Recording-2025-03-04T16:49:35

Overview of Genetic Information Transmission

• Genetic information is transmitted to individuals through the processes of cell division.

• Mitosis results in two cells with identical genetic information, while meiosis involves two rounds of division leading to gametes.

• Every gamete (sperm or egg) has half the genetic information of the parental cell, which in humans is a diploid number of 46 chromosomes (2n = 46).

Meiosis Process

• First Cell Division (Meiosis I): Each gamete produced is diploid with 46 chromosomes.

• Second Cell Division (Meiosis II): Gametes are haploid with 23 chromosomes.

• Fertilization: The union of a sperm and an egg forms a zygote, which is diploid (46 chromosomes).

Gregor Mendel and Heredity

• Gregor Mendel is known as the father of genetics, working in the 1860s.

• Mendel studied inheritance patterns and how traits are passed from parents to offspring using garden pea plants:

  • Recognized that offspring resemble their parents, evident in agriculture.

• He did not observe chromosomes or understand the concept of genes as we know today, referring to them as "heritable units."

• Established that genetic traits are inherited in predictable ways.

Gene and Trait Concepts

• Genes: Basic units of heredity contained in the chromosomes; they carry the information for traits.

• Mendel's observations on traits included:

  • Trait variations (e.g., flower color, stem length) come in distinct forms (e.g., purple vs. white flowers).

• Traits are determined by the proteins produced according to the genetic instructions in DNA.

Expressions of Traits

• Traits can be influenced by proteins, affecting characteristics such as hair texture and skin color.

• Genes are responsible for traits observed in individuals, and these traits can be dominant or recessive.

• Dominant traits are expressed over recessive ones in offspring.

Mendel's Experiments with Pea Plants

• Chose pea plants for experimentation due to their fast reproduction and distinct varieties:

  • Could control breeding between plants.

  • Observed traits such as flower color, seed shape, and pea pod characteristics.

• Characteristic vs. Trait:

  • A characteristic is a general category (e.g., flower color), while a trait is the specific variant (e.g., purple or white).

Mendel's Findings

• Established the principle of dominance, where dominant traits mask the expression of recessive traits.

• Conducted monohybrid crosses focusing on one trait at a time:

  • Parental generation (P): Purple and white flower plants.

  • Offspring (F1) produced only purple flowers.

• When F1 individuals were crossed, the F2 generation included both purple and white flowers, confirming recessive traits can appear after skipping a generation.

Genetic Ratios

• In F2 generation, Mendel observed a ratio of approximately:

  • 3 (dominant trait) to 1 (recessive trait).

• Resulted in the concept of dominant and recessive alleles:

  • Dominant = expressed trait (capital letter), Recessive = hidden trait (lowercase letter).

Understanding Alleles

• Alleles are different variations of a gene that determine traits.

• An organism can be homozygous (same alleles) or heterozygous (different alleles).

• The dominant allele is expressed in a heterozygous individual, masking the recessive allele.

Application of Punnett Squares

• Used to predict offspring genotypes from parental alleles in a cross:

  • Gametes from parents (dominant and recessive) combine, resulting in various possible genotypes for offspring:

  • Ratios observed would apply to larger-scale genetic studies.

Conclusion

• Gregor Mendel laid the foundation for modern genetics, discovering principles that govern heredity.

• His insights on dominant and recessive traits remain fundamental to biological sciences today.