Heredity and Evolution Quiz

Heredity and Evolution

• Living organisms produce offspring similar to their parents, but not exact copies.
• Variations arise from changes in DNA or sexual reproduction.
• Errors in DNA copying and random fertilization contribute to variation.
• Sexual reproduction results in more variations compared to asexual reproduction.
• Variations are less noticeable in asexually reproduced plants, such as sugarcane.
• Humans have more distinct variations due to sexual reproduction.
• Inheritance is the process where characteristics are passed from one generation to the next.
• Heredity is the inheritance of characteristics from parents to offspring.
• Variations are differences among individuals within a species.
• Genetics is the branch of biology studying heredity and variations.

Accumulation of Variations During Reproduction

• Inheritance provides a common basic body design and slight variations.
• Offspring inherit parental characteristics but are not exact copies.
• Variation exists among individuals of a species in some traits.
• Variations, particularly beneficial ones, are selected by nature.

Earlobes as an Example of Variation

• Earlobes are either free-hanging (free earlobes) or attached to the head (attached earlobes).
• These variations exist in the human population.

Heredity

• Gregor Mendel was the first to systematically study inheritance.
• He experimented with pea plants, focusing on seven contrasting traits.

Mendel's Seven Traits in Pea Plants

• Pea shape (round or wrinkled)
• Pea color (green or yellow)
• Pod shape (constricted or inflated)
• Pod color (green or yellow)
• Flower color (purple or white)
• Plant size (tall or dwarf)
• Position of flowers (axial or terminal)

Genetical Terms

• Trait: A specific characteristic of an organism (e.g., tallness, color).
• Phenotype: The observable traits of an organism.
• Genotype: The genetic makeup of an organism.
• F1 generation: First generation of offspring from a cross.
• F2 generation: Second generation of offspring from a cross.
• Selfing: Crossing of two organisms of the same kind.
• Homozygous: Having two similar factors for a trait (e.g., TT for tall).
• Heterozygous: Having two dissimilar factors for a trait (e.g., Tt for tall).

Principles of Inheritance

• Principle of paired factors: Each trait is controlled by a pair of factors (now called genes).
• Principle of dominance: In heterozygous individuals, one factor (dominant) expresses itself while the other (recessive) does not.
• Principle of segregation: Each gamete receives only one factor of each pair during gamete formation.
• Principle of independent assortment: Factors for different traits segregate independently during gamete formation.

Dihybrid Cross

• A cross involving two traits.
• Mendel's dihybrid crosses showed that traits can be inherited independently.

How Traits are Expressed

• Inheritance of traits occurs through hereditary units (genes).
• Genes are a pair of factors that work in pairs.
• Each parent has a pair of genes for each trait.

Mechanism of Heredity

• Genes are segments of DNA located on chromosomes.
• DNA carries the information for making proteins.
• Dominant genes code for fully functional proteins or enzymes.
• Recessive genes code for partially functional or defective proteins or enzymes.

Sex Determination

• Sex in humans is determined genetically by chromosomes.
• Human cells have 46 chromosomes (23 pairs).
• 22 pairs are autosomes, while one pair (23rd) are sex chromosomes.
• Females have XX chromosomes.
• Males have XY chromosomes.
• The sex of the offspring is determined by the male gamete (sperm).

Sex Determination in Other Animals

• In some animals, the sex is determined by environmental factors, like temperature during incubation.