Chapter 4 - Genetics
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Gregor Mendel
Austrian monk and botanist whose experiments in breeding garden peas led to his eventual recognition as founder of the science of genetics (1822-1884)
Reginald Punnett
created the Punnett square based on Gregor Mendel’s work
Allele
an alternative form of a gene
Dominant allele
one whose trait always shows up in the organism when the allele is present
Recessive allele
an allele that is hidden whenever the dominant allele is present
Homozygous
both alleles of a gene are the same
Heterozygous
the alleles of a particular gene are different
homozygous dominant
both alleles (factors) for a trait are the same and dominant (AA)
homozygous recessive
both alleles (factors) for a trait are the same and recessive (aa)
Genotype
an organism’s genetic makeup, or allele combinations
phenotype
physical characteristics of an organism
heredity
the study of how traits are passed from one generation to the next
principles of heredity
• Traits are controlled by alleles on chromosomes • An allele’s effect is dominant or recessive • When a pair of chromosomes separates during meiosis, the different alleles for a trait move into separate sex cells
purebred
an organism that always produces offspring with the same form of a trait as the parent
hybrid
an offspring with a mix of alleles for a specific character
hybrid cross
a cross of two individuals heterozygous for the same trait; results in a 3:1 phenotypic ratio