Download Name: Period: _____ Date

Name: __________________________________ Period: _____ Date: _____________________
Jelly Beans and Pedigrees
Purpose: To become familiar with the way genes are passed from one generation to
the next and to observe pedigrees.
Materials: paper cups
sets of 6 jellybeans of four different colors each (see on board)
Hypothesis:
1. Do you think you’ll have any twins or triplets? Explain why or why not.
2. The red jellybeans are going to represent a disease. How many children do you
think will have it if the red jellybean is dominant?
3. How many children do you think will have it if the red jellybean is recessive?
Procedure:
1. Place the beans in the cups as follows:
Grandmother 1: 6 _____________
Grandfather 1: 6 _____________
Grandmother 2: 6 _____________
Grandfather 2: 6 _____________
2. Color the diagram (it’s called a pedigree) to show this arrangement.
3. Without looking, choose three beans from the Grandfather 1 cup and three beans
from the Grandmother 1 cup. Place them in the Mother cup.
4. Without looking, choose three beans from the Grandfather 2 cup and three beans
from the Grandmother 2 cup. Place them in the Father cup.
5. Color the diagram to show this arrangement.
6. The Mother and Father have four children as shown on page 3. Without looking,
choose three beans from the Father cup and three beans from the Mother cup.
Place them in Sarah’s cup. Color Sarah’s beans to match what you have drawn.
7. Return all of the beans to the Mother and Father cups.
8. Repeat steps seven and eight for Brian, Cathy and Hugh. Each time be sure to
choose beans without looking, color in the pedigree and return the beans.
9. The entire pedigree should be filled in. Answer the questions on the next
page while you eat your jelly beans.
Conclusions:
1. What do the beans really represent?
2. Where in the cell (specifically) do you find these?
3. Were any of the children exactly alike?
If yes, what do you think would have happened if you were working with
hundreds of beans instead of only six?
If no, why do you think it turned out this way?
4. Why was it necessary to take three from the father and three from the mother to
make the children?
5. Why was it necessary to return the beans to the mother and father cup each time?
6. Suppose the beans really were genes. Which children would look the most alike?
Explain.
7. Suppose the beans really were genes. Which children would look the most like one
of their parents or grandparents? Explain.
8. If the red bean represents a dominant gene for a disease, who in the family has the
disease?
9. If the red bean represents a recessive gene for a disease, who in the family has the
disease?
10. If the red bean represents a recessive gene for a disease, who in the family is a
carrier of the disease?
Part 2: Reading Pedigrees:
Background: refer to pages 241 and 243 of the blue book, which has more detail
than the red book, pgs 396-397.
11. A pedigree shows…
12. You can tell if a trait is sex linked if…
13. You can tell if a trait is autosomal if…
14. You can tell if a trait is dominant if…
15. You can tell if a trait is recessive if…
16. Someone who does not exhibit a disorder, but passes it on is called a …
17. When we say that a characteristic is polygenic, we mean that…. (include some
examples)
18. When we say that many conditions are complex characters, we mean that…
(include some examples)
Example A: Pedigree for attached earlobes
19. Are attached earlobes sex linked or autosomal? Explain how you can tell.
20. Are attached earlobes dominant or recessive? Explain how you can tell.
21. Look at the F1 and F2 generations. Circle people we know to be carriers.
22. How do we know that they are carriers?
23. Do we know in the P1 generation if the Mom or dad is the carrier? Explain.
24. If the girl in the F3 with attached earlobes were to mate with someone
homozygous for unattached earlobes, what are the chances their children
would have attached earlobes? Show the Punnett Square.
25. If the girl in the F3 with attached earlobes were to mate with someone
heterozygous for unattached earlobes, what are the chances their children
would have attached earlobes? Show the Punnett Square.
Example B: pedigree for tongue rolling
26. Is tongue rolling sex linked or autosomal? Explain how you can tell.
27. Is tongue rolling dominant or recessive? Explain how you can tell.
28. Look at the people in the P1 generation. Using the letter R for the trait, what are
their genotypes.
29. Explain how you figured this out.
30. Are the children in the F3 hybrid or pure bred?
31. Explain how you figured this out.
32. Will any of the children in the F3 have children that can not roll their tongue?
Explain (or show Punnett Squares).
Example C: Pedigree for color blindness
33. Is color blindness sex linked or autosomal? Explain how you can tell.
34. Is color blindness dominant or recessive? Explain how you can tell.
35. Look at the F1 and F2 generations. Circle people we know to be carriers.
36. How do we know that they are carriers?
37. In the F3 generation, one female is colorblind. Is the other a carrier? Explain.
38. Can a male be a carrier for a sex-linked trait that’s on the X-chromosome?
Explain.
39. If the colorblind female in the F3 generation has babies with a not colorblind
male, what is the chance her sons will be colorblind? What is the chance her
daughters will be colorblind? Explain. (You may want to show Punnett
Squares, but you don’t have to if you explain well enough.
Answer key:
Conclusions:
1. What do the beans really represent?
Alleles (genes or chromosomes, but alleles
best answer)
2. Where in the cell (specifically) do you find these?
Nucleus
3. Were any of the children exactly alike?
If yes, what do you think would have happened if you were working with
hundreds of beans instead of only six?
If no, why do you think it turned out this way?
4. Why was it necessary to take three from the father and three from the mother to
make the children?
Simulate ½ genes from mom and ½ from dad
5. Why was it necessary to return the beans to the mother and father cup each time?
Just to have enough to make 4 babies;
chromosomes copy in your cells, but jellybeans
do not copy
6. Suppose the beans really were genes. Which children would look the most alike?
Explain.
7. Suppose the beans really were genes. Which children would look the most like one
of their parents or grandparents? Explain.
8. If the red bean represents a dominant gene for a disease, who in the family has the
disease?
(would need only 1 red bean)
9. If the red bean represents a recessive gene for a disease, who in the family has the
disease?
(would need 2 red beans)
10. If the red bean represents a recessive gene for a disease, who in the family is a
carrier of the disease?
(would have 1 red bean)
Part 2: Reading Pedigrees:
Background: refer to pages 241 and 243 of your book
11. A pedigree shows…
Trait inherited over generations
12. You can tell if a trait is sex linked if…
Primarily males (much more than females)
13. You can tell if a trait is autosomal if…
Roughly = males and females (or more females)
14. You can tell if a trait is dominant if…
Every child with it has at least 1 parent with it
15. You can tell if a trait is recessive if…
Someone with it has parents without it
16. Someone who does not exhibit a disorder, but passes it on is called a …
Carrier (and is heterozygous)
17. When we say that a characteristic is polygenic, we mean that…. (include some
examples)
several genes control it
e.g. skin color (3 – 6 genes), eye color, height,
hair color…
18. When we say that many conditions are complex characters, we mean that…
(include some examples)
Influenced by environment as well as genetics
e.g. skin color, height, breast cancer, diabetes,
heart disease, stroke,
Example A: Pedigree for attached earlobes
or
19. Are attached earlobes sex linked or autosomal? Explain how you can tell.
Autosomal, roughly equal numbers of males and
females
20. Are attached earlobes dominant or recessive? Explain how you can tell.
Recessive…kids with the trait have parents
without; skipped generation
21. Look at the F1 and F2 generations. Circle people we know to be carriers.
22. How do we know that they are carriers?
Passed it on to girl in F3.
23. Do we know in the P1 generation if the Mom or dad is the carrier? Explain.
Both are, because son has it.
24. If the girl in the F3 with attached earlobes were to mate with someone
homozygous for unattached earlobes, what are the chances their children
would have attached earlobes? Show the Punnett Square.
0%...EE x ee…all babies will be Ee…carriers
25. If the girl in the F3 with attached earlobes were to mate with someone
heterozygous for unattached earlobes, what are the chances their children
would have attached earlobes? Show the Punnett Square.
50%...ee x Ee….50% Ee and 50% ee
Example B: pedigree for tongue rolling
26. Is tongue rolling sex linked or autosomal? Explain how you can tell.
Autosomal, more females than males
27. Is tongue rolling dominant or recessive? Explain how you can tell.
Dominant every child that has it has a parent
with it
28. Look at the people in the P1 generation. Using the letter R for the trait, what are
their genotypes.
Dad = rr (doesn’t have it)
Mom = Rr (she is heterozygous because 1
daughter does not have it)
29. Explain how you figured this out.
I already did. :-)
30. Are the children in the F3 hybrid or pure bred?
Hybrid … they have to be because dad does not
have the trait (rr)
31. Explain how you figured this out.
I already did. Sheesh :-)
32. Will any of the children in the F3 have children that can not roll their tongue?
Explain (or show Punnett Squares).
Yes only
if they marry someone who is a carrier, there is
a 25% chance Rr x Rr
If they marry someone who can not roll their
tongue, 50% chance
Example C: Pedigree for color blindness
33. Is color blindness sex linked or autosomal? Explain how you can tell.
sex linked more males than females
34. Is color blindness dominant or recessive? Explain how you can tell.
Recessive … boy in F2 has parents without it.
35. Look at the F1 and F2 generations. Circle people we know to be carriers.
36. How do we know that they are carriers?
F1…got from dad
F2…daughter in F3 has, so got from both
37. Is the female in the F3 generation a carrier? Explain.
Yes…got from dad
38. Can a male be a carrier for a sex-linked trait that’s on the X-chromosome?
Explain.
Nope, because he has only 1 X chromosome, if
he has recessive allele he will show trait.
39. If the female in the F3 generation has babies with a not colorblind male, what is
the chance her sons will be colorblind? What is the chance her daughters will
be colorblind? Explain. (You may want to show Punnett Squares, but you
don’t have to if you explain well enough.
Sons…100%...they get their X chromosome
from her and she is colorblind. Doesn’t matter
what dad is.
Daughters…0%...they get their Xs one from
Mom and one from Dad. Since Dad is not
colorblind, he passes down the dominant allele.
They will all be carriers, though.