Download Inherited Human Traits

 Inherited Human Traits
Background: Many inherited traits in humans are observable. In this
activity you will examine several traits that are controlled by a single gene.
The table below lists those traits that are to be surveyed and shows which
are dominant and which are recessive characteristics.
Some Inherited Human Traits
TRAIT
PTC tasting
Earlobes
Hairline – widow’s peak
Hitchhiker’s thumb
Tongue rolling
Thumb crossing
Bent pinky
Eye color
Mid-digital hair
Cheek dimples
DOMINANT
Tastes (TT or Tt)
Free (EE or Ee)
Peak (WW or Ww)
Straight (HH or Hh)
Rolls (RR or Rr)
Left/right (CC or Cc)
Bent (BB or Bb)
Brown, hazel, green (PP
or Pp)
Hair present (MM or
Mm)
Dimple present (DD or
Dd)
RECESSIVE
No taste (tt)
Attached (ee)
Straight (ww)
Bent (hh)
Can not roll (rr)
Right/left (cc)
Straight (bb)
Blue or grey (pp)
No hair present (mm)
No dimple (dd)
Purpose:
1. To observe the expression of a series of genes in an individual’s
phenotype.
2. To demonstrate a small part of the range of human variation.
3. To understand the genetic basis for human diversity.
Procedure:
1. Set up a data table to record your personal genetic profile for the ten
traits listed above. Use the pictures and explanations on the last page
of this lab to help you. Don’t forget a title for your data table.
2. When your profile is completed your teacher will pool your data with
those of the rest of your classmates to produce a class data table.
Copy this table.
Analysis:
1. How many dominant traits do you have?
2. How many recessive traits do you have?
3. Looking at the class data table what was the most common dominant
trait?
4. What was the most common recessive trait in the class?
5. Calculate the frequency of each dominant trait in the class. Use the
following formula:
Frequency as a % =
number of students with the trait
Total number of students
X 100
6. Do any members of the class have all the surveyed traits in common?
Would this be expected? Explain.
7. Is it true that dominant phenotypes are always the most common in a
population? Explain your answer.
8. Is it possible to determine the genotype of a person showing a
dominant phenotype? A recessive phenotype? Why?
TRAITS
EARLOBE ATTACHMENT
Attached
Earlobes
Examine the lower part of your earlobes. If
they hang free you have detached earlobes.
If they attach directly to the side of your
head, you have attached earlobes.
Detached
Earlobes
HAIRLINE SHAPE
Examine the shape of your hairline
across your forehead. If it forms a
V-shaped point, you have a widow’s
peak. If not, you have a straight
hairline.
Widow’s Peak
hairline
Straight
hairline
HAND CLASPING
Cross left thumb Cross right
over right
thumb over left
Without thinking about it, fold your
hands together by interlocking your
fingers. Which thumb is on top – your
left or your right?
HITCHHIKER’S THUMB
Try to bend your thumb backwards at
the joints. Some people can from at
least a 45-degree angle, which is
called a hitchhiker’s thumb.
Straight
Hitchhiker
TONGUE ROLLING
Can you roll your tongue into a U
shape?
can roll
can’t roll
BENT PINKY
Hold your hands
together as if you are
covering your face. If
the tips of the pinkies
point away from one
another, the pinkies
are bent.
MID-DIGITAL HAIR
Look for hair only on the finger
shown by the arrow.