recessive

What causes PKU? How is it treated? People (including infants) with PKU need to follow a diet that limits foods with phenylalanine. This includes infants. Pregnant woman with PKU need to strictly follow the low-phenylalanine diet throughout pregnancy to ensure the healthy development of infant. PKU is caused by mutations in the gene that helps make an enzyme to break down phenylalanine in the body.

Recessive? Dominant? Codominant? Sickle-Cell Disease Recessive? Dominant? Codominant? Sickle-cell disease affects one out of 400 African-Americans The disease is caused by the substitution of a single amino acid in the hemoglobin protein in red blood cells Symptoms include physical weakness, pain, organ damage, and even paralysis Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Sickle Cell Anemia Sickle cell disease is more common in certain ethnic groups, including: People of African descent, including African-Americans (among whom 1 in 12 carries a sickle cell gene) Hispanic-Americans from Central and South America. People of Middle Eastern, Asian, Indian, and Mediterranean descent.

Distribution of.... Malaria Sickle Cell Gene

polydactyly Frequency of Dominant Alleles Dominant alleles are not necessarily more common in populations than recessive alleles For example, one baby out of 400 in the United States is born with extra fingers or toes                                Photos: eHand.com (the electronic textbook for hand surgery) Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Inheritance of Sex-Linked Genes The sex chromosomes have genes for many characters unrelated to sex A gene located on either sex chromosome is called a sex-linked gene In humans, sex-linked usually refers to a gene on the larger X chromosome Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Sex-linked genes follow specific patterns of inheritance For a recessive sex-linked trait to be expressed A female needs two copies of the allele A male needs only one copy of the allele Sex-linked recessive disorders are much more common in males than in females Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Write down this example in your notes. Fill in the last box of the Punnett square.

Fig. 26.14b Sex-linked recessive

Color Blindness some forms are Sex-linked

Hemophilia Sex-linked recessive pingrybiology.pbwiki.com www.kelleycom.com Hemophilia is a rare, inherited bleeding disorder in which blood doesn’t clot normally. People with hemophilia may bleed for a longer time than others after an injury. Individuals with the disorder may bleed internally, especially in knees, ankles, and elbows. This bleeding can damage organs or tissues and, sometimes, be fatal.

Click here to view Sex-Linked Video Fig. 15-5 Click here to view Sex-Linked Video X Figure 15.5 Human sex chromosomes Y

Now do problems 13 and 14 in your 2-page genetics problems packet Now do problems 13 and 14 in your 2-page genetics problems packet. They are sex-linked problems.

The Romanovs Photo: www.freewebs.com/georgeromanov/Foto%201913.jpg

Hemophilia & The Royal Family The European Royal Family                                                                                                                                                                         back Click here to watch pedigree video

Time for Harry Potter Pedigrees

Time for Genetic Disorders Crosses (shade out the boxes of each 4-square Punnett that are not needed as you work each problem).