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Questions and Answers
What is the main characteristic of codominance?
What is the main characteristic of codominance?
In codominance, one allele may be recessive and suppressed by another allele.
In codominance, one allele may be recessive and suppressed by another allele.
False
What phenotype is produced in individuals with the genotype IAIB?
What phenotype is produced in individuals with the genotype IAIB?
Blood type AB
In sickle-cell anemia, the genotype ____ results in the production of both normal and mutated hemoglobin.
In sickle-cell anemia, the genotype ____ results in the production of both normal and mutated hemoglobin.
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Match the following blood type genotypes with their corresponding phenotypes:
Match the following blood type genotypes with their corresponding phenotypes:
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Which of the following statements about the expression level in codominance is true?
Which of the following statements about the expression level in codominance is true?
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In codominance, the phenotypic ratio is typically 1:2:1.
In codominance, the phenotypic ratio is typically 1:2:1.
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What occurs at the chromosomal level in codominance?
What occurs at the chromosomal level in codominance?
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What color feathers do the heterozygous offspring of black and white-feathered chickens exhibit?
What color feathers do the heterozygous offspring of black and white-feathered chickens exhibit?
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In incomplete dominance, one allele fully dominates the other.
In incomplete dominance, one allele fully dominates the other.
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What is the genotype of a gray-furred rabbit resulting from a cross between a black-furred rabbit and a white-furred rabbit?
What is the genotype of a gray-furred rabbit resulting from a cross between a black-furred rabbit and a white-furred rabbit?
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The color of feathers in F1 generation heterozygous chickens results from the ______ of black and white pigments.
The color of feathers in F1 generation heterozygous chickens results from the ______ of black and white pigments.
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Which of the following explains why the blue-gray feathers are not a pure gray?
Which of the following explains why the blue-gray feathers are not a pure gray?
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Name an example of a trait that is inherited through codominance.
Name an example of a trait that is inherited through codominance.
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Match the following traits with their inheritance types:
Match the following traits with their inheritance types:
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In incomplete dominance, the resulting phenotype is an intermediate form between two ______.
In incomplete dominance, the resulting phenotype is an intermediate form between two ______.
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What happens to red blood cells in individuals with the HbAHbS genotype during low oxygen conditions?
What happens to red blood cells in individuals with the HbAHbS genotype during low oxygen conditions?
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Individuals with HbAHbS usually experience severe symptoms.
Individuals with HbAHbS usually experience severe symptoms.
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What term describes the condition where both normal and sickle-shaped red blood cells are present?
What term describes the condition where both normal and sickle-shaped red blood cells are present?
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A homozygous condition of a lethal gene must inherit two copies of the allele for it to be _____
A homozygous condition of a lethal gene must inherit two copies of the allele for it to be _____
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Match the type of lethal gene with its description:
Match the type of lethal gene with its description:
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When a person with sickle cell trait has a child with someone who has normal hemoglobin, what is one possible genotype of their offspring?
When a person with sickle cell trait has a child with someone who has normal hemoglobin, what is one possible genotype of their offspring?
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Lethal genes can only cause death during embryonic development.
Lethal genes can only cause death during embryonic development.
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Define lethal genes in the context of genetics.
Define lethal genes in the context of genetics.
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How many alleles can an individual organism inherit for a given gene?
How many alleles can an individual organism inherit for a given gene?
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The ABO blood group system is an example of a trait controlled by multiple alleles.
The ABO blood group system is an example of a trait controlled by multiple alleles.
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What is meant by 'hierarchy of dominance' in the context of multiple alleles?
What is meant by 'hierarchy of dominance' in the context of multiple alleles?
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In the ABO blood group system, the alleles IA and IB are considered to be ____ to each other.
In the ABO blood group system, the alleles IA and IB are considered to be ____ to each other.
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Match the following alleles with their corresponding blood types:
Match the following alleles with their corresponding blood types:
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Which of the following statements is true regarding phenotypic variety and multiple alleles?
Which of the following statements is true regarding phenotypic variety and multiple alleles?
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With multiple alleles, an organism can express all alleles present in the population.
With multiple alleles, an organism can express all alleles present in the population.
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What are the three alleles that determine an individual's blood type in the ABO blood group system?
What are the three alleles that determine an individual's blood type in the ABO blood group system?
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What is the observed phenotypic ratio in the offspring of two heterozygous yellow-coated mice (Yy)?
What is the observed phenotypic ratio in the offspring of two heterozygous yellow-coated mice (Yy)?
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A homozygous lethal individual (yy) will survive to adulthood.
A homozygous lethal individual (yy) will survive to adulthood.
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Name a prominent example of a dominant lethal gene.
Name a prominent example of a dominant lethal gene.
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The lethal allele in the case of two heterozygous yellow-coated mice results in death during the _____ stage.
The lethal allele in the case of two heterozygous yellow-coated mice results in death during the _____ stage.
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What happens to individuals with a dominant lethal allele?
What happens to individuals with a dominant lethal allele?
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Individuals with one copy of the mutated allele of Huntington's disease remain symptom-free until later in life.
Individuals with one copy of the mutated allele of Huntington's disease remain symptom-free until later in life.
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What is the genotypic outcome ratio expected from two heterozygous yellow-coated mice?
What is the genotypic outcome ratio expected from two heterozygous yellow-coated mice?
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Match the type of lethal genes with their characteristics:
Match the type of lethal genes with their characteristics:
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What is an example of a dominant lethal gene in chickens?
What is an example of a dominant lethal gene in chickens?
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Homozygous Manx cats can survive without any issues.
Homozygous Manx cats can survive without any issues.
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What phenotype do heterozygous individuals (Aa) with achondroplasia exhibit?
What phenotype do heterozygous individuals (Aa) with achondroplasia exhibit?
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In Chickens, the _______ allele is lethal when homozygous.
In Chickens, the _______ allele is lethal when homozygous.
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Match the following animals with their corresponding lethal gene characteristics:
Match the following animals with their corresponding lethal gene characteristics:
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Multiple alleles refer to more than two forms of a gene in a population.
Multiple alleles refer to more than two forms of a gene in a population.
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The gene responsible for taillessness in Manx cats is a _______ lethal gene.
The gene responsible for taillessness in Manx cats is a _______ lethal gene.
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Study Notes
Chapter 4: Variations of Mendelian Inheritance
- This chapter discusses variations on Mendelian inheritance principles, going beyond simple dominant/recessive patterns.
Mendelian Inheritance?
- Questions the fundamental concepts of Mendelian inheritance.
Variations of Mendelian Inheritance
- Incomplete Dominance
- Codominance
- Lethal Genes
- Multiple Alleles
- Polygenes
- Epistasis
Gene Interaction
- Gene interactions describe various ways two or more genes influence each other impacting the phenotype.
- Allelic or Non-epistatic
- Non-allelic or Epistatic
Incomplete Dominance
- Definition: A form of inheritance where the heterozygote's phenotype is an intermediate blend of both homozygous parents.
- Deviation from Mendelian Dominance: Unlike Mendel's concept of complete dominance, where one allele masks the other, incomplete dominance blends parental traits.
- Phenotype Result: A distinct intermediate phenotype is produced (neither dominant nor recessive). Example 1:2:1 ratio
Mechanism of Incomplete Dominance
- Dosage Effect: The heterozygote produces less of the gene product (usually a protein) compared to the homozygote for the dominant allele.
- Gene Expression: Both alleles contribute to the phenotype, but the gene products are insufficient to fully express either trait alone.
Example: Flower Color in Snapdragon
- Parental Generation: Red-flowered plant (CRCR) and White-flowered plant (CWCW)
- F1 Generation: All offspring are heterozygous (CRCW) and display a pink phenotype (intermediate phenotype)
- Reason for Pink Color: The red allele (CR) only partially contributes to flower color, and the white allele (CW) also contributes but not fully, resulting in a blend or an intermediate trait between red and white-pink.
Example: Andalusian Chicken Feather Color
- Parental Generation: Black-feathered chicken (CBCB) and White-feathered chicken (CWCW)
- F1 Generation: All offspring are heterozygous (CBCW) and display a blue-gray phenotype
- Reason for Blue-Gray Color: The black allele (CB) doesn't entirely dominate the white allele(CW), but instead, the black pigment is diluted, resulting in a "softer," blue-gray color.
Why Blue, Not Gray?
- Blue-gray is not simply an average of black and white. The color arises from the partial expression of black pigment.
- When diluted, it creates a bluish tone due to how light interacts with the diluted pigment, creating a more distinct blue-gray color (instead of pure gray, which is a mix of black and white)
Sample Problem: Incomplete Dominance (Rabbits)
- In a certain breed of rabbits, the allele for black fur (B) is incompletely dominant to the allele for white fur (W).
- A gray-furred rabbit (BW) is crossed with a white-furred rabbit (WW).
- Expected genotypes and phenotypes of 16 offspring (problem-solving example).
Codominance
- Definition: A form of inheritance where both alleles in a heterozygous organism are fully and equally expressed, simultaneously displaying both traits.
- Phenotypic Result: Traits from both alleles are visible. Example ratio: 1:2:1
Mechanism of Codominance
- Chromosomal Level: Both alleles at a specific locus on homologous chromosomes remain active and equally contribute to the phenotype.
- Expression Level: Both alleles independently code for proteins, co-expressed; proteins function independently but are observable in the phenotype.
Example: Codominance of Blood Types A and B
- Alleles: IA codes for the A antigen, IB codes for the B antigen, i codes for neither antigen (O)
- Genotype: IAIB (Blood type AB) - both A and B antigens are displayed equally on red blood cells.
Example: Codominance in Sickle-Cell Anemia
- Alleles: HbA (normal hemoglobin), HbS (mutated, sickle-shaped hemoglobin)
- Genotype: HbAHbS (Heterozygous)
- Phenotype: Both normal and sickle-shaped hemoglobin proteins are produced.
- Health Effects: Heterozygous individuals usually have mild symptoms, but they may experience mild sickling under low oxygen conditions.
Sample Problem: Codominance
- In humans, the allele for normal hemoglobin (HbA) and the allele for sickle-cell hemoglobin are codominant.
- Problem-solving exercise (creating a Punnett square to predict offspring genotypes and phenotypes).
Lethal Genes
- Definition: Lethal genes cause an organism's death when present in a particular combination.
- Types: Recessive and Dominant Lethal Genes
Recessive Lethal Genes
- Definition: An individual must inherit two copies of the lethal allele to be fatal. Example: In mice, the yellow coat color is controlled by a lethal gene.
Dominant Lethal Genes
- A dominant lethal allele is fatal when present in a single copy.
- Example: Huntington's Disease
- Example: Creeper Chickens
- Example: Manx Cats
Sample Problem: Lethal Genes
- Achondroplasia: A form of dwarfism; dominant allele (A), but homozygous genotype is lethal before birth.
Multiple Alleles
- Definition: More than two alternative forms of a gene (alleles) exist for a particular trait in a population (leading to greater genetic variation).
- Organisms only carry two alleles, but there are over two gene variants.
- Example: ABO Blood Group System in Humans (IA, IB, i)
- Example: Coat Color in Rabbits (C, cch, ch, c)
Sample Problems (Multiple Alleles)
- Problems related to specific genetic inheritance patterns involving multiple alleles for traits like coat color in rabbits.
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Description
Explore the variations of Mendelian inheritance in this quiz, including concepts like incomplete dominance, codominance, and lethal genes. Understand how gene interactions impact phenotypes beyond simple dominant and recessive models. Test your knowledge of these complex genetic principles.