Human Inheritance Human Inheritance Mrs. Wharton’ Science Class

Height and skin color Some human traits are controlled by many genes Some human traits are controlled by many genes There is an enormous variety of phenotypes for height for example and skin color ranges from nearly white to almost black There is an enormous variety of phenotypes for height for example and skin color ranges from nearly white to almost black

Multiple Alleles Human traits that are controlled by a single gene that has more than two alleles (three or more forms of a gene that codes for a single trait) Human traits that are controlled by a single gene that has more than two alleles (three or more forms of a gene that codes for a single trait) Blood type is an example Blood type is an example

Sex chromosomes One of 23 pairs of chromosomes in each body cell One of 23 pairs of chromosomes in each body cell Carries genes that determine whether a person male or female. Carries genes that determine whether a person male or female. Also may determine other traits Also may determine other traits Males XY Female XX

Sex Linked Genes The X or Y chromosomes that determines your gender The X or Y chromosomes that determines your gender Traits controlled by sex linked genes are called sex linked traits Traits controlled by sex linked genes are called sex linked traits Because males have only one X chromosome they are more likely to get a sex linked trait controlled by a recessive allele. Because males have only one X chromosome they are more likely to get a sex linked trait controlled by a recessive allele.

Sex Linked Genes Example: Colorblindness Example: Colorblindness Carrier- a person who has one recessive allele for a trait and one dominant. Carrier- a person who has one recessive allele for a trait and one dominant. Although a carrier does not have the trait, that carrier can pass the recessive allele to their offspring. Although a carrier does not have the trait, that carrier can pass the recessive allele to their offspring. In sex linked genes only females can be carriers In sex linked genes only females can be carriers

Effects of the environment Many of a person’s characteristics are determined by an interaction between genes and the environment Many of a person’s characteristics are determined by an interaction between genes and the environment Several genes determine a person’s height however environment also influences a person’s height (A poor diet can prevent a person from growing as tall as might be possible). Several genes determine a person’s height however environment also influences a person’s height (A poor diet can prevent a person from growing as tall as might be possible).