chapter 24

Used to predict genetic inheritance.
Genetics course encompasses numerous concepts, but today focuses on Punnett squares.

Less than 2% of genetic structure codes for observable traits (phenotypes).
- Observable traits: hair color, eye color, physical characteristics.
- Non-observable traits: lactose intolerance, predisposition to thyroid disorders, diabetes.

Alleles: Different forms of a gene that arise by mutation and are found at the same place on a chromosome.
Homozygous: Identical alleles for a trait (e.g., both alleles for black hair).
Heterozygous: Different alleles for a trait (e.g., blue eyes from one parent, green from another).
Karyotype: Illustration of chromosomes, containing information that gets expressed in the body.
- Consists of 23 pairs of chromosomes, one from each parent.

Chromosome 1: Always the longest chromosome.
Each chromosome has specific traits described by alleles.
- Alleles can be homozygous (e.g., both parents have black hair) or heterozygous (e.g., one parent has blue eyes, the other green eyes).

Genotype: The genetic constitution of an individual (the alleles).
Phenotype: The physical expression of the genotype (appearance or trait).
Connection between genotype and phenotype via worksheets to identify traits based on given genotypes.

Dominant alleles represented by uppercase letters; recessive alleles by lowercase letters.
- Example: Capital letter indicates a dominant trait; lowercase indicates a recessive one.
- If one dominant and one recessive allele are present, the dominant trait will be expressed.

Punnett squares used to predict offspring traits based on parents' genotypes.
- Example sheet: Contains female monster and male monster genotypes.
- Mom's genotype inputs from the side, dad's genotype from the top of the square.
- Calculation of percentages of dominant and recessive traits expressed.

Example 1: Female monster genotype: $Ed$ (capital E, lowercase d); Male monster genotype: $EE$ (two capital E's).
- Resulting allele combinations for offspring: All combinations with capital E lead to expression of dominant traits.
  - 100% chance for offspring to express the dominant trait of the female monster.
- Example 2: When including recessive alleles, adjustments to percentages calculated.
  - 75% chance of expressing one trait, 25% for another when mixing traits.

Reference to popular culture (Game of Thrones) regarding genetic traits.
- Example: A family tree where a child does not match expected dominant traits indicates possible genetic discrepancies.
Discussion of recessive traits that may not be expressed until two recessive alleles are combined.

Autosomal dominant: Trait appears if at least one dominant allele is present. (50% chance if one parent has the trait).
Autosomal recessive: Trait appears only if both alleles are recessive. (1 in 4 chance if both parents carry the allele).
- Example: Sickle cell trait provides malaria resistance; however, two recessive alleles lead to sickle cell disease.

Discussion of conditions like Huntington's disease (autosomal dominant) versus sickle cell anemia (autosomal recessive).
Mention of sporadic genetic conditions such as Alzheimer's disease, which have complex genetic and environmental influences.

Overall emphasis on the significance of understanding genetic principles: how traits are inherited, the role of dominant and recessive alleles, and the implications for health and inheritance.