Genetics

History Genetics is the study of genes. Genetics is the study of genes. Inheritance is how traits/characteristics, are passed on from generation to generation. Inheritance is how traits/characteristics, are passed on from generation to generation. Genes are passed parents  offspring; – get one allele for each gene from each parent during Meiosis cell division Chromosomes are made up of genes Chromosomes are made up of genes – Alleles=diff. versions of a gene Gene is made up of DNA. Gene is made up of DNA. Gregor Mendel is considered “The Father of Genetics“…Used Pea Plants to discover inheritance. Gregor Mendel is considered “The Father of Genetics“…Used Pea Plants to discover inheritance.

Mendel Breeding Experiment P generation (parental generation) F1 generation the hybrid offspring. Allowing these F1 hybrids to self-pollinate produces: F2 generation (second filial generation). Mendel’s analysis of this that lead to an understanding of genetic crosses.

Mendelian Genetics Dominant traits- traits that are expressed. Dominant traits- traits that are expressed. Recessive traits- traits that are covered up. Recessive traits- traits that are covered up. Genotype- the types of genes (Alleles) present. Genotype- the types of genes (Alleles) present. Phenotype- what it looks like. Phenotype- what it looks like. Homozygous- two of the same alleles. Homozygous- two of the same alleles. Heterozygous- two different alleles. Heterozygous- two different alleles.

How do Alleles differ? Dominant - a term applied to the trait (allele) that is expressed irregardless of the second allele. Usually indicated with a Capital Letter (ex. A, L, P) Recessive - a term applied to a trait that is only expressed when the second allele is the same (Usually indicated with a lower-case letter (ex. a, l, p) Dominant allele Recessive allele

Probability and Punnett Squares Punnett square: diagram showing the probabilities of the possible outcomes of a genetic cross

Genotype versus phenotype. How does a genotype ratio differ from the phenotype ratio?

Punnett squares - probability diagram illustrating the possible offspring of a mating. Ss X Ss gametes

How Does it Work?

Pedigree analysis reveals patterns in human inheritance In these family trees, sqaures=male, circles= females. A horizontal line connecting a male and female (--) indicates a mating, with offspring listed below in their order of birth, from left to right. Shaded symbols stand for individuals with the trait being traced.

Incomplete Dominance Every genotype has its own phenotype. – (One allele not completely dominant over the other.) Third phenotype that is a blending of the parental traits. – (2 alleles produce 3 phenotypes.) Result: Heterozygous phenotype somewhere inbetween homozygous phenotype.

Incomplete Dominance Examples: Trait: Flower Color Expressions: Red x White  Pink RR= Red; RW= pink; WW= white straight hair x curly  wavy

2. Codominance Both alleles contribute to the phenotype. In codominance, neither allele are dominant; both are expressed. – Example: In some chickens Black Chicken x White Chicken  Speckled Chicken

YOU tell me which type of dominance…Incomplete or Codominace? Codominance!

Type of Dominance? Incomplete Dominance!

Type of Dominance? Incomplete Dominance!