Lesson Worksheet: Lack of Dominance Biology

In this worksheet, we will practice explaining what occurs when alleles do not have complete dominance, and interpreting Punnett squares that show this.

Q1:

The table provided shows the different genotypes of the 4 blood groups in humans.

 Blood Group Genotype A B AB O IAIA or IAIO IBIB or IBIO IAIB IOIO

A female with the genotype IOIO reproduces with a male with the genotype IAIB. What is the probability, in percent, that their offspring will have blood group A?

Q2:

Snapdragon flowers (pictured) show incomplete dominance in the color of their petals. The petals can be red (CRCR), white (CWCW), or pink (CRCW). Two pink flowers are crossed. What is the probability, in percent, that their offspring will also have pink flowers?

Q3:

Shorthorn cows show codominance in their coat color. They can be red, white, or roan—a mixture of the two (pictured).

Which of the following Punnett squares shows the correct cross when a cow homozygous for a red coat and a bull with a roan coat breed?

• A
• B
• C
• D

Q4:

Snapdragon flowers (pictured) show incomplete dominance in the color of their petals. The petals can be red (CRCR), white (CWCW), or pink (CRCW).

Which of the following Punnet squares shows the correct cross between two pink flowers?

• A
• B
• C
• D

Q5:

The table provided shows the different genotypes of the 4 blood groups in humans.

 Blood Group Genotype A B AB O IAIA or IAIO IBIB or IBIO IAIB IOIO

A female with the genotype IAIB reproduces with a male with the genotype IAIO. What is the probability, in percent, that their offspring will have blood group A?

Q6:

A dispute about the paternity of a child is occurring between a couple. The mother is blood type A and the child is blood type AB. The man claiming to be the father is blood type O. Is this man likely to be the father? Why? Use the blood group table provided to help you.

 Blood Group Genotype A B AB O IAIA or IAIO IBIB or IBIO IAIB IOIO
• AYes, because the child could have inherited an O allele from the father that is not being expressed because AB is dominant.
• BYes, because it is impossible to tell paternity from blood group.
• CNo, because the child has inherited an allele for blood type A from their father and this is not possible with blood type O.
• DNo, because the child has inherited an allele for blood type B from their father and this is not possible with blood type O.

Q7:

Which of the following best defines “multiple alleles” for a given trait?

• AMultiple alleles refer to both alleles for a trait being simultaneously expressed in the phenotype.
• BMultiple alleles refer to three or more alleles occupying the same locus.
• CMultiple alleles refer to an organism that is heterozygous for an allele expressing a distinct, intermediate phenotype.

Q8:

A man claiming to be a long lost child of a recently deceased millionaire argues he has a claim to the inheritance. The millionaire has blood group O and the child has blood group AB. Could the millionaire be the father? Why? Use the blood group table provided to help you.

 Blood Group Genotype A B AB O IAIA or IAIO IBIB or IBIO IAIB IOIO
• AYes, as the child could have inherited the alleles for group AB from their mother alone.
• BNo, as the child would have inherited one allele for group O from the father.
• CNo, as the man would have blood group O if the father did.
• DYes, because it is impossible to tell paternity from the blood group.

Q9:

The table provided shows the different genotypes of the 4 blood groups in humans.

 Blood Group Genotype A B AB O IAIA or IAIO IBIB or IBIO IAIB IOIO

The table shows that if one allele for A is inherited and one allele for B is inherited, both are expressed simultaneously in the blood type. What trait is this demonstrating?

• ACodominance
• BIncomplete dominance
• CRecessive alleles
• DComplete dominance

Q10:

The shape of hemoglobin, the pigment in red blood cells, can demonstrate codominance. The genotypes and phenotypes are outlined in the table provided.

 Genotype Phenotype HbAHbA HbsHbs HbAHbs Red blood cells have a normal, biconcave shape. Sickle cell anemia: Red blood cells have a sickle shape, which causes severe anemia. Sickle cell trait: The majority of red blood cells have a normal shape and do not cause anemia under normal conditions.

Both parents have the genotype HbAHbs. What is the probability that their offspring will have sickle cell anemia?

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