HL IB Biology - Inheritance
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Questions and Answers

What is the definition of phenotype?

  • The observable characteristics of an organism (correct)
  • The structural elements of DNA
  • The combination of alleles for a gene
  • The genetic makeup of an organism

    • Which of the following factors can influence an organism's phenotype?

  • Combination of genotype and environment (correct)
  • Environmental factors only
  • Genotype only
  • Mutation of a single allele

    • What is true about dominant alleles?

  • They can be masked by recessive alleles
  • They always lead to a dominant phenotype
  • They require both parents to express the phenotype
  • They need to be inherited from one parent to be expressed (correct)

    • How do recessive alleles affect phenotype expression?

    <p>They are expressed only when inherited from both parents</p> Signup and view all the answers

    Which statement correctly describes the relationship between alleles and genotype?

    <p>Genotype is the combination of alleles for a specific gene</p> Signup and view all the answers

    What is the expected ratio of phenotypes in a dihybrid cross of Drosophila for the given genes?

    <p>9 : 3 : 3 : 1</p> Signup and view all the answers

    What can the chi-squared test help determine in the Drosophila experiment?

    <p>If variations are likely due to chance</p> Signup and view all the answers

    What fraction represents the expected number of flies with the black body and curved wings phenotype?

    <p>3/16</p> Signup and view all the answers

    In the context of the chi-squared test, what does a high chi-squared value, such as 235, indicate?

    <p>The differences between observed and expected data are likely not due to chance</p> Signup and view all the answers

    Which component must be determined to use the chi-squared test effectively?

    <p>The degrees of freedom from the results</p> Signup and view all the answers

    What type of inheritance is illustrated by the ABO blood groups?

    <p>Co-dominance</p> Signup and view all the answers

    Which genotype corresponds to blood group A?

    <p>IAIA or IAi</p> Signup and view all the answers

    What can result from using the wrong blood group in a transfusion?

    <p>Immune response leading to clotting</p> Signup and view all the answers

    Which of the following alleles is recessive in the ABO blood group system?

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

    How many alleles control a person's blood group in the ABO system?

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

    In a Punnett square, what is the purpose of predicting the outcome of blood group inheritance?

    <p>To anticipate the likelihood of blood group variations</p> Signup and view all the answers

    What antigens does genotype IBi produce?

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

    If both parents are heterozygous for blood groups A and B, what is the probability of producing a type O offspring?

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

    What combination of sex chromosomes do females have in humans?

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

    Which chromosome pair is responsible for sex determination in humans?

    <p>Pair 23</p> Signup and view all the answers

    Who determines the sex of the child in humans?

    <p>The father</p> Signup and view all the answers

    How are sex chromosomes inherited from the father?

    <p>Half of the sperm carry an X chromosome and half a Y chromosome</p> Signup and view all the answers

    What are chromosomes 1-22 classified as in humans?

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

    In a genetic diagram to show sex inheritance, what replaces the usual alleles?

    <p>X and Y chromosomes</p> Signup and view all the answers

    What characteristic do mammals share regarding sex chromosomes?

    <p>The rule of XX for females and XY for males</p> Signup and view all the answers

    What is the result of fertilization by an X chromosome-carrying sperm?

    <p>The child will be female</p> Signup and view all the answers

    What is the likelihood of the offspring of PKU carrier parents having PKU?

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

    How are genetic conditions such as PKU typically screened for in newborns in the UK?

    <p>Using a small prick of blood from the sole of the foot</p> Signup and view all the answers

    Which of the following is true regarding the inheritance pattern of autosomal recessive conditions?

    <p>Both parents must be affected for the child to be affected</p> Signup and view all the answers

    What do Single Nucleotide Polymorphisms (SNPs) represent in genetics?

    <p>The bases that differ between two alleles</p> Signup and view all the answers

    What will happen if a diploid individual inherits more than two alleles for a gene?

    <p>They will only inherit two of the possible alleles</p> Signup and view all the answers

    Why is it important to differentiate between upper and lowercase letters in genetic crosses?

    <p>It reduces ambiguity during marking</p> Signup and view all the answers

    How can different alleles of a gene vary despite occupying the same locus?

    <p>They differ by one or only a few bases</p> Signup and view all the answers

    What is a common outcome of even a small change in base sequence in a gene?

    <p>A large knock-on effect on the phenotype</p> Signup and view all the answers

    What does the '7' in the gene CFTR signify?

    <p>It is located on chromosome 7.</p> Signup and view all the answers

    Which of the following best describes the inheritance of the CFTR and coagulation factor X genes?

    <p>They are found on different chromosomes and thus are not linked.</p> Signup and view all the answers

    What does the 'p' represent in the notation for chromosome structure?

    <p>The short arm of the chromosome.</p> Signup and view all the answers

    Which characteristic increases the likelihood of gene linkage?

    <p>Genes located on the same chromosome and arm.</p> Signup and view all the answers

    How does the numbering in gene location notation relate to proximity to the centromere?

    <p>Lower numbers indicate closer proximity to the centromere.</p> Signup and view all the answers

    Which gene is associated with the disorder hemophilia?

    <p>Coagulation factor X</p> Signup and view all the answers

    What is the significance of genes being located on the same arm of a chromosome?

    <p>They are likely to be inherited together.</p> Signup and view all the answers

    What does the notation '13q34' indicate?

    <p>The gene is on chromosome 13, long arm, positioned far from the centromere.</p> Signup and view all the answers

    Study Notes

    HL IB Biology - Inheritance

    • Genetic Inheritance & Genetic Crossing:

      • Gametes are sex cells (e.g., sperm and egg)
      • Eggs are larger than sperm, containing food for the embryo
      • Sperm have many mitochondria for energy
      • Fertilization: Fusion of gamete nuclei forming a zygote
      • Zygotes are diploid (two sets of chromosomes)
      • Gametes are haploid (one set of chromosomes)
      • Humans have 23 pairs of chromosomes, 22 autosomes and 1 sex chromosome
      • Meiosis produces sex cells with a single copy of each chromosome
      • Alleles are different forms of a gene

    • Inheritance: Terminology

      • Gene: Short length of DNA coding for a characteristic (and protein)
      • Allele: Variations of the same gene
      • Genotype: Combination of alleles an organism inherits
      • Homozygous: Two identical alleles at a locus
      • Heterozygous: Two different alleles at a locus
      • Phenotype: Observable characteristics
      • Dominant allele: Expressed even if only one copy is present
      • Recessive allele: Expressed only if two copies are present

    • Dominant & Recessive Alleles

      • Dominant alleles are expressed in the phenotype even if only one copy is present
      • Recessive alleles are only expressed if both copies (two) are present
      • Homozygous dominant: Two copies of the dominant allele
      • Homozygous recessive: Two copies of the recessive allele
      • Heterozygous: One copy of the dominant allele and one copy of the recessive allele

    • Incomplete & Codominance

      • Codominance: Both alleles are expressed equally in the phenotype
      • Example: Speckled chickens (both black and white feathers expressed)
      • Incomplete dominance: Both alleles are partially expressed in the phenotype
      • Example: Pink flowers (blend of red and white)

    • Inheriting Alleles

      • Phenotypic plasticity: The way a phenotype is expressed can vary during an organism's lifetime due to its environment.
      • Environmental factors can influence gene expression, impacting physical characteristics.
      • An example is the Himalayan rabbit—pigmentation occurs in cooler parts of the body.

    • Inheriting Recessive Alleles: Phenylketonuria (PKU)

      • PKU is a recessive genetic disorder
      • Caused by a mutation to the PAH gene, resulting in a non-functional enzyme
      • It leads to a buildup of phenylalanine in the body.

    • Multiple Alleles: ABO Blood Groups

      • Blood type is determined by multiple alleles (more than two possible alleles)
      • Example: Blood group A, B, AB, or O
      • Critical in blood transfusions

    • Sex Determination

      • Sex determined by chromosomes (e.g., XX for female, XY for male)
      • Males determine the sex of offspring
      • Females only have X chromosomes
      • One X chromosome from each parent determines the child's sex.

    • Sex Linked Disorders: Hemophilia

      • Sex-linked disorders are inherited on the X chromosome
      • Females (XX): Two X chromosomes
      • Males (XY): One X chromosome, one Y chromosome
      • Hemophilia: A sex-linked genetic disorder affecting blood clotting
      • Recessive allele on the X chromosome makes a person with hemophilia unable to clot blood properly
      • Males have a higher chance of having hemophilia due to only receiving one X chromosome

    • Pedigree Charts

      • Charts tracing inheritance of characteristics (often disease) across generations
      • Squares for males and circles for females
      • Shading or cross-hatching indicates affected individuals

    • Continuous Variation

      • Variation across a range (e.g., height, weight); influenced by many genes and environment
      • Characteristics can be quantitatively measured

    • Dihybrid Crosses & Unlinked Genes (HL)

      • Studying inheritance involving two characteristics; controlled by two different genes
      • Unlinked genes reside on separate chromosomes
      • Assortment: Alleles inherited independently of each other
      • Segregation: Homologous chromosomes separate during meiosis

    • Genes & Polypeptides: Skills (HL)

      • Using databases for gene location and protein structure
      • Comparing DNA, mRNA, and protein sequences between species
      • Locating and Identifying Genes' Positions on Chromosomes

    • Identifying Recombinants (HL)

      • Recombination frequency: Likelihood of crossing over between linked genes during meiosis
      • Test crosses help identify recombinants and identify linked genes

    • Statistical Analysis of Dihybrid Crosses (HL): Chi-squared Test

      • Analyzing if difference between expected and observed results is significant (due to chance or other factors)
      • Calculating chi-squared value
      • Comparing chi-squared value with critical values to determine probability
      • Probability is used to decide if the expected ratio differs from the observed ratio.

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    Related Documents

    HL IB Biology Inheritance PDF

    Description

    Test your knowledge on genetic inheritance and crossing in this HL IB Biology quiz. Explore essential concepts such as gametes, zygotes, alleles, and key terms in inheritance terminology. Perfect for students preparing for their assessments!

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