Chapter 4 Lesson 2 Modeling Inheritance Learning Objective

Chapter 4 Lesson 2 Modeling Inheritance

Learning Objective: l Using your family history to predict genetic outcomes with phenotypes.

Modeling Inheritance l Two tools can be used to identify and predict traits among genetically related individuals. • Punnett square – using family histories to • predict genotypes and phenotypes. Pedigree – Creating a map using family histories to predict phenotypes.

One more thing about Punnetts l l Human Gender XX = girl XY = boy You ALWAYS have a 50% chance of having a boy or girl EVERY time. X XX XX Y XY XY

Pedigrees l l l A pedigree shows genetic traits that were inherited by members of a family. Pedigrees focus more on phenotypes. They are also used with Punnett Squares to determine genotypes.

Pedigree chart 1 2 Normal Affected Female 3 9 10 4 11 5 6 7 12 8 13 Male Married 14 Children

Pedigrees to evaluate l Go to page 201 and do problems #7 - 9 l #7 = Not affected = dd = C l #8 = affected = Dd = B l #9 = not affected = dd = C

Draw a pedigree l One couple has a son and a daughter with normal pigmentation. Another couple has one son and two daughters with normal pigmentation. The daughter of the first couple has three children with the son of the second couple. Their son and one daughter have albinism; their daughter has normal pigmentation.

Answer l Albino Female l Male 1 st couple 1 2 6 l 2 nd couple 3 7 8 4 5 Is albinism, recessive or dominant? It is recessive. What must the genotype be of #2 and #3? (hint: make a Punnett Sq. )

Answer l l Both parents must be Aa. Not all their children are albino. A a A AA Aa aa

Learning Objective – Part 2 l l By chance, Mendel studied traits only influenced by one gene with two alleles. However, we know that some inherited traits have There are more complex patterns.

Incomplete Dominance l Incomplete dominance produces a THIRD phenotype that is a blend of parents phenotype. R = red flowers W = white flowers Red x white = 100% pink R R W RW RW

Codominance l l When BOTH alleles can be observed in the phenotype. Black horses (BB) are codominant to white horses (WW). The heterozygous horses (BW) is an appaloosa horse. B B W BW BW

Codominance continued l Blood types are unique because they are an example of: • Codominance: A and B are both dominant. AND • Multiple Alleles: There are three different alleles.

Multiple Alleles l l l Some genes only have two alleles, like in Mendel’s experiments. However, there are genes that have more then two alleles. But remember you can still only inherit two of the alleles. One from each parent.

Multiple Alleles continued l l l In a Labrador retriever, coat color is determined by one gene with 4 alleles. Black is dominant to chocolate = B or b. Yellow is recessive epitstatic = E (when present, it blocks the black and chocolate alleles) Phenotype Possible genotypes Black BBEE, Bd. EE, BBEe, Bb. Ee Chocolate bb. EE bb. Ee Yellow BBee Bbee bbee

Sex-linked l l Because the Y chromosome is shorter than the X chromosome it has fewer genes. Therefore if you are a boy you only get one copy of these genes. So you get what your Mom gives you.

Sex-linked continued l Examples in humans include: • • Colorblindness Hemophilia

Polygenic Inheritance l l l When multiple genes determine the phenotype. Many phenotypes are possible Examples in humans include: • Height • Weight • Skin color

Polygenic - Skin color l l l There may be 100 different genes involved and many mutations. Melanin is a pigment responsible for skin color and is a natural sunblock. Lighter skin allows for more absorption of UV rays from sunlight. This is important for making vitamin C.

Polygenic - Skin color

Polygenic - Skin color l The long standing, but unproven hypothesis is that. . . • If you lived near the equator you needed • darker skin to protect you from the intense UV rays. . . If you lived farther north you needed lighter skin to help you get more UV rays because there is less sunlight.

Genes and the Environment l Environment can affect an organisms phenotype. • Genes effect heart disease, but so do diet and • • exercise. Genes affect skin color, so does exposure to sunlight. Go to page 189 and write down, on the left side of your notebook, two more examples of how the environment can affect genes.

Learning Objective To learn about different types of genetic disorders.

Genetic Disorders l l If a change occurs in a gene, the organism with the mutation may not be able to function as it should. An inherited mutation can result in a phenotype called a genetic disorder.

Sickle Cell Anemia l l This disease affects millions of people world wide. About 2 million Americans have the sickle cell trait. About 1 in 12 are African Americans.

Sickle Cell Continued

T-Boz l Many people came to know more about SCD through the efforts of Tionne “T-Boz” Watkins of the R&B group, TLC. Many people with SCD grow up knowing that this disease could greatly impact their life, but at 35, T-Boz is going strong and is an inspiration to many. Not only did she sing and dance her way to stardom with the pop group TLC, she gave birth to a child at 30. “Everything I ever wanted to do, I did. I'm all for taking over the disease instead of letting it take over me. "