7c Genotypes and phenotypes Flashcards
What is a genotype?
Definition: A genotype is the genetic makeup of an organism, specifically the alleles it possesses at a particular gene locus.
How is a genotype written? Give an example.
Writing Genotype: Genotypes are written as a combination of alleles, using letters to represent different alleles.
Example: For a gene with alleles A and a, possible genotypes include AA, Aa, and aa.
Define the term, Homozygous and give an example.
Definition: Homozygous means having two identical alleles for a particular gene.
Example: AA or aa.
Define the term, Heterozygous and give an example.
Definition: Heterozygous means having two different alleles for a particular gene.
Example: Aa.
Define the term, Hemizygous and give an example.
Definition: Hemizygous refers to having only one allele of a gene instead of the usual two. This term is commonly used in reference to X-linked genes in males.
Example: A male with an X-linked gene allele (X^A Y) where A is an allele on the X chromosome.
What is an X-linked (sex-linked) trait? Give an example and write a genotype for this trait.
Definition: An X-linked trait is a characteristic determined by a gene located on the X chromosome.
Example: Color blindness is an X-linked trait.
Genotype Example: X^cX^c for a female with color blindness; X^cY for a male with color blindness.
What is a carrier?
Definition: A carrier is an individual who has one copy of a recessive allele that does not produce a phenotype in the presence of a dominant allele but can pass the allele to offspring.
Example: A person with the genotype Aa for a recessive disorder is a carrier.
What is a phenotype?
Definition: A phenotype is the observable physical or physiological traits of an organism, determined by its genotype and environment.
Explain the difference between a dominant and recessive phenotype.
Dominant Phenotype: Expressed when at least one dominant allele (A) is present.
Recessive Phenotype: Expressed only when two recessive alleles (aa) are present.
What is codominance? Give an example of a trait that is codominant and write the alleles.
Definition: Codominance occurs when both alleles contribute equally to the phenotype.
Example: The ABO blood group system, where IA and IB alleles are codominant.
Alleles: IAIB genotype results in AB blood type.
What are the 6 genotypes and their phenotypes in the ABO blood group?
IAIA - Type A
IAi - Type A
IBIB - Type B
IBi - Type B
IAIB - Type AB
ii - Type O
What is incomplete dominance? Give an example of a trait that shows incomplete dominance and write the alleles.
Definition: Incomplete dominance is when the heterozygous phenotype is an intermediate of the two homozygous phenotypes.
Example: In snapdragons, red (RR) and white (rr) flowers can produce pink (Rr) flowers.
What is a monogenic trait? Give an example.
Definition: A monogenic trait is controlled by a single gene.
Example: Cystic fibrosis is caused by mutations in the CFTR gene.
What is a polygenic trait? Give two examples.
Definition: A polygenic trait is influenced by multiple genes.
Examples:
Height
Skin color
Describe the difference between a graph that shows a monogenic phenotype and a graph that shows a polygenic phenotype.
Monogenic Phenotype Graph: Typically shows distinct categories or classes, with little variation between individuals.
Polygenic Phenotype Graph: Displays a continuous range of phenotypes, often forming a bell-shaped curve, indicating a wide range of variation due to multiple genes and environmental factors.
