Modern Genetics

Chp 4 Section 1

Notes

Some human traits are controlled by single genes with two alleles, and others by single genes with multiple alleles. Still other traits are controlled by many genes that act together.

Multiple alleles - three or more forms of a gene for a single trait.

Sex chromosomes are one of 23 pairs of chromosomes in each body cell.

Sex chromosomes carry genes that determine whether a person is male or female as well as genes that determine other traits.

XX = girls

XY = boy

Sex linked genes are genes that are passed on the X and Y chromosomes.

Males are more likely to receive recessive sex linked traits.

Carrier - a person that has one recessive allele for a trait and one dominant allele.

Many of a person's characteristics are determined by an interaction between genes and the environment.