Some elements exist naturally as molecules. For example, hydrogen and oxygen exist as two-atom molecules.

TLS Online TPP Program

#Id: 2237

#Section 3: Genetics, Cellular and Molecular Biology

Neutral selection (Ka/Ks = 1)

Positive selection (Ka/Ks > 1)

Purifying selection (Ka/Ks < 1)

TLS Online TPP Program

#Id: 8968

#Section 3: Genetics, Cellular and Molecular Biology

TLS Online TPP Program

#Id: 8969

#Section 3: Genetics, Cellular and Molecular Biology

The amount of genetic variation by examining phenotypic variation was difficult because many traits, a complex interaction of many genes and environmental factors determines the phenotype

TLS Online TPP Program

#Id: 2240

#Section 3: Genetics, Cellular and Molecular Biology

The neutral-mutation hypothesis proposes that most molecular variation is neutral with regard to natural selection and is shaped largely by mutation and genetic drift.

TLS Online TPP Program

#Id: 8971

#Section 3: Genetics, Cellular and Molecular Biology

The Death of a Gene

When a gene is duplicated, the new copy is often dead-on arrival (lacks the regulatory elements). 

TLS Online TPP Program

#Id: 2244

#Section 3: Genetics, Cellular and Molecular Biology

When a nonfunctioning duplicate is fixed in the population, or a functioning gene becomes nonfunctional, the result is a genetic skeleton called a pseudogene.

Deletions are important in shaping the genome.