Heredity and Genetics Fundamentals

Heredity and Genetics

• Heredity is the passing of physical and mental characteristics from one generation to another through genes.
• Genetics is the study of heredity and how inherited characteristics vary.
• Phenotype refers to the physical expression of an individual's genetic information, while genotype represents the two forms of their genetic information.

Understanding Gene Pairs

• Individuals can be heterozygous, having two different alleles for a gene, or homozygous, having two of the same alleles.
• Dominant alleles express their trait even when paired with a recessive allele, while recessive alleles only express their trait when paired with another recessive allele.
• True-breeding individuals consistently produce offspring with the same traits as themselves.

Key Concepts in Genetics

• Traits are specific physical characteristics, determined by genes - sections of DNA that code for proteins.
• Alleles are variations of a gene, influencing trait expression.
• Inheritance patterns describe how traits are passed from parents to offspring.
• Chromosomes, found in the nucleus of cells, contain DNA tightly coiled around proteins.

Experiments and Generations

• The P generation refers to the original parental pair in a genetic cross experiment.
• The F1 generation is the first generation of offspring produced by the parents.
• The F2 generation results from crossing two F1 individuals.

Mendel's Laws of Inheritance

• Law of Dominance: When multiple alleles exist for a trait, the dominant allele is expressed when two versions are present in the same individual.
• Law of Segregation: Each offspring inherits one allele for each trait from each parent.
• Law of Independent Assortment: Different traits do not influence the inheritance of each other.

Example: Monohybrid Cross

• A monohybrid cross example explores the inheritance of brown eyes (B, dominant) and blue eyes (b, recessive).
• There's a 50% chance of an offspring inheriting brown eyes and a 50% chance of blue eyes.

Example: Dihybrid Cross

• A dihybrid cross example explores the inheritance of round seeds (R, dominant) and wrinkled seeds (r, recessive), as well as yellow seeds (Y, dominant) and green seeds (y, recessive).
• There are 16 possible combinations of these traits in the offspring.

Heredity and Genetics

• Heredity is the passing of physical and mental characteristics from one generation to the next.
• Genetics is the study of heredity and the variation of inherited characteristics
• Phenotype is the physical expression of genetic information.
• Genotype is the two forms of genetic information an individual contains.

Terms Related to Inheritance

• Heterozygous: An individual who has inherited two different alleles for a gene.
• Carrier: A person who carries a genetic difference in one copy of a gene but doesn't have the disease.
• Hybrid: An individual capable of producing offspring with different versions of a trait from the parent.
• Homozygous: An individual who has inherited two of the same alleles for a gene.
• Dominant: If inherited, the dominant trait will be expressed over the recessive trait.
• Recessive: If inherited, the recessive trait will be expressed only if there is no dominant allele present.
• True-breeding: An individual who has always produced offspring with the same versions of a trait from the parent.
• Trait: A specific physical characteristic.
• Gene: A section of DNA that codes for the proteins that make up a physical trait.
• Allele: An option for what a gene can code for. Most genes have at least two options for alleles.
• Inheritance pattern: Different ways in which traits are passed from one generation to the next.

Structures and Processes

• Chromosome: A structure found inside the nucleus of a cell made up of DNA tightly coiled around proteins.

Genetic Crosses

• P generation: The original pair of parents at the start of a genetic cross experiment.
• F1 generation: The first generation of offspring produced by the parents.
• F2 generation: The result of a cross between two F1 individuals.

Examples of Genetic Crosses

• Monohybrid cross example: B for brown eyes (dominant) and b for blue eyes (recessive). There is a 50% chance of brown eyes and a 50% chance of blue eyes.
• Dihybrid cross example: R for round seed (dominant), r for wrinkled seed (recessive), Y for yellow seed (dominant) and y for green seed (recessive). There are 16 possible combinations in this example.

Laws of Inheritance

• Law of dominance: When more than one allele for a trait exists, the trait that is expressed when two versions are present in the same individual is dominant.
• Law of segregation: Each offspring will inherit only one allele for each trait from each parent.
• Law of independent assortment: Different traits do not influence the inheritance of each other.