Patterns of Inheritance sex linked traits

Review How many chromosomes do each of our cells have? 46 Do all of these chromosomes have the same function, or do they all serve a different purpose? They are different; each individual chromosome has specific proteins that control certain traits.

Chromosomes 46 chromosomes are found in each of our cells. 22 pairs of autosomes (body chromosomes) 1 pair of sex chromosomes (XX or XY) * Remember * Males and Females have two different sex chromosomes Males = XY Females = XX

Sex Chromosomes The X chromosome carries a variety of genes that are necessary for the development of both females and males. The Y chromosome mainly has genes that relate to the development of male characteristics.

Sex-Linked Traits So far, all of the traits that we have discussed are found on the autosomes. Any gene that is carried on either the X or Y chromosome in known as a sex-linked gene. Therefore, the trait that is shown due to this gene is called the sex-linked trait. Most sex-linked traits (or diseases) are carried on the X chromosome. Very few are carried on the Y chromosome.

Notation for sex-linked traits If the majority of sex-linked traits/diseases are carried on the X chromosome, who is more likely to be affected? Males or Females Since males have only one X chromosome, they are affected by recessive X-linked traits more often than females. This time we have to show the chromosomes. R = Red Eyes r = White Eyes XRXR = Red Eyes XRXr = Red Eyes XrXr = White Eyes XRY = Red Eyes XrY = White Eyes

Dominant or Recessive Sex-linked traits can still be dominant or recessive. XRXR = Homozygous Dominant XRXr = Heterozygous XrXr = Homozygous Recessive XRY = Dominant XrY = Recessive

Examples of Sex-Linked Traits Red-Green color blindness Insensitive to green and purplish-red ~ 8% of males in the U.S. have red-green color blindness

How is it passed on?

Are you color blind?