Download Mendelian Genetics

Mendel’s Theory
Section 2
Explaining Mendel’s Results
• Mendelian theory of heredity explains
simple patterns of inheritance. In these
patterns, two of several versions of a gene
combine and result in one of several
possible traits.
Alternate versions of genes
• Allele- a version of a gene
Dominant and recessive alleles
• Dominant- An allele that is fully expressed
whenever the allele is present in an
individual.
• Recessive- An allele that is expressed only
when no dominant allele is present for an
individual.
Random segregation of Alleles
• In modern terms, the law of segregation
holds that when an organism produces
gametes, each pair of alleles is separated
and each gamete has an equal chance of
receiving either one of the alleles.
Genotype and Phenotype
• Genotype- the set of alleles that an
individual has for a character
• Phenotype- the trait that results from a set
of alleles
• Genotype results from phenotype
Homozygous and
Heterozygous
• Homozygous- Describes an individual
that has identical alleles for a trait on both
homologous chromosomes.
• Heterozygous-Describes an individual that
carries two different alleles of a gene.
Mendel’s second
experiments
• Dihybrid cross- involves to
characters, such as seed color
and seed shape
Independent Assortment
• In modern terms, the law of independent
assortment holds that during gamete
formation, the alleles of each gene segregate
independently.