3.4 Inheritance

Recessive

Sex linked genes

Genetic diseases

Colour blindness

Haemophilia

Genes found on sex chromosomes

Dominant

Cystic fibrosis

Huntington's

Mendel's laws of inheritance

Sex-Linked Inheritance

This theory describes inheritance patterns that are determined by genes on the sex chromosomes, such as X-linked and Y-linked traits

Gene Expression

This theory describes the processes by which genetic information is converted into functional proteins, including transcription, RNA processing, translation, and post-translational modifications.

  1. Law of Segregation: When gametes form, alleles are separated so that each gamete carries only one allele for each gene
  1. Law of Independent Assortment: The segregation of alleles for one gene occurs independently to that of any other gene
  1. Principle of Dominance: Recessive alleles will be masked by dominant alleles

Dominant allele is expressed in heterozygote

Recessive allele is masked in heterozygote

Co-Dominant

Both alleles are equally expressed in the phenotype

Heterozygotes have a distinct phenotype

ABO blood system

Punnett grid

Autosomal Recessive

Cystic fibrosis

Autosomal Dominant

Huntington’s disease

Autosomal Codominant

Sickle cell anemia

caused by a mutated HBB gene (chromosome 11)

caused by a mutated HTT gene (chromosome 4)

caused by a mutated CFTR gene (chromosome 7)

Cancer

Monohybrid Crosses

Pedigree diagram

If both parents are affected by a trait and any offspring is
not, the trait must be dominant (parents must be heterozygous)

If neither parents is affected by a trait but any offspring is,
the trait must be recessive (parents must be heterozygous)

Autosomal codominant inheritance refers to two alleles of an autosomal gene where each allele contributes to the phenotype.