Questions and Answers
What is the difference between heterozygous and homozygous individuals?
Homozygous individuals have two identical copies of a gene, while heterozygous individuals have two different versions of a gene.
What do the symbols on the outside of a Punnett square represent?
Gametes
Can the same phenotype be produced by more than one genotype?
True
Is a dominant phenotype only expressed if an individual is homozygous dominant for that trait?
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What proportion of gametes from an organism with the genotype AaBb would be Bb?
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What percentage of offspring from two heterozygous mice for albinism would have an albino phenotype?
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What is the genotype of a plant with a phenotype that appears once out of every 16 offspring in a 9:3:3:1 ratio?
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What is an allele?
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What differentiates between independent assortment and segregation?
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What does a 3:1 ratio of offspring for a particular trait suggest?
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What genotype is possible in a gamete from an organism with the genotype HhTt?
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What is the chance of producing an offspring with the homozygous recessive phenotype when crossing an organism that is homozygous recessive for a single trait with a heterozygote?
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What phase of cell division is the basis for Mendel's observation of the segregation of alleles in gamete formation?
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What event of meiosis I is the basis for Mendel's second law of independent assortment?
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What does a test cross illustrate?
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Study Notes
Key Genetic Concepts
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Homozygous vs. Heterozygous
Homozygous individuals carry identical gene copies; all gametes have the same allele. Heterozygous individuals carry different gene copies; gametes have distinct alleles. -
Punnett Square
Symbols on the outside represent gametes, while interior symbols indicate the potential progeny from the cross. -
Phenotype and Genotype Relationship
A single phenotype can arise from multiple genotypes due to the presence of dominant and recessive alleles. -
Expression of Dominant Phenotype
Dominant phenotypes manifest in both homozygous dominant (AA) and heterozygous (Aa) individuals.
Gamete Formation and Ratios
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Gametes from AaBb Parent
No gametes will be of the genotype Bb due to segregation; alleles of the same gene separate during gamete formation. -
Albino Offspring Probability
There is a 25% chance of producing an albino phenotype (aa) from two heterozygous parents. -
Phenotypic Ratios in Pea Plants
A tall, purple-flowered (TtPp) pea plant produces a 9:3:3:1 phenotypic ratio when self-pollinating, with ttpp genotype appearing as the least common phenotype.
Alleles and Genetic Laws
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Definition of Allele
An allele is an alternative version of a gene; diploid organisms possess two alleles for each autosomal gene. -
Independent Assortment vs. Segregation
Independent assortment concerns the inheritance of two or more genes, while segregation relates to the separation of alleles for a single gene. -
3:1 Ratio Implication
A 3:1 offspring ratio from a cross indicates both parents are heterozygous for the trait in question.
Gamete Genotype and Offspring Probability
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Possible Gamete Genotypes from HhTt
A gamete from an HhTt organism could be HT, representing one combination of alleles. -
Chance of Homozygous Recessive Offspring
Crossing a homozygous recessive individual with a heterozygote gives a 50% chance for their offspring to express the homozygous recessive phenotype.
Mendel's Contributions and Cell Division
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Mendel's Observations in Meiosis
The segregation of alleles observed by Mendel occurs during anaphase I of meiosis, while the law of independent assortment is based on the alignment of tetrads at the metaphase plate during meiosis I. -
Law of Segregation Illustration
A test cross demonstrating that a green-pod plant is heterozygous (Gg) illustrates Mendel's law of segregation, showing the separation of alleles into different gametes.
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Description
Explore the fundamental concepts of genetics in this quiz based on Chapter 14 of Biology. Learn the differences between homozygous and heterozygous individuals and other key genetic terms. This quiz is perfect for reinforcing your understanding of Mendelian genetics.
