LABORATORY PRACTICE SL
Exercise 1. FINDING YOUR GENOTYPE
Based on the following guide of hereditary characteristics, make a list of your phenotypic characters and deduce your genotype.
1. Curly hair RR is co-dominant with straight hair R’R’. The condition heterozygote gives a undulated texture R R’
2. The hair color is determined by a great number of factors. However, it can be explained by the interaction of two pairs of genes.
a. DD, Dd = brown pigment
b.
dd = lack of brown pigment
c. RR, Rr = absence of red pigment
d.
rr = presence of red pigment
Of the combination of these pair of genes we can obtain:
Dark hair: presence of brown pigment and absence of red = DDRR, DDRr, DdRr, DdRR
Dark hair with red highlights: presence of two pigments = DDrr, Ddrr.
Blond hair: absence of both pigments = ddRR, ddRr
Silver hair: absence of brown and presence of red = ddrr.
3. Examine the line of hair in your forehead. There are two alternatives: If the line forms a V in the middle of the forehead the character is
called “widows peak” and this is a dominant condition (V). If the line is straight, the character is absent and this is due to a recessive gene
(v)
4. The brown color of eyes is dominant over blue or gray. In the same way, the colors light brown and green are dominant over blue or gray.
This is symbolized as: A = brown; A’= light brown or green and a= blue or grey
5. A convex and prominent nose (N) is dominant over the straight and moderate nose (n)
6. The cheek holes are a dominant character. The holes can be more than one per cheek or may appear one in one cheek and not in the
other. The presence of holes (H) is dominant over the absence (h)
7. The presence of freckles (P) is dominant over the absence (p)
8. Free earlobes (L) is a dominant condition over adhered earlobes (l)
9. Long eyelashes (1 cm or more) is dominant (G) over short eyelashes (less than 1 cm) (g).
10. The ability to roll the edges of the tongue in a U form is dominant (B) over the incapacity to do so (b)
11. The right handed condition (Z) is dominant over the left handed condition (z)
12. Join the palms of your hands by the edges so your pinkie fingers are joined together. Observe if they are parallel through all the length or if
they are separated in the extremes. Each bone that forms your finger is called phalange. A curved phalange (F) is dominant over the
straight phalange (f)
13. Some people can separate the thumb to form a 90o angle. A recessive gene determines this quality (i). The dominant gene (I) prevents a
separation greater than 45o
14. Observe the back of your fingers. If there is hair in the middle of them it will be caused because of a dominant gene for this condition (D); if
you have no hair, you have a recessive gene (d)
15. Extend your hand and examine the wrist. Observe if there are two or three visible tendons. If three tendons are visible, your palm muscle is
long; if there are only two tendons, you lack this muscle. The absence of palm muscle is dominant (M) over the presence (m).
16. Cross the fingers of your hands. The left thumb over the right is dominant (K), the opposite is recessive (k).
17. See if your index is shorter than your ring finger. This is a sex linked character. That means that the same genotype (the heterozygote) is
expressed in different ways in man and woman. The same happens with boldness.
So:
Man
Woman
DD
Short
Short
Index
Dd
Short
Long
Dd
Long
Long
18. Low stature is most likely to be dominant (S) over high stature (s)
19. The blood group of a person can be A, B, AB or O. The genotypes might be AA or Ai, BB or Bi, AB, ii (O). Remember that A and B are codominant genes.
20. The blood factor RH + (W) is dominant over the type RH – (w)
Exercise 2. DISPLAYING DISCONTINUOUS VARIATION.
For the following activity you will:
a) Design an experiment to determine the frequency of individuals in a sample of at least 100 individuals with any ONE -easy to identifygenetic characteristic (must be discontinuous).
b) Display your results in a data table and bar graph using Excel.
c) Select an adequate statistical analysis test to process and analyze your results.
d) Follow the lab rubrics (design, data-collection and processing, conclusion and evaluation) to complete the assignment. (Syllabus).
Source: Rafael, Violeta, 1995, Manual de Laboratorio de Genética I, Pontificia Universidad Católica del Ecuador, Departamento de Ciencias
Biologías, Quito – Ecuador, pg 61 – 65.