Genetic Disorders and Variations on Mendel's Principles
USE THIS POWERPOINT TO ANSWER QUESTIONSON PAGES 4-7 OF THE MENDELIAN GENETICS PACKET GENE LOCI P a B P a b GENOTYPE: PHENOTYPE:
Autosomal Recessive Disorders7. Connection: Many inherited disorders in humans are controlled by a single geneMost such disorders are caused byautosomal recessive alleles.Examples include and cystic fibrosis and Tay-Sachs Disease Watch a simple explanation of CF here
Practice Problem Practice Problem: A couple is planning on having children and they would like to know what is the chance that they will have a child that is deaf. The ability to hear is dominant and deafness is recessive. Both parents are heterozygous dominant. Fill in the punnet square below and the genotypic and phenotypic results.
Practice Problem Practice Problem: A couple is planning on having children and they would like to know what is the chance that they will have a child that is deaf. The ability to hear is dominant and deafness is recessive. Both parents are heterozygous dominant. Fill in the punnett square below and the genotypic and phenotypic results.
#8: Connection 8. Connection: Fetal testing can spot many inherited disorders early in pregnancy Two types of tests are amniocentesis and chorionic villus sampling
Chorionic villi sampling Chorionic villus sampling (CVS) is the removal of a small piece of tissue (chorionic villi) from the uterus during early pregnancy to screen the baby for genetic defects.
Interested in learning more about genetic disorders?Check out the Utah Genetics Disorders Library here.
Variations on Mendel 9. The relationship of genotype to phenotype is rarely simple. Mendel’s principles are valid for all sexually reproducing species. However, often the genotype does not dictate the phenotype in the simple way his principles describe.
Practice Problem Incomplete dominance results in intermediate phenotypes Practice Problem: A certain type of flower exhibits incomplete dominance. Flowers that are homozygous dominant are red, flowers that are homozygous recessive are white and heterozygous flowers are pink. Complete the punnet square below for a cross between two heterozygous flowers.
11. Codominance More than one dominant trait is present and both are expressed in their original form.
#12 Pleiotropy The ability of a single allele to have more than one distinguishable effect. For example the allele responsible for color pattern in Siamese cats.
http://www.thecitychicken.com/mainpagemarch24-2011c.jpgThe Frizzle Effect:an example of pleiotropy In 1936, researchers Walter Landauer andElizabeth Upham observed that chickens thatexpressed the dominant frizzle gene producedfeathers that curled outward rather than lying flatagainst their bodies (Figure 2). However, this wasnot the only phenotypic effect of this gene — alongwith producing defective feathers, the frizzle genecaused the fowl to have abnormal bodytemperatures, higher metabolic and blood flowrates, and greater digestive capacity.Furthermore, chickens who had this allele also laidfewer eggs than their wild-typecounterparts, further highlighting the pleiotropicnature of the frizzle gene . http://www.nature.com/scitable/resource action=showFullImageForTopic&imgSrc=/scitable/content/37535/poncho_MID
Pleiotropy in HumansMarfan Syndrome Marfan syndrome is a condition in which your bodys connective tissue is abnormal. Connective tissue helps support all parts of your body. It also helps control how your body grows and develops. Marfan syndrome most often affects the connective tissue of the heart and blood vessels, eyes, bones, lungs, and covering of the spinal cord. Because the condition affects many parts of http://www.marfan.net.au/images/human_body.jpg the body, it can cause many complications. Sometimes the complications are life threatening. Interested? Read more here.
13. A single characteristic may be influenced by many genes. This situation creates acontinuum of phenotypes, an example is height
Typical ‘Bell Curve’ for a polygenic traitSome scientists suggest this accounts for behavioral traitsNot completely predetermined, but associated with genes
High blood pressure is a polygenic trait. Food For Thought: What genes could combine to contribute to high blood pressure?
High blood pressure is a polygenic trait. The phenotype is an interaction between a persons weight (one or more obesity genes), cholesterol level (one or more genes controlling metabolism), kidney function (salt transporter genes), smoking (a tendency to addiction), and probably lots of others too. Each of the contributing genes can also have multiple alleles.
Environmental Effect on PhenotypeFood for Thought:What do you think is happening in this picture? Why do you think somephenotypes are effect by the environment? Can you think of other phenotypesthat are effected by the environment?
14. Meiosis is a process by which…Before watching the video or looking at your notes, see if you can answer thequestions on page 6 and 7 about meiosis.
STOP WHEN YOU GET TO:THE CHROMOSOMAL BASISOF INHERITANCE ON PAGE 7