Genetics Published on October 4, 2020 by ehudspeth Welcome to your Replication, Mutation, Repair and Regulation of Gene Expression Many DNA-based diagnostic tests use a DNA polymerase from Thermus aquaticusa bacterium that can surface high temperatures. Compared with the DNA of bacteria that grow at 25ºC, the DNA of T. aquaticusis expected to have higher fraction of which of the following nucleotides? Adenine and cytosine Cytosine and Guanine Adenine and Guanine Cytosine and Thymine Many DNA-based diagnostic tests use a DNA polymerase from Thermus aquaticusa bacterium that can surface high temperatures. Compared with the DNA of bacteria that grow at 25ºC, the DNA of T. aquaticusis expected to have higher fraction of which of the following nucleotides?Many DNA-based diagnostic tests use a DNA polymerase from Thermus aquaticusa bacterium that can surface high temperatures. Compared with the DNA of bacteria that grow at 25ºC, the DNA of T. aquaticusis expected to have higher fraction of which of the following nucleotides? Adenine and cytosine Cytosine and Guanine Adenine and Guanine Cytosine and Thymine Some nitrofurans form adducts with bases in DNA that cannot be repaired via the base-excision repair pathways. The adducts leads to distortions of the DNA double helix. The lesion is most likely repaired by which one of the following DNA repair pathways? Homologous recombination repair Mismatch repair Nonhomologous end joint Nucleotide-excision repair Base-excision repair In DNA replication, DNA “unwinds” to form two template strands, the leading strand and the lagging strand. Which of the following statements about these strands is true? Okazaki fragments are used to synthesize the leading strand of DNA. The leading strand of DNA is synthesized continuously. DNA polymerase can only synthesize DNA on the leading strand. The lagging strand can only be synthesized once the leading strand has been completed. The leading and lagging strand are synthesized by RNA polymerase. A 48-year-old woman had endometrial cancer and undergoes a hysterectomy. Immunohistochemistry of tumor tissue reveals the presence of MLH1 and PMS2, but an absence of MSH2 and MSH6. Based on this finding, the most likely diagnosis is which of the following? Cockayne syndrome Hereditary breast and ovarian cancer syndrome Lynch syndrome MUTYH-associated polyposis A 69-year-old male patient with metastatic colon cancer receives treatment with a cocktail of chemotherapeutic drugs that contains irinotecan (inhibitor of topoisomerase). This drug inhibits which of the following processes? Modification of histone tails Pairing of complementary bases Reading of bases in the major groove Relaxation of supercoiled DNA Ligation of Okazaki fragments Mutations in DNA large distances from a structural gene can lead to over or under expression of that gene. Which of the following eukaryotic DNA control sequences does not need to be in a fixed location and is most responsible for high rates of transcription of particular genes? Promoter Promoter-proximal element Enhancer Operator Splice donor site It is common for large eukaryotic genomes to express more proteins than there are genes in the genome. Which mechanism best explains this phenomenon? Promoters Enhancers Alternative splicing Exon skipping RNA editing Methylation at a promoter of a gene is most likely to result in which of the following? Increase transcription by active recruitment of transcription factors and recruitment of histone acetyltransferases Decreases transcription by physically impeding the binding of transcription factors and through the recruitment of histone acetyltransferases Increase transcription by active recruitment of histone deacetylases Decrease transcription by physically impeding the binding of transcription factors and through the recruitment of histone deacetylases There is minimal impact on transcription resulting from methylation at promoters Regulation of gene expression by thyroid hormones is mediated via thyroid hormone receptors. The receptors act as molecular switches in response to ligand binding. In the absence of ligand, how do thyroid hormone receptors function? They are coupled with a corepressor complex containing HDAC, which halts transcription. They are coupled with a corepressor complex lacking HDAC, which leads to cell proliferation. They are coupled with coregulators that contain HDAC, which leads to cell proliferation. They are coupled with coregulators that contain HAT, which halts transcription. They are coupled with coregulators that contain HAT, which leads to cell proliferation For a particular protein, the template strand contains the sequence 5’-ACCGT-3’. After transcription into mRNA, the RNA contains which of the following sequences? 5’-ACGGU-3’ 5’-ACCGU-3’ 5’-UGCCA-3’ 5’-UGGCA-3’ 5’-ACGGT-3’ Which of these would lead to gene suppression? Administration of a HDAC inhibitor Addition of HAT activity to transcription factors Deficiency in DNA methyltransferase Methylation of CG islands An increase in transcription factors Which of the following is most likely to occur when a ribosome encounters a UAG codon of an mRNA that derives from a normal non pathogenic allele? Release factor binds` to UAG Met is incorporated into the nascent peptides The ribosomes binds to the signal recognition particle The ribosome stalls the mRNA is degraded by nonsense-mediated decay The genetic code derives its specificity through which of the following interactions Hydrogen bonds and disulfide bonds that maintain the shape of the tRNAs Complementary base pairing between amino acids and tRNA Complementary base pairing between tRNA and mRNA Ionic bonds between the small and large subunits pf the ribosome Hydrogen bonding between the ribosomal subunits and the mRNA Many commonly used antibiotic drugs are able to target both eukaryotic and prokaryotic genetic machinery, but preferentially act on prokaryotic cellular structures. One such bacteriostatic drug works by binding to the aminoacyl site of the 30s ribosomal subunit, preventing translation of mRNA templates into amino acids. This mechanism most accurately describes which drug? Tetracyclines Aminoglycosides Macrolides Clindamycin PARP inhibitors A 33-year-old patient presents to your office with fatigue, muscle weakness, and shortness of breath. You perform some blood work and notice a low red blood cell count and, as a result, high levels of Epo. You know that Epo should be signalling the Jak/STAT receptors for gene transcription, so you worry there may be an issue at the genomic and/or DNA level. If you know the protein sequence should code for an His (CAU, CAC) near the C terminus, what would you expect the template sequence to appear as? Note, the entire sequence is given below: 5’ CTACGATGATAACTGCAT 3’ 5’ TCAATGTTCAGACCGCAT 3 5’ TTAATGTTCGGACCGCGT 3’ 5’ TCAATGTCGGACCGCGT 3’ 5’ TTAATGATCGAATCGCGT 3’ Which of the following is the enzyme involved in adding an amino acid to the 3’ end of the tRNA? ATP synthase Aminoacyl tRNA synthetase tRNA polymerase RNA polymerase III Aminoacyl mRNA synthetase Diphtheria toxin is an extremely potent poison derived from Corynebacterium diphtheriae bacteria, and ultimately inhibits protein synthesis by which mechanism? Inactivation of peptidyl transferase Inactivation of eIF2 Inhibition of the ATP hydrolysis step of eIF4’s helicase activity Inactivation of eEF2 Inhibition of the GTP hydrolysis step of eIF4’s helicase activity A drug targeting inhibition of which of the following would NOT assist in ceasing the cell cycle, causing apoptosis: RTKs P21 CDK2-E CDK2-A CDK1-A Which of the following would result in formation of a novel protein? Gene amplification of a proto-oncogene Coding mutation of an oncogene Regulatory mutation of an oncogene Translocation of a proto-oncogene Coding mutation of a proto-oncogene Which of these results from DNA damage? Inactive Rb/E2F complex, therefore decreased nuclear transcription Phosphorylation of MDM2, therefore decreased nuclear transcription Active Rb/E2F complex, therefore recruitment of DNA repair enzymes Decrease in p21, therefore recruitment of DNA repair enzymes Activation of Bax via p53, therefore an increase in nuclear transcription What roles in regulating the intrinsic pathway of apoptosis are played by the Bcl-2 protein family members Bax and Bcl-2? Bax inhibits apoptosis while Bcl-2 stimulates apoptosis. Bax stimulates apoptosis while Bcl-2 inhibits apoptosis. Both Bax and Bcl-2 inhibit apoptosis. Both Bax and Bcl-2 stimulate apoptosis. Bax activates Bcl-2, which stimulates apoptosis. Your 42 year old, female patient presents with chest pain and difficulty breathing. Upon taking a history, you find she has a family history of breast cancer. Your exam shows potential breast lumps in the upper-right, lateral quadrant of her left breast. Thinking back to what you learned from Dr. Ree regarding gene mutation, you contemplate the following possibilities for your patient’s condition: Von Hippel-Lindau Syndrome Lynch syndrome Familial adenomatous polyposis Retinoblastoma Li-Fraummeni syndrome Loss of both p53 protein alleles is found in >50% of human tumors. Which one of the following is a function of the p53 protein? Halting replication in cells that have suffered DNA damage Targeting repaired cells to undergo apoptosis Stimulating cyclin production Simulating CDK production Stimulating phosphorylation of Rb Consider a woman who is a known heterozygous carrier of the mutant gene that causes Hemophilia A. She is considering trying to conceive her first child. Her husband is not a carrier of the disease. What is the probability that her first born child will exhibit symptoms of Hemophilia A? None of her children will have the disease, they could only be carriers of the disease. ¼ chance ¼ chance ¾ chance All of her children will have the disease Which is true regarding X-chromosome inactivation? X-inactivation is most likely to occur in the maternal X than the paternal X chromosome. Expression of X-chromosome inactivation occurs at a 50:50 ratio in females. Barr bodies are found in both male and female dividing somatic cells. X-inactivation usually leads to death in females during the prenatal period and normal function in males. Once random X-chromosome inactivation occurs, it is permanent in all descendants of that cell. Rodney was diagnosed with Xeroderma pigmentosum (XP) at a very young age. Xeroderma pigmentosum is a rare disease caused by mutation in genes that are involved in repairing damaged DNA. How did Rodney most likely inherit this disease? His parents, who met at random, were both heterozygous carriers of the mutation that causes XP. His parents are first cousins, and they were both recessive carriers of the mutation that causes XP. His parents, who met at random, had a mosaic mutation for XP that occured prior to conception of Rodney. His parents are first cousins, and they were both homozygous dominant for the XP allele. His parents are first cousins. His mother is homozygous recessive for the XP mutation; his father is homozygous dominant for the XP allele. In which instance could two affected parents produce unaffected children for an autosomal dominant disease? Both heterozygous parents Homozygous dominant mother, heterozygous father Homozygous dominant mother, homozygous recessive father Heterozygous mother, homozygous dominant father Both homozygous recessive parents The crossing of an unaffected male and a heterozygous recessive carrier of an X-linked recessive disorder could lead to which of the following? All unaffected daughters, 50% sons affected 50% daughters affected, 50% sons affected 50% daughters affected, all unaffected sons 25% daughters affected, all sons affected All children unaffected A baby was born with syndactyly (webbing between her fingers). The doctor stated that this minor defect can be easily corrected surgically. What is the embryologic basis of syndactyly? Type III symmelia occurred during development, leading to fused fingers. A HOX mutation most likely caused the fingers to fuse during development. A defect in apoptosis resulted in the webbing between fingers to break down properly. The baby is part labrador retriever. She should be AKC registered for her unique development. A premature AER secretion of FGF10 at the distal limb bud Which of the following correctly matches the term to the definition? Euchromatin: less densely packed, more accessible to transcription factors Euchromatin: more densely packed, more accessible to transcription factors Euchromatin: less densely packed, less accessible to transcription factors Euchromatin: more densely packed, less accessible to transcription factors Which of the following enzymes is responsible for replacing the RNA bases of the primer with DNA bases? Helicase Single Strand Binding Proteins (SSBPs) DNA Polymerase III DNA Polymerase I Primase Time is Up!