Genetics Inheritance Patterns Quiz

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General Biology 2 - Lesson 1: Heredity and Patterns of Inheritance

Introduction

• Stink-Free Gene (ABCC11): A mutated gene that affects the secretion of odorants and their precursors from apocrine sweat glands (armpits)
• Heredity (Inheritance): The process of traits being passed from one generation to the next (parents to offspring)
• Genetics: The branch of science that studies heredity

Foundations of Heredity

• Gregor Mendel (1822-1884): Known as the "Father of Genetics"
• Mendel conducted breeding experiments with garden peas ( Pisum sativum) to study inheritance patterns
• Mendel's Laws of Inheritance (later details are given)

Garden Pea ( Pisum sativum)

• Easy to cultivate
• Short generation time
• Can be cross-pollinated by hand
• Exhibits clear and distinguishable traits

Genes, Traits, and Alleles

• Gene: Units in organisms that control the expression of traits
• Trait: Distinguishable characteristics
• Allele: Alternative forms of a gene (B=dominant, b=recessive)

Dominant vs. Recessive

• Dominant (B): The allele that masks the recessive allele. Expressed always.
• Recessive (b): An allele only expressed in the absence of the dominant allele

Homozygous vs. Heterozygous

• Homozygous: Describes an individual with the same allele of a gene on both homologous chromosomes
• Heterozygous: Describes an individual with different alleles for a gene on homologous chromosomes

Genotype and Phenotype

• Genotype: The genetic makeup of an organism; the set of alleles present in an individual's chromosomes.
• Phenotype: The observable physical traits expressed by an organism.

Breeding (Mating)- Punnett Square

• True-Breeding: Parents with certain traits consistently pass those traits to every offspring
• Punnett Square: A square diagram use to predict possible genetic outcomes of a cross-breeding experiment

Mendel's Laws of Inheritance

• (Details on the three laws are later explained in a more sophisticated manner)*

Inheritance Patterns (Non-Mendelian)

• Incomplete Dominance: One allele is not fully dominant over the other; the heterozygous phenotype is an intermediate blend of the homozygous phenotypes.
• Codominance: Both alleles are simultaneously expressed, resulting in a combined phenotypic expression.
• Pleiotropy: A single gene affecting multiple traits.
• Polygenic Inheritance: Multiple genes control the phenotype of an organism.
• Epistasis: Two or more genes contribute to a phenotype but one gene may overshadow the other contributing genes

Inheritance Patterns in Humans

• Autosomal Dominant: A single copy of a mutated gene (from one parent) is enough to cause the disorder in both sexes.
• Autosomal Recessive: Two copies of the mutated gene (from both parents) are needed to cause the disorder in both sexes
• X-linked Dominant: Affected fathers pass the trait to all daughters, no carriers.
• X-linked Recessive: Males are more frequently affected than females; mothers pass down to their sons

Chromosomal Abnormalities

• Polyploidy: Species with three or more sets of chromosomes
• Aneuploidy: Too many or too few copies of a particular chromosome (nondisjunction)
• Specific Syndrome Examples: (e.g., Down Syndrome, Patau Syndrome, Turner Syndrome, Klinefelter Syndrome, etc.)

Additional topics

• Types of genetic disorders
• Pedigree analysis
• Determining if traits are dominant or recessive
• Identifying if traits are sex-linked or autosomal
• Other diseases like Albinism, Tay-Sachs disease etc
• (Further details and explanations are given throughout the following pages)*