Questions and Answers
What is the difference between dominant and recessive traits?
Dominant traits appear when the dominant alleles are present. Recessive traits appear only when dominant traits are not present.
What is a genotype? What is a phenotype?
Genotype: the actual alleles that represent a trait on a chromosome. Phenotype: the physical appearance.
What is the difference between homozygous and heterozygous?
Heterozygous genotypes have two different alleles for a trait (e.g., Tt), whereas homozygous genotypes have two of the same alleles (e.g., TT, tt).
What is the relationship between a chromosome, nucleus, and gene?
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What is a Punnett Square? Do they help predict probability?
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What is a gene? What is an allele?
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What is incomplete dominance? Is it common in nature?
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What is codominance?
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What are sex-linked traits?
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What does the law of segregation say?
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What does the law of independent assortment say?
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What is probability?
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What do you use a test cross for?
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Can you see genotypes?
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Can you see phenotypes?
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What is the structure of DNA?
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What are purebreds? What are hybrids?
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What is self-pollination? Cross pollination?
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What allows different tissues that have the same DNA to function differently?
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What are multiple alleles?
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What phenotypic ratio do you get when you cross two heterozygous organisms?
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What is the probability that the child of a heterozygous man and a homozygous recessive woman will develop Huntington's disease?
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What is the probability that the puppies would have wire-hair when a homozygous wire-haired male is mated to a smooth-haired female?
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What is the probability that the puppies would have smooth hair when a homozygous wire-haired male is mated to a smooth-haired female?
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Study Notes
Genetics Basics
- Dominant vs. Recessive Traits: Dominant traits manifest with one dominant allele, while recessive traits require both alleles to be recessive.
- Genotype vs. Phenotype: Genotype refers to the genetic makeup, while phenotype is the observable physical expression of traits.
Alleles and Genotypes
- Homozygous vs. Heterozygous: Homozygous has two identical alleles (e.g., TT, tt); heterozygous has two different alleles (e.g., Tt).
- Alleles: Variants of a gene that represent different expressions of a trait, such as T and t.
Chromosomes and Genes
- Relationship: Genes are located on chromosomes, which reside in the nucleus of the cell.
Predictive Genetics Tools
- Punnett Square: A diagram used to predict the probability of genetic outcomes from crosses.
Genetic Expressions
- Incomplete Dominance: A genetic condition where the heterozygous phenotype is an intermediate between the two homozygous phenotypes (e.g., red and white flowers producing pink).
- Codominance: A situation where both traits from homozygous parents are fully expressed in the offspring (e.g., black and white chickens producing black and white offspring).
Special Trait Considerations
- Sex-linked Traits: Traits associated with genes located on sex chromosomes, such as color blindness linked to the X chromosome.
Mendelian Laws
- Law of Segregation: Chromosomes segregate independently and randomly during gamete formation.
- Law of Independent Assortment: The inheritance of one trait does not affect the inheritance of another.
Probabilities in Genetics
- Probability: The mathematical likelihood of a specific genetic outcome.
- Test Cross: A method to determine an unknown genotype by crossing it with a homozygous recessive individual.
Visibility of Genotypes and Phenotypes
- Genotype Visibility: Genotypes cannot be directly observed as they exist within DNA; phenotypes can be directly observed as physical traits.
DNA Structure and Genetic Diversity
- DNA Structure: Comprises a double-helix formation.
- Purebreds vs. Hybrids: Purebreds are homozygous, whereas hybrids are heterozygous individuals.
Pollination Types
- Self-Pollination: Occurs when flowers fertilize themselves on the same plant.
- Cross-Pollination: Involves fertilization between flowers from different plants.
Tissue Functionality
- Gene Expression: Different genes in the same DNA can lead to varied tissue functions due to selective gene expression.
Multiple Alleles
- Multiple Alleles: Genes that can be represented by more than two alleles, contributing to trait diversity.
Punnett Square Outcomes
- Heterozygous Cross Ratio: Crossing two heterozygous organisms typically yields a phenotypic ratio of 3:1.
Example Scenarios
- Huntington's Disease: A person with a dominant allele has a 50% chance of passing it to offspring if partnered with a homozygous recessive individual.
- Dog Coat Types: Crossing a homozygous wire-haired dog with a smooth-haired dog results in all offspring having wire-haired fur (100% probability) and none with smooth fur (0% probability).
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Description
This quiz explores key concepts in genetics, including the distinctions between dominant and recessive traits, as well as the definitions of genotype and phenotype. Perfect for students preparing for exams or to enhance their understanding of genetic principles.