BIOCHEM C785 Readiness Exam

BIOCHEM C785 Readiness Exam The LEP gene codes for an anorexigenic hormone. Interestingly, breastfeeding has been shown to alter methylation of the promoter of this gene, leading to increased LEP expression. What is likely happening in response to breastfeeding? Correct answer- Breastfeeding decreases the methylation of the promoter of the LEP gene, increasing the spacing between nucleosomes. A patient with xeroderma pigmentosum is prone to developing multiple skin cancers starting in childhood. This occurs because of a mutation in a gene that codes for enzymes that help repair DNA damage through the nucleotide excision repair (NER) pathways. How does NER differ from other repair mechanisms? In NER: Correct answer- The error in one strand of DNA is removed as well as several nucleotides on either side of the error. The gap that was removed is filled in by DNA polymerase Several components of cigarette smoke, including benzopyrene, insert themselves (intercalate) into the DNA and lead to several types of mutations such as frameshift mutations, including both insertions and deletion. Which of the following repair pathways would be used to repair this type of damage? Correct answer- Nucleotide excision repair is used to repair deletions, insertions, and helix-distorting lesions, such as thymine dimers Interaction between the two amino acids shown below can help stabilize the structure of a protein. What kind of interaction is this? Correct answer- Hydrophobic Interaction Which of the following forces can lead to aggregation as a result of protein misfolding? Correct answer- Hydrophobic interactions Which of the following statements about protein structure and stability is true? Correct answer- Ionic bonds between the side chains of the charged amino acids stabilize the protein structure Primary structure consists of the order of ______ in a protein. These are held together with ______ bonds that are formed by a ______ reaction. Correct answer- Amino acids, peptide, dehydration What type of reaction breaks peptide bonds apart? Correct answer- Hydrolysis Reaction A particular amino acid in a protein helps to stabilize the protein by forming disulfide bonds. What amino acid is likely to form this type of bond? Correct answer- Cysteine