Incomplete Dominance & Codominance Flashcards

Questions and Answers

What is complete dominance?

Two alleles affect the phenotype in separate ways

Neither allele is completely dominant over the other

One allele completely overpowers another allele (correct)

More than two alleles exist for the same trait

What is incomplete dominance?

Neither allele is completely dominant and they mix (correct)

A trait is determined by multiple genes

Both alleles are expressed in distinguishable ways

One allele completely overpowers another

What is codominance?

Only recessive traits appear

Only one allele is expressed

Two alleles are expressed equally and visibly (correct)

One allele is dominant over the other

How many pairs of chromosomes do humans have in every cell except gametes?

23 Signup and view all the answers

What do sex chromosomes carry?

Genes for gender and secondary sexual characteristics Signup and view all the answers

What is unique about the X chromosome compared to the Y chromosome?

It is much larger and carries more genes Signup and view all the answers

A colorblind female has the genotype ______.

XcXc Signup and view all the answers

A normal, but carrier female has the genotype ______.

XcX Signup and view all the answers

A colorblind male has the genotype ______.

XcY Signup and view all the answers

A normal male has the genotype ______.

XY Signup and view all the answers

What does it mean for a trait to have multiple alleles?

Many genes have more than two alleles. Signup and view all the answers

What is polygenic inheritance?

The combined effect from two or more genes Signup and view all the answers

What are X-linked traits?

Sex-linked traits that are passed on through the X chromosome Signup and view all the answers

Study Notes

Incomplete Dominance & Codominance

Complete Dominance: One allele completely masks another, resulting in a singular phenotype. For example, if a dominant allele represents red color and a recessive one represents white, the presence of the dominant allele will yield red flowers.
Incomplete Dominance: Neither allele is fully dominant, leading to a blending of traits in the phenotype. An example is pink flowers resulting from red and white allele combinations.
Codominance: Both alleles are expressed simultaneously and distinctly in the phenotype. For instance, speckled chickens display traits from both parent alleles without one masking the other.

Chromosomal Information

Number of Chromosomes: Humans possess 23 pairs of chromosomes, totaling 46 in each somatic cell, with gametes containing only 23 individual chromosomes.
Sex Chromosomes: These chromosomes determine gender and influence secondary sexual characteristics. Males and females typically have one X and one Y chromosome or two X chromosomes, respectively.
X Chromosome: Significantly larger than the Y chromosome, it contains numerous genes, including those associated with colorblindness, a condition caused by a recessive allele on the X chromosome.

Genetic Makeup and Disorders

Colorblind Female: Represented genetically as XcXc, inheriting two colorblind alleles from both parents results in colorblindness.
Normal but Carrier Female: Genetically indicated as XcX, this individual possesses one allele for colorblindness (Xc) but also one normal allele (X), hence is not colorblind but can pass the trait to offspring.
Colorblind Male: Denoted as XcY, possessing one colorblind allele (Xc) and one Y chromosome results in colorblindness, as males have only one X chromosome.
Normal Male: Represented as XY, this male exhibits normal vision, carrying one X chromosome with the normal allele and one Y chromosome.

Genetic Concepts

Multiple Alleles: Many traits are governed by more than two alleles, creating a greater genetic diversity within a population, although any individual can only inherit two alleles for a specific gene.
Polygenic Inheritance: Characteristics are often influenced by several genes working in combination, leading to a variety of phenotypes across a spectrum rather than discrete categories.
X-Linked Traits: These traits are associated with genes found on the X chromosome; they follow specific inheritance patterns and can result in conditions that are more prevalent in males due to the presence of a single X chromosome.

Description

Explore the concepts of complete dominance, incomplete dominance, and codominance with these flashcards. Each card provides clear definitions and examples to help you understand how different alleles interact in genetics. Perfect for studying the basics of genetic inheritance!