Genetics: Multiple Alleles
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Questions and Answers

What is the maximum number of alleles an individual can possess at a gene locus?

  • Two (correct)
  • Three
  • Any number
  • One

    • What is the process by which genes can change to alternative forms?

  • Natural selection
  • Gene expression
  • Genetic drift
  • Mutation (correct)

    • What is the typical approach to teaching genetics?

  • Using only real-world examples
  • Using a combination of simple and complicated genetic situations
  • Using the most complicated genetic situations
  • Using the simplest possible genetic situations (correct)

    • What is the relationship between the number of alleles and the complexity of gene interactions?

    <p>The more alleles, the more complex the gene interactions</p> Signup and view all the answers

    What is the result of a single pair of alleles in a genetic system?

    <p>A limited genetic system</p> Signup and view all the answers

    What is the theoretical possibility of alleles in a population of individuals?

    <p>A large number of alleles</p> Signup and view all the answers

    What is the term used to describe a gene locus in a population with more than two alleles?

    <p>Multiple alleles</p> Signup and view all the answers

    How many alleles are present in the ABO blood group gene?

    <p>3</p> Signup and view all the answers

    What is the number of possible genotypes for a gene with three alleles?

    <p>6</p> Signup and view all the answers

    What is the relationship between the number of alleles and the number of possible genotypes?

    <p>The number of possible genotypes is proportional to the square of the number of alleles</p> Signup and view all the answers

    What is the symbol used to represent the dominant allele in a multiple allele system?

    <p>Capital letter</p> Signup and view all the answers

    What is the term used to describe the hierarchy of dominance among multiple alleles?

    <p>Dominance hierarchy</p> Signup and view all the answers

    How many alleles can be present in any one diploid organism?

    <p>2</p> Signup and view all the answers

    What is the formula used to calculate the number of possible genotypes for a gene with n alleles?

    <p>$n(n+1)/2$</p> Signup and view all the answers

    What is the number of possible genotypes for a gene with 4 alleles?

    <p>10</p> Signup and view all the answers

    What is the relationship between the number of alleles and the number of possible phenotypes?

    <p>There is no fixed relationship between the number of alleles and the number of possible phenotypes</p> Signup and view all the answers

    What is the term for a molecule that triggers an immune response in the body?

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

    What is the genotype of an individual with ABO blood type AB?

    <p>IA IB</p> Signup and view all the answers

    Why is it essential to cross-match blood types before transfusion?

    <p>To prevent agglutination or clumping of cells</p> Signup and view all the answers

    What is the function of glycosyltransferases in the ABO blood type system?

    <p>They specify the type of glycolipids found on the surface of erythrocytes</p> Signup and view all the answers

    Which of the following ABO blood type combinations is NOT possible?

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

    What is the term for a protein produced by the immune system in response to the presence of an antigen?

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

    Which of the following is a practical application of knowledge on ABO blood types?

    <p>Blood transfusions</p> Signup and view all the answers

    Which of the following is NOT a phenotype resulting from the mating A x O?

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

    What is the genotype of an individual with ABO blood type O?

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

    In the case described in question 1, what can be concluded about the man's paternity of the child?

    <p>He is not the father</p> Signup and view all the answers

    What can be inferred from a child's blood type if it is different from the mother's blood type?

    <p>The child is not the biological child of the mother.</p> Signup and view all the answers

    What is the probability of a child having Type O blood if the parents are both heterozygous for the 'B' blood type?

    <p>25%</p> Signup and view all the answers

    What is the RhD factor?

    <p>A protein found on the surface of red blood cells.</p> Signup and view all the answers

    What is the significance of the RhD factor in pregnancy?

    <p>It can cause an immune response in the mother.</p> Signup and view all the answers

    What is the term for the complication of pregnancy caused by the RhD factor?

    <p>Rh (D) disease</p> Signup and view all the answers

    What is the probability of an RhD- mother conceiving an RhD+ baby if the father is RhD+?

    <p>50%</p> Signup and view all the answers

    What is the genotype of a person who is Type A and Rh+?

    <p>AA or AO</p> Signup and view all the answers

    What is the purpose of the Anti-D antibodies in the mother's immune system?

    <p>To attack the RhD+ blood cells of the baby</p> Signup and view all the answers

    What is the significance of the ABO blood type system?

    <p>It determines the blood type of an individual.</p> Signup and view all the answers

    What is the term for the antibodies produced by the mother's immune system against the RhD+ blood cells?

    <p>Anti-D antibodies</p> Signup and view all the answers

    Study Notes

    Introduction to Multiple Alleles

    • The genetic systems proposed so far have been limited to a single pair of alleles.
    • An individual possesses a maximum of two alleles at a gene locus, one on each of the homologous chromosomes.
    • Genes can change to alternative forms through the process of mutation, making a large number of alleles theoretically possible in a population.

    Characteristics of Multiple Alleles

    • Multiple alleles occur when more than two alleles are identified at a gene locus in a population.
    • Each individual has only two alleles for a particular trait, despite the presence of multiple alleles in the population.
    • The presence of multiple alleles increases the number of possible genotypes among diploid organisms.

    ABO Blood Group Example

    • The ABO blood group gene has three alleles: A, B, and O.
    • Each individual has only two alleles for the ABO blood group gene, resulting in six possible genotypes: AA, AB, AO, BB, BO, and OO.
    • These six genotypes produce four possible phenotypes: A, B, AB, and O.

    Calculating the Number of Genotypes

    • The number of possible genotypes is a function of the number of alleles that exist for a given gene.
    • The formula to calculate the number of genotypes is: 𝐧(𝐧 + 𝟏) / 𝟐, where n is the number of alleles.

    Dominance Hierarchy

    • The dominance hierarchy should be defined at the beginning of each problem involving multiple alleles.
    • A capital letter is used to designate the allele that is dominant, while a lower-case letter designates the allele that is recessive to all others in the series.### Symbols for Multiple Alleles
    • The dominance hierarchy: capital letters for dominant alleles and lower case letters for recessive alleles
    • Example: Coat Color in Rabbits
      • Four alleles of the rabbit coat color (c) gene have been studied
      • Alleles: C (wild-type), cch (Chinchilla), ch (Himalayan), and c (Albino)
      • Gradation in dominance: C > cch > ch > c
      • Dominant allele: C
      • Recessive alleles: cch, ch, and c

    ABO Blood Type Alleles in Humans

    • One of the most firmly established series of multiple alleles in humans involves the genetic locus controlling the blood types, A, B, and O
    • Three alleles: I (A), I (B), and i (O)
    • ABO blood group system:
      • Type A: I and i alleles
      • Type B: I and i alleles
      • Type AB: I and I alleles
      • Type O: i allele
    • Antigens and antibodies:
      • A antigen: found on the surface of red blood cells of type A individuals
      • B antigen: found on the surface of red blood cells of type B individuals
      • Anti-A antibody: produced by type B and type O individuals in response to A antigen
      • Anti-B antibody: produced by type A and type O individuals in response to B antigen
    • ABO blood type inheritance:
      • IAIO heterozygous individuals have A and B antigens on their red blood cells
      • IOIO homozygous individuals have no ABO antigens on their red blood cells

    Blood Transfusion Compatibility for the ABO Blood Groups

    • Compatible blood transfusions:
      • Type O blood can be transfused to individuals of any blood type
      • Type AB blood can receive blood from individuals of any blood type
    • Incompatible blood transfusions:
      • Type A blood cannot be transfused to type B or type O individuals
      • Type B blood cannot be transfused to type A or type O individuals
      • Type AB blood cannot be transfused to type A, type B, or type O individuals

    Applications of Knowledge on Blood Types

    • Blood transfusions: compatible blood transfusions can be achieved by matching the ABO blood types of the donor and recipient
    • Disputed parentage: decisions of disputed parentage can be accurately made by examining the ABO phenotypes of the possible parents and the child### Blood Type and Rh Factor
    • The blood type of a person is determined by the genes inherited from their mother and father.
    • There are four main blood types: A, B, AB, and O, each with a positive (RhD+) or negative (RhD-) Rh factor.

    Rh Factor

    • The RhD (Rhesus) factor is a protein that is either present (RhD+) or absent (RhD-) on the surface of a person's red blood cells.
    • A person's Rh factor is determined by their genotype, with RhD+ being dominant and RhD- being recessive.

    Rh Factor Status

    • An individual is either Rh positive (Rh+) if they have the D antigen or Rh negative (Rh-) if they do not.
    • The Rh factor is important in blood transfusions and pregnancy, as an Rh- individual may have an immune response to RhD+ blood cells.

    Blood Type Inheritance

    • The possible blood types of a child depend on the blood types of their parents.
    • For example, if both parents are heterozygous for the "B" blood type, the possible blood types of their child are BB, BO, or OO.

    Paternity and Blood Type

    • Blood type information can be used to determine paternity in certain cases.
    • For example, if a woman with blood type AB claims a child with blood type O, the biological father cannot be a man with blood type A.

    Hemolytic Disease of the Newborn (HDN)

    • HDN, also known as 'Rh (D) disease', occurs when an RhD- mother has anti-D antibodies that attack her unborn RhD+ baby's red blood cells.
    • This can happen if the mother has had a previous pregnancy with an RhD+ baby or has had a blood transfusion with RhD+ blood.

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    Description

    This quiz covers the concept of multiple alleles in genetics, including the characteristics and implications of having more than two alleles at a gene locus.

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