AP Biology: Chapters 18 – Flashcards
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Why are all genes not "on" all the time?(e.g. E. Coli)
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E.Coli live in very fickle environments. If an E. Coli in the human gut is lacking an amino acid, it will turn the gene that makes it "on." If the human ate a meal rich in that amino acid, it turns that gene "off", an doesn't us up excess resources.
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What are two main ways of controlling enzyme activity?
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1)regulation of enzyme activity 2)regulation of enzyme production
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In the case of E. coli regulating tryptophan is it positive or negative inhibition?
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In bacterial cells, enzymatic reactions may be regulated by 2 unrelated modes: (1) control or regulation of enzyme activity, which mainly operates to regulate biosynthetic pathways; and (2) control or regulation of enzyme synthesis, including end-product repression.The processes which regulate the synthesis of enzymes may be either a form of positive control or negative.
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What is a promoter?
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Region of DNA where RNA polymerase can bind
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What is an operator? What does it do?
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An operator is the "on-off" switch controlling a cluster of functionally related genes.
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What is an operon?
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A segment of DNA that consists of three parts: 1-the operator 2-the promoter 3-the genes being controlled
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List 3 components of an operon and explain the role of each
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repressor-produces a repressor protein that fits into the operator to turn it off promoter-RNA polymerase attaches here to begin transcription of genes operator-active repressor fits in notches to block RNA polymerase and turn off transcription
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How does a repressor protein work?
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they bind to the operator and block attachment of RNA polymerase II to the promoter
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What are regulatory genes?
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A gene that produces repressor proteins
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Distinguish between inducible and repressible operons, and describe one example of each type.
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Inucible operon-operon that is usually off, but can be induced to turn on by interacton between molecules and regulatory proteins (e.g. lac operon) repressible operon-operon that is usually on, but can be inhibited when a molecule, like tryptophan binds to a regulatory protein
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Compare and contrast the lac operon and the trp operon
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Both are in prokaryotes and each have a promoter, operator, and genes.
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What happens when a repressor is bound to an operator?
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RNA polymerase cannot bind. Transcription cannot occur
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What is CAP? How does it work?
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catabolite activater protein;CAP assumes its active shape and attaches to the DNA molecule later upstream which increases RNA polymerases affinity to the promoter
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How can both repressible and inducible operons be negative regulators?
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repressible operons can be a negative regulator when tryptophan activates regulatory proteins which doesn't allow RNA polymerase to bind to the promoter region. This decreases protein yield. In inducible operons, if glucose is increases CAP unbinds and genes are expressed less.
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What is the common control point of gene expression in all organisms?
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transcription
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Distinguish between heterochromatin and euchromatin as to their structure and activity.
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heterochromtin-highly condensed; usually not expressed euchromatin-not very condensed, expressed
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What occurs in histone acetylation? How does it affect the gene expression?
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acytyl groups(-COCH 3) is attached to histone tails. This causes a looser structure and encourages expression
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What is DNA methylation? What role may it play in gene expression?
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addition of methyl groups to DNA. It discourages gene expression
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What is the result of the heavy methylation of the inactive mammalian X chromosome?
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these genes aren't expressed; if methylation were removed, they would "turn on."
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What is genomic imprinting and how is it maintained? Give examples
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the passing down of methylation patterns; specialized tissues keep a chemeical record during embryonic developement. Methylation regulates expression of paternal or maternal alleles of genes
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What is meant by epigenetic inheritence?give examples of epigenetic changes discussed in the text or in class
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inheritence of traits transmitted by mechanisms not directly involved in nucleotide sequence. Enzymes that modify chromatin structure are an example.
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What has been found in the case of eukaryotes concerning functionality related genes?
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There are no operons in eukaryotes. Genes coding for the enzymes of particular metabolic pathways are usually on different chromosomes.
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What is a plausible mechanism for the coordination of gene expression?
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Multiple genes could be regulated by a single transcription factor.
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How can alternative RNA splicing result in different proteins derived from the same intitial RNA transcript?
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Different sequences are treated as exons and introns
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Posttranscriptional control includes regulation of mRNA degradation. Explain how this affects translation?
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depending on how long it takes for mRNA to degrade, translation can last from a few minutes to weeks
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How can proteins be activated, processed, and degraded? give an example or description of each process.
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proteins are degraded by the attachment of ubiquiton . Some cell surface proteins must be transported to proper destinations to work
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Explain how proteins are targeted for degradation and give specific example of when this might occur
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Ubiquiton tag is attached. an example is the recycling of cyclin to allow healthy cell cycle
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What role do noncoding RNAs play?
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they play an important role in the regulation of gene expression by molecules such as miRNA
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What three processes lead to the transformation of a zygote into an organism?
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1-cell division 2-cell differentiation 3-mophogenesis
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Explain what occurs in cell differentiation and morphogenesis.
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cell differentiation-cells become specialized in structure and function morphogenesis-physical processing that gives an organism its shape
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How does distribution of cytoplasmic determinants occur?
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substances in the mother's egg in the cytoplasm are not evenly distrubuted, so when cell division occurs, these cytoplasmic determinants ar enot equally divided.
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How do different inductive signals occur?
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Depending on what cells surround other cells, different inductive signals are released
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What is meant by determination?What does this mean within an embryonic cell?
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It is the process by which embryonic cells take on specific developmental characteristics
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What process ensures that all tissues and organs of an organism are in their characteristic places?Where do the molecular cues that control this process arise?
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pattern formation, position information cytoplasmic determinants, inductive signals
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What is controlled by homeotic genes?
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genes that regulate pattern formation in late embryo, larva, and adults
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What mechanism is involved in the beginning of tumor growth?Discuss oncogenes and proto-oncogenes.
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oncogenes-cancer causing genes proto-oncogenes-normal genes
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What are three mechanisms for converting a proto-oncogene to an oncogene?
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1-point mutations in proto-oncogenes that result in a constitutionally active protein product 2-localized reduplication (gene amplification) of a DNA segment that includes a proto-oncogene, leading to overexpression of the encoded protein 3-chromosomal translocation that brings a growth-regulatory gene under the control of a different promoter and that causes inappropriate expression of the gene
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Explain the lac operon and its function.
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Lactose binds to repressor molecule which releases repressor from binding cite, allowing RNA polymerase to attach and transcription to begin. (when lactose isn't available, glucose is used-otherwise the repressor stays attached to the binding cite, stopping transcription.)
