Mendelian Ratios in Genetics
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Questions and Answers

What is a wild-type allele?

  • The most frequently encountered allele in a population (correct)
  • An allele that is the least frequently found in a population
  • An allele that does not alter the phenotype
  • An allele that causes a loss of function due to mutation
  • What characterizes a loss of function mutation?

  • It enhances gene activity significantly
  • It produces a neutral outcome for the organism
  • It results in diminished functionality of the gene (correct)
  • It leads to no change in gene functionality
  • In codominance, what is true about the expression of genes in heterozygotes?

  • Both alleles are expressed equally and distinctly (correct)
  • Only the wild-type allele is visible in the phenotype
  • One allele is dominant and suppresses the other
  • It results in a blending of traits
  • Which statement describes a gain of function mutation?

    <p>It results in increased activity of a gene</p> Signup and view all the answers

    What characteristic distinguishes the Barr body in human cells?

    <p>It is formed from one of the X chromosomes in females.</p> Signup and view all the answers

    What signifies a null allele?

    <p>The eventual total loss of gene function due to mutation</p> Signup and view all the answers

    Which method is typically used to enable the study of karyotypes?

    <p>Staining with suitable dyes</p> Signup and view all the answers

    How many Barr bodies would a normal human female typically have?

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

    What is true regarding incomplete dominance?

    <p>Both alleles blend to form a third phenotype</p> Signup and view all the answers

    In the context of chromosome abnormalities, what does '47, XX, +21' signify?

    <p>A female with an additional chromosome 21.</p> Signup and view all the answers

    What type of mutation might not alter the activity of a gene?

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

    How are dominant alleles represented in notation?

    <p>In uppercase letters without italics</p> Signup and view all the answers

    What is the fundamental number (FN) in karyotyping?

    <p>The total number of chromosomes in a somatic cell.</p> Signup and view all the answers

    Which of the following cells can provide information about the sex of an unborn fetus?

    <p>Amniotic cells</p> Signup and view all the answers

    What typically reflects an extra chromosome in a karyotype analysis?

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

    Which stage of cell division is most suitable for staining to observe chromosomes?

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

    What characterizes the Bombay phenotype in blood type classification?

    <p>Absence of A and B antigens, presenting as type O</p> Signup and view all the answers

    What does genetic linkage refer to?

    <p>Tendency for alleles on the same chromosome to be inherited together</p> Signup and view all the answers

    What is epistasis in genetics?

    <p>A situation where one gene masks or modifies the expression of another gene</p> Signup and view all the answers

    What is a novel phenotype based on gene interaction?

    <p>A new phenotype that arises due to interactions between two genes</p> Signup and view all the answers

    What is the primary function of genes according to the content?

    <p>To facilitate essential life processes</p> Signup and view all the answers

    Which option describes lethal alleles?

    <p>Genetic mutations that may lead to death</p> Signup and view all the answers

    Who was responsible for the earliest drawing of chromosomes?

    <p>Walter Flemming</p> Signup and view all the answers

    What does the 9:3:3:1 Mendelian ratio represent?

    <p>Expected phenotypic ratios in a dihybrid cross</p> Signup and view all the answers

    What substance was used by cytogeneticists to arrest cells during division for chromosome observation?

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

    What technology improves the visibility of chromosomes for karyotyping?

    <p>Image Analysis Software</p> Signup and view all the answers

    What does FISH stand for in the context of chromosome observation?

    <p>Fluorescence In Situ Hybridization</p> Signup and view all the answers

    Which of the following best describes the purpose of colchicine in chromosome preparation?

    <p>To arrest cells during division</p> Signup and view all the answers

    What is the primary benefit of using computer scans in the karyotyping process?

    <p>To select a cell with visible chromosomes</p> Signup and view all the answers

    What role does the SkyView EXPO system play in karyotyping?

    <p>It allows interaction with banded and multi-color images</p> Signup and view all the answers

    What is the result when the software detects an abnormal band pattern in a karyotype?

    <p>It accesses a database with similar karyotypes</p> Signup and view all the answers

    What is one of the significant challenges faced while preparing cells for chromosome observation?

    <p>Ensuring chromosomes do not overlap</p> Signup and view all the answers

    What does the fundamental number (FN) represent in a karyotype?

    <p>The number of major chromosomal arms per set</p> Signup and view all the answers

    In the context of diploid and haploid conditions, which group commonly exhibits haplo-diploidy?

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

    What is defined as the fundamental autosomal number (FNa) in a karyotype?

    <p>The number of major chromosomal arms seen in non-sex linked chromosomes</p> Signup and view all the answers

    What process results in a polyploid nucleus without division of the cell nucleus?

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

    Which chromosomes are classified as acrocentric in humans?

    <p>Chromosomes 13, 14, 15, 21, 22</p> Signup and view all the answers

    Which correct inequality represents the relationship involving FN and haploid sets?

    <p>FN ≤ 2 x 2n</p> Signup and view all the answers

    What is the primary significance of polyploidy in plant evolution?

    <p>Increases genetic diversity</p> Signup and view all the answers

    In what scenario do cells typically undergo endomitosis?

    <p>In fully differentiated adult tissues</p> Signup and view all the answers

    What role does Giemsa play in chromosome banding?

    <p>It specifically stains phosphate groups of DNA.</p> Signup and view all the answers

    How does digital karyotyping help in analysis?

    <p>It allows for the quantification of DNA copy number.</p> Signup and view all the answers

    What characteristic is used to classify chromosomes into groups?

    <p>Size and centromere location.</p> Signup and view all the answers

    Which group of chromosomes is identified as having median centromeres?

    <p>Group C: chromosomes 6-12.</p> Signup and view all the answers

    Which chromosomes are classified as acrocentric?

    <p>Chromosomes 21-22.</p> Signup and view all the answers

    Which statement accurately describes quinacrine's function?

    <p>It binds to adenine-thymine rich regions.</p> Signup and view all the answers

    What feature differentiates Group B chromosomes from others?

    <p>They consist of chromosomes 4-5 which are large.</p> Signup and view all the answers

    What is the purpose of assigning pseudo colors in image processing for karyotyping?

    <p>To represent spectrally different combinations distinctly.</p> Signup and view all the answers

    Study Notes

    Modification of Mendelian Ratios

    • Alleles alter phenotypes in various ways.
    • Wild-type allele (R1) is red, Mutant allele (R2) is white.
    • This mutation type is loss of function.
    • Terminologies include wild-type, null allele, mutation, gain-of-function mutation, and loss-of-function mutation.
    • Gain-of-function mutation—increased activity of a gene due to mutation.
    • Loss-of-function mutation—mutation decreases the gene's function.
    • Neutral mutation—a mutation that does not alter gene activity.
    • Geneticists use lowercase and italicized for recessive alleles and an uppercase and italicized for dominant alleles.
    • Incomplete/Partial dominance—neither allele is dominant, resulting in an intermediate phenotype.
    • Codominance—both alleles are dominant in heterozygotes, expressing two distinct gene products equally.
    • MN Blood group system—illustrates codominance, where inheriting both alleles leads to production of both glycoproteins (M and N).
      • The MN blood group system shows the expression of both alleles (M and N) in a heterozygote (LM LN).

    Multiple Alleles of a Gene

    • Multiple alleles—the existence of three or more alleles for one gene in a population.

    • ABO blood group—an example, featuring three alternative alleles of one gene (A, B, and O).

    • Four ABO blood phenotypes: A, B, AB, and O. - A antigen (A phenotype) - B antigen (B phenotype) - A and B antigen (AB phenotype) - Neither antigen (O phenotype)

    • Bombay phenotype—a rare variant where individuals don’t have A or B antigens, appearing as type O despite having a different genotype.

    Karyotyping

    • Karyotyping—analysis of chromosomes to detect abnormalities.
    • Used in prenatal testing, cancer detection, and unknown etiology diagnosis.
    • Karyotyping prep involves culturing cells, synchronizing cell division, harvesting cells, analyzing chromosomes, staining slides, and preparing slides.
    • Techniques like squashing and swelling cells aid in separating chromosomes.
    • Karyotypes are once constructed by manually viewing cell under microscope, photographing, and arranging chromosomes by size to create karyotype chart. Modern approach uses computerized image analysis.
    • Giemsa stain is commonly used in karyotype studies.
    • Chromosomal abnormalities, like Down Syndrome, Turner Syndrome, Klinefelter syndrome, can be detected by analyzing chromosome structure and number.

    FISH and Fluorescence In Situ Hybridization

    • FISH (Fluorescence In Situ Hybridization)—a more precise chromosome staining method using DNA probes that are complementary to specific DNA sequences, highlighting specific regions or chromosomes.

    Ploidy

    • Ploidy—the number of complete sets of chromosomes in a cell.
    • Polyploidy—occurs when a cell contains more than two sets of homologous chromosomes, commonly in plants.
    • Haplo-diploidy—a reproductive system where one sex is haploid, and the other diploid, frequently seen in Hymenoptera (e.g., bees and ants).

    Aneuploidy

    • Aneuploidy—abnormal number of chromosomes in cells, causing developmental abnormalities.
    • Examples include Down syndrome (extra chromosome 21) and Turner syndrome (missing or abnormal X chromosome).

    Euploidy

    • Euploidy—having complete sets of chromosomes (e.g., 2n).
    • Some individuals may have more than one complete diploid genome in a cell.

    Techniques

    • G-banding, R-banding, C-banding, and Q-banding, are different techniques to visualize chromosomes under a microscope in different colors using stains on chromosomes
      • T-banding visualizes telomeres.

    Chromosome Classification

    • Chromosomes are grouped based on size and centromere position (median, submedian, acrocentric) into seven groups. (A-G)
    • Specific chromosome banding patterns are used by geneticists to identify and differentiate chromosomes. For example, chromosome 19 and 20 are in group F.

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    Description

    Explore the modification of Mendelian ratios through various mutation types and genetic terminology. This quiz covers concepts such as wild-type, gain-of-function, loss-of-function, codominance, and the MN blood group system. Test your understanding of genetic principles and their implications for phenotypes.

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