Mendelian Genetics Monohybrid Crosses
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Questions and Answers

What factor complicates the interpretation of single gene inheritance?

  • It generally results in distinct phenotypes.
  • Other genes and environmental factors influence the phenotype. (correct)
  • Single gene traits are unaffected by environmental conditions.
  • Single gene traits are always dominant.

    • During Metaphase I, how are homologous chromosomes arranged?

  • In alternating order along the metaphase plate.
  • Completely random, allowing for a mix of maternal and paternal chromosomes. (correct)
  • In a fixed orientation determined by one parent.
  • Completely random, determined by environmental factors.

    • What is a key feature of polygenic inheritance?

  • It involves multiple genes contributing to a single trait. (correct)
  • It is determined by a single gene only.
  • It is exclusively affected by environmental factors.
  • It only applies to recessive traits.

    • Which of the following plays a significant role in gene expression?

    <p>Environmental factors such as diet and lifestyle.</p> Signup and view all the answers

    What occurs during Anaphase I regarding homologous chromosomes?

    <p>They segregate, resulting in each daughter cell receiving a unique mixture.</p> Signup and view all the answers

    What is the outcome of a dihybrid cross in the F2 generation regarding the phenotypic ratio?

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

    Which trait is expressed in all F1 plants when crossing a homozygous dominant and a homozygous recessive parent?

    <p>The dominant trait</p> Signup and view all the answers

    What does Mendel's Law of Independent Assortment describe?

    <p>The inheritance of traits determined by two genes</p> Signup and view all the answers

    In a test cross involving a dihybrid individual, what would be the expected genotypes of the offspring?

    <p>Heterozygous and homozygous recessive in equal proportions</p> Signup and view all the answers

    What trait reappeared in the F2 generation after crossing plants with purple and white flowers?

    <p>The white flower trait in approximately one-quarter of the plants</p> Signup and view all the answers

    What is the primary effect of a mutation in the FGFR3 gene?

    <p>Abnormal bone growth and dwarfism</p> Signup and view all the answers

    What condition is associated with mutations in the NF1 gene?

    <p>Neurofibromatosis Type 1</p> Signup and view all the answers

    What role does the HBB gene have in the body?

    <p>Codes for beta-globin in hemoglobin</p> Signup and view all the answers

    What is the consequence of mutations in the HEXA gene on chromosome 15?

    <p>Buildup of GM2 ganglioside and neurological damage</p> Signup and view all the answers

    What type of genetic inheritance is associated with Cystic Fibrosis?

    <p>Autosomal recessive</p> Signup and view all the answers

    What condition might be indicated by high levels of LDL cholesterol?

    <p>Familial Hypercholesterolemia</p> Signup and view all the answers

    Which gene produces an enzyme to break down GM2 ganglioside?

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

    What is a significant symptom of Sickle Cell Disease?

    <p>Pain and blockage of blood flow</p> Signup and view all the answers

    What is the genotypic characterization of a zygote formed from two different alleles?

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

    What is the typical phenotypic ratio observed in the F2 generation of a monohybrid cross?

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

    According to Mendel's Law of Segregation, how do gametes receive alleles?

    <p>By receiving one allele of each gene</p> Signup and view all the answers

    What is the primary distinction between true-breeding organisms and the F1 progeny from different parental strains?

    <p>F1 progeny are not true-breeders</p> Signup and view all the answers

    What does a Punnett Square illustrate in genetics?

    <p>The combinatory outcomes of parental gene contributions</p> Signup and view all the answers

    In the F2 generation, which trait consistently appears according to Mendel's findings?

    <p>The recessive trait reappearing</p> Signup and view all the answers

    During meiosis, what happens to homologous chromosomes containing genes for a trait?

    <p>They segregate into separate gametes</p> Signup and view all the answers

    What is the expected ratio of recessive to dominant traits observed in Mendelian genetics?

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

    What is the role of the enzyme produced by the PAH gene in relation to phenylalanine?

    <p>It breaks down phenylalanine.</p> Signup and view all the answers

    Which of the following genetic disorders is characterized by a deficiency of melanin?

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

    For a recessive trait to be expressed in an individual, how many copies of the recessive allele must be inherited?

    <p>Two copies</p> Signup and view all the answers

    What method do scientists and doctors utilize to determine if a person has a specific dominant or recessive allele?

    <p>Genetic testing</p> Signup and view all the answers

    Which of the following genes is NOT associated with albinism?

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

    What is the primary consequence of mutations in the PAH gene?

    <p>Buildup of phenylalanine</p> Signup and view all the answers

    Which of the following statements about dominant traits is true?

    <p>They can be expressed with only one copy of the dominant allele.</p> Signup and view all the answers

    What condition can result from the accumulation of phenylalanine in the body due to a PAH mutation?

    <p>Brain and nervous system damage</p> Signup and view all the answers

    Study Notes

    Mendelian Genetics

    • Zygotes formed from monohybrid crosses result in hybrids, with the F1 generation containing mixed alleles.
    • In the F2 generation, the phenotypic ratio of traits typically follows a 3:1 pattern, demonstrating Mendel's Law of Segregation.
    • During meiosis, homologous chromosomes segregate into gametes, ensuring genetic variation in offspring.
    • The Punnett Square visualizes the combination of parental gene contributions to offspring traits.

    Law of Segregation & F1 Generation

    • Gametes receive only one allele from each gene due to the segregation of alleles during gamete formation.
    • True-breeding organisms consistently pass phenotypic traits to offspring.
    • Recessive traits can emerge in the F2 generation, typically in a ratio of about 3 dominant to 1 recessive.

    Dihybrid Inheritance

    • Dihybrid crosses analyze the inheritance of two traits simultaneously, such as pea color and shape.
    • Crossing homozygous round yellow seeds (RRYY) with homozygous wrinkled green seeds (rryy) produces entirely heterozygous offspring (RrYy).
    • In the F2 generation of a dihybrid cross, the phenotypic ratio is typically 9:3:3:1, illustrating Mendel's Law of Independent Assortment.

    Single-Gene Inheritance

    • Traits determined by a single gene, also termed Mendelian inheritance, can be influenced by other genes and environmental factors.
    • Polygenic inheritance involves multiple genes affecting a single trait, with environmental factors also playing a critical role in trait expression.

    Examples of Genetic Disorders

    • Achondroplasia: Genetic mutation in the FGFR3 gene on chromosome 4 leads to dwarfism and skeletal abnormalities.
    • Neurofibromatosis Type 1 (NF1): Caused by mutations in the NF1 gene on chromosome 17, which regulate cell growth and can result in tumors and learning disabilities.
    • Sickle Cell Disease: Mutation in the HBB gene on chromosome 11 affects hemoglobin, resulting in sickle-shaped red blood cells and associated complications.
    • Familial Hypercholesterolemia: Mutation on chromosome 19 in the LDLR gene leads to high LDL cholesterol levels and increased heart disease risk.
    • Tay-Sachs Disease: Resulting from a mutation in the HEXA gene on chromosome 15, leading to severe neurological problems due to GM2 ganglioside buildup.
    • Phenylketonuria (PKU): Mutation in the PAH gene on chromosome 12 affects amino acid breakdown, potentially leading to brain damage.
    • Albinism: A group of genetic disorders caused by deficiencies in melanin production, influenced by several genes.

    Genetic Testing

    • DNA analysis can identify specific genes and alleles, helping determine the presence of dominant or recessive traits.
    • Observational methods, such as phenotypic examination, allow for the identification of visible traits like eye or hair color.
    • Punnett Squares and genetic testing aid in predicting inheritance patterns and probabilities of particular alleles in offspring.

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    Description

    This quiz explores key concepts in Mendelian genetics, specifically focusing on monohybrid crosses and the resulting genotypic and phenotypic ratios in offspring. It covers the law of segregation and the definition of heterozygous and homozygous traits. Prepare to test your understanding of gene inheritance patterns!

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