Genetics: Basic Inheritance Ch & 2

Genetics Genetics is the study of heredity. Genetics is the study of heredity. Traits are controlled through genes, which are found on chromosomes. Traits are controlled through genes, which are found on chromosomes. Different forms of a gene are called alleles. Different forms of a gene are called alleles.

Gregor Mendel Gregor Mendel = father of genetics Gregor Mendel = father of genetics Studied pea plants Studied pea plants Cross-pollinated pea plants to determine how traits were transmitted (pg. 264) Cross-pollinated pea plants to determine how traits were transmitted (pg. 264)

Mendel’s Principles Inheritance of traits is determined by genes. Genes are passed on from parents. Inheritance of traits is determined by genes. Genes are passed on from parents. Some forms of a gene are dominant and others are recessive. Some forms of a gene are dominant and others are recessive. Organisms have 2 copies of each gene, one from each parent. Organisms have 2 copies of each gene, one from each parent. Alleles for different genes segregate independently of one another. Alleles for different genes segregate independently of one another.

Dominant/Recessive Some alleles are dominant; represented by a capital letter; Some alleles are dominant; represented by a capital letter; ex. Tall = T ex. Tall = T Some alleles are recessive; represented by lower case letter; Some alleles are recessive; represented by lower case letter; ex. Short = t ex. Short = t If the dominant allele is present, it will mask the recessive allele. If the dominant allele is present, it will mask the recessive allele.

Homozygous/Heterozygous Homozygous— “same gamete;” 2 identical alleles Homozygous— “same gamete;” 2 identical alleles Homozygous dominant = TT Homozygous dominant = TT Homozygous recessive = tt Homozygous recessive = tt Heterozygous— “different gamete;” 2 different alleles; Tt Heterozygous— “different gamete;” 2 different alleles; Tt

Phenotype/Genotype Phenotype = physical characteristics Phenotype = physical characteristics ex: Tall or Short ex: Tall or Short Genotype = actual genetic make-up Genotype = actual genetic make-up ex: TT or Tt or tt ex: TT or Tt or tt

Punnett Squares Tool used to determine the probability that a trait will be transmitted. Tool used to determine the probability that a trait will be transmitted. Punnett Squares do NOT show ACTUAL results of a cross. Punnett Squares do NOT show ACTUAL results of a cross.