Inheritance of Traits

Inheritance of Traits

Traits

  • A characteristic or feature that can be used to distinguish one individual from another
    • Hair colour, eye colour, height
  • They are inherited
    • Passed down from one generation to the next
  • Located on chromosomes
  • Genes are associated with expression of traits

Heredity

  • Study of how traits are passed along from one generation to the next

Genetics

  • Study of inheritance and genes

The study of genetics started in plants

  • Gregor Mendel, establish the principles of heredity, live in a monastery
  • Experimented with pea plants
  • 29,000 plants
  • Pea plants have many observed traits (tall/short, purple flowers/white flowers) phenotypes
  • Pea plants can be self fertilized or cross fertilized
  • Used 7 traits in his initial testing

Crosses

  • Where male gametes or pollen were transfer to female flower to produce seeds

Parent Generation

  • Purple X white flowers

F1 Generation (hybrids)

  • All plants had purple flowers

F2 Generation

  • 3:1 ratio of purple to white

Allele

  • Multiple forms of the same gene
  • There is dominant and recessive
  • For every gene you can have 2 alleles
  • A recessive allele will only produce a phenotype if there is no dominant allele present
  • Need 2 copies of recessive allele in order to have the trait that it codes for

Dominant allele

  • Expressed when 2 different alleles or 2 dominant alleles are present (upper case letter = A)

Recessive allele

  • Only expressed when 2 copies are present

Homozygous

  • Same 2 alleles

Heterozygous

  • 2 Different alleles

Mendel's Laws

  • So important to allow us to tell what dominant and what's recessive

Law of segregation

  • Segregates and divides when cell replicates

Recessive

  • Not expressed when the dominant form of the trait is present

Dominant

  • Expressed form of the trait when present (even if its just one)

Blood Types

  • Type O is recessive
  • Type A and B is dominant
  • When A and B allele are together, they are codominant to create type AB

Expression of traits is affected by cellular interactions and environmental factors

  • DNA can't explain all inherited traits
  • Traits passed between generation are not decided only by DNA but can be brought about by other materials in cells

Intelligence is a combination of genetics and environment as well as many other factors