Biology Exam #4 Flashcards
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Questions and Answers

After a tautomeric shift, adenine bonds with?

  • Cytosine (correct)
  • Guanine
  • Thymine
  • Uracil

    • What happens during a tautomeric shift?

    Hydrogen atoms move from a nucleotide base with altered bonding properties.

    When a tautomeric shift occurs, the resulting nucleotide is an ______ of the nucleotide prior to the shift.

    structural isomer

    The nucleic acid sequence in mRNA is determined by what?

    <p>Nucleotide sequence in DNA.</p> Signup and view all the answers

    If a frameshift mutation causes a stop codon to be inserted into the DNA sequence, what will happen?

    <p>The resulting protein will be too short and non-functional.</p> Signup and view all the answers

    A nucleotide deletion in DNA replication will cause what?

    <p>Causes the amino acids inserted after the deletion to be incorrect.</p> Signup and view all the answers

    UV light damages DNA by causing what?

    <p>Covalent bonds to form between thymine nucleotides next to each other on the same DNA strand.</p> Signup and view all the answers

    What happens to the covalent bonds in light repair?

    <p>They're broken between the thymine dimers.</p> Signup and view all the answers

    Excision repair of thymine dimers is possible because there are 2 strands of DNA.

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

    Excision repair can be used to repair thymine dimers as well as other types of damaged DNA.

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

    How often does ultraviolet light result in the formation of thymine dimers?

    <p>Ultraviolet light provides the energy for covalent bond formation between 2 thymines.</p> Signup and view all the answers

    What protein cuts the damaged DNA strand?

    <p>UvrC.</p> Signup and view all the answers

    Which protein has a helicase function?

    <p>UvrD.</p> Signup and view all the answers

    What synthesizes the new DNA strand?

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

    A mutation has occurred that prevents the UvrA and UvrB from forming a complex. What result will this have on the damaged DNA?

    <p>The damaged DNA will not be recognized.</p> Signup and view all the answers

    A mutation has occurred that has made UvrD non-functional. What result will this have on the damaged DNA?

    <p>The damaged segment of DNA will be recognized and cut, but will not be separated from the healthy strand.</p> Signup and view all the answers

    What is the difference in the DNA sequence of the normal individual and that of the individual with sickle cell anemia?

    <p>A single base has been changed.</p> Signup and view all the answers

    What is the difference in the amino acid sequence of the normal individual and that of the individual with sickle cell anemia?

    <p>A single amino acid has been changed.</p> Signup and view all the answers

    A single point mutation in the DNA sequence leads to a change in the protein structure, which leads to a change in the protein's function and causes sickle cell anemia.

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

    The process by which two haploid gametes unite to form a zygote is called ______ reproduction.

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

    Crossing over during prophase occurs commonly in?

    <p>Meiosis I.</p> Signup and view all the answers

    What are some characteristics of meiosis II?

    <p>The sorting event is similar to that of mitosis; sister chromatids are separated; the resulting daughter cells are haploid.</p> Signup and view all the answers

    Name the order of meiosis I starting from the earliest.

    <ol> <li>Replicated chromosomes condense from bivalents and crossing over occurs. 2. Nuclear envelope is completely broken down and spindle apparatus is entirely formed. 3. Bivalents are aligned along the center of the cell. 4. Homologous chromosomes separate and move toward opposite poles. 5. Chromosomes decondense and nuclear envelope reforms.</li> </ol> Signup and view all the answers

    What is a haploid?

    <p>One chromosome set per cell.</p> Signup and view all the answers

    What is a diploid?

    <p>Two chromosome sets per cell.</p> Signup and view all the answers

    What is a polyploid?

    <p>Three or more chromosome sets per cell.</p> Signup and view all the answers

    What is a tetraploid?

    <p>Four chromosome sets per cell.</p> Signup and view all the answers

    What is triploid?

    <p>Three chromosome sets per cell.</p> Signup and view all the answers

    A zygote is created when 2 haploid cells called what fuse?

    <p>Gametes.</p> Signup and view all the answers

    When 2 haploid gametes unite, they create a diploid cell called?

    <p>A zygote.</p> Signup and view all the answers

    During anaphase II of meiosis, ______ are separated.

    <p>Sister chromatids.</p> Signup and view all the answers

    Which two key events occur at the beginning of meiosis but not mitosis?

    <p>Crossing over; bivalent formation.</p> Signup and view all the answers

    During what phase do homologous chromosomes align along the center of the cell as bivalents?

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

    What do mitosis and meiosis have in common?

    <p>Sister chromatids are separated.</p> Signup and view all the answers

    What is the correct order of meiosis I?

    <ol> <li>Prophase I 2. Prometaphase I 3. Metaphase I 4. Anaphase I 5. Telophase I.</li> </ol> Signup and view all the answers

    Trisomies 21, 18, 13, or abnormalities in the number of the sex chromosomes are most likely due to what?

    <p>Nondisjunction.</p> Signup and view all the answers

    Polyploidy is generally a lethal condition in?

    <p>Mammals.</p> Signup and view all the answers

    Organisms possessing chromosomes that occur in one or more complete sets are termed what?

    <p>Euploid.</p> Signup and view all the answers

    Aneuploidy refers to an alteration in the number of particular what?

    <p>Chromosomes.</p> Signup and view all the answers

    During which phase of meiosis I are bivalents segregated?

    <p>Anaphase I.</p> Signup and view all the answers

    What two suffixes refer to a complete set of chromosomes?

    <p>Ploid; ploidy.</p> Signup and view all the answers

    In a certain cell a pair of sister chromatids is attached to kinetochore microtubules from just one pole. This cell must be in?

    <p>Meiosis I.</p> Signup and view all the answers

    Some characteristics of Trisomy 21 or Down syndrome are?

    <p>Short stature; mental impairment; slanted eyes; flattened face.</p> Signup and view all the answers

    During meiosis I, what does it separate?

    <p>Homologous chromosomes.</p> Signup and view all the answers

    A diploid cell divides by a process called what to produce haploid cells?

    <p>Meiosis.</p> Signup and view all the answers

    What are the characteristics of meiosis II?

    <p>Sister chromatids are separated; the resulting daughter cells are haploid; the sorting event is similar to that of mitosis.</p> Signup and view all the answers

    In what phase of meiosis are the replicated chromosomes condensed, the homologous chromosomes form bivalents, and crossing over occurs?

    <p>Prophase I.</p> Signup and view all the answers

    What is the end result of mitosis in a diploid organism?

    <p>Two daughter cells that are diploid.</p> Signup and view all the answers

    Unlike animals, plants often possess more than two sets of chromosomes. Plants thus exhibit what?

    <p>Polyploidy.</p> Signup and view all the answers

    Synapsis is the process of forming what?

    <p>Bivalent.</p> Signup and view all the answers

    Which process involves a physical exchange between chromosome segments of the bivalent?

    <p>Crossing over.</p> Signup and view all the answers

    What is the significant result of meiosis?

    <p>Created haploid gametes for sexual reproduction.</p> Signup and view all the answers

    A human gamete contains how many chromosomes?

    <ol start="23"> <li></li> </ol> Signup and view all the answers

    At what stage of meiosis I do the joined pairs of sister chromatids reach their respective poles and decondense?

    <p>Telophase I.</p> Signup and view all the answers

    In prometaphase I of meiosis, the nuclear envelope is completely broken down into vesicles and the what is entirely formed?

    <p>Spindle apparatus.</p> Signup and view all the answers

    Because meiosis I produces 2 haploid nuclei, it's called?

    <p>Reduction division.</p> Signup and view all the answers

    The bivalents are organized along the metaphase plate with their sister chromatids randomly aligned in a double row. What phase of cell division is this?

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

    What describes an animal that is 2n-1?

    <p>Monosomic.</p> Signup and view all the answers

    What metaphase I event provides a mechanism for vast genetic diversity?

    <p>Random alignment.</p> Signup and view all the answers

    The end result of meiosis II is?

    <p>Four daughter cells that are haploid.</p> Signup and view all the answers

    Study Notes

    Tautomeric Shifts and Mutations

    • A tautomeric shift in adenine causes it to bond with cytosine.
    • Tautomeric shifts involve the movement of hydrogen atoms, altering the bonding properties of nucleotide bases.
    • Resultant nucleotide after a tautomeric shift is a structural isomer.
    • Frameshift mutations can introduce stop codons, resulting in non-functional short proteins.
    • Nucleotide deletions during DNA replication lead to incorrect amino acid insertions.

    DNA Damage and Repair Mechanisms

    • UV light induces DNA damage by forming covalent bonds between adjacent thymine nucleotides.
    • Light repair involves breaking covalent bonds between thymine dimers.
    • Excision repair relies on the presence of two DNA strands to be effective.
    • Excision repair can fix various types of DNA damage, including thymine dimers.
    • UV light frequently causes thymine dimers due to energy facilitating covalent bonding.

    Repair Proteins and Functions

    • UvrC is the protein responsible for cutting damaged DNA strands.
    • UvrD has helicase function to unwind DNA during repair.
    • DNA polymerase synthesizes new DNA strands following repair.
    • If UvrA and UvrB cannot form a complex, damaged DNA remains unrecognized.
    • If UvrD is non-functional, cut damaged segments remain attached to healthy strands.

    Nucleotide Differences and Genetic Mutations

    • Sickle cell anemia results from a single base change in DNA sequence.
    • The alteration leads to a change in a single amino acid within proteins.
    • Point mutations can change protein structure and function, causing diseases like sickle cell anemia.

    Meiosis Overview

    • The union of two haploid gametes to form a zygote is classified as sexual reproduction.
    • Crossing over typically occurs during prophase I of meiosis I, enhancing genetic diversity.
    • Meiosis II involves separating sister chromatids, creating haploid daughter cells.

    Chromosome Sets and Definitions

    • A haploid cell contains one set of chromosomes.
    • Diploid cells have two sets of chromosomes, and polyploid cells contain three or more sets.
    • Triploid cells consist of three chromosome sets, while tetraploid cells have four sets.

    Meiosis and Genetic Diversity

    • During metaphase I, homologous chromosomes align as bivalents.
    • Characteristics of meiosis II include sister chromatids separation and similar sorting events to mitosis.
    • Anaphase I is where bivalents are segregated, ensuring genetic diversity through random alignment.

    Chromosomal Abnormalities

    • Trisomies and chromosomal number abnormalities result from nondisjunction during meiosis.
    • Polyploidy is typically lethal in mammals but can be common in plants.
    • Euploid organisms have complete sets of chromosomes, whereas aneuploidy refers to specific chromosome number alterations.

    Major Events in Meiosis

    • Characteristics of Trisomy 21 (Down syndrome) include short stature and mental impairment.
    • The end result of meiosis I is two haploid nuclei, leading to the term reduction division.
    • During telophase I, joined sister chromatids reach poles and decondense.

    Final Outcomes of Meiosis

    • Meiosis II culminates in four haploid daughter cells, essential for sexual reproduction.
    • Human gametes contain 23 chromosomes, half the diploid number.
    • The metaphase plate organization during metaphase I promotes genetic variability through random alignment.

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    Description

    Prepare for your Biology Exam #4 with these flashcards focusing on tautomeric shifts and their impact on nucleotide bonding. Each card presents key terms and definitions that will enhance your understanding of nucleic acids and molecular biology concepts.

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