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Questions and Answers
Who is the father of modern genetics?
Gregor Mendel
What should you know about page 119 regarding the basics of probability math?
know
Law of Dominance basically means that ______ alleles will always be masked by ___ alleles (except for heterozygous).
recessive; dominant
Law of Segregation occurs during ___ Phase (meiosis).
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Law of Independent Assortment occurs during ___ Phase (meiosis).
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The law of segregation basically states that the homologs ____ during metaphase (meiosis).
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What does Mendel's law of segregation state about homologous chromosomes?
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What does the law of independent assortment state?
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If the phenotype ratio of the offspring is 3 to 1, then both of the parents are ____ of the trait.
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If the phenotype ratio of the offspring is 1 to 1, then one of the parents is ____ recessive and the other is ___.
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The law of independent assortment applies when a cross is carried out between 2 individuals that are ____ for 2 traits on separate chromosomes.
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What determines how alleles are inherited in the law of Independent Assortment?
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When would you use a dihybrid cross? - when you need to cross individuals that are hybrid for ___ different traits.
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What is the phenotype ratio for a dihybrid cross?
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In incomplete dominance, a red flower + a white flower = __ flower.
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In codominance, a white cow + a red cow = ___ cow.
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What is an example of codominance in humans?
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Multiple alleles is where there are more than __ allelic forms of a ___.
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How many different blood groups are there in humans?
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What are the alleles that determine blood types?
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What are traits controlled by two or more genes called?
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What are genes located on either sex chromosome called?
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Why are males more vulnerable to diseases?
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Females must inherit ___ copies of sex-linked genes but males only need to inherit __.
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If a female inherits 1 copy of the sex-linked genes, she will be called a ___. If she inherits 2, then she will express the ___.
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In sex-linked inheritance, who passes the trait to his daughters only?
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Where does mitochondria come from?
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What are common examples of recessive sex-linked traits?
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What is hemophilia?
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What is true about all daughters of affected fathers?
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Can sons inherit a sex-linked trait from the father?
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What percentage chance does a son have of inheriting a sex-linked trait from a carrier mother?
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There is a carrier state for X-linked traits in males.
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Can the environment alter the expression of genes?
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Study Notes
Classical Genetics Overview
- Gregor Mendel is recognized as the father of modern genetics.
- Probability math fundamentals are crucial for understanding genetic inheritance.
Key Genetic Laws
- Law of Dominance: Recessive alleles are masked by dominant alleles, except in heterozygous situations.
- Law of Segregation: Homologous chromosomes separate during Anaphase of meiosis, ensuring only one chromosome from each pair is present in each gamete.
- Law of Independent Assortment: Genes independently separate during metaphase of meiosis, resulting in random combinations of traits.
Phenotype Ratios
- A 3:1 phenotype ratio in offspring indicates that both parents are heterozygous for the trait.
- A 1:1 phenotype ratio suggests one parent is homozygous recessive and the other is heterozygous.
Genetic Crosses and Ratios
- Dihybrid crosses involve individuals that are hybrid for two different traits.
- The phenotype ratio for a dihybrid cross is 9:3:3:1.
Inheritance Patterns
- Incomplete dominance: Example where a red flower crossed with a white flower produces a pink flower.
- Codominance: Example is a white cow crossed with a red cow resulting in a roan cow; also applies to human blood types.
- Multiple alleles refer to more than two allelic forms for a gene, like blood type (A, B, AB, O).
- In humans, four different blood groups are dictated by three alleles: A, B, and O.
Genetic Traits and Sex Linkage
- Polygenic traits are controlled by two or more genes.
- Sex-linked genes are located on sex chromosomes, and males are more vulnerable to related diseases due to inheriting only one X chromosome.
- Females need two copies of a sex-linked gene to express the trait, while males only need one.
- Fathers transmit sex-linked traits to their daughters but not their sons, since sons inherit the Y chromosome.
Mitochondrial Inheritance
- Mitochondria are inherited maternally.
Common Sex-linked Disorders
- Color blindness and hemophilia are examples of recessive sex-linked disorders.
- Hemophilia is a hereditary condition that impairs blood coagulation, leading to excessive bleeding.
- All daughters of affected fathers will be carriers of the trait, while sons cannot inherit the trait from their fathers. The chance of a son inheriting a trait from a carrier mother is 50%.
Miscellaneous
- There is no carrier state for X-linked traits in males; they either express the trait or they do not.
- Environmental factors can potentially alter gene expression, demonstrating the interaction between genetics and surroundings.
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Test your knowledge of classical genetics with these flashcards. Cover key concepts such as Gregor Mendel, laws of dominance and segregation, and probabilities in genetics. Ideal for students looking to reinforce their understanding of foundational genetics principles.