GN 311 EXAM 3 SET 3 QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026

GN 311 EXAM 3 SET 3 QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026 What are the four major levels of eukaryotic gene regulation? - Answers Chromatin structure, transcription, RNA processing, protein modification What are chromosome puffs? - Answers Regions of active transcription What are Balbiani rings? - Answers Large chromosome puffs with intense transcription Active chromatin is sensitive to what enzyme? - Answers DNase I What are DNase hypersensitive sites? - Answers Regions lacking nucleosomes where regulatory proteins bind What are the three major chromatin modifications? - Answers Histone modification, chromatin remodeling, DNA methylation What part of histones interacts with DNA? - Answers Histone tails What does histone acetylation usually do? - Answers Increases transcription What does histone methylation do? - Answers Can increase or decrease transcription What enzyme adds acetyl groups to histones? - Answers HAT What does HAT stand for? - Answers Histone Acetyltransferase What enzyme removes acetyl groups from histones? - Answers HDAC What does HDAC stand for? - Answers Histone Deacetylase What does histone deacetylation do? - Answers Decreases transcription Why does acetylation increase transcription? - Answers Weakens DNA-histone interaction What is the histone code? - Answers Pattern of histone modifications affecting transcription What is chromatin remodeling? - Answers Movement or alteration of nucleosomes What sequence is commonly methylated in DNA? - Answers CpG islands What enzyme methylates DNA? - Answers DNA methyltransferase What modified base is produced by DNA methylation? - Answers 5-methylcytosine What is the general effect of DNA methylation? - Answers Decreased transcription What percentage of mammalian CpG sites are methylated? - Answers About 70-80% What is a Barr body? - Answers Inactive X chromosome What relationship exists between methylation and transcription? - Answers More methylation = less transcription What is epigenetics? - Answers Heritable gene regulation without DNA sequence changes What is the epigenome? - Answers Pattern of chromatin and DNA modifications What does Dnmt3 do? - Answers Adds methyl groups to DNA What does royal jelly do to Dnmt3? - Answers Inhibits it What happens when Dnmt3 is inhibited? - Answers Less DNA methylation What gene suppresses flowering? - Answers FLC What gene promotes flowering by repressing FLC? - Answers FLD What happens when FLC is active? - Answers Flowering is suppressed What is the core promoter? - Answers Region where basal transcription machinery binds What binds the core promoter? - Answers RNA polymerase II and general transcription factors What is a transcription factor? - Answers DNA-binding protein regulating transcription What is an enhancer? - Answers DNA sequence that increases transcription Can enhancers act far from a gene? - Answers Yes What is an insulator? - Answers DNA sequence that blocks enhancer activity What type of hormones bind intracellular receptors? - Answers Steroid hormones Examples of steroid hormones? - Answers Estrogen, testosterone, progesterone What type of hormones bind cell surface receptors? - Answers Peptide hormones Example of a peptide hormone? - Answers Insulin Which RNA polymerase produces pre-mRNA? - Answers RNA polymerase II What are the three major mRNA processing steps? - Answers 5' cap, poly-A tail, splicing What is alternative splicing? - Answers Different exon combinations from one transcript What is alternative polyadenylation? - Answers Different poly-A addition sites What does the calcitonin gene produce in thyroid tissue? - Answers Calcitonin What does the calcitonin gene produce in brain tissue? - Answers CGRP What determines sex in Drosophila? - Answers X:A ratio What X:A ratio produces females? - Answers 1.0 What X:A ratio produces males? - Answers 0.5 What does Sxl stand for? - Answers Sex-lethal What happens to exon 3 in female Sxl transcripts? - Answers Skipped What happens to exon 3 in male Sxl transcripts? - Answers Included What does tra stand for? - Answers Transformer What does dsx stand for? - Answers Doublesex What developmental pathway determines sex in Drosophila? - Answers Sxl → tra → dsx What happens before mRNA degradation begins? - Answers Poly-A tail shortens What enzymes degrade RNA? - Answers RNases What is RNA interference? - Answers Gene silencing by small RNAs What enzyme produces miRNA and siRNA? - Answers Dicer What complex uses miRNA and siRNA? - Answers RISC What does RISC stand for? - Answers RNA-Induced Silencing Complex What does miRNA usually do? - Answers Block translation What does siRNA usually do? - Answers Cleave mRNA Can RNA interference silence transcription? - Answers Yes What type of immunity uses antibodies? - Answers Humoral immunity Which cells mediate humoral immunity? - Answers B cells What type of immunity uses T cells? - Answers Cellular immunity Where do B cells mature? - Answers Bone marrow Where do T cells mature? - Answers Thymus What are plasma cells? - Answers Antibody-producing B cells What are memory cells? - Answers Long-lived cells responsible for secondary response What is the purpose of memory cells? - Answers Faster response upon re-exposure How many heavy chains are in an antibody? - Answers 2 How many light chains are in an antibody? - Answers 2 Where is the antigen-binding site located? - Answers Variable region How many classes of immunoglobulins exist? - Answers 5 Name the five immunoglobulin classes. - Answers IgM, IgG, IgA, IgE, IgD What is somatic recombination? - Answers DNA rearrangement creating antibody diversity What regions recombine in light chains? - Answers V and J What regions recombine in heavy chains? - Answers V, D, and J What is junctional diversity? - Answers Imprecise joining during recombination What is hypermutation? - Answers High mutation rate in antibody variable regions Approximately how high is the hypermutation rate? - Answers About 2% What is allele exclusion? - Answers Only one antibody allele is expressed Why is allele exclusion important? - Answers Each B cell produces one specificity What happens if the first antibody allele fails? - Answers The second allele is used What is Bruton's disease? - Answers X-linked absence of functional B cells What happens in Bruton's disease? - Answers No antibodies are produced Are T cells functional in Bruton's disease? - Answers Yes What does SCID stand for? - Answers Severe Combined Immunodeficiency What cells are defective in SCID? - Answers B cells and T cells What enzyme deficiency can cause SCID? - Answers ADA deficiency What does ADA stand for? - Answers Adenosine Deaminase What is the goal of SCID gene therapy? - Answers Restore ADA function What are the three major sources of antibody diversity? - Answers Somatic recombination, junctional diversity, hypermutation What is development? - Answers Programmed growth and differentiation What is differentiation? - Answers Formation of specialized cell types What did cloning demonstrate? - Answers Differentiated cells retain a complete genome What model organism is commonly used in developmental genetics? - Answers Drosophila melanogaster What are maternal genes? - Answers Genes establishing body axes Name three maternal genes. - Answers Dorsal, Bicoid, Nanos What are segmentation genes? - Answers Genes determining segment organization What are homeotic genes? - Answers Genes determining segment identity When are maternal genes transcribed? - Answers During egg development