Biology 17.4 (Monohybrid Inheritance)

What is inheritance?

Transmission of genetic information occurs from generation to generation

What is genotype?

• Genetic make-up of an organism 

• Always represented by two letters

What is phenotype?

Observable feature of organisms

What is it to be homozygous?

Having two identical alleles of a gene (AA, aa)

What is it to be heterozygous?

Having two different alleles of a gene (Aa)

What is pure-breeding?

Breeding of two identical homozygous individuals

What is the dominnat allele?

• Allele that is expressed if present in genotype

• Only needs to be inherited from one parent to be expressed in phenotype

• Shown as a capital letter

What is the recessive allele?

• Allele that is only expressed when there is no dominant allele

• It needs to appear twice

• Needs to be inherited from both parents in order to be expressed in phenotype

EXTENDED ONLY: What is a test cross?

Crossing of an unknown genotype with its homozygous recessive

EXTENDED ONLY: What is co-dominance

Neither allele is recessive, and both are expressed in phenotype

EXTENDED ONLY: What is meant by sex-linked characteristics?

The gene responsible for feature is located on sex chromosome (Y cannot carry, only X)

EXTENDED ONLY: What is a female with one dominant and one recessive allele called?

Carrier