Genetic Inheritance Quiz

Genetic Inheritance

• Homologous Pairs: A pair of chromosomes with the same length, shape, and carry alleles for the same genes; one from each parent.
• Human Chromosomes: Humans have 23 pairs (46 total) of chromosomes per cell; 22 are homologous pairs, and the 23rd are sex chromosomes.
• Single-Gene Traits: Some traits are determined by a single gene with two alleles (dominant and recessive).
• Dominant Allele: Expressed even with only one copy present (A).
• Recessive Allele: Expressed only when two copies are present (a).
• Phenotype: Observable traits (e.g., freckled).
• Genotype: Genes determining the phenotype (e.g., Ff, ff, FF).
• Gene: A short stretch of DNA determining a trait.
• Allele: A specific version of a gene (typically two versions).
• Chromosome: A long stretch of DNA containing genes.
• Homozygous: Both alleles for a gene are the same (AA, aa).
• Heterozygous: Alleles for a gene are different (Aa).
• Punnett Square: Predicts offspring trait probabilities based on parental genotypes.

Non-Mendelian Inheritance

• Complex Traits: Most traits are controlled in more complex ways than a simple dominant/recessive pattern.
• Incomplete Dominance: Neither allele is completely dominant; the phenotype blends (e.g., red x white flower = pink flower).
• Codominance: Both alleles contribute fully to the phenotype (e.g., red x white flower = red and white spotted/freckled flower).
• Multiple Alleles: Some traits have more than two alleles, but an individual can only possess two of these.
• Blood Type: A classic example of multiple alleles influencing a trait (A, B, AB, O); controlled by the I gene with three forms: IA, IB, i.
• Polygenic Inheritance: Traits controlled by multiple genes (e.g., hair color, height, complexion, which can result in quantitative traits).

Recombination Frequencies

• Genetic Recombination: Production of offspring with new combinations of traits from two parents.
• Recombinant Offspring: Offspring with trait combinations not found in either parent.
• Crossing Over: Exchange of segments between non-sister chromatids during prophase I.
• Independent Assortment: Random orientation of homologous chromosomes during meiosis.
• Random Fertilization: Random combination of gametes from both parents.
• Recombination Frequency: Percentage of recombinant offspring; reflects the distance between genes on a chromosome.
• Genetic Maps (Linkage Maps): Ordered list of genetic loci along a chromosome; based on recombination frequencies.
• Linked Genes: Genes located close together on the same chromosome tend to be inherited together.
• 50% Recombination Frequency: Could indicate genes are unlinked or very far apart on the same chromosome.

Blood Types

• Antigens: Molecules on red blood cells.
• Antibodies: Molecules in plasma; react with antigens.
• Blood Type Compatibility: Blood type compatibility is crucial for safe blood transfusion.
• Blood Type Genotypes & Phenotypes summarized in chart format.

Gender Determination

• Sex Chromosomes: X and Y chromosomes determine sex.
• XX: Female
• XY: Male
• Meiosis (Males): Spermatocytes produce four sperm; half with X, half with Y.
• Meiosis (Females): Oocytes produce one egg with X.
• Probability: 50% chance for either sex.

Sex-Linked Traits

• X-Linked Traits: Traits located on the X chromosome.
• Males (XY): Express the trait if present on their single X chromosome.
• Females (XX): Need two copies of the recessive allele to express a recessive X-linked trait.
• Examples: Red-green color blindness, hemophilia.

Pedigrees

• Family History: Tracks affected and unaffected individuals; used to infer inheritance patterns (dominant or recessive).
• Dominant Traits: Affected offspring often have at least one affected parent.
• Recessive Traits: Affected offspring can have unaffected parents (who are heterozygous carriers).

Nondisjunction, Aneuploidy, and Polyploidy

• Nondisjunction: Chromosomes fail to separate properly during meiosis.
• Aneuploidy: Abnormal number of chromosomes.
• Trisomic: Three copies of a chromosome (e.g., Down Syndrome).
• Monosomic: One copy of a chromosome (e.g., Turner Syndrome).
• Polyploidy: Extra sets of chromosomes (common in plants).

Alterations in Chromosomal Structure

• Chromosome Breakage: Errors during crossing over or other processes can lead to structural alterations:
  • Deletion: Loss of chromosomal segment.
  • Duplication: Extra copy of chromosomal segment.
  • Inversion: Segment flips and reattaches.
  • Translocation: Segment moves to a different chromosome.

Additional Vocab

• Epistasis: One gene affecting the expression of another.
• Pleiotropy: One gene affecting multiple traits.

Diseases/Syndromes

• Klinefelter's Syndrome: XXY
• Turner Syndrome: X
• Supermale Syndrome: XYY

Hybrid Crosses

• Law of Segregation: Alleles separate during gamete formation.
• Law of Independent Assortment: Alleles for different traits segregate independently.
• Probability Rules for Multi-hybrid Crosses (Multiplication & Addition): Used to predict offspring probabilities when multiple traits are involved.

Test your understanding of genetic inheritance concepts such as homologous pairs, alleles, genotypes, and phenotypes. This quiz covers key definitions and examples related to single-gene traits and inheritance patterns. Enhance your knowledge of genetics and understand the basics of heredity.