Biology Chapter 11: Mendelian Inheritance
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Questions and Answers

What genotype combinations would indicate an individual has an autosomal dominant disorder?

  • AA or Aa (correct)
  • AA or aa
  • Aa only
  • Aa or aa

In an autosomal recessive disorder, what does the genotype Aa represent?

  • Carrier (correct)
  • Individuals with multiple disorders
  • Affected individual
  • Unaffected individual

Which of the following statements about autosomal dominant disorders is true?

  • An affected individual has at least one affected parent. (correct)
  • Individuals can have the disorder if they are aa.
  • Only affected individuals can pass the disorder to their offspring.
  • Both parents must be affected for a child to have the disorder.

Which disorder is characterized by the accumulation of methemoglobin in the blood?

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

What is a key characteristic of codominance as seen in ABO blood types?

<p>Both alleles are fully expressed. (D)</p> Signup and view all the answers

What does Mendel's Law of Segregation state about alleles during gamete formation?

<p>Alleles for a trait segregate so that each gamete contains one allele. (A)</p> Signup and view all the answers

What does the law of segregation state?

<p>Alleles separate during gamete formation. (A)</p> Signup and view all the answers

In a dihybrid cross, what does Mendel's Law of Independent Assortment demonstrate?

<p>The inheritance of one trait does not influence the inheritance of another trait. (B)</p> Signup and view all the answers

Why did Mendel choose the garden pea for his experiments?

<p>They had simple, objective traits. (B)</p> Signup and view all the answers

What distinguishes homozygous genotypes from heterozygous genotypes?

<p>Homozygous genotypes are formed by identical alleles, while heterozygous includes different alleles. (C)</p> Signup and view all the answers

Which of the following best describes a monohybrid cross?

<p>A cross between true-breeding plants differing in only one trait. (A)</p> Signup and view all the answers

Which of the following correctly describes a Punnett square's function?

<p>It predicts possible allele combinations of offspring from parental genotypes. (A)</p> Signup and view all the answers

What is the significance of recessive alleles in Mendelian genetics?

<p>Recessive alleles can only express their traits when homozygous. (C)</p> Signup and view all the answers

How did Mendel demonstrate that the blending hypothesis was incorrect?

<p>By conducting experiments with contrasting traits. (B)</p> Signup and view all the answers

Which statement accurately represents the relationship between genotype and phenotype?

<p>Genotype can be homozygous or heterozygous, affecting the phenotype. (B)</p> Signup and view all the answers

In a Punnett square, what does each box represent?

<p>A possible phenotype of offspring. (C)</p> Signup and view all the answers

During which process do homologous chromosomes segregate?

<p>Meiosis I (D)</p> Signup and view all the answers

Which of the following statements about true-breeding plants is accurate?

<p>They always produce offspring with the same traits. (D)</p> Signup and view all the answers

What happens during the fertilization process in Mendel's experiments?

<p>Pollen is transferred from the anther of one plant to the stigma of another. (D)</p> Signup and view all the answers

What role do alleles play in genetics?

<p>Alleles represent different forms of a gene that influence traits. (D)</p> Signup and view all the answers

What is not a characteristic of Mendel’s laws of inheritance?

<p>They apply exclusively to pea plants. (D)</p> Signup and view all the answers

Which aspect of Mendel’s research provided a framework for the understanding of genetic inheritance?

<p>His experiments with simple traits in plants. (D)</p> Signup and view all the answers

What does multifactorial inheritance refer to?

<p>Traits influenced by multiple genes and environmental factors. (C)</p> Signup and view all the answers

Which of the following is an example of a polygenic trait?

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

Which statement about X-linked inheritance is true?

<p>Morgan's experiments with fruit flies are relevant to human X-linked genes. (C)</p> Signup and view all the answers

What condition results from the absence of the muscle protein dystrophin?

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

In polygenic inheritance, which of the following is NOT true?

<p>The environment plays no role in expression. (C)</p> Signup and view all the answers

Which of the following conditions is caused by a deficiency in clotting factor VIII?

<p>Hemophilia (B)</p> Signup and view all the answers

Which environmental factor influences skin color in humans?

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

What does the term X-linked refer to in genetics?

<p>Genes that are located on the X chromosome and unrelated to gender. (D)</p> Signup and view all the answers

Which trait is NOT considered polygenic?

<p>Albinism (B)</p> Signup and view all the answers

Which of the following disorders is autosomal rather than X-linked?

<p>The allele for blue-sensitive protein (D)</p> Signup and view all the answers

What is the expected phenotypic ratio for a two-trait testcross involving a heterozygous individual for both traits?

<p>1:1:1:1 (A)</p> Signup and view all the answers

Which statement best defines the law of independent assortment?

<p>Alleles of different genes assort independently of each other during gamete formation. (A)</p> Signup and view all the answers

How can a testcross be used to determine the genotype of an individual with a dominant phenotype?

<p>By crossing with a homozygous recessive individual. (B)</p> Signup and view all the answers

What is the chance of obtaining the genotype 'aa' if the alleles are inherited with a probability of 1/2 for each parent?

<p>1/4 (C)</p> Signup and view all the answers

Which of the following genotypes represents a homozygous recessive individual?

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

What does the Punnett square calculate?

<p>The probabilities of genotype and phenotype combinations among offspring. (D)</p> Signup and view all the answers

Which of the following accurately describes the outcome when two homozygous individuals are crossed?

<p>All offspring will display a dominant phenotype. (C)</p> Signup and view all the answers

In a dihybrid cross, what phenotypic ratio is expected if both parents are heterozygous for two traits?

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

What is the function of the sum rule in genetics?

<p>To add probabilities of different genotypes to find a phenotype chance. (D)</p> Signup and view all the answers

Which of the following is a key characteristic of autosomes?

<p>They are any chromosome other than sex chromosomes. (D)</p> Signup and view all the answers

Flashcards

Autosomal Recessive Disorder

A genetic disorder where an individual needs two copies of a mutated gene (aa) to have the condition. Individuals with one copy (Aa) are carriers but do not exhibit the disorder.

Cystic Fibrosis

An autosomal recessive disorder characterized by thick, viscous mucus in the airways and pancreatic ducts, leading to breathing difficulties and digestive issues.

Autosomal Dominant Disorder

A genetic disorder where an individual only needs one copy of a mutated gene (Aa) to have the condition. Individuals with two copies (AA) also have the disorder.

Osteogenesis Imperfecta

An autosomal dominant disorder characterized by weak, brittle bones due to mutations in the gene for type I collagen.

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Huntington Disease

An autosomal dominant disorder causing progressive degeneration of brain cells due to a mutated huntingtin gene.

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Independent Assortment

During meiosis, homologous chromosomes separate randomly, resulting in different combinations of alleles in gametes.

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Segregation

During meiosis, alleles of a gene separate into different gametes, ensuring each gamete receives only one allele per gene.

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Dihybrid Cross

A breeding experiment involving two traits, tracking the inheritance of two different genes.

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Punnett Square

A diagram used to predict the possible genotypes and phenotypes of offspring from a cross.

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Testcross

A breeding experiment to determine the genotype of an individual displaying a dominant phenotype.

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Autosome

Any chromosome other than a sex chromosome (X or Y).

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Genotype

The genetic makeup of an individual, represented by the combination of alleles for a specific gene.

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Phenotype

The observable characteristics of an individual, resulting from their genotype and environmental influences.

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Homozygous

An individual with two identical alleles for a specific gene.

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Heterozygous

An individual with two different alleles for a specific gene.

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Law of Segregation

Each individual has two alleles (versions of a gene) for a trait. These alleles separate during gamete (sperm/egg) formation, so each gamete receives only one allele from the pair. Fertilization combines these single alleles, resulting in the offspring inheriting two alleles for each trait.

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Dominant Allele

An allele whose trait is expressed even when paired with a recessive allele. It masks the recessive allele's effect.

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Recessive Allele

An allele whose trait is only expressed when paired with another recessive allele. It is masked by the dominant allele.

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Law of Independent Assortment

During gamete formation, the alleles for different traits segregate independently of each other. This means that the inheritance of one trait does not influence the inheritance of another trait.

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Polygenic Inheritance

A trait controlled by multiple genes, where each gene contributes a small effect, leading to a continuous range of phenotypes.

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Multifactorial Inheritance

Traits influenced by both multiple genes (polygenes) and environmental factors.

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X-Linked Genes

Genes located on the X chromosome, which is one of the two sex chromosomes.

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X-Linked Inheritance

The pattern of inheritance of genes located on the X chromosome.

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Fruit Flies and X-Linked Inheritance

Fruit flies are used in genetic studies because they have a similar sex chromosome system to humans and are easy to breed.

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Color Blindness

A condition where an individual cannot perceive certain colors due to a faulty gene on the X chromosome.

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Muscular Dystrophy

A genetic disorder affecting muscle tissue, often due to a faulty gene on the X chromosome.

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Hemophilia

A genetic blood clotting disorder, often due to a faulty gene on the X chromosome, causing slow or absent clotting.

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X-Linked Recessive Pedigree

A family tree diagram showing the inheritance pattern of a recessive gene located on the X chromosome.

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Dystrophin

A protein vital for muscle function, the absence of which can cause muscular dystrophy.

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Blending Concept of Inheritance

The idea that offspring inherit a blend of traits from their parents, resulting in intermediate appearances.

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Particulate Theory of Inheritance

Mendel's theory stating that inheritance involves discrete units of heredity (genes) that are passed on unchanged from generation to generation.

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Mendel's Laws

Principles that explain the patterns of inheritance: Law of Segregation and Law of Independent Assortment.

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True-breeding

Organisms that produce offspring with the same trait when self-pollinated; they are homozygous for the trait.

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Monohybrid Cross

A cross between individuals that differ in only one trait.

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Reciprocal Cross

A cross where the traits of the male and female parents are reversed; used to test if inheritance is influenced by the sex of the parent.

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Parental Generation (P)

The original generation of individuals used in a cross.

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First Filial Generation (F1)

The offspring of the parental generation.

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Second Filial Generation (F2)

The offspring resulting from a cross between two individuals from the F1 generation.

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Study Notes

Biology Chapter 11: Mendelian Patterns of Inheritance

  • This chapter explores Mendelian patterns of inheritance, focusing on how traits are passed from parents to offspring.
  • Early ideas about inheritance emphasized a "blending" concept, where traits from parents mixed to create an intermediate offspring.
  • Gregor Mendel, through experiments with pea plants, formulated the particulate theory of inheritance, proposing that traits are inherited as discrete units.
  • Mendel's experiments utilized true-breeding plants (homozygous) and monohybrid crosses (differences in only one trait) to study inheritance.
  • Critical to his work were reciprocal crosses and studying the P (parental), F₁ (first filial), and F₂ (second filial) generations of offspring.
  • Mendel's laws of segregation and independent assortment are fundamental principles explaining this inheritance.

The Law of Segregation

  • Each individual has a pair of factors (alleles) for each trait.
  • These factors segregate (separate) during gamete formation (sperm and egg).
  • Each gamete contains only one factor (allele) from each gene pair.
  • Fertilization restores the paired condition in the offspring.

The Law of Independent Assortment

  • The pair of factors (alleles) for separate traits segregate independently during gamete formation.
  • This means that alleles for different traits are passed down randomly to offspring.
  • All possible combinations of factors can occur in the gamete.

Dominance and Recessive Alleles

  • A dominant allele masks the expression of a recessive allele, even if both are present.
  • Alleles are alternate forms of a gene and occupy corresponding positions on homologous chromosomes (a gene locus).
  • Homozygous individuals have identical alleles for a trait.
  • Heterozygous individuals have different alleles for a trait.

Genotype vs. Phenotype

  • Genotype refers to the specific alleles an organism possesses for a particular trait.
  • Phenotype refers to the observable physical characteristics or traits determined by the genotype.

Testcrosses

  • Used to determine the genotype of an individual showing a dominant phenotype.
  • A testcross involves crossing the organism with an individual showing the recessive phenotype.

Beyond Mendelian Inheritance

  • Some traits are controlled by more than two alleles (multiple alleles).
  • The ABO blood type system is an example of both multiple alleles and codominance (in which more than one allele is fully expressed).
  • Incomplete dominance occurs when the heterozygote's phenotype is intermediate between the two homozygous phenotypes.

Autosomal Disorders

  • Autosomal disorders are inherited through genes located on autosomes (not sex chromosomes).
  • Some autosomal disorders are dominant; others are recessive.

Examples of Human Genetic Disorders Explained in Chapter 11

  • Methemoglobinemia
  • Cystic fibrosis
  • Familial Hypercholesterolemia
  • Marfan Syndrome

Polygenic Inheritance

  • Traits influenced by multiple genes, resulting in continuous variation within a population, like human skin color, height, or eye color.

Multifactorial Inheritance

  • Traits influenced by multiple genes and environmental factors, such as the example of fur color in Himalayan rabbits.

X-Linked Inheritance

  • Traits carried on the X chromosome have different inheritance patterns compared to autosomal traits, impacting mostly males of a family.
  • Morgan's experiments on fruit flies provide key insights into X-linked inheritance.

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Chapter 11 Mendelian Patterns of Inheritance PDF

Description

This chapter delves into Mendelian patterns of inheritance, highlighting how traits are transmitted from parents to offspring. It covers key concepts like the laws of segregation and independent assortment, as introduced by Gregor Mendel through his pioneering pea plant experiments.

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