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Exam 131 Questions and Answers

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Compare and contrast purines and pyrimidines and provide examples of each. - CORRECT ANSWERS Purines contain two carbon-nitrogen rings and four nitrogen atoms, while the pyrimidines contain one carbon-nitrogen ring and two nitrogen atoms. Adenine and guanine are purines, and thymine and cytosine are pyrimidines Describe the structure and arrangement of DNA. - CORRECT ANSWERS DNA is a double helix, which means it is composed of two helical strands. The two strands are held together by the 'rungs', which are made of complementary pairs. The pairs are held together by weak hydrogen bonds. Just as the nucleotides are paired in a complementary fashion, the strands are also arranged in a complementary-type pattern and are said to be antiparallel. In this antiparallel arrangement, the strands are oriented with one strand being in the 5'→3' orientation and the other strand in the 3'→5' orientation What is a genome? - CORRECT ANSWERS The entire sequence of all the paired bases in DNA _______ is a broad term that includes all of the body's cells except gametes. - CORRECT ANSWERS somatic cell What are the four phases of the cell cycle? - CORRECT ANSWERS Gap phase (G1) DNA synthesis (S-phase) Gap phase 2 (G2) Miotic Phase (M-phase) Prophase - CORRECT ANSWERS (1) condensation of chromatin (2) centrosome movement (3) miotic spindle formation (4) dissolution of the nucleolus

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What is condensation? - CORRECT ANSWERS occurs as the strands coil even further and become densely packed What are the sister chromatids help together by? - CORRECT ANSWERS cohesins What is centrosome movement? - CORRECT ANSWERS occurs as the microtubles within the centrosome complex begin to move to opposite poles of the cell What are asters? - CORRECT ANSWERS radial-like microtuble proteins that extend from each centrosome What is the mitotic spindle? - CORRECT ANSWERS a cytoskeletal apparatus composed of different kinds of microtubles that will separate the sister chromatids What does the spindle apparatus consist of? - CORRECT ANSWERS centrosomes, spindle microtubules, and radial asters What is the nucleolus responsible for? - CORRECT ANSWERS synthesizing ribosomal subunits for the cell to assemble complete, functioning ribosomes Prometaphase - CORRECT ANSWERS (1) continued chromatin condensation, (2) changes to the nuclear envelope, (3) reorganization and changes to the miotic spindle apparatus What is the kinetochore? - CORRECT ANSWERS a structured region used for microtuble attachment, there are two regions Metaphase - CORRECT ANSWERS (1) polarization of the centrosomes, (2) chromosome alignment along the equatorial line of the cell, (3) kinetochore attachment

Exam 131 Questions and Answers

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What is the metaphase plate? - CORRECT ANSWERS a symmetrical plane across the cell, an imaginary equator spanning across the cell that is equidistant from the centrosomes located at opposite ends Anaphase - CORRECT ANSWERS (1) separation of the sister chromatids, (2) movement of the separated chromatids toward the centrosome poles, (3) elongation of the cell What is the beginning of anaphase highlighted by? - CORRECT ANSWERS the enzyme separase, which cleaves the cohesion proteins that are holding the sister chromatids together at their centrosomes Telophase - CORRECT ANSWERS (1) reformation of the nuclei, some organelles, and nucleoli; (2) decondensing of chromosomes; (3) dissolution of the spindle microtuble (4) mitotic phase completion (5) cytokinesis What does the mitotic phase end with? - CORRECT ANSWERS telophase What is cleavage? - CORRECT ANSWERS the process through which cytokinesis occurs in animal cells What is the clevage furrow? - CORRECT ANSWERS a visable groove that forms in the same location that the metaphase plate was previously located What is the role of the centriole during the cell cycle? - CORRECT ANSWERS A centriole is a short, cylindrical protein filament composed of tubulin that plays a role in the formation of the mitotic spindle

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Why is the cell cycle control system important? - CORRECT ANSWERS The cell cycle control system is essential for normal cellular growth and development, which is achieved by controlling the timing and rate of the cell cycle True or False: The cell cycle control system is regulated by (1) molecules called cyclins and cyclin- dependent kinases and (2) cellular signals. - CORRECT ANSWERS True Describe each of the major checkpoints of the cell cycle. - CORRECT ANSWERS The G checkpoint, the G2 checkpoint, and the M-checkpoint Describe the G1 checkpoint - CORRECT ANSWERS The G1 checkpoint is considered the major checkpoint of the cycle because, once the cell proceeds through this checkpoint, it has committed to division. Describe the G2 checkpoint - CORRECT ANSWERS This checkpoint serves as a mechanism to evaluate newly duplicated DNA before mitotic division occurs. Essentially, this checkpoint focuses on ensuring the quality and completion of DNA replication Describe the M-checkpoint - CORRECT ANSWERS the M checkpoint is also known as the spindle checkpoint and occurs during anaphase. This is because the main purpose of this checkpoint is to ensure that the spindles are correctly attached to the kinetochore regions of the sister chromatids Cell cycle dysregulation is the sole cause of cancer cell development. - CORRECT ANSWERS False Why are some other reasons cancer develops? - CORRECT ANSWERS Cancer cells can develop from causes other than cell cycle dysregulation that results in uncontrolled growth. Cancer cells may develop and secrete their own growth factors, lose the ability to respond to cell surface signals, or may even develop internal signaling abnormalities that allow immortal growth

Exam 131 Questions and Answers

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What is the difference between diploid and haploid cells? - CORRECT ANSWERS Diploid cells, like somatic cells, contain sets of chromosomes, while haploid cells, like gametes, only have one set of chromosomes What occurs in each of the two main phases of meiosis? - CORRECT ANSWERS Meiosis is divided into meiosis I, which consists of the separation of homologous chromosomes, and meiosis II, which consists of the separation of sister chromatids What phase of meiosis I is marked by the separation of homologous chromosomes? - CORRECT ANSWERS Anaphase What is the most common chromosomal abnormality in humans? - CORRECT ANSWERS Trisomy 21, also known as Down Syndrome Describe the law of segregation - CORRECT ANSWERS The law of segregation hypothesizes that the alleles for a trait become separated and end up in two different gametes during gamete formation. Describe the law of independent assortment. - CORRECT ANSWERS The law of independent assortment states that two or more genes (inheritable characteristics) are independent of the other. Specifically, each pair of alleles in a somatic cell will separate and segregate into separate gametes randomly Which type of dominance occurs when the offspring of the parent cross have phenotypes that are different from the parent? - CORRECT ANSWERS Incomplete dominance Fill-in-the-Blank: An organism is ________ for a trait if the alleles are different. - CORRECT ANSWERS Heterozygous

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What is the difference between a genotype and a phenotype? - CORRECT ANSWERS Genotype refers to an organism's genetic make-up, where phenotype refers only to the physical observable traits for an organism What is pleiotropy? Provide an example of a pleiotropic abnormality. - CORRECT ANSWERS When one gene results in multiple phenotypic effects, it is called pleiotropy. Cystic fibrosis, albinism, sickle cell anemia, schizophrenia, and some forms of autism are examples of pleiotropic abnormalities in which a single genetic mutation results in systematic symptoms What are the four nitrogenous bases? - CORRECT ANSWERS adenine, guanine, cytosine, thymine Which bases are purines and which are pyrimidines? - CORRECT ANSWERS Adenine and Guanine are purines Cytosine and Thymine are pyrimidines. What is a base plus a deoxyribose? - CORRECT ANSWERS nucleoside What is a base plus a deoxyribose plus a phosphate group? - CORRECT ANSWERS nucleotide What is the purpose of all four bases? - CORRECT ANSWERS to form the structural basis of DNA What are complimentary pairs? - CORRECT ANSWERS a pruine will always pair with a pyrimidine A & T and C & G

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When do hydrogen bonds occur? - CORRECT ANSWERS when two negatively charged atoms share a hydrogen atoms How many bonds are formed when adenine pairs with thymine? - CORRECT ANSWERS two hydrogen bonds How many bonds are formed when guanine pairs with cytosine? - CORRECT ANSWERS three hydrogen bonds What is a sequence? - CORRECT ANSWERS Nucleotides that are linked to a polynucleotide which is ordered in a specified linear arrangement, it determines the entire organism What is a 5' (5 prime) - CORRECT ANSWERS the nucleotide end that terminates with a phosphate group What is a 3' (3 prime) - CORRECT ANSWERS a strand that terminates with a hydroxyl group What is the antiparallel arrangement? - CORRECT ANSWERS one strand is in the 5'3' orientation and the other strand in the 3'5' orientation What are histone proteins? - CORRECT ANSWERS Proteins in which DNA wraps its self around, necessary for the replication of DNA What is chromatin? - CORRECT ANSWERS the sequences and their associated pairs What are chromosomes? - CORRECT ANSWERS chromatin complexes that are further packaged into structures called chromosomes

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What is a somatic cell? - CORRECT ANSWERS a broad term that includes all the body's cells except gametes What are gametes? - CORRECT ANSWERS the sperm and egg cells What is the cell cycle? - CORRECT ANSWERS the process of a parent cell replicating its genetic information and physically dividing into two new daughter cells What is cytokinesis? - CORRECT ANSWERS the division of cytoplasm What is interphase? - CORRECT ANSWERS includes everything except for active division and accounts for 90% of the time needed to complete the cell cycle What is G0 phase? - CORRECT ANSWERS resting phase What is the G1 phase? - CORRECT ANSWERS the growth phase, production of mRNA and proteins needed for DNA synthesis What is mRNA? - CORRECT ANSWERS transfers the genetic information from DNA to ribosomes What happens during DNA synthesis (S-phase)? - CORRECT ANSWERS the cell will spend 10- 12 hours in interphase, while DNA is replicated What happens during G2 phase? - CORRECT ANSWERS characterized by another period of cellular growth as the cell begins to synthesize proteins and organelles necessary for mitosis

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What is a centrosome? - CORRECT ANSWERS the region of the cell that functions to organize microtubles for cell division What are centrosomes comprised of? - CORRECT ANSWERS several filament and microtuble fibers with a pair of centrioles located in the centrosome What is a centriole? - CORRECT ANSWERS a short, cylindrical protein filament composed of tuulin that plays a role in the formation of the mitotic spindle What is the M phase? - CORRECT ANSWERS Consists of two phases mitosis and cytokensis What are the five subphases of mitosis? - CORRECT ANSWERS prophase, prometaphase, metaphase, anaphase, telophase What is the cell cycle control system? - CORRECT ANSWERS Several molecular surveillance mechanisms that can either halt or permit the cell cycle to proceed What are cell checkpoints? - CORRECT ANSWERS places along the cycle where processes are halted and mechanisms are deployed to ensure the cell is ready to proceed to the next phase What are protein kinases? - CORRECT ANSWERS specialized enzymes that phosphorylate (chemically add a phosphate group) other proteins to activate or inactivate them What is a cyclin? - CORRECT ANSWERS a protein that fluctuates in concentration at different phases of the cell cycle

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What are the names of cyclins? - CORRECT ANSWERS G1 cyclins, G1/S cyclins, S-cyclins, M- cyclins What are dependent kinases (Cdks)? - CORRECT ANSWERS kinases that depend on the presence of cyclins to become active What is maturation promoting factor (MPF)? - CORRECT ANSWERS a cyclin-Cdk complex that triggers a cell's passage past the G2 checkpoint into the M phase What is a growth factor? - CORRECT ANSWERS a protein messanger released from neighboring cells that stimulates nearby cells to proliferate What is density-dependent inhibition? - CORRECT ANSWERS cell surface proteins signal to adjoining cells to stop proliferation if they sense they are being crowded What is anchorage dependence? - CORRECT ANSWERS cells must be physically anchored to a surface to proliferate What is a tumor? - CORRECT ANSWERS a mass of abnormal cells within normal body tissues What are benign tumors? - CORRECT ANSWERS have not developed the ability to spread to other parts of the body What are malignant tumors? - CORRECT ANSWERS composed of cells that have accumulated genetic changes allowing them to grow without restraint and to also spread to new tissues What is metastasis? - CORRECT ANSWERS the spreading of cancer cells from one location to another in the body

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What is an autosome? - CORRECT ANSWERS a term for all the chromosomes except the one that determines the sex of the offspring What is a karyotype? - CORRECT ANSWERS an ordered display of homologus chromasomes What are homologous chromosomes (or homologs)? - CORRECT ANSWERS contain the same genes for inherited characteristics, are of the same size, the centomeres are in the same place, and their appearance will be the same upon chemical staining What does meiosis I include? - CORRECT ANSWERS Prophase I, Metaphase I, Anaphase I, Telophase I What does meosis II include? - CORRECT ANSWERS Prophase II, Metaphase II, Anaphase II, Telophase II What happens in prophase I of meiosis? - CORRECT ANSWERS centrosome movement, chromosome condensation and coiling, spindle formation, and dissolution of the nuclear envelope into vesicle-like structures What is crossing-over? - CORRECT ANSWERS a mechanism that increases genetic variety. The sister chromatids are paired together by cohesion proteins called cohesins and the maternal pair will align exactly with the paternal pair. What are cohesins? - CORRECT ANSWERS Proteins that hold sister chromatids together What is the synaptonemal complex? - CORRECT ANSWERS a zipper-like protein complex that brings the non-sister chromatids in close association with one another

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What is synapsis? - CORRECT ANSWERS the pairing of homologous chromosomes during meiosis What is chiasmata? - CORRECT ANSWERS The point where chromosomes crossover What are recombinant chromosomes? - CORRECT ANSWERS distinct chromosomes that will carry genetic information from both parents but it will not be identical to that of the parent What happens in metaphase I of meiosis? - CORRECT ANSWERS The homologous pairs of chromosomes move to the middle of the cell What happens in anaphase I of meiosis? - CORRECT ANSWERS Homologous chromosomes separate What happens during telophase I and cytokinesis of meiosis? - CORRECT ANSWERS the first meiotic division ends as the cytoplasm divide into two daughter cells What is meiosis II? - CORRECT ANSWERS the process of separating sister chromatids and ensuring that the daughter cells have unique crossed-over chromatids unlike the parent cell What happens in prophase II in meiosis? - CORRECT ANSWERS A new spindle forms around the chromosomes What happens in metaphase II in meiosis? - CORRECT ANSWERS Chromatid pairs line up along equator

Exam 131 Questions and Answers

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What happens in anaphase II in meiosis? - CORRECT ANSWERS marked by the degredation of the proteins that hold together the sister chromatids What happens in telophase II and cytokinesis? - CORRECT ANSWERS the nuclear membranes re-form and the cells divide. There are four daughter cells. Each cell is haploid. What is independent assortment? - CORRECT ANSWERS occurs when maternal and paternal homologus chromosomes are shuffled into daughter cells at random, promotes genetic diversity What is trisomy 21? - CORRECT ANSWERS Down syndrome, the most common chromosomal abnormality in humans Why does trisomy 21 happen? - CORRECT ANSWERS In most cases it is because there are three copies of the genetic material on chromosome 21 raher than the normal two copies What is non-disjunction? - CORRECT ANSWERS failure of sister chromatids to separate properly What is true-breeding? - CORRECT ANSWERS Plants that produce offspring of the same variety when they self-pollinate. What is hybridization? - CORRECT ANSWERS when two true-breeding plants are crossed Why were Mendel's experiments important? - CORRECT ANSWERS he discovered the law of segregation and the law of independent assortment What is a dominant trait? - CORRECT ANSWERS a genetic factor that blocks another genetic factor

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What is a recessive trait? - CORRECT ANSWERS a genetic factor that is blocked by the presence of a dominant factor What are alleles? - CORRECT ANSWERS different versions of the same gene What is a locus? - CORRECT ANSWERS the precise location of a gene on a chromosome What is the law of segregation? - CORRECT ANSWERS hypothesizes that the alleles for a trait become separated and end up in two different gametes during gamete formation What does it mean if an organism is homozygous? - CORRECT ANSWERS If its 2 alleles for a particular gene are the same. What is a monohybrid cross? - CORRECT ANSWERS when only one trait is being studied during a cross What are dihybrid crosses? - CORRECT ANSWERS more complicated crosses that include two traits What is dihybridization? - CORRECT ANSWERS Dihybridization occurs when two traits from true-breeding parents are studied to determine if the traits will be inherited together or separately. What is dependent assortment? - CORRECT ANSWERS Phenotypic ratio of the F2 generation will be 3:1, just as in a monohybrid cross

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What is the law of independent assortment? - CORRECT ANSWERS two or more genes are independent of the other What is complete dominance? - CORRECT ANSWERS the phenotype for a dominant trait is exhibited regardless of the genotype What is incomplete dominance? - CORRECT ANSWERS when the offspring of the parent cross have phenotypes that are different from the parent (red + white = pink) What is codominance? - CORRECT ANSWERS the traits of both alleles are expressed in the phenotype What is pleiotropy? - CORRECT ANSWERS when one gene results in multiple phenotypic effects What does cystic fibrosis result from? - CORRECT ANSWERS a mutation in the Cystic Fibrosis transmembrane conductance regulator gene (CFTR) What is cystic fibrosis an example of? - CORRECT ANSWERS where one genetic mutation impacts a host of organ systems