For Questions 1-6, match the labels to the parts of the pedigree chart shown below. Some of the labels may be used more than once.

            

1. A person who expresses the trait 2. A male 3. A person who does not express the trait 4. A marriage 5. A female 6. A connection between parents and offspring

BellRinger◦ Pedigree

Objectives◦ Conduct a chi-squared analysis to determine the

validity of a hypothesis◦ Recognize the inheritance patterns of recessive,

dominant, and sex-linked traits in pedigrees◦

Homework◦ Chp 15 notes (sec 4&5)◦ Chp 14 & 15 quiz on Friday

The actual results of an experiment are unlikely to match the expected results precisely. ◦ But how great a variance is significant?

One way to decide is to use the chi-square (x2) test.

Analytical tool tests the validity of a null hypothesis◦ there is no statistically significant difference between

the observed results of your experiment and the expected results.

little difference between the observed results and the expected results = very low chi-square value = your hypothesis is supported.

The formula for chi-square is:X2 = the sum of

where:o = observed number of individualse = expected number of individuals

This value is then compared to a value on the critical values table to determine if your hypothesis accepted or rejected

Degrees of freedom. ◦ number is one less than the total number of classes of

offspring in a cross. In a monohybrid cross there are two classes of offspring

(red eyes and sepia eyes) = one degree of freedom. In a dihybrid cross, there are four possible classes of

offspring = three degrees of freedom.

Probability. ◦ probability value (p) = probability that a deviation as

great as or greater than each chi-square value would occur simply by chance. Biologists use 0.05 (5%)

Return to your online notebook and complete a report using the data you accumulated yesterday◦ There are questions that will prompt your thinking

for each section

Complete the optional quiz for extra credit

Submit online by 12 midnight Sunday

For Questions 1-6, match the labels to the parts of the pedigree chart shown below. Some of the labels may be used more than once.

            

1. A person who expresses the trait 2. A male 3. A person who does not express the trait 4. A marriage 5. A female 6. A connection between parents and offspring

Create a pedigree using the information below:

Dimples in the cheeks are inherited as a dominant trait on a gene.

Using the proper form and symbols, draw a pedigree chart, beginning with a dimpled father (Dd), and a nondimpled mother (dd).

Show four children of the expected types: boys, girls, dimples, and no dimples. Label your pedigree with phenotypes and genotypes.

Read the directions and work through the pedigrees on the handout

In pairs, write down 3-4 rules that apply to the recessive allele inheritance patterns and 3-4 rules that apply to dominant allele inheritance patterns

Share your results with another pair and pick out 2 rules-(one for dominant one for recessive) to share with the class

Recessive allele inheritance patterns1. Unaffected parents can have affected offspring2. The phenotype can skip a generation3. Individuals with no sign of the allele can be

carriers

Dominant allele inheritance patterns1. Affected offspring must have at least one affected

parent2. The phenotype appears in every generation without

skipping3. Two unaffected parents have normal offspring

The pedigree below traces the inheritance of alkaptonuria, a biochemical disorder. Affected individuals, indicated here by the colored circles and squares, are unable to metabolize a substance called alkapton, which colors the urine and stains body tissues. 1. Does alkaptonuria appear to be caused by a dominant

allele or by a recessive allele? 2. Fill in the genotypes of the individuals whose genotypes

can be deduced. 3. What genotypes are possible for each of the other

individuals?  

With a partner, you will construct a pedigree for a family with color-blindness◦ 3 generations

2 sets of grandparents in the first generation 1 grandmother is a carrier for the trait 1 grandfather (on the other side of the family) is

colorblind 8 people in the second generation (4 male, 4 female)

1 male and 1 female are married 6 people in the 3rd generation (half male, half female)

◦ Use the genotypes XBXB for a normal female, XBXb for a female carrier,

XbXb for a female who is colorblind XBY for a normal male, XbY for a male who is

colorblind

Recessive allele inheritance patterns1. Unaffected parents can have affected offspring2. The phenotype can skip a generation3. Individuals with no sign of the allele can be

carriers

Dominant allele inheritance patterns1. Affected offspring must have at least one affected

parent2. The phenotype appears in every generation without

skipping3. Two unaffected parents have normal offspring