Complex patterns of inheritance Section 12 2 Essential

Complex patterns of inheritance Section 12. 2

Essential Question • How can you use a parent's genetic information to determine the probability of offspring having certain genotypes and phenotypes?

Activating Strategy • • • Define homozygous. Define heterozygous. Define dominant. Define recessive. Define genotype. Define phenotype.

Incomplete dominance • Phenotype of heterozygous individuals is intermediate between those of the 2 homozygotes.

Incomplete Dominance example C RC R C RC W C WC W

Codominance • Phenotypes of both homozygotes produced in heterozygous individuals. (both alleles expressed equally).

Codominance Example RR RW RW WW

Time Out! 1’s do Incomplete Dominance & 2’s do Codominance

Multiple Alleles • An inheritance pattern in which traits are controlled by more than 2 alleles

Multiple Alleles example IA IA Ii IA Ii

Sex Determination • Humans have 23 pairs of chromosomes

Sex Determination • Of the 23 pairs of chromosomes in humans, 22 are autosomes (pairs that look alike) and 1 are sex chromosomes.

Sex Determination • A karyotype is a diagram of the chromosomes (arranged in order for study)

Sex Determination • Sex chromosomes are indicated by the letters X and Y • Females sex chromosomes are XX • Male sex chromosomes are XY • Who controls the sex of offspring? – Males (Sperm) • Why? – All female eggs carry X chromosome. Sperm carry X or Y

Sex-linked inheritance • Sex-linked traits: characteristics determined by genes on sex chromosomes • Can sex-linked traits be on the X or Y chromosome? – Yes • Which is more common? – X chromosome

Sex-linked inheritance • Alleles are written as superscripts for X and Y for sex linked traits • What does it look like? – XRXr or Xr. Y

Color Blindness • • C = normal c = color blind Male with color blindness = Xc. Y Female with color blindness = Xc. Xc

Color Blindness • Female carrier of color blindness = XCXc • Normal (non-carrier) = XCXC • Why can only females be carriers of X-linked traits? – Males only have one X-chromosome. If the trait is on the X chromosome they will be colorblind. • Can males or females pass on y-linked traits? – Only males

Time Out! 1’s do Multiple Alleles & 2’s do Sex-linked

Practice Hemophilia is a lethal recessive sex linked trait. It causes your blood to be unable to clot. So, if you fall and cut your chin open, the blood will keep spurting out of your chin! If Queen Victoria carries a recessive trait for hemophilia XHXh and marries Albert who has hemophilia Xh. Y. How many of their children will die from hemophilia?

Polygenic traits • Traits caused by more than one gene

Time Out! Complete your graphic organizer