Mutations inheritance and genetic screening

Key Definition Mutations are random changes in the DNA base sequence that arise during replication or from mutagens.

The three types are substitution, insertion and deletion.

Substitution affects only one codon, while insertion and deletion cause a frame shift that disrupts the entire downstream protein.

Many mutations have no observable effect because the genetic code is degenerate or the change occurs in non-coding DNA.

Some mutations cause genetic disorders, and a small number lead to cancer.

Inheritance

Inheritance involves alleles passing from parent to offspring through gametes.

Genotypes determine phenotypes through interactions between dominant, recessive, and codominant alleles.

Pedigree diagrams help track inheritance patterns across generations and indicate whether a trait is dominant or recessive.

Sex linkage on the X chromosome explains why males express recessive conditions like red-green colour blindness more frequently than females.

Cystic Fibrosis

Cystic fibrosis is caused by a recessive CFTR mutation that produces thick mucus, affecting the gaseous exchange, digestive and reproductive systems.

Genetic Screening

Genetic screening through carrier testing, PGD, amniocentesis and CVS helps identify risk, but raises ethical, religious, moral and social concerns that require balanced judgement.