Download Polygenic Inheritance Date Period_____ Background

Name __________________________
Polygenic Inheritance
Date _______________ Period_____
Background
Characteristics that we inherit from our parents are called traits.
Traits are determined by the genes that are passed to use from our
parents. Genes come in pairs on chromosomes, so every person has two
versions of each gene in a pair – one inherited from Dad and one from
Mom. How many shades of blue or brown eye color can you detect
among your classmates? You’ll probably have trouble naming all of the
different shades of eye color. Eye color is an example of a single trait that
is produced by a combination of many genes. Polygenic inheritance
occurs when a group of gene pairs act together to produce a single trait.
The combination of many genes acting together produces a wide variety
for a single trait. The study of genetics is not a simple look at a single trait
controlled by just one pair of genes because many human traits such as
height, body build, the shape of eyes – lips – ears, and skin and hair color
are controlled by groups of gene pairs. In this lab investigation, we will
study two traits to determine if they are produced by polygenic
inheritance. In other words, we’ll determine if several gene pairs act
together to produce a single trait with a variety of phenotypes for that
trait. If there is a variety in a sample population, then that trait is
produced by polygenic inheritance.
Part A – Fingerprint Patterns
Problem:
Are fingerprint patterns a trait that is controlled by polygenic
inheritance?
Materials:
pencil, scrap paper, transparent tape, magnifiers, calculator
Procedures for Part A:
1. Turn your pencil sideways and rub a thick spot of graphite onto your
scrap paper.
2. Place your right index finger (tip to the first joint of your finger) in the
graphite spot and rub from side to side.
3. To lift the fingerprint, place a strip of tape on your index finger
covered by the graphite. Gently remove the tape and stick it in the
box on the back of this lab sheet.
4. Wash your index finger.
Right index fingerprint
5. There are three patterns that are found in fingerprints: whorl, arch,
and loop. Use a magnifier to study your fingerprint pattern.
Compare your print with the patterns below to see if you can find a
whorl, arch, or loop.
Circle the pattern that best matches your fingerprint.
Whorls
Arches
Loops
6. Your teacher will take a verbal survey of the class. Record the
number of people participating in the survey in the title of Data
Table 1. Then record the number of participants that have each
fingerprint pattern.
Data Table 1 – Number of participants in class with whorls, arches, and
loops.
Total number of participants: ____________________
Number of Participants Number of Participants Number of Participants
with Whorls
with Arches
with Loops
Analysis and Conclusion:
1. Calculate the percentage of whorls by dividing the number of
participants with whorls by the total number of participants in class.
Do the same for arches and loops.
% whorls ________
% arches _________
% loops _________
2. What was the most common index fingerprint pattern in the class?
3. Whorls are found in 35% of the population, arches are found in 5% of
the population, and loops are found in 65% of the population. Are
the percentages you calculated for participants in your survey
similar to the worldwide percentages for each type of print?
Explain your answer.
4. Although the three basic fingerprint patterns are common in the
population, everyone’s fingerprints are unique. Even identical twins have
unique fingerprints from each other. Are fingerprints a trait that is
controlled by polygenic inheritance? Justify your answer.
Part B – Hand Span
Problem: Your hand span is the distance from the tip of your thumb to the tip
of your pinky finger when your fingers are spread as far apart as you can
make them. Is your hand span a trait that is controlled by polygenic
inheritance?
Materials: cm ruled graph paper, calculator
Procedures for Part B
1. Turn the graph paper sideways (hamburger). Measure your hand span by
spreading your fingers as far apart as you are able to without hurting
yourself. Place your hand on the graph paper. Each line segment on the
graph paper is one centimeter. Measure your hand span to the nearest
centimeter. Record the distance of your hand span here:
My hand span is ____________ centimeters long.
2. To determine if there is a wide range of phenotypes for hand span, collect
data from participants in the class.
Scientists keep personal information in a survey confidential. To
practice working like scientists, we will keep the measurement of hand
span confidential.
Record the measurement of your hand span next to any number on
the class data table transparency on the overhead projector. Do not
turn on the overhead projector until all participants have recorded
their hand span.
3. Return the graph paper to your storage box. Copy the class data table.
Data Table 2 – Class data on hand spans to the nearest centimeter.
Participant #
Hand span (cm)
Participant #
Hand span (cm)
1
13
2
14
3
15
4
16
5
17
6
18
7
19
8
20
9
21
10
22
11
23
12
24
Analysis and Conclusion:
1. The range of a set of data is the difference between the smallest
and largest quantities. What is the range of hand spans of
participants in this survey?
2. The mean of a set of data is the average. What is the average
hand span of participants in this survey?
3. The median of a set of data is the number in the middle when all
data has been put in order from lowest number to highest number.
What is the median hand span of participants in this survey?
4. The mode is the number that occurs most often in a set of data.
What is the mode of your data?
5. Based on your data, is hand span a trait that is controlled by
polygenic inheritance? Justify your answer.
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