Just Genes - Module 2 - Inheritance and Pedigrees

DNA

The genetic material that controls the characteristics of organisms by coding for different proteins.

Inheritance

The passing of traits from one generation to the next, involving DNA and genes.

How are traits passed down from parent to offspring?

Genetic information is passed from both parents to offspring, with each parent contributing one allele for each trait.

Gene

A segment of DNA that codes for a specific protein

Allele

Different versions/variations of the same gene. Located at the same gene loci on homologous chromosomes

Chromosome

Small structures composed of DNA and proteins that carries genetic information

Genotype

The genetic make-up of an organism

• The combination of the 2 alleles inherited from each parent

Phenotype

The physical expression/observable outcomes of a trait

Ex. Ginger hair

Phenotypes are a result of…

• The genotype

• The environment

Dominant

The allele that will always be expressed whenever it is present.

Only requires one copy to be expressed

Will always mask the presence of a recessive allele

Recessive

The allele that is only expressed if the dominant allele is not present

Requires 2 copies to be expressed

Is always masked by the presence of a dominant allele

Diploid

Describes 2 sets of chromosomes within a cell

• Somatic cells

• One chromosome inherited from father and one chromosome inherited from mother

Homozygous

When the 2 alleles inherited from each parent are the same

(Homozygous dominant or Homozygous recessive)

Ex. RR or rr

Heterozygous

When the 2 alleles inherited from each parent are not the same

Ex Rr

Pedigree

A chart/family tree that shows the inheritance of a trait or health condition through generations of a family

Autosomal Dominant Traits in Pedigrees

Trait does not skip generations +

• If both parents are affected, the offspring may be unaffected

• If neither parent is affected, the offspring must be unaffected

• If an offspring is affected, there must be an affected parent

Autosomal Recessive Traits in Pedigrees

Trait skips generations +

• If both parents are affected, the offspring must be affected

• If neither parent is affected, the offspring may be unaffected

• If an offspring is affected, there may be an affected parent

• The trait can skip a generation

Mode of Inheritance

Whether a trait is recessive or dominant