Questions and Answers
What do individuals carry for each trait?
Two alleles
Alleles segregate so that each gamete carries two alleles for each trait.
False
What is represented by uppercase letters in genetic traits?
Dominant traits
What must occur for a recessive trait to be expressed in the phenotype?
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What is an example of a dominant allele?
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What relates to incomplete dominance?
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What is codominance?
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Which of the following is an example of polygenic inheritance?
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What is the purpose of a Punnett square?
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What type of genetic disorder is hemophilia?
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Factors refer to ______ that determine traits.
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Carriers of autosomal recessive disorders express the disorder.
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Study Notes
Mendelian Inheritance
Principles of Segregation
- Each individual carries two alleles for each trait (one from each parent).
- During gamete formation, alleles segregate so that each gamete carries only one allele for each trait.
- This principle explains genetic variation among offspring.
Dominant and Recessive Traits
- Dominant traits: expressed in the phenotype if at least one dominant allele is present (represented by uppercase letters).
- Recessive traits: expressed in the phenotype only when two recessive alleles are present (represented by lowercase letters).
- Example:
- Dominant: T (Tall)
- Recessive: t (Short)
Exceptions to Mendel's Laws
- Incomplete dominance: phenotype is a blend of both alleles (e.g., red and white flowers producing pink offspring).
- Codominance: both alleles are fully expressed in the phenotype (e.g., AB blood type).
- Multiple alleles: more than two alleles exist for a trait (e.g., ABO blood group system).
- Polygenic inheritance: traits controlled by multiple genes (e.g., skin color, height).
Punnett Squares
- A tool used to predict the genotypic and phenotypic ratios of offspring from a cross between two parents.
- Grids show all possible combinations of parental alleles.
- Allows visualization of dominant and recessive trait inheritance.
Disorders
- Genetic disorders can be inherited following Mendelian patterns:
- Autosomal dominant (e.g., Huntington's disease)
- Autosomal recessive (e.g., cystic fibrosis)
- X-linked recessive (e.g., hemophilia)
- Carriers may not express the disorder but can pass it to offspring.
Factors
- Factors refer to alleles or genes that determine traits.
- Each trait is influenced by two alleles (one from each parent).
- The interaction between these factors dictates the observable characteristics in an organism.
Principles of Segregation
- Individuals possess two alleles for each trait, acquired from each parent.
- During gamete production, alleles segregate, ensuring each gamete carries a single allele for each trait.
- This segregation is crucial for genetic diversity in offspring.
Dominant and Recessive Traits
- Dominant traits are expressed in the phenotype with just one dominant allele present, denoted by uppercase letters.
- Recessive traits require two copies of the recessive allele for expression, represented by lowercase letters.
- Dominant example: T (Tall), Recessive example: t (Short).
Exceptions to Mendel's Laws
- Incomplete dominance results in a phenotype that is a blend of both alleles, such as pink flowers from red and white parents.
- Codominance shows both alleles equally in the phenotype, exemplified by the AB blood type.
- Multiple alleles indicate that more than two variations can exist for a single trait, as seen in the ABO blood group.
- Polygenic inheritance involves multiple genes influencing a single trait, affecting characteristics like skin color and height.
Punnett Squares
- Punnett squares serve as a predictive tool for determining the genotypic and phenotypic ratios of offspring from parental crosses.
- They visually represent all potential combinations of parental alleles, illustrating the inheritance of dominant and recessive traits.
Disorders
- Genetic disorders may follow Mendelian inheritance; examples include:
- Autosomal dominant disorders like Huntington's disease.
- Autosomal recessive disorders such as cystic fibrosis.
- X-linked recessive disorders, for instance, hemophilia.
- Individuals can be carriers of genetic disorders without exhibiting symptoms, but they can transmit the disorder to their children.
Factors
- Factors denote the alleles or genes responsible for traits.
- Each trait is influenced by a pair of alleles, one from each parent.
- The interaction between these factors shapes the observable traits in an organism.
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Description
Test your knowledge on Mendelian inheritance principles, including the segregation of alleles and the dominance of traits. This quiz covers key concepts in genetics that explain how traits are passed from parents to offspring.
