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Name: ____________________________________ Chapter 12 Inheritance Homework
PEDIGREE:
The Components of a Pedigree:
Squares are used to indicate males in a family.
Circles are used to indicate females.
If the individual is “affected" by the trait (dominant or recessive) we darken the shape.
A line between a male and a female indicates a marriage or union.
A line drawn down from the marriage line indicates offspring.
Sometimes, you will see some shapes filled in only half way this notation indicates a hybrid (heterozygous) or carrier of the trait.
Analyzing Simple Pedigrees:
A pedigree is just like a family tree except that it focuses on a specific genetic trait. A
pedigree usually only shows the phenotype of each family member, and with a little
thought, and the hints below, you may be able to determine the genotype of each family
member as well! Use the pedigree above as an example.
Hints for analyzing pedigrees:
*If the individual is homozygous recessive, then both parents MUST have at least
one recessive allele (parents are heterozygous or homozygous recessive).
*If an individual shows the dominant trait, then at least one of the parents MUST
have the dominant phenotype. This one will be pretty obvious when you look at
the pedigree.
*If both parents are homozygous recessive, then ALL offspring will be
homozygous recessive.
NOTE: In a pedigree, the trait of interest can be dominant or recessive. The majority of
harmful genetic conditions are only seen when an individual is homozygous recessive examples of conditions caused by recessive alleles include cystic fibrosis (a disease of the
secretory glands, including those that make mucus and sweat), Falconi anemia (a blood
disorder), albinism (a lack of pigmentation), and phenylketonuria (a metabolic disorder).
Some genetic conditions are caused by dominant alleles (and may therefore be expressed in
homozygous dominant or heterozygous individuals)- examples of conditions caused by
dominant alleles include polydactyly (presence of extra fingers), achondroplasia (a type of
dwarfism), neurofibromatosis (a nervous disorder), and a disease known as familial
hypercholesterolemia in which affected individuals suffer from heart disease due to
abnormally high cholesterol levels
Human Pedigrees
For Questions 1-9, use the pedigree chart shown below. Some of the labels may be
used more than once. PLEASE LABEL THE PEDIGREE WITH GENERATIONS AND
INDIVIDUALS.
Assuming the chart above is tracing the dominant trait of "White Forelock (F)" through
the family. F is a tuft of white hair on the forehead.
________ 1. Person II-4 is?
2. A female in the 2nd generation that is infected?
________ 3. A married couple that the male is infected
4. A person who expresses the trait
5. A person who does not express the trait
6. A connection between parents and offspring
________ 7. How many generations are shown on this chart?
________8. What is the most likely genotype of individual “A”? (FF, Ff or ff?)
________9. What is the most likely genotype of individual “C”? (FF, Ff or ff?)
Figure 7-2
10. What is the possible mode if inheritance for
this pedigree above?
11. What do you know about individual III-1’s
mother?
12. How many of the offspring in the III
generation show a normal trait?
13. What generation shows the first affected female?
14. What is the relationship between I-1 and IV-2?
Figure 7-3
15. How many generations are represented in the pedigree:
16. In generation I, which parent is heterozygous for the recessive allele?
17. Which individual in generation II marries a spouse who is homozygous
dominates?
18. In which generation does the first case of sickle cell anemia appear?
19. Which generation contains the most male carriers?
20. Can two carriers produce an individual with sickle-cell anemia?
21. Can a normal homozygous individual produce offspring with sickle cell
anemia?
22. Which parents produce two children with sickle cell anemia?
INCOMPLETE DOMINANCE
Phenotype may be an intermediate between the homozygotes. One gene is not
dominant over the other
23. In snapdragons, a red and white flower is crossed and the heterozygote results
in a pink flower. In the space below shown this cross and the possible
genotypes and phenotypes.
24. Complete the Punnett square for a cross between a homozygous red-flowered
snapdragon (RR) and a homozygous white-flower (WW). Give the genotype
and phenotype of the offspring in the F1 generation.
25. Cross 2 pink flowers and list the possible genotypes and phenotypes
26. Cross a red flower with a pink flower. What are the possible genotypes and
phenotypes?
27. Cross a white flower with a pink flower. What are the possible genotypes and
phenotypes?
CODOMINANCE INHERITANCE
Both alleles are expressed
28. In chickens if a black chicken is crossed with a white chicken the
heterozygote is checkered. Show this in the space below.
29. Cross 2-checkered chickens. List the possible genotypes and phenotypes of
this cross.
30. Cross a black chicken with a checkered chicken. List the possible genotypes
and phenotypes.
31. Cross a white chicken with a checkered chicken. List the possible genotypes
and phenotypes.
32. In cats, the gene for calico (multicolored) cats is codominant. Females that
receive a B and an R gene have black and oRange splotches on white coats.
Males can only be black or orange, but never calico.
Here’s what a calico female’s genotype would look like: X B X R
Show the cross of a female calico cat with a black male?
What percentage of the kittens will be black and male? _________
What percentage of the kittens will be calico and male? _________
What percentage of the kittens will be calico and female? _________
33. Show the cross of a female black cat, with a male orange cat.
What percentage of the kittens will be calico and female? _____
What color will all the male cats be? ______
SEX LINKED INHERITANCE
Traits controlled by alleles on the sex chromosomes are said to be SEX LINKED, and an
allele that is only on the X chromosome is X-linked. An allele that is only on the Y
chromosome is Y linked.
X linked traits/diseases occur more often in males than females
A male always receives a sex-linked condition from his mother. WHY?
Carriers are individuals that appear normal but can pass on an allele for a genetic
disorder.
Disorders that are X linked: Muscular Dystrophy, Red Green Color Blindness,
Hemophilia
**In fruit flies, eye color is a sex linked trait. Red is dominant to white.**
34. What are the sexes and eye colors of flies with the following genotypes?
X R X r _________ X R Y __________ X r X r __________
X R X R ____________ X r Y ____________
35. What are the genotypes of these flies:
white eyed, male ________ red eyed female (heterozygous) ______
white eyed, female _______ red eyed, male ________
36. Show the cross of a white eyed female X r X r with a red-eyed male X R Y
37. Show a cross between a pure red eyed female and a white eyed male.
What are the genotypes of the parents:
What are the Genotypes and Phenotypes of their offspring?
38. Show the cross of a red eyed female (heterozygous) and a red eyed male.
What are the genotypes of the parents?
What are the Genotypes and Phenotypes of their offspring?
39. If a female fruit fly heterozygous for red eyes (XRXr) crossed with a whiteeyed male (XrY), what percent of their offspring will have white eyes?
40. In humans, hemophilia is a sex-linked recessive trait. If a female who is a
carrier for hemophilia marries a male with normal blood clotting, answer the
following questions.
What fraction of the female children will have hemophilia?
What fraction of the female children will be carriers?
What fraction of the male children will have normal blood clotting?
What fraction of the male children will be carriers?
What fraction of the male children will have hemophilia?
41. Two normal vision parents have a color-blind son. Give the genotype of both
parents and the son.
42. A hemophilic (x linked recessive) man reproduces with a homozygous normal
woman. What are the chances that their son will be hemophiliac? That their
daughter will be hemophiliac? That their daughters will be carriers?
43. Red green color blindness is x linked. If a male is red green color blind, and
both parents have normal color vision, which of the male’s grandparents is
most likely to be red green color blind? (maternal grandmother, maternal
grandfather, paternal grandmother, paternal grandfather or either grandfather
is likely)
44. The only colorblind member of Arlene’s family is her brother. What is her
brother’s genotype? What is her father’s genotype? What is her mother’s
genotype? What is Arlene’s genotype if she later has a colorblind son?
45. A normal woman, whose father was a hemophiliac marries a normal male.
What are the possible genotypes and phenotypes of their offspring?
46. What are the genotypes of the parents of a female hemophiliac?
47. If a female homozygous for normal vision marries a colorblind male, what are
the possible genotypes and phenotypes of their offspring?
Here are some patient charts. You are a physician. Write a diagnosis for each case. Use
these choices: Tay-Sachs disease, PKU, cystic fibrosis, Huntington’s disease, sicklecell anemia.
48. Name: Troy Jackson
Age: 20
Ethnic Background:
African-Amer
Patient complains about extreme weakness and lack of energy. Results of
blood test show that the red blood cells are abnormally shaped and that the
patient is anemic.
Diagnosis:__________________________________________
49. Name: Katie Murray
Age: 3 months
Ethnic Background: White
American
The infant appears very unresponsive. Mother feels she is
developmentally delayed. Katie did not receive a blood test at birth. She
has been on a milk-based formula.
Diagnosis:__________________________________________
50. Name: Meghan Smyth Age: 2 years Ethnic Background: White American
Patient has difficulty breathing and has frequent lung infections. The
mucus in the lungs and digestive track are extremely thick and viscous.
Child is also having difficulty digesting food.
Diagnosis:__________________________________________
51. Name: Abraham Stocker Age: 11 months Ethnic Background: Penns.
Dutch.
Abraham appeared normal at birth. He is now blind and appears very
lethargic. Abraham cannot sit up or crawl. His overall gross motor ability
to be extremely delayed.
Diagnosis:__________________________________________