Download Non-Mendelian Inheritance

Non-Mendelian Inheritance
1. How many natural variations in hair color or eye color are there? What could be the reason
there are not just one or two colors?
2. Biological inheritance of certain _______________________________ is determined by
individual units called genes. Different forms of a gene are called alleles. Two alleles make up a
gene set, which in turn produces a specific trait.
3. During meiosis, alleles usually assort independently from each other when the gametes are
formed. Thus each parent donates one of the two alleles for each trait to their offspring. Some
alleles may be dominant, and others may be recessive.
4. Occasionally, the simple rules of Mendelian ____________________________, such as
dominance and recessiveness, do not apply. In these instances, they are said to have nonMendelian inheritance.
5. Incomplete dominance occurs when neither allele is dominant, resulting in a blending of traits.
An example of incomplete dominance occurs in some species of flowers. If a pure red flower of
a species is crossed with a pure white flower of the same species, a hybrid pink flower is
produced.
6. A cross of the F1 generation, the ______________________________ pink hybrids, yields a
genotypic and phenotypic ratio of 1 to 2 to 1. Phenotype is the physical appearance, and
genotype is the actual genetic makeup of the organism.
7. For some traits, two alleles can be codominant. This means that both traits are expressed
simultaneously in heterozygous individuals. They are equally dominant. In cattle and horses, for
example, a cross between a pure red animal and a pure white animal produces an animal with a
roan coloration.
8. Roan cattle and horses actually have both red and white hairs intermixed, so they are spotted.
Roan is a third, unique _____________________________ produced in this cross. In a cross of
the F1 generations, the genotypic and phenotypic ratios are again 1 to 2 to 1.
9. The blood type AB is another example of codominance. All humans have one of four blood
types: A, B, AB, or O. These types are identified by the surface markers on the red blood cells.
10. The gene that determines blood type is represented by the capital letter I. In humans, it has
more than one dominant _______________________________. The alleles for type A and type
B are codominant, whereas the allele for type O, little i, is recessive to both. The different
combinations of the alleles produce four different phenotypes: A, B, AB, and O.
11. Non-Mendelian inheritance may also occur when there are more than two alleles controlling a
particular gene. These traits are controlled by multiple alleles. Blood type in humans is also an
Scientific Minds, LLC © 2011 All Rights Reserved
Page 1
example of a trait controlled by multiple alleles. The four different phenotypes (A, B, AB, and O)
are produced by three different alleles.
12. Traits that are controlled by two or more genes are called ___________________________
traits, which literally means “having many genes.” In humans, eye, skin, and hair color are
polygenic traits.
Non-Mendelian Inheritance: Questions
1. For the ABO blood group, IA codes for ‘A’, IB codes for ‘B’ and i codes for ‘O’ blood. Can two
parents having type-AB blood have a type-O child? Explain your answer.
2. The reason why there are so many skin colors, eye colors, and hair colors in humans is because
many genes control these traits. Can you describe another such feature in humans that could
have a similar inheritance pattern?
Scientific Minds, LLC © 2011 All Rights Reserved
Page 2