Chromosomal Rearrangements - Module 10
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Questions and Answers

What is the result when a gene is expressed properly?

  • Functional protein is produced at an appropriate level. (correct)
  • Functional protein is produced at an incorrect level.
  • Only one copy of protein is produced.
  • No protein is produced.
  • What can occur if one copy of a gene that requires two copies is deleted?

  • Haploinsufficiency may lead to a mutant phenotype. (correct)
  • Protein overproduction is likely.
  • No change in phenotype is observed.
  • Increased stability of the organism is ensured.
  • How do duplications primarily affect gene dosage?

  • They result in gene deletions.
  • They always lead to non-viable offspring.
  • They do not affect gene dosage at all.
  • They can cause an unbalanced dosage of gene products. (correct)
  • What is a major consequence of unequal crossing over during meiosis?

    <p>It generates both duplications and deletions. (B)</p> Signup and view all the answers

    Which of the following statements is true about tandem duplications?

    <p>They are a simple form of duplications. (C)</p> Signup and view all the answers

    What are two general types of chromosomal variations?

    <p>Chromosome rearrangement and variation in chromosome numbers (B)</p> Signup and view all the answers

    What happens during a deletion in chromosomal rearrangement?

    <p>A segment of the chromosome is lost (C)</p> Signup and view all the answers

    What is the major consequence of a chromosomal deletion?

    <p>Loss of genetic information (A)</p> Signup and view all the answers

    During meiosis, how can deletions be detected?

    <p>Using deletion loops and molecular methods (A)</p> Signup and view all the answers

    What can deletion of DNA sequences lead to regarding allele expression?

    <p>Pseudodominance of normally recessive alleles (C)</p> Signup and view all the answers

    What is the effect of a deletion that spans a centromere during cell division?

    <p>Development of an acentric chromosome that may be lost (D)</p> Signup and view all the answers

    Which method can be used to study chromosomal variations?

    <p>Molecular methods and genetic engineering techniques (C)</p> Signup and view all the answers

    What role does genetic variation play in biology?

    <p>It is foundational to biodiversity and adaptation (B)</p> Signup and view all the answers

    What is one consequence of gene duplication?

    <p>Alteration of gene dosage (C)</p> Signup and view all the answers

    What event can lead to the formation of pseudogenes?

    <p>Gene inactivation (A)</p> Signup and view all the answers

    Which process describes the acquisition of a new function following gene duplication?

    <p>Neofunctionalization (A)</p> Signup and view all the answers

    What is a significant effect of increased gene dosage on phenotype?

    <p>Increased protein synthesis (C)</p> Signup and view all the answers

    What is an example of a multigene family resulting from gene duplication?

    <p>Globin gene family (C)</p> Signup and view all the answers

    What is one type of chromosomal rearrangement defined by two breaks on a chromosome and reinsertion in the opposite orientation?

    <p>Inversion (C)</p> Signup and view all the answers

    What is a potential outcome of an inversion on phenotype?

    <p>Often none (A)</p> Signup and view all the answers

    How many copies of the salivary amylase gene do humans typically have as a result of duplication?

    <p>Five to eight (D)</p> Signup and view all the answers

    What effect can a change in the position of genes have on phenotype?

    <p>It can alter gene expression. (B)</p> Signup and view all the answers

    What is the outcome of crossing over occurring within an inverted region?

    <p>Reduction in the frequency of recombination. (A)</p> Signup and view all the answers

    Which type of inversion can happen without the use of centromeres?

    <p>Paracentric inversion. (A)</p> Signup and view all the answers

    What happens to gametes produced when no crossing over occurs within an inverted region?

    <p>They retain genetic information without any loss. (B)</p> Signup and view all the answers

    What is a characteristic of a dicentric chromatid during cell division?

    <p>It often breaks as centromeres are pulled apart. (B)</p> Signup and view all the answers

    In terms of chromosomal rearrangements, what does translocation involve?

    <p>The exchange of segments between nonhomologous chromosomes. (B)</p> Signup and view all the answers

    Which of the following is NOT a consequence of crossing over within a pericentric inversion?

    <p>Stable production of viable gametes. (C)</p> Signup and view all the answers

    What can result from the crossing over between inverted and non-inverted chromosomes?

    <p>Formation of an acentric chromatid. (C)</p> Signup and view all the answers

    What defines a balanced translocation between chromosomes?

    <p>No genetic material is lost. (B)</p> Signup and view all the answers

    Which of the following describes a consequence of reciprocal translocations?

    <p>It can create fusion proteins that function incorrectly. (A)</p> Signup and view all the answers

    What is the genetic feature associated with the 'Philadelphia' chromosome?

    <p>Fusion of BCR-ABL gene segments. (D)</p> Signup and view all the answers

    What is one significant consequence of chromosomal inversions?

    <p>They allow genes to diverge for adaptations. (A)</p> Signup and view all the answers

    In the context of Ruff males, which statement regarding the chromosomal inversion is true?

    <p>The inversion arose around 3.8 million years ago. (B)</p> Signup and view all the answers

    What is the result of a chromosomal inversion in the homozygous condition for the Ruff's inversion?

    <p>Lethal effects. (B)</p> Signup and view all the answers

    What initiates the formation of different male types in Ruff sandpipers?

    <p>A rare crossover event restoring independent versions. (C)</p> Signup and view all the answers

    Which of the following best explains the concept of gene expression alteration due to translocations?

    <p>Genes can associate with different proteins after translocations. (A)</p> Signup and view all the answers

    What is the potential outcome for offspring that are homozygous for the inversion in ruffs?

    <p>They are not viable. (A)</p> Signup and view all the answers

    Why has the inversion persisted for 3.8 million years in ruffs?

    <p>The benefits of being heterozygous outweigh the costs. (D)</p> Signup and view all the answers

    What does the lack of recombination within inversion regions facilitate?

    <p>The divergence of genes within the inversion. (B)</p> Signup and view all the answers

    How does the chromosomal inversion in Atlantic cod affect their adaptability to water temperature?

    <p>It allows the cod to adapt to both warm and cold waters. (C)</p> Signup and view all the answers

    What is the significance of the sequence divergence observed within inversions in the context of ruffs?

    <p>It supports the evolution of unique adaptations. (A)</p> Signup and view all the answers

    What kind of variations are influenced by major inversions in Atlantic cod?

    <p>Both temperature adaptations and migratory behavior. (B)</p> Signup and view all the answers

    What does the term 'Faeder' male refer to in the context of ruff reproduction?

    <p>A successful heterozygous male. (A)</p> Signup and view all the answers

    In hook of the chromosomal variations, which concept is touched upon regarding inversions?

    <p>Chromosomal inversions can limit genetic exchange. (B)</p> Signup and view all the answers

    Flashcards

    Chromosomal Rearrangement

    A permanent change in the structure of a chromosome, passed on to offspring if the change occurs in germline cells.

    Deletion (Chromosomal)

    Loss of a chromosome segment; either at the end or internally.

    Deletion Loop

    A structure formed during meiosis in a cell containing a deletion that is detected.

    Acentric Chromosome

    A chromosome lacking a centromere; likely lost during cell division.

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    Pseudodominance

    Expression of a normally recessive allele due to deletion of a dominant allele's region.

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    Gene Dosage

    The number of copies of a gene affecting its function.

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    Unequal crossing over

    A mechanism that can create deletions.

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    Terminal Deletion

    Loss of a chromosome segment at the end of a chromosome.

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    Haploinsufficiency

    A mutant phenotype caused because a gene only has one copy when two are needed for normal function; a loss of a gene's function.

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    Chromosome Duplication

    A section of a chromosome is repeated. Often, the repetition is in tandem (right next to the original segment).

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    Tandem Duplication

    A duplication where the repeated segment is adjacent to the original segment, often the simplest type of duplication.

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    Gene duplication

    A process where a segment of DNA is copied, creating two or more copies of a gene.

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    Pseudogene

    A gene that has lost its ability to code for a functional protein.

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    Neofunctionalization

    One copy of a duplicated gene acquires a new function.

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    Gene family

    A group of genes with related functions, often resulting from gene duplication events.

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    Inversion (chromosome rearrangement)

    A type of chromosomal rearrangement where a segment of a chromosome is flipped and reinserted.

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    Pericentric inversion

    An inversion that includes the centromere.

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    Paracentric inversion

    An inversion that does not include the centromere.

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    Position Effect

    The change in gene expression due to a change in the gene's position on a chromosome. This can occur when moving a gene to a region that has different regulatory elements or when altering chromatin structure.

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    Variegation

    A pattern of different colored areas on a plant or animal due to a change in gene expression, often caused by a position effect.

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    Dicentric Chromatid

    A chromatid with two centromeres, formed during crossing over within a paracentric inversion.

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    Acentric Chromatid

    A chromatid without a centromere, formed during crossing over within a paracentric inversion.

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    Crossing Over Within an Inversion

    The exchange of genetic material between homologous chromosomes during meiosis that occurs within an inverted region.

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    Translocation

    An exchange of segments between nonhomologous chromosomes or between different regions on the same chromosome.

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    Reciprocal Translocation

    A type of translocation where two chromosomes exchange segments. No genetic material is lost or gained, creating a balanced translocation.

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    Non-reciprocal Translocation

    A type of translocation where a chromosome segment moves to a different chromosome without any reciprocal exchange. This can lead to an unbalanced translocation with a gain or loss of genetic material.

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    Balanced Translocation

    A translocation where no genetic material is lost or gained. The total amount of genetic material remains the same.

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    Philadelphia Chromosome

    An abnormal chromosome found in some leukemia patients, caused by a reciprocal translocation between chromosomes 9 and 22, leading to a fusion gene that promotes uncontrolled cell growth.

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    Fusion Protein

    A protein formed when two or more different proteins are joined together through genetic recombination. This can occur due to chromosomal rearrangements.

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    How can translocations affect gene expression?

    Translocations can change the position of genes, potentially altering their expression by influencing their association with different regulatory proteins or creating new gene products, like fusion proteins. These alterations can lead to various cellular changes and even disease.

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    What is the connection between chromosomal rearrangements and disease?

    Chromosomal rearrangements, like translocations, can disrupt the normal functioning of genes and lead to various diseases, including cancer. For example, the Philadelphia chromosome, a product of a specific translocation, is associated with chronic myelogenous leukemia.

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    Chromosomal Inversion

    A type of chromosomal rearrangement where a segment of a chromosome is flipped and re-inserted, changing the gene order.

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    Faeder Male

    A male ruff with an inverted chromosome, specifically the chromosome containing the 'S' gene, which influences mating displays.

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    Independent Male

    A male ruff with a non-inverted chromosome, carrying the 'S' gene, involved in mating displays.

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    What is the 'Cost' of Inversion?

    The potential for offspring to be homozygous for the inversion, leading to non-viability, meaning they cannot survive.

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    Why Has Inversion Persisted?

    Despite the cost, being heterozygous for the inversion, resulting in being a 'Faeder' male, is a successful reproductive strategy, outweighing the cost.

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    Sequence Divergence Inside vs. Outside Inversion

    Genes within the inversion region show significantly greater sequence divergence compared to those outside the inversion.

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    Chromosomal Rearrangements and Adaptation

    Chromosomal rearrangements can influence adaptation to different environments, as seen with the Atlantic Cod, where inversions affect temperature preference.

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    Cod and 'Warm' vs. 'Cold' Water

    Cod with different inversion orientations have genes that favor either colder or warmer water conditions, demonstrating adaptation driven by inversions.

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    Study Notes

    Chromosomal Rearrangements

    • Module 10 covers chromosomal rearrangements
    • Genetic variations are fundamental to biology
    • This module explores types of genetic variation, their origins, detection methods, and biological/societal applications.

    Types of Chromosomal Rearrangements

    • Two main categories: structural changes and numerical changes
    • Structural changes affect chromosome structure
    • Numerical changes alter the chromosome number

    (1) Deletions

    • Loss of a segment (internal/terminal) from a chromosome

    • Deletion origins: terminal-end break-off or internal incorrect end rejoining

    • Unequal crossing over is another origin

    • Major effect: loss of genetic information; impact depends on segment size and location

    • Consequences of Deletions:

      • Phenotypic effects dependent on deleted sequence size and location
      • Deletion crossing a centromere produces an acentric chromosome (likely lethal during cell division)
      • Deletions can lead to pseudodominance (expression of normally recessive alleles)
      • Deletions impact gene dosage
      • Correct gene dosage = normal functional protein production
      • Haploinsufficiency: one gene copy deleted = mutant phenotype
    • Detection of Deletions:

      • Deletion loops can be observed during meiosis
      • Molecular methods detect lower heterozygosity/gene dosage

    (2) Duplications

    • Repetition of a chromosome segment
    • Simplest form: tandem duplication
    • Can affect entire gene or gene clusters
    • Often, have little/no effect on viability (phenotype)
    • Consequences of Duplications:
      • Excess or unbalanced gene products can lead to problems
      • Duplications important in evolution- provide raw material for new genes and adaptations
    • Origins of Duplications: unequal crossing over of misaligned chromosomes during meiosis.

    (3) Inversions

    • Two breaks on a chromosome followed by reinsertion in inverted order
    • Two types: pericentric (includes centromere) and paracentric (outside of centromere)
    • Consequences of Inversions:
      • Often have no noticeable effect on phenotype
      • Position effects in inversions can alter gene expression/ affect gene regulation
    • Consequences for Recombination and Gamete Production:
      • Inversions may suppress or reduce recombination frequency
      • Improper segregation can result in nonviable gametes
    • Inversions are important for understanding of evolution and adaptation

    (4) Translocations

    • Exchange of segments between non-homologous chromosomes or rearrangement within a chromosome.

    • Two main types: reciprocal (two-way) and non-reciprocal (one-way).

    • Balanced translocation: no genetic material is lost (no phenotypic effect)

    • Consequences of Reciprocal Translocations:

      • Altering gene position impacts gene expression
      • Potential for gene fusion with different protein products and functions

    Example Diseases from Chromosome Variations

    • Cri du chat syndrome: deletion in chromosome 5
    • Chronic Myelogenous Leukemia (CML): reciprocal translocation (Philadelphia chromosome)

    Summary

    • Chromosome rearrangements are significant for understanding genetic variations, adaptation, evolution and disease.
    • They highlight how alterations in chromosome structure or number can significantly impact organisms, contributing to the diversity of life and diseases.

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    Description

    Explore the fundamental concepts of chromosomal rearrangements in this Module 10 quiz. Delve into the types of genetic variations, their structural and numerical changes, and the consequences of deletions on phenotypes. Understanding these mechanisms is crucial for various biological and societal applications.

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