Reference no: EM132298851

Genetics Laboratory exercise - Fingerprint Ridge Count: an example of a polygenic trait

Introduction - In this exercise, you will explore a polygenic model of inheritance by examination of the trait 'total fingerprint ridge count' or TRC. Student fingerprint data will be collected and scored for type and ridge counts. The data from genetics lab classes will be pooled and made available on vUWS for analysis.

Objectives - Upon completion of this investigation, you should be able to

1. Construct a chart of your own fingerprints,

2. Classify fingerprints into arches, loops, and whorls,

3. Determine the total ridge count for your full set of fingerprints (i.e. 10 fingers),

4. Construct a single histogram using the pooled (males plus females) data of total ridge counts (bins must be in increments of 20) see the support material on vUWS,

5. Discuss the characteristics of the polygenic inheritance model and why polygenic traits are more difficult to study than single-gene traits, and

6. Solve problems concerning TRC by using a four-gene model to explain the inheritance of human fingerprint total ridge counts.

Materials needed for each student for this investigation:

• semi-inkless fingerprint pad (to role fingertip in and load ridges with dye).
• sheet of plain white paper or use space reserved for fingerprints in lab book.
• hand lens, magnifying glass, or dissecting microscope or magnifying lamp.

Procedure -

1. Use the semi-inkless fingerprint pad provided to coat each finger (and thumb). Coat one finger at a time using a gentle rolling action so as to coat both left and right sides of the finger. This should be done in a single action and will be demonstrated for you.

2. To obtain a print (on paper) again roll your coated finger in the same single action as above. Make certain that you include any triradii on the outer edges of the finger by rolling the finger over the paper in one continuous motion.

3. Repeat this process, preparing a print of each of your 10 fingers.

4. Examine each print carefully; if a print is incomplete, prepare a new one. Use a hand lens, magnifying glass, or dissecting microscope etc to classify the pattern (e.g. arch, loop, or whorl) and to determine the ridge count for each print.

5. Record your fingerprint pattern data, total ridge count, and sex in Table 4 and in the XL spreadsheet, as directed by the lab supervisor. Note if you have an arch pattern your ridge count for that finger should be zero.

6. Use the pooled data set assigned to you (it will be assigned either by lab class or by surname - see vUWS) to answer the following questions and to construct a single histogram (combine the male and female data such that there is only one column for each bin) (see example in Figure 4 in this document and the exemplar provided on vUWS) in which frequencies are plotted against total ridge count (TRC). Remember to attach your histogram. Your bins must be in increments of 20. See instructions on vUWS for making histograms.

Questions -

Using the pooled data set issued to you calculate the average, median and mode values for the TRC of males, females and both male and female combined. Write the values in Table 2 below.

Table 2. Average, median and mode values for the TRCs for male, females and male and female combined. Answers must be correct to 2 decimal places.

	males	females	males & females
average TRC
median TRC
mode TRC

1. What is your TRC _______________ and how does your TRC compare to

a. The average for the data set (above, below or the same)?

b. The average for your sex?

2. How does the data set compare to the averages published by Holt (1968): 145 for males and 126 for females?

Questions 3-5 refer to the overall values or the male and female combined class values.

3. In what bin (see your histogram) did the average value occur in (e.g. bin 20 or 40 etc)?

4. In what bin (see your histogram) did the median value occur in (e.g. bin 20 or 40 etc)?

5. In what bin (see your histogram) did the mode value occur in (e.g. bin 20 or 40 etc.)?

Using the data set issued to you (XL sheet from vUWS) calculate the percentage frequency of occurrence for the three fingerprint patterns (arch, loop and whorl) for males, females and male and females combined. Enter the percentages in Table 3 below.

Table 3. Percentage frequency for the fingerprint patterns arches, loops and whorls. Values must be correct to 2 decimal places.

	males	females	males & females
arch %
loop %
whorl %

6. Was there a difference in the rank order of fingerprint patterns between the males and females? i.e. were the same patterns the most frequent and the least frequent in males and females?

7. If you had collected TRC data from more people, do you think the histogram for this larger sample of data would look different from the one you prepared? Explain.

8. Predict the TRC for each of the following individuals.

Genotype	Male	Female
AABBCCDD
AabbCcDd
AaBbCcDD
aaBbCCDd

9a. Write the genotypes of both parents (the parental cross) who are heterozygous for all four genes or loci (i.e. tetrahybrid cross).

b. Write the genotype of a child (from the cross above in Question 9a) who has the minimum number of active alleles possible.

c. What are the TRCs for the parents and their child above (assume that the child is a male)?

Parents:

Male Child:

d. Calculate the probability that these parents (above in 9a) would produce a child with a single active allele assuming independent assortment of the 4 loci. Show your calculations.

10. a. If an AaBbCcdd male mates with an AaBbCCDD female.

b. What is the minimum number of ridge-producing alleles possible in one of their children?

c. What would be the TRC for this child if it is a male?

d. What would be the TRC for this child if it is a female?

e. If this child is a male, will he have a higher or lower TRC than the parent with the lower ridge count?

f. What is the maximum number of ridge-producing alleles possible in a child of this couple?

g. If this child is a female, will she have a higher or lower TRC than the parent with the higher ridge count?

11. If an AaBBCcdd male mates with an AABbCcDd female,

a. What is the minimum number of active alleles possible in a child this couple could produce?

b. What would be the probability of producing a child with the minimum number of active alleles?

c. What would be the TRC for this child if it were male?

d. What would be the TRC for this child if it were female?

12. In solving some problems above, you made some predictions of TRCs based on the genotypes of the individuals involved. Suppose we could measure the TRCs for some people with those genotypes and found the actual values to be different from those predicted by your calculations. How would you explain these discrepancies (think about multifactorial inheritance -you could consult your textbook and look in the chapter that covers quantitative genetics)?

Attachment:- Assignment Files.rar