Review worksheet covering IB Biology content in Genetics (Topic 3.4)

1. IB Biology: Genetics Review (3.4) NAME:
1. Define the following:
Genotype
Phenotype
Dominant (allele)
Recessive (allele)
Codominant (allele)
Carrier
2. The allele for tall plants (T) is dominant over the allele for dwarf plants (t). State
the possible genotypes and phenotypes of a plant for this trait:
3. Mendel is known as the father of genetics for his extensive experimental work with peas and
different types of crosses. In a classic example of Mendel’s work, he determined that the gene
for pea color had two alleles. The allele for yellow color was dominant (Y) and the allele for
green color (y) is recessive. Draw a Punnett square to cross two heterozygous yellow peas and
determine the predicted genotype and phenotype ratios of the possible offspring:
4. Human ABO blood types follow a codominant inheritance pattern.
a. How is the ABO blood group gene an example of ‘multiple alleles’
b. Complete the table below to show how blood type is inherited.
alleles i IA
IB
i ii (Type O)
IA IA
IA
(Type A)
IB
c. Highlight the genotype and phenotype which is an example of codominance.
d. Complete this pedigree chart
to show the inheritance of
blood types in this family.
Genotype Phenotype

2. 5. The pedigree chart below shows a family affected by sickle cell. Deduce the genotype of each individual with a letter.
A HbA
HbS
F
B G
C H
D $ HbA
HbS
E #
6. Circle the individuals in the pedigree, above, who are carriers for Sickle cell.
7. Use a Punnett grid to predict the chance that “D” and “$” will have a child with Sickle cell:
8. Distinguish between autosomal and sex-linked genes:
9. State a named example of each of the following:
a. An autosomal dominant genetic disease: _______________________________
b. An autosomal recessive genetic disease: _______________________________
c. An autosomal genetic disease with a codominant feature:_______________________________
d. A sex-linked recessive genetic disease: _______________________________
10. Some inherited disorders are associated with gender.
a. Explain why sex-linked disorders are more common in males than females.
b. The allele for colour blindness (n) is recessive to the allele for
normal vision (N). This gene is carried on the X chromosome.
Complete the table to the right to show the possible genotypes of
individuals with regard to colour blindness.
c. Complete a Punnett grid to show a cross between a normal-vision
male and a carrier female. What is the expected ratio of
phenotypes in their children?
11. Define the term mutation and identify factors that can increase mutation rate in cells:
12. Outline severalconsequences of radioactive fallout in Hiroshima, Nagasaki, and Chernobyl:
Female Male
Normal XN
XN
Affected
Carrier Not possible!