{ Genetics Mrs. Magee

Why do we look like our parents?  Parents pass their DNA to their children  Each parent’s sex cell (egg or sperm) contains ½ of the DNA needed to create a new organism  The passing of traits from one generation to the next is called Heredity or Inheritance

Chromosome – A structure found in the nucleus of a cell that contains the DNA

Gene – A segment of DNA found on a chromosome that determines the inheritance of a particular trait. One gene

 Genes are responsible for the inherited characteristics that make each living thing unique  Genes for a specific trait come in pairs  One gene from the pair is called an allele.

GGGGenes may be expressed in two different forms: Genotype – the set of genes carried by the organism (the 2 alleles) EX: BB, Bb, or bb Phenotype – the physical expression of the genes. EX: blue eyes, tongue rolling, curly hair Tongue rolling gene

 Dominant Trait – will always be expressed in the phenotype  Alleles for dominant traits are represented by CAPITAL LETTERS GGG g OR Purebred Hybrid

 Recessive Trait – will only be expressed if two recessive alleles are present  Alleles for recessive traits are represented by lowercase letters g g Purebred

 Inherited Traits – characteristics that are passed from parent to offspring  Examples:  Eye color  Eye shape  Hair type  Face shape  Blood type

 Acquired Traits – characteristics that are influenced by the environment  Nutrition – can affect weight  Injuries – can cause scars  Exposure to Sun – can change skin and hair color  Preferences are acquired  Ex: I like chocolate