Genes, chromosomes, DNA, and genome

• LO 3.1.A Explain how genes, chromosomes, DNA,

and genomes all relate to one another.

• LO 3.1.B Explain why the study of epigenetics

offers an important avenue for understanding the

genetic components of thought and behavior.

The Human Genome (1 of 8)

• In general, behavioral geneticists study our

differences, such as those originating in heredity.

• Researchers attempt to tease apart the relative

contributions of:

– heredity

– environment

• They adopt a nature and nurture approach in their

investigations.

The Human Genome (2 of 8)

• Genes, the basic units of heredity, are located on

chromosomes, which consist of strands of DNA.

• Each sperm cell and each egg cell (ovum)

contains 23 chromosomes.

• At conception, the fertilized egg and all the body

cells that eventually develop from it (except for

sperm cells and ova) contain:

– 46 chromosomes

– arranged in 23 pairs

The Human Genome (3 of 8)

• Our genes, together with noncoding DNA, make

up the human genome.

– Many genes contribute directly to a particular trait.

– Others work indirectly by switching other genes on or

off.

– Many genes are inherited in the same form by

everyone.

– Others vary, contributing to our individuality.

The Human Genome (4 of 8)

• Most human traits depend on more than one gene

pair.

• This makes tracking down the genetic

contributions to a trait extremely difficult.

The Human Genome (5 of 8)

• However, advances in technology now permit

scientists to carry out:

– genome-wide association studies

 examining variations in many DNA elements at once

– whole-genome sequencing

 examines the entire 3 billion base pairs of DNA

• The researchers start by looking for DNA

differences called genetic markers.

The Human Genome (6 of 8)

• Locating a gene does not automatically tell us:

– what it does

– how it does it

– how multiple genes interact and influence behavior

• Usually, locating a gene is just the first small step

in understanding exactly what it does and how it

works.