating—and proper X chromosome inactivation—by restoring the function of the BRCA1 protein in breast cancer cells

© Cengage Learning 2015 If a strand of DNA has the sequence AAGCTC, transcription will result in a(n) ______. A) single RNA strand with the sequence TTCGAG B) DNA double helix with the sequence AAGCTC for one strand and TTCGAG for the complementary strand C) single DNA strand with the sequence TTCGAG D) single RNA strand with the sequence UUCGAG E) RNA double helix with the sequence UUCGAG for one strand and AAGCUC for the complimentary strand

© Cengage Learning 2015 If a strand of DNA has the sequence AAGCTC, transcription will result in a(n) ______. A) single RNA strand with the sequence TTCGAG B) DNA double helix with the sequence AAGCTC for one strand and TTCGAG for the complementary strand C) single DNA strand with the sequence TTCGAG D) single RNA strand with the sequence UUCGAG E) RNA double helix with the sequence UUCGAG for one strand and AAGCUC for the complimentary strand

© Cengage Learning 2015 Translation converts the information stored in ______ to ______. A) DNA... RNA B) RNA... a polypeptide C) protein... DNA D) DNA... a polypeptide E) RNA... DNA

© Cengage Learning 2015 Translation converts the information stored in ______ to ______. A) DNA... RNA B) RNA... a polypeptide C) protein... DNA D) DNA... a polypeptide E) RNA... DNA

© Cengage Learning 2015 Where is translation accomplished? A) lysosomes B) smooth endoplasmic reticulum C) peroxisomes D) ribosomes E) nucleoli

© Cengage Learning 2015 Where is translation accomplished? A) lysosomes B) smooth endoplasmic reticulum C) peroxisomes D) ribosomes E) nucleoli

© Cengage Learning 2015 A mutation within a gene that will insert a premature stop codon in mRNA would ______. A) result in a polypeptide that is one amino acid shorter than the one produced prior to the mutation B) result in a shortened polypeptide chain C) result in a missense mutation D) change the location at which transcription of the next gene begins E) have the same effect as deleting a single nucleotide in the gene

© Cengage Learning 2015 A mutation within a gene that will insert a premature stop codon in mRNA would ______. A) result in a polypeptide that is one amino acid shorter than the one produced prior to the mutation B) result in a shortened polypeptide chain C) result in a missense mutation D) change the location at which transcription of the next gene begins E) have the same effect as deleting a single nucleotide in the gene

© Cengage Learning 2015 What is the smallest number of nucleotides that must be added or subtracted to change the triplet grouping of the genetic message? A) one B) two C) three D) four E) five

© Cengage Learning 2015 What is the smallest number of nucleotides that must be added or subtracted to change the triplet grouping of the genetic message? A) one B) two C) three D) four E) five

© Cengage Learning 2015 Examine the genetic code table, shown below. The codon AGC codes for the amino acid ______. A) serine B) arginine C) threonine D) alanine E) glycine

© Cengage Learning 2015 Examine the genetic code table, shown below. The codon AGC codes for the amino acid ______. A) serine B) arginine C) threonine D) alanine E) glycine

© Cengage Learning 2015 A mutation would be most harmful to the cells if it resulted in ______. A) a single nucleotide insertion near the start of the coding sequence B) a single nucleotide deletion near the end of the coding sequence C) a single nucleotide in the middle of an intron D) substitution of a base pair E) deletion of a triplet near the middle of the gene

© Cengage Learning 2015 A mutation would be most harmful to the cells if it resulted in ______. A) a single nucleotide insertion near the start of the coding sequence B) a single nucleotide deletion near the end of the coding sequence C) a single nucleotide in the middle of an intron D) substitution of a base pair E) deletion of a triplet near the middle of the gene

© Cengage Learning /8 Protein Synthesis 910/10 Genes 10 10/15 Mitosis 1110/17 Meiosis 12 10/22 Genotype & Phenotype 1310/24 Biotechnology 14 10/29 Exam #2 10/31 Begin Evolution