Genetics Quiz: Alleles and Traits

Definitions

• Homozygote: Having two identical alleles (e.g., BB).
• Heterozygote: A genotype consisting of two different alleles (e.g., Bb).
• Genotype: The alleles an individual carries on their chromosomes (e.g., Bb, BB, bb).
• Phenotype: The outward appearance of an organism (e.g., blue eyes).
• Dominant: The stronger allele, needing only one copy to be expressed (e.g., B).
• Recessive: The weaker allele, needing two copies to be expressed (e.g., b).
• Alleles: Different versions of a gene (e.g., B or b).
• Traits: Visible characteristics determined by alleles (e.g., brown eyes, blue eyes).
• Dominant trait: A trait expressed with one or two dominant alleles.
• Recessive trait: A trait expressed only when both copies of the recessive allele are present.

Phenotypes and Genotypes

• Phenotype: Physical appearance (e.g., brown eyes, blue eyes).
• Genotype: Genetic makeup (e.g., BB, Bb, bb).

Homozygous and Heterozygous

• Homozygous: Having two identical alleles (e.g., BB, bb).
• Heterozygous: Having two different alleles (e.g., Bb, Bb).

Punnett Squares

• Used to predict possible genotypes and phenotypes of offspring.
• Father's traits go on top row.
• Mother's traits go on the side column.
• Genotypes and Phenotypes are predicted.
• Accurate example ratios for the F1 and F2 generations are possible.

F1 and F2 Generations

• P generation: Parent generation.
• F1 generation: First filial generation (offspring of the P generation).
• F2 generation: Second filial generation (offspring of the F1 generation).

Mendel's Laws of Inheritance

• Law of Dominance: In a pair of alleles, one allele is stronger (dominant) and masks the presence of the other.
• Law of Independent Assortment: Genes for separate traits are inherited independently.
• Law of Segregation: Parents pass just one of their two gene copies for each trait to their children.

Codominance and Incomplete Dominance

• Codominance: Both alleles are dominant, and both traits are expressed in the phenotype (e.g., Roan cows).
• Incomplete Dominance: Neither allele is dominant, resulting in a blended phenotype (e.g., a mix of red and white flowers).

Multiple Alleles and Polygenic Traits

• Multiple allels: More than two possible alleles for a gene.
• Polygenic traits: Traits controlled by multiple genes (e.g., height, hair color).

Sex-linked Inheritance

• Traits carried on the sex chromosomes, causing variations in inheritance patterns.
• Males have XY sex chromosomes, females have XX.
• Examples of sex-linked traits are hemophilia.
• Understanding the superscripts (e.g., XHXh) is important.

Blood Types

• The presence of specific antigens on blood cells contributes to blood types A, B, AB and O.
• Blood type O is the universal donor, AB is the universal recipient.