Genetics Flashcards
Law of Independent Assortment
Allele pairs separate independently during the formation of gametes. The inheritance of one gene does not affect the inheritance of another gene.
Codominance
Occurs when multiple alleles exist for a given gene and more than one of them is dominant.
Example: ABO blood groups
Incomplete Dominance
A form of inheritance in which one allele is not completely expressed over its paired allele. Formation of intermediate phenotypes.
Examples: Snapdragons, Skin and Eye Colors
Crossing Over
The exchange of genetic material between homologous chromosomes that result in recombinant chromosomes during sexual reproduction. Occurs between prophase I and metaphase I.
Nondisjunction
The failure of homologous chromosomes to separate properly during meiosis I (anaphase I) or the failure of sister chromatids to separate properly during meiosis II (anaphase II).
Example: Down Syndrome
Gene
The linear sequence of nucleotides along a segment of DNA that provides be coded instructions for synthesis of RNA, which, when translated into protein, leads to the expression of hereditary character.
Allele
An alternative form of a gene that is located at a specific position on a specific chromosome.
Genotype
The genetic makeup of an organism.
Phenotype
The physical manifestation of an organisms genetic makeup.
Homozygous Dominant
Two copies of the same dominant allele present within an organism.
Example: YY
Homozygous Recessive
Two copies of the same recessive allele present within an organism.
Example: yy
Heterozygous
A pair of genes where one is dominant and one is recessive.
Example: Yy
Complete Dominance
When the dominant allele is completely expressed over the recessive allele. The recessive allele remains silent.
Example: Flowers in Mendel’s Pea Plants
Penetrance
The proportion of a population with a given genotype who express the phenotype.
Point Mutations
The substitution of one nucleotide for another. Includes silent mutation, missense mutation, and nonsense mutation.
Silent Mutation
Occurs when the change in the nucleotide had no effect on the final protein synthesized from the gene.
Missense Mutation
Occurs when the change in the nucleotide results in substituting one amino acid for another in the final protein synthesized from the gene.
Nonsense Mutation
Occurs when the change in the nucleotide results in substituting a premature stop codon for an amino acid in the final protein synthesized.
Frameshift Mutation
Occurs when nucleotides are inserted into or deleted from the genome resulting in either changes in the amino acid sequence or premature truncation of the protein. Includes deletion and insertion mutations.
Law of Segregation (Four Basic Tenets)
- Genes exist in alternative forms (alleles)
- Two alleles for each gene, one inherited from each parent
- Alleles segregate during meiosis, resulting in gametes that carry only one allele for any inherited trait
- The expressed allele is dominant while the silent allele is recessive
