Biology Chapter: Cell Cycle and Mitosis
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Questions and Answers

Which nitrogenous base pairs with adenine in DNA?

  • Uracil
  • Thymine (correct)
  • Guanine
  • Cytosine

    • What is the role of helicase during DNA replication?

  • It removes introns from mRNA
  • It adds base pairs to the DNA strand
  • It binds Okazaki fragments together
  • It splits the DNA helix creating a replication fork (correct)

    • What is the primary difference between RNA and DNA?

  • RNA is composed of deoxyribose sugar and DNA contains ribose
  • RNA is double-stranded whereas DNA is single-stranded
  • RNA contains Thymine while DNA contains Uracil
  • RNA is a single helix and contains Uracil instead of Thymine (correct)

    • In the transcription process, which phase follows initiation?

    <p>Elongation</p> Signup and view all the answers

    Which of the following best describes Okazaki fragments?

    <p>Short sequences on the lagging strand of DNA</p> Signup and view all the answers

    What is the function of tRNA during the translation process?

    <p>To transfer amino acids to the ribosome</p> Signup and view all the answers

    Which enzyme is responsible for adding nucleotide base pairs in DNA's leading strand?

    <p>DNA polymerase</p> Signup and view all the answers

    Which step is NOT involved in the post-processing of mRNA before it leaves the nucleus?

    <p>Binding to ribosomes</p> Signup and view all the answers

    What occurs during prophase I that contributes to genetic variation?

    <p>Exchange of chromosome segments between non-sister homologous chromatids.</p> Signup and view all the answers

    During which phase do homologous chromosomes align along the equator?

    <p>Metaphase I</p> Signup and view all the answers

    How can the number of chromosomes in a sex cell be determined from a body cell of the same organism?

    <p>By dividing the number of body cell chromosomes by two</p> Signup and view all the answers

    What is the result of independent assortment during meiosis?

    <p>Each gamete receives a mixture of maternal and paternal chromosomes.</p> Signup and view all the answers

    What phase of the cell cycle does a cell spend the most time in?

    <p>Interphase</p> Signup and view all the answers

    What is nondisjunction?

    <p>A chromosome separation error.</p> Signup and view all the answers

    During which phase of mitosis do chromosomes align on the mitotic spindle?

    <p>Metaphase</p> Signup and view all the answers

    What is the primary outcome of meiosis as compared to mitosis?

    <p>Meiosis leads to four genetically unique haploid daughter cells</p> Signup and view all the answers

    How does nondisjunction during Anaphase I affect the daughter cells?

    <p>All daughter cells will have incorrect numbers of chromosomes.</p> Signup and view all the answers

    What was the phenotype ratio in the F1 generation of Mendel's pea plant crosses with purebred parents?

    <p>All plants were purple.</p> Signup and view all the answers

    What happens during Anaphase I of meiosis?

    <p>Homologous chromosomes are separated and pulled to opposite poles</p> Signup and view all the answers

    What is the function of the cleavage furrow during cytokinesis?

    <p>To separate the cell into two daughter cells</p> Signup and view all the answers

    What fundamental concept is demonstrated by crossing-over during prophase I?

    <p>Genetic variation</p> Signup and view all the answers

    What is a potential drawback to sexual reproduction?

    <p>Higher energy expenditure in creating offspring</p> Signup and view all the answers

    Which of the following is a result of independent assortment during meiosis?

    <p>Different combinations of alleles distributed to gametes.</p> Signup and view all the answers

    What is 'dinofuzz' associated with in fossils?

    <p>The fluff surrounding the dinosaur fossil</p> Signup and view all the answers

    What is the term for organisms that have identical alleles?

    <p>Homozygous</p> Signup and view all the answers

    Which of the following accurately describes a dominant allele?

    <p>It is always expressed over the recessive allele.</p> Signup and view all the answers

    How do genotype and phenotype differ?

    <p>Genotype is the genetic make-up, phenotype is the expression of those genes.</p> Signup and view all the answers

    What distinguishes codominance from incomplete dominance?

    <p>In codominance, both parent phenotypes are equally expressed.</p> Signup and view all the answers

    What is pleiotropy?

    <p>One gene controlling multiple traits.</p> Signup and view all the answers

    What outcome can be expected from a cross between a red flower and a white flower if incomplete dominance is observed?

    <p>Offspring will be pink.</p> Signup and view all the answers

    How can the genotype of potential offspring be determined?

    <p>Using a Punnett Square and the parents' genotypes.</p> Signup and view all the answers

    What primarily makes up a DNA molecule?

    <p>Nucleotides</p> Signup and view all the answers

    What is the function of a codon in a DNA or RNA molecule?

    <p>It codes for a specific amino acid.</p> Signup and view all the answers

    What type of mutation results in a premature stop codon?

    <p>Nonsense mutation</p> Signup and view all the answers

    How do silent mutations affect the resulting protein?

    <p>They have no effect on the protein.</p> Signup and view all the answers

    Where do transcription and translation occur in prokaryotic cells?

    <p>Cytoplasm</p> Signup and view all the answers

    What happens to lactase expression when lactose is absent in prokaryotes?

    <p>Lactase expression is silenced.</p> Signup and view all the answers

    Which type of mutation can lead to little or big changes in the protein structure?

    <p>Missense mutation</p> Signup and view all the answers

    What is the result of a substitution mutation in DNA?

    <p>Replacement of one nucleotide with another.</p> Signup and view all the answers

    How do cells become specialized despite having the same DNA?

    <p>Through regulation of gene expression.</p> Signup and view all the answers

    Study Notes

    The Cell Cycle

    • 90% of a cell's life is spent in interphase
    • Interphase is comprised of three phases:
      • G1: gathering energy and proteins for DNA replication
      • S: DNA replication occurs, resulting in two copies of the chromosomes
      • G2: storing more energy and proteins, some organelles are duplicated

    Mitosis

    • Prophase: nuclear membrane breaks down, mitotic spindle begins to form
    • Metaphase: chromosomes align on the mitotic spindle
    • Anaphase: sister chromatids separate and move to opposite poles
    • Telophase: nuclear membrane begins to form, a cleavage furrow develops

    Cytokinesis

    • At the equator of the cell, a cleavage furrow pulls inward
    • Microfilaments force the cell membrane to contract and separate the cell into two daughter cells

    Dinofuzz

    • "Dinofuzz" is the fluff that surrounded a dinosaur fossil (simple structure)
    • Sinosauropteryx likely used feathers for attracting mates or keeping warm

    Sexual Reproduction

    • Sexual reproduction requires a lot of energy
    • Finding and attracting mates is an essential part of sexual reproduction
    • Forming haploid (sex) cells requires energy
    • Less offspring are produced in sexual reproduction compared to asexual reproduction

    Meiosis

    • Meiosis results in four genetically unique haploid daughter cells for reproduction
    • Meiosis reduces the number of chromosomes by half
    • Mitosis results in two genetically similar diploid daughter cells for growth and repair
    • Mitosis maintains the number of chromosomes

    Meiosis I

    • Prophase I: membrane around the nucleus breaks down, spindle fibers begin to form
    • Crossing-over: exchange of chromosome segments between non-sister homologous chromatids
    • Metaphase I: the meiotic spindle is fully formed, pairs of homologous chromosomes align along the "equator," chromosomes attach to spindle tracks to prepare for separation
    • Independent Assortment: many arrangements of homologous chromosomes during Metaphase I, different combinations of chromosomes in the final daughter cells
    • Anaphase I: homologous chromosomes are pulled away from the equator, sister chromatids stay together
    • Telophase I: chromosomes reach the poles, the nuclear membrane forms
    • Cytokinesis: two daughter cells form

    Meiosis II

    • Sister chromatids separate

    Genetic Variation During Meiosis

    • Crossing over occurs after Prophase I
    • Independent Assortment occurs after Metaphase I

    Nondisjunction

    • Error in chromosome distribution during Anaphase I or Anaphase II
    • In Anaphase I: chromosome pairs fail to separate, all daughter cells have the incorrect number of chromosomes
    • In Anaphase II: sister chromatids fail to separate, some daughter cells have the incorrect number of chromosomes

    Patterns of Inheritance

    • Mendel observed traits such as pea color and plant height in his experiments
    • Hybrids are the result of two parents that differ in a given trait
    • In the F1 generation of a cross between purebred purple and white flowers, all flowers are purple, not blended colors
    • F2 generation shows a 3:1 ratio of purple to white flowers, regardless of which parent was purple
    • Alleles are versions of genes
    • Homozygous: identical alleles
    • Heterozygous: different alleles
    • Dominant alleles are expressed in a hybrid, while recessive alleles have no noticeable effect

    Genotype vs. Phenotype

    • Genotype is the genetic makeup of an individual
    • Phenotype is the outward expression of those genes

    Punnett Squares

    • Punnett squares can be used to determine the possible genotypes of offspring from two parents with known genotypes

    Chickenosaurus

    • Jack Horner proposed that a small "pet dinosaur" could be created by manipulating the genes of a chicken embryo and reversing evolution to bring dinosaur-like features

    Variations on Dominance

    • Incomplete dominance: heterozygotes appear as a mix between parent appearances
    • Codominance: both parent alleles are expressed in the phenotype of the offspring

    Pleiotropy

    • One gene that affects many traits
    • Sickle cell anemia can lead to:
      • Affects the hemoglobin protein and RBC shape
      • Retinal detachment, liver enlargement, renal failure, stroke, heart attack

    Structure of DNA

    • Double helix composed of nucleotides
    • Nucleotides are composed of: nitrogen base, phosphate group, and deoxyribose sugar
    • Bases form pairs between one purine (adenine, guanine) and one pyrimidine (thymine, cytosine)

    DNA Replication

    • Helicase splits the helix, forming a replication fork
    • DNA polymerase adds base pairs to the 3' end of the leading strand, and in sections to the lagging strand
    • DNA ligase binds Okazaki fragments together
    • The end result of DNA replication is two new DNA strands that are exact copies of the original

    RNA

    • RNA is a single helix
    • Uracil replaces thymine in RNA

    Transcription

    • Initiation: RNA polymerase binds to the promoter region of the gene
    • Elongation: RNA polymerase moves along the DNA, adding RNA nucleotides
    • Termination: RNA polymerase reaches the termination sequence and detaches

    mRNA Processing

    • In eukaryotes, mRNA undergoes post-processing before it is ready for translation
    • Stabilizing proteins are added to prevent degradation
    • Caps are added to the ends of mRNA
    • Introns are removed
    • Exons remain

    Translation

    • The process of building proteins from mRNA
    • Ribosomes and mRNA are involved
    • tRNA interacts with the start codon to begin translation

    Mutations

    • A codon is a sequence of three consecutive nucleotides in a DNA or RNA molecule that codes for a specific amino acid
    • Mutations are permanent changes in the genetic information of a cell or virus
    • Substitutions: replacement of one nucleotide base for another
    • Silent mutation: codon for the same amino acid
    • Missense mutation: codon for different amino acid
    • Nonsense mutation: stop codon, resulting in a prematurely ended protein

    Gene Control

    • Cells containing the same DNA become specialized by regulating gene expression
    • Gene expression is regulated by activating and deactivating genes
    • Proteins are created at specific times

    Gene Regulation in Prokaryotes

    • Transcription and translation occur in the same location (cytoplasm) almost simultaneously in prokaryotes
    • Prokaryotes control gene expression by regulating the transcription step
    • Example: lactose and lactase
    • Operon: related genes and sequences, such as lac operon

    How Prokaryotes Regulate Gene Expression

    • Prokaryotes regulate gene expression by regulating the transcription step

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    Description

    Explore the intricacies of the cell cycle, including interphase and mitosis, where cellular division prepares for reproduction. Learn about the steps of cytokinesis and the unique concept of 'Dinofuzz' found in dinosaur fossils. This quiz will test your knowledge on these fundamental biological processes.

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