Genetics

Gregor Mendel Gregor Mendel- an Austrian Monk who studied how pea plants pass on specific characteristics to their offspring His experiments were later summarized in 2 Laws Law of Segregation- only 1 allele passes from each parent to its offspring (the allele that is passed on is RANDOMLY selected) Alleles- 2 forms of a gene Law of Independent Assortment- Multiple offspring from the same parent can have different genes

Genetics Vocabulary Genotype- the genes an individual has (ex. Aa, aa, AA) Phenotype- the individual’s physical appearance (Tall, Short) Homozygous- has 2 identical alleles for the same gene (AA, aa) Heterozygous- has 2 different alleles for the same gene (Aa)

Incomplete Dominance Incomplete Dominance- neither allele is dominant nor recessive, the heterozygous form blends Ex: Homozygous Red Flower and Homozygous White Flower has all Pink Offspring

Co-Dominance Co-Dominance- both versions of the trait are equal and BOTH are shown Ex: Cows- Can be Red (RR), White(WW), or Roan (RW)

Sex-Linked Traits Traits that are carried on the X-Chromosome Females: XX Males: XY Tend to show up more often in males because Males only have 1 copy of the X Chromosome Females can be carriers (have one copy of the gene, and one normal X Chromosome)

Pedigrees A Pedigree is a diagram of family relationships that represent genetic relationships Pedigrees are often used to determine the inheritance of sex- linked traits Have disease/disorder/ trait: Fully Shaded Carrier: half shaded No disease/disorder/trait: not shaded

Genetic Disorders- Autosomal Recessive Autosomal Recessive- need both recessive alleles to have the disease Tay-Sachs Disease Fat accumulates in brain destroying tissue Severe impairment and death Cystic Fibrosis Most common in Caucasian population Mucus in respiratory tract, difficulty breathing Phenylketonuria (PKU) Lack enzyme for normal metasbolism

Genetic Disorders- Autosomal Dominant Autosomal Dominant- Need one copy of the dominant allele to have the disease

Multiple Alleles More than 2 alleles code for a single trait Ex: There are 3 alleles that code for an individual’s Blood Type (A,B,O) A and B show co-dominance (a heterozygous individual shows BOTH alleles, AB) A and B are both Dominant to the O allele An individual can have the genotype AA, AO, AB, BB, BO, or OO and the phenotype Type A blood, Type B blood, Type AB blood, or Type O blood

Polygenic Inheritance Multiple GENES code for one trait Ex: Height, Skin Color