Genetics: Principles of Heredity Quiz

Basic Principles of Heredity

• Mendel discovered the basic principles of heredity
• A gene is the fundamental unit of heredity and comes in multiple forms called alleles
• Alleles are alternative forms of a gene and reside on a specific location on a chromosome called a locus
• Genotype is the set of alleles an organism carries, phenotype is the observable trait
• An individual carrying two different alleles at a locus is a heterozygote
• An individual carrying two of the same alleles at a locus is a homozygote
• Genetic information is transferred from DNA to RNA to protein

Monohybrid Cross

• A monohybrid cross involves the crossing of two individuals differing in only one trait
• The offspring of a monohybrid cross are called F1 (first filial generation)
• The F1 generation is heterozygous
• The F2 generation is produced by self-fertilizing the F1 generation
• The F2 generation exhibits a 3:1 phenotypic ratio (dominant to recessive)

Dihybrid Cross

• A dihybrid cross involves the crossing of two individuals differing in two traits
• The offspring of a dihybrid cross are called F1 (first filial generation)
• The F1 generation is heterozygous
• The F2 generation is produced by self-fertilizing the F1 generation
• The F2 generation exhibits a 9:3:3:1 phenotypic ratio

Mitosis and Meiosis

• Mitosis is a type of cell division that produces two daughter cells identical to the parent cell
• Meiosis is a type of cell division producing four daughter cells, each with half the number of chromosomes as the parent cell
• Meiosis involves two divisions: Meiosis I (separating homologous chromosomes) and Meiosis II (separating sister chromatids)

Human Karyotype

• A karyotype is a visual representation of the chromosomes in a cell
• Humans have 46 chromosomes arranged in 23 pairs (diploid)
• Each chromosome pair consists of one paternal and one maternal chromosome

Gene Location

• Genes are located on chromosomes
• Many genes locate on each chromosome, with thousands of genes per chromosome

Autosomal Dominant Traits

• Autosomal dominant traits are traits expressed when an individual has only one copy of the dominant allele
• Examples of autosomal dominant traits include Huntington disease
• Individuals with autosomal dominant traits are most likely heterozygous, especially if the trait is rare in the population

Pedigree Analysis

• A pedigree is a diagram showing the inheritance of a trait within a family
• Pedigree analysis is useful for determining the mode of inheritance for a trait
• Common symbols used in pedigrees include circles for females and squares for males, filled symbols for affected individuals and unfilled symbols for unaffected individuals
• Using the rules of probability, genotypes can be assigned to individuals in a pedigree

Albinism

• Albinism is a recessive genetic condition resulting from the inability to produce melanin
• For albinism, an individual must inherit two copies of the recessive allele to be affected

Dominant Mutations

• Dominant mutations often involve a gain or change in gene function
• Dominant hypermorphic alleles result in an overproduction of a normal protein or a protein with increased activity
• Neomorphic alleles result in an altered protein with a new function or a protein that interferes with the wildtype protein (dominant-negative allele)