Non-Mendelian Inheritance Quiz

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Questions and Answers

What defines incomplete dominance in genetic inheritance?

  • One allele completely masks the other in the phenotype.
  • The heterozygote exhibits a phenotype that is intermediate between the two homozygotes. (correct)
  • Both alleles are fully expressed in the phenotype.
  • The traits of the homozygotes are expressed simultaneously.

Which concept involves a single gene affecting multiple traits?

  • Pleiotropy (correct)
  • Codominance
  • Polygenic inheritance
  • Multiple alleles

Which of the following describes codominance?

  • Both alleles contribute to the phenotype without blending. (correct)
  • The offspring express a trait that is a mix of the parents' traits.
  • One allele completely controls the trait.
  • Only the dominant allele is expressed.

Which of the following examples illustrates multiple alleles?

<p>The ABO blood group system in humans. (C)</p> Signup and view all the answers

What effect can environmental factors have on gene expression?

<p>They can interact with genes to alter phenotypic expressions. (A)</p> Signup and view all the answers

Which scenario best exemplifies lethal alleles?

<p>An allele that can cause an organism to die if homozygous dominant. (B)</p> Signup and view all the answers

Which is a characteristic of polygenic inheritance?

<p>Results in a wide phenotypic range due to multiple genes. (C)</p> Signup and view all the answers

Which example illustrates how gene interaction can alter phenotypic ratios?

<p>The influence of environmental conditions on corn pigmentation. (C)</p> Signup and view all the answers

Why might Mendel’s laws not be observed in certain genetic scenarios?

<p>More than one gene might be affecting a single trait. (C)</p> Signup and view all the answers

What is the phenotype of a mouse with the genotype AY/A?

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

Which statement about the yellow allele (AY) in mice is true?

<p>It causes yellow coat color in heterozygous conditions. (D)</p> Signup and view all the answers

Which of the following ratios represents the modified dihybrid ratio when one gene locus exhibits codominance?

<p>3:6:3:1:2:1 (D)</p> Signup and view all the answers

Which allele combinations produce a 1:2:1:2:4:2:1:2:1 ratio in inheritance patterns?

<p>Incompletely dominant alleles at both gene loci. (D)</p> Signup and view all the answers

What phenotypic ratio arises from a dihybrid cross involving one dominant and one recessive allele at one locus and codominant alleles at another?

<p>3:6:3:1:2:1 (A)</p> Signup and view all the answers

Which of the following represents a situation of a lethal allele?

<p>AY/AY offspring dying before birth. (D)</p> Signup and view all the answers

What type of inheritance pattern is seen in the ABO blood group system?

<p>Multiple alleles with simple dominance. (D)</p> Signup and view all the answers

What is the expected phenotype for a genotype of AB in the ABO blood grouping system?

<p>Type AB blood (B)</p> Signup and view all the answers

In the context of snapdragons, which trait exhibits incomplete dominance?

<p>Red flower versus white flower. (B)</p> Signup and view all the answers

What is true about the presence of homozygous yellow mice?

<p>They do not exist due to their lethality. (A)</p> Signup and view all the answers

What is the genotypic ratio of the F2 generation when crossing red and white snapdragons?

<p>1:2:1 (B)</p> Signup and view all the answers

What phenotype results from the cross between a homozygous black feathered fowl and a homozygous splashed white feathered fowl?

<p>Blue feathers (C)</p> Signup and view all the answers

In the context of snapdragons, which term best describes the expression of alleles when pink flowers are produced from red and white parents?

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

What ratio is generally expected in the offspring when a lethal gene is involved in a cross?

<p>2:1 (C)</p> Signup and view all the answers

What is the outcome when red and white cattle are crossed with respect to coat color?

<p>Offspring display both red and white hairs (B)</p> Signup and view all the answers

For a mutation resulting in a nonfunctional gene product, what occurs in the homozygous recessive individuals?

<p>They die before birth (C)</p> Signup and view all the answers

In the case of palomino horses, what genetic interaction is primarily illustrated?

<p>Incomplete dominance (C)</p> Signup and view all the answers

Which phenomenon allows for both alleles to be expressed in offspring from red and white parent plants?

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

When yellow-coated mice exhibit a wild-type coat pattern, what is the expected offspring ratio from a cross between two yellow-coated mice?

<p>2:1 (B)</p> Signup and view all the answers

What do heterozygotes of a recessive lethal allele express phenotypically?

<p>They are unaffected by the lethal allele (D)</p> Signup and view all the answers

Flashcards

Incomplete Dominance

A pattern of inheritance where neither allele is completely dominant, resulting in a heterozygote phenotype that's a blend of both homozygous phenotypes.

Codominance

A type of inheritance where both alleles are expressed equally in the heterozygote, resulting in a phenotype that shows characteristics of both alleles.

Lethal Allele

An allele that, when present in a homozygous state, causes the death of the organism.

Multiple Alleles

The situation where a gene has more than two possible alleles within a population.

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Polygenic Inheritance

The inheritance pattern where a single trait is influenced by multiple genes.

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Pleiotropy

A phenomenon where a single gene affects multiple traits.

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Environmental Factors

The influence of environmental factors on gene expression and phenotype.

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Gene Interaction

The interaction between different gene products to produce a combined effect.

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Incomplete Dominance (phenotype)

The phenotype of a heterozygote is intermediate between the homozygous phenotypes, not a mix of both.

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Codominance (phenotype)

Both alleles are fully expressed in the heterozygote, resulting in a phenotype that exhibits both allelic traits.

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F1 Generation

The offspring resulting from the first cross of two purebred parents.

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F2 Generation

The offspring produced from self-pollination of the F1 generation.

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P Generation

The parental generation in a genetic cross.

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Allele

A specific variation of a gene, represented by letters.

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Genotype

The combination of alleles an individual possesses for a particular trait.

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Phenotype

The observable characteristics of an individual, influenced by genotype.

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Recessive Lethal Allele

A mutation that causes a gene product to become nonfunctional, often fatal in homozygous recessive individuals.

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Dominant Lethal Allele

When one copy of an allele results in the death of the individual.

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3:6:3:1:2:1 Ratio

The phenotype that results from a combination of two gene pairs, with a dominant-recessive relationship at one locus, and codominance or incomplete dominance at the other.

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1:2:1:2:4:2:1:2:1 Ratio

The phenotype that occurs when both gene pairs have incomplete dominance. Each gene pair creates a 1:2:1 ratio, leading to a 1:2:1:2:4:2:1:2:1 ratio.

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9:3:3:1 Ratio

The phenotypic ratio of a dihybrid cross where both genes show a dominant-recessive relationship.

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Modified Dihybrid Ratios

A variation of the Mendelian dihybrid phenotypic ratio that occurs when the alleles at one or both genes are not purely dominant or recessive.

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ABO blood grouping Allele

An allele that determines the blood type of an individual. There are three main alleles: A, B, and O.

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Study Notes

Non-Mendelian Inheritance

  • Non-Mendelian inheritance refers to variations on Mendel's laws, where inheritance patterns don't always follow the typical dominant/recessive pairings.
  • Key types of Non-Mendelian inheritance include:
    • Incomplete dominance
    • Codominance
    • Lethal alleles
    • Multiple alleles
    • Polygenic inheritance
    • Pleiotropy
    • Environmental factors
    • Gene interaction

Incomplete Dominance

  • Neither allele is completely dominant over the other.
  • The heterozygous phenotype is an intermediate between the two homozygous phenotypes.
  • Example: Pink snapdragons resulting from a cross between red and white snapdragons.

Codominance

  • Both alleles in the heterozygote are fully and separately expressed.
  • Example: Roan cattle that exhibit both red and white hairs.

Lethal Alleles

  • Alleles that cause the death of the organism that carries them.
  • Often recessive, only expressed in homozygous state.
  • Example: in mice, the yellow coat allele (AY) is dominant to the normal agouti allele (A), heterozygotes are yellow. However, homozygous AY mice die before birth

Multiple Alleles

  • More than two alleles for a gene at a particular locus exist within a population.
  • Only two alleles are present in any single individual.
  • Example: ABO blood groups (IA, IB, i).

Polygenic Inheritance

  • Multiple genes contribute to a single trait.
  • Example: Human height, skin color.

Pleiotropy

  • A single gene affects multiple traits.
  • Example: Sickle cell anaemia affects red blood cells, causing anaemia, and also affects the function of other organs.

Environmental Factors

  • Environmental factors can influence the expression of a gene.
  • Example: Siamese cats express different fur colors based on temperature.

Gene Interaction

  • Products of genes interact to modify genetic ratios from the expected Mendelian ratios.
  • Different genes can influence one particular trait.
  • Example: The production of a purple pigment in corn shows gene interaction between various genes

Extensions to Mendel (Summary)

  • Mendel's laws don't always perfectly predict inheritance patterns in all cases.
  • Various situations exist where inheritance outcomes are different from the 9:3:3:1 ratio.
  • Incomplete dominance, codominance, lethal alleles, multiple alleles, gene interaction and environmental factors all play a role in non-Mendelian inheritance.

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