Complex Patterns of Inheritance Height in Humans Height in pea plants is controlled by one of two alleles; the allele for a tall plant is the dominant allele, while the allele for a short plant is the ecessive one. What about people? Are the factors that determine height more complicated in humans? Section 11-3 Interest Grabber Go to Section:

Complex Patterns of Inheritance 1. Make a list of 10 adults whom you know. Next to the name of each adult, write his or her approximate height in feet and inches. 2. What can you observe about the heights of the ten people? 3. Do you think height in humans is controlled by 2 alleles, as it is in pea plants? Explain your answer. Section 11-3 Go to Section:

Complex Patterns of Inheritance 11–3Exploring Mendelian Genetics A.Independent Assortment 1.The Two-Factor Cross: F 1 2.The Two-Factor Cross: F 2 B.A Summary of Mendel’s Principles C.Beyond Dominant and Recessive Alleles 1.Incomplete Dominance 2.Codominance 3.Multiple Alleles 4.Polygenic Traits D.Applying Mendel’s Principles Section 11-3 Section Outline Go to Section:

Complex Patterns of Inheritance Mendel’s Principles 1. Inheritance of traits is determined by genes that are passed from parents to offspring. 2. When two or more forms of a gene exist they may be dominant or recessive 3. In sexually reproducing organisms, genes are segregated during gamete formation and a new individual receives a set from each parent. 4. Alleles for different genes usually segregate independently.

Complex Patterns of Inheritance KEY CONCEPT Phenotype is affected by many different factors.

Complex Patterns of Inheritance Genetics can be affected by 5 other different heredity patterns. 1.Incomplete Dominance 2.Codominance 3.Polygenic Traits (Multiple Genes) 4.Environmental Influences 5.Sex linked traits

Complex Patterns of Inheritance Other Dominance Possibilities: What is incomplete dominance? Occurs when one allele is not completely dominant over another. Example: Mixing of colors in flowers. What is Codominance? Similar to incomplete, occurs when both alleles contribute to the phenotype. Example: Blending of fur color.

Complex Patterns of Inheritance Phenotype can depend on interactions of alleles. In incomplete dominance, neither allele is completely dominant nor completely recessive. –Heterozygous phenotype is intermediate between the two homozygous phenotypes –Homozygous parental phenotypes not seen in F 1 offspring

Complex patterns of inheritance Section 11-3 Figure Incomplete Dominance in Four O’Clock Flowers Go to Section:

Complex patterns of inheritance Section 11-3 Figure Incomplete Dominance in Four O’Clock Flowers Go to Section:

Complex Patterns of Inheritance Incomplete Dominance cross between red- flowered (RR) and white-flowered (WW) plants consists of pink-colored flowers (RW). What happens if you breed the pink flowers? neither allele is completely dominant so creates a BLEND

Complex Patterns of Inheritance Codominant alleles will both be completely expressed. –Codominant alleles are neither dominant nor recessive. –The ABO blood types result from codominant alleles. Many genes have more than two alleles.

Complex Patterns of Inheritance 2. Codominance both alleles expressed in the phenotype – NOT blended.

Complex Patterns of Inheritance CBCB CBCB CWCW CWCW CBCWCBCW CBCWCBCW CBCWCBCW CBCWCBCW CODOMINANCE In Chickens Speckled NOT grey!

Complex Patterns of Inheritance

Checkpoint What is the difference between incomplete dominance and codominance? If a A is codominant with B and O is recessive to both, what blood types could the offspring be for a heterozygous blood type A crossed with a heterozygous blood type B? What is the antigen attached to RBCs for type A blood? Type B blood? Type O Blood? 16 ANY QUESTIONS?

Complex Patterns of Inheritance What are multiple alleles? Genes that have more than two alleles for a trait. Example: Blood type in humans What are polygenic traits? Traits that are controlled by two or more genes. Example: Skin color in humans.

Complex Patterns of Inheritance Many genes may interact to produce one trait. Polygenic traits are produced by two or more genes. Order of dominance: brown > green > blue.

Complex Patterns of Inheritance Multiple Alleles Genes with more than two alleles This does not mean that an individual can have more than two alleles. It only means that more than two possible alleles exist in a population. One of the best-known examples is blood type in humans.

Complex Patterns of Inheritance Human Blood Types 3 blood type alleles gene: –A = makes A surface protein/or antigen –B = makes B surface protein/or antigen –O doesn’t make either. A and B alleles are codominant to each other & both are dominant over recessive O allele. 20

Complex Patterns of Inheritance Antigens: Proteins produced on the blood cells. Antibodies are produced in the blood plasma against these A and B antigens, and continue to be produced throughout a person’s life. A person normally produces antibodies against the antigens that are not present on his or her red blood cells. For example, a person with antigen A on his red blood cells will produce anti-B antibodies; a person with antigen B will produce anti-A antibodies; a person with neither A or B antigens will produce both anti-A and anti- B antibodies; and, a person with both antigens A and B will not produce these antibodies. If blood cells are mixed with antibodies the cells will clump together. This is called agglutination. This is why it can be very dangerous if you receive the wrong blood type in a transfusion.

Complex Patterns of Inheritance Blood typing Blood typing is performed by mixing a small sample of blood with anti-A or anti-B antibodies (called antiserum), and the presence or absence of clumping is determined for each type of antiserum used. If clumping occurs with only anti-A serum, then the blood type is A. If clumping occurs only with anti-B serum, then the blood type is B. Clumping with both antiserums indicates that the blood type is AB. No clumping with either serum indicates that you have blood type O.

Complex Patterns of Inheritance Human Blood Types What antibodies would be made by a person with type A blood? Type B blood? Type AB blood? Type O blood? What is antisera? Which type is the universal donor? Which type is the universal receiver? Is your blood type a genotype or phenotype?

Complex Patterns of Inheritance Polygenic Traits Traits controlled by interaction of two or more genes Polygenic =“many genes.” Ex: Hair color, eye color, skin color all the result of several genes

Complex Patterns of Inheritance Labrador retrievers can be black, brown, or yellow. Two genes control this. One for producing color (Black over brown) and one for depositing the color in the fur (homozygous recessive = yellow).

Complex Patterns of Inheritance Skin and eye color are polygenic traits in humans. At least 7 for eye color.

Complex Patterns of Inheritance

Environmental Influences: Phenotype can depend on conditions in the environment. Conditions can cause a gene to shut down or turn on in coat color. This allows the animal to blend in with its background.

Complex Patterns of Inheritance The environment interacts with genotype. Height is an example of a phenotype strongly affected by the environment. The sex of sea turtles depends on both genes and the environment Phenotype is a combination of genotype and environment.

Complex Patterns of Inheritance An epistatic gene can interfere with other genes.

Complex Patterns of Inheritance 31 ENVIRONMENT INFLUENCES GENETIC TRAITS Environment factors like diet, exercise, exposure to toxic agents, or medications can all influence our genes and traits. I got the “fat” gene.

Complex patterns of inheritance concluded that which is called the Gregor Mendel Law of Dominance Law of Segregation Pea plants “Factors” determine traits Some alleles are dominant, and some alleles are recessive Alleles are separated during gamete formation Section 11-3 Concept Map Go to Section: experimented with

Complex Patterns of Inheritance Linked Genes Mendel concluded that traits are assorted independently, but some traits are Linked Linked genes: Genes usually inherited together because on same chromosome

Complex Patterns of Inheritance Linked Genes Ex: Blue eyes, white fur tigers

Complex Patterns of Inheritance Genes on the sex chromosomes are linked. i. Y- Linked genes Y has few genes – mostly gender determining (boy or girl). –Y only in males so these genes only affect males. ii. X-linked genes Many genes on X chromosome –Affects mostly males because only one copy of X –Male copy of X from MOM (Dad gave Y to son) –Females less affected because two copies of X = have to inherit trait from both parents. –Heterozygous females are carriers for sex linked traits. –EX: baldness, colorblindness Sex-Linked Genes

Complex Patterns of Inheritance Baldness is X-linked recessive. Grandpa bald = X b YXGrandma = X B X B Daughter = X B X b marries normal Male her sons – 50% X B (normal) 50% X b (bald) Sex-Linked Baldness This is why men should look their mom’s dad for probability of baldness. But beware grandma could be a carrier too!

Complex Patterns of Inheritance Crossing Over affects linked genes. Crossing over – exchanging DNA during prophase Genes closer on the chromosome LESS likely to be separated by crossing over.

Complex Patterns of Inheritance Chromosome Mapping The farther apart genes are, the higher probability that they will be separated by crossing over. –Scientists conduct experiments to determine how frequently genes of a particular trait are separated from one another. Chromosome map - diagram of the linear sequence of genes on a chromosome. Two genes that are separated by crossing-over 1 percent of the time are considered to be one map unit apart.

Complex Patterns of Inheritance Summary of Mendel’s Principles 1.Traits come from your inherited genes. 2.Genes may have more than one allele and some are dominant. 3.Your two copies of each gene (one from each parent) are segregated or separated when gametes form. 4.Alleles for different genes usually segregate independently of one another.

Complex Patterns of Inheritance Beyond Mendel – Other Patterns of Inheritance 1.Most genes have more than two alleles. 2.Some alleles are neither dominant nor recessive (codominance & incomplete dominance) 3.many traits are controlled by multiple genes. 4.Some genes are linked and do not segregate independently - on the same chromosome so inherited together.

Complex Patterns of Inheritance Checkpoint What is a linked gene? Why do X-linked traits affect males more than females? How does crossing over affect linked genes? If the sequence of genes on a chromosome are X, Y, Z, D; which two genes are most likely to be unlinked by crossing over? ANY QUESTIONS?