Traits

[D] Traits #

Traits #

(See 2-3 genetics for the same allele / genotype / phenotype framing applied to mental-health traits, including the polymorphism concept used below.)

• Aa — Allele (each letter), Monogenic trait (the pair)
• Genotype vs Phenotype
  • Genotype: actual genetic material — possible combinations of alleles (Aa, AA, aa)
  • Phenotype: expression of genes — possible observable traits ((Aa, AA) or (aa))
• Homozygous vs Heterozygous
  • Homozygous: both alleles same — AA or aa
  • Heterozygous: different alleles — Aa
• Dominant vs Recessive (alleles)
  • Dominant: A
  • Recessive: a
• Chromosomes are associated w/ passing of traits

Mendel’s Principles #

Law of Segregation #

Since offspring inherit one allele from each parent, traits cannot be blended — either inherits from one parent or the other.

Law of Independent Assortment #

Genes are inherited separately from one another.

Sex-Linked Traits #

• Controlled by genes on X or Y chromosomes
• Y chromosome has male traits, but X chromosome has many other functions
• X, Y not homologous (no match)
  • More likely to produce disorders in males (e.g. colorblindness [color sensitive rhodopsin proteins], hemophilia [blood clots])
  • Females can be carriers (heterozygous)
• Father has hemophilia: XY XX → XY or YX, XX or XX

Non-Mendelian Inheritance #

• Polygenic / continuous traits
• Coded by multiple alleles
• Examples: blood type, skin color
• Phenotypes can also be affected by environment (e.g. height)

Mutation #

• New changes in DNA that cause genetic variation
• Occurs when codon is changed, altering the amino acid produced
• Mechanical errors during gene replication

Point Mutation #

Affects one part of a protein.

• Example: Albinism occurs when there is a mutation in one locus in the production of melanin

Pedigree Diagrams #

• Male: square
• Female: circle
• Mates: horizontal line connecting two individuals
• Offspring: vertical line descending from mates
• Affected by trait: shaded shape