Take notes on the following slides on your foldable. Patterns of Heredity Take notes on the following slides on your foldable.

White or Red Offspring, Right? Patterns of Heredity Based on what we have learned, what offspring phenotypes would you expect from a cross between these two horses? White or Red Offspring, Right? Not necessarily… White Horse Red Horse Strawberry Roan

Patterns of heredity How did this happen? Most of the time, traits display more complex patterns of heredity than the simple dominant-recessive pattern What is the simple dominant-recessive pattern known as? Mendelian Genetics Let’s look at Mendelian Genetics one more time…and then let’s look at the other patterns of inheritance!

Mendelian Genetics Again, Mendelian genetics shows a pattern where a clear dominant trait masks a recessive trait. Cleft chins, dimples, and freckles are all examples of traits that follow Mendelian patterns.

Mendelian Genetics D d Genotype: 1:2:1 Phenotype: 3:1 D DD Dd Dd dd d Punnett Square Dimples (D) are dominant over no dimples (d) Cross two parents that are heterozygous for dimples. Complete the ratios for genotype and phenotype. D d Genotype: 1:2:1 Phenotype: 3:1 D DD Dd Dd dd d

Incomplete Dominance Occurs when the heterozygous allele combination results in a blend of the dominant and recessive trait. Remember the horses…

Incomplete Dominance Straight, wavy and curly hair is one example of incomplete dominance. Another example is carnation color. If the red and white alleles are both present, the resulting offspring will be pink (a blend of red and white).

Incomplete Dominance R r RR Rr R r Rr rr Punnett Square Red flower color (R) is incompletely dominant over white flower color (r) in carnations. Cross two parents that are heterozygous for flower color. Complete the ratios for genotype and phenotype. R r RR Rr R r Rr rr Genotype: 1:2:1 Phenotype:1:2:1

Co-dominance Occurs when both alleles are expressed when the heterozygous allele combination is present. Not a Blend!! Human blood is an example of co-dominance. A and B alleles are both dominant over the recessive allele, O. If both the A and B alleles are present, both will be expressed.

Co-dominance IA IB Genotype: 1:2:1 Phenotype:1:2:1 IA IAIA IAIB IAIB Punnett Square Cross two parents that are co-dominant for blood type. Give the ratios for genotype and phenotype. IA IB Genotype: 1:2:1 Phenotype:1:2:1 IA IAIA IAIB IAIB IBIB IB

Sex-linked (X) Traits XRY XrY XRXR XRXr XrXr Occurs when a trait is passed on from generation to generation on one of the sex- determining chromosomes (X, Y) The dominant and recessive representative alleles are written as superscripts on the X and Y. XRY XrY Only females can be carriers of X-Linked traits. What is a carrier? Why can’t males be carriers of X-Linked traits? XRXR XRXr XrXr

Sex-linked Traits XB Xb XB XBXB XBXb y XBy Xby Punnett Square Cross a female carrier for colorblindness with a normal male. List the possible phenotypes. B – not affected b - affected XB Xb XB XBXB XBXb Possible Phenotypes: Normal Female Carrier Female Normal Male Colorblind Male y XBy Xby

Polygenic Traits So POLY GENIC means MANY GENES!!! What does Poly mean? Many Genic looks like? Genes! Occurs when several genes influence a trait The genes may be on the same chromosome or on different chromosomes So POLY GENIC means MANY GENES!!!

Polygenic Traits Eye color, height, weight, and hair and skin color are all polygenic traits.

Multiple Alleles i i How many possible genotypes for blood? 6 How many possible phenotypes? 4 Genes with three or more alleles are said to have multiple alleles. Human blood has 3 alleles: A, B, and O. i i

Multiple Alleles IA IO IB IAIB IBIO IAIO IOIO IO Punnet Square Cross a parent with an IAIO genotype with a parent that has the genotype IBIO for blood. List the possible phenotypes. IA IO Possible Phenotypes: Type AB Blood Type A Blood Type B Blood Type O Blood IB IAIB IBIO IAIO IOIO IO