Genetics and Heredity Flashcards

Grade 9 · Science · Flashcards

Master genetics vocabulary with these 12 flashcards on alleles, inheritance patterns, and Mendel's laws.

Flashcards

Gene: A segment of DNA on a chromosome that codes for a specific trait or protein.
Allele: One of two or more versions of a gene; you inherit one allele from each parent.
Dominant Allele: Allele that is expressed in the phenotype whenever at least one copy is present; written in uppercase (e.g., B).
Recessive Allele: Allele that is only expressed in the phenotype when two copies are present (bb); written in lowercase.
Homozygous: Having two identical alleles for a gene (BB or bb).
Heterozygous: Having two different alleles for a gene (Bb); also called hybrid.
Genotype: The actual genetic composition of an organism (e.g., Tt, AABB).
Phenotype: The observable trait produced by the genotype (e.g., tall, brown eyes).
Punnett Square: A diagram used to predict the probability of genotype and phenotype combinations in offspring.
Law of Segregation: Mendel's 1st law: allele pairs separate during meiosis so each gamete carries only one allele per gene.
Incomplete Dominance: Neither allele is fully dominant; heterozygous offspring show a blended intermediate phenotype.
Codominance: Both alleles are fully expressed simultaneously in the heterozygous phenotype (e.g., AB blood type).