10 Questions
______ Sometimes both alleles can be expressed in the phenotype at the same time
Codominance
When an individual is heterozygous they will express both alleles in their phenotype
codominance
The gene for ______ types is represented in the genotype by I and the three alleles for human ______ types are represented by A, B and O
blood
If both allele A and allele B are present in a heterozygous ______ they will have blood type AB (IAIB)
individual
When a homozygous dominant individual is crossed with a homozygous recessive individual the ______ are called the F1 generation
offspring
If two individuals from the F1 ______ are then crossed, the offspring they produce are called the F2 ______
generation
A test ______ can be used to try and deduce the genotype of an unknown individual that is expressing a dominant phenotype
cross
Some genes are found on a region of a sex chromosome that is not present on the other sex chromosome
linkage
Haemophilia is well known example of a sex-linked ______
disease
Sex-linked ______ are represented in the genotype by writing the alleles as superscript next to the sex chromosome
genes
Study Notes
Inheritance of Traits
- Both alleles can be expressed in the phenotype at the same time in heterozygous individuals.
- In heterozygous individuals, both alleles are expressed in their phenotype.
Blood Type Inheritance
- The gene for blood types is represented in the genotype by I.
- The three alleles for human blood types are represented by A, B, and O.
- If both allele A and allele B are present in a heterozygous individual, they will have blood type AB (IAIB).
Generation Terminology
- The offspring produced by crossing a homozygous dominant individual with a homozygous recessive individual are called the F1 generation.
- The offspring produced by crossing two individuals from the F1 generation are called the F2 generation.
Genotype Testing
- A test cross can be used to deduce the genotype of an unknown individual that is expressing a dominant phenotype.
Sex-Linked Traits
- Some genes are found on a region of a sex chromosome that is not present on the other sex chromosome.
- Haemophilia is a well-known example of a sex-linked disorder.
- Sex-linked traits are represented in the genotype by writing the alleles as superscript next to the sex chromosome.
Test your knowledge of codominance and phenotype expression with this quiz. Explore how both alleles can be expressed in the phenotype, and learn how to write the genotype for codominance using different superscript letters to represent alleles.
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