Genotype and Phenotype: Mendelian Inheritance

Genotype and Phenotype

• Genotype refers to an organism's genetic makeup.
• Phenotype refers to an organism's physical traits.

True Breeding Parents

• True breeding parents, when self-pollinated, produce offspring identical to themselves.

Generations

• The original pair of plants is the P (parental) generation.
• The resulting offspring are the F1 (first filial) generation.

Mendel's Study

• Mendel studied the inheritance of traits like flower color and seed shape.
• His conclusions were that biological inheritance follows factors passed from generation to generation.
• These factors were later called genes.
• Different forms of a gene are called alleles.

Principles of Inheritance

• Principle of dominance: Some alleles are dominant (and mask the effect of recessive alleles) and others are recessive.
• Recessive alleles are only expressed when a dominant allele isn't present. Dominant alleles mask recessive alleles.
• Codominance: Both alleles are expressed equally.
• Incomplete dominance: The phenotype blends the effects of both alleles.

Punnett Squares

• A Punnett square is used to predict genetic variations from crosses.
• Capital letters represent dominant alleles (e.g., tall = T).
• Lowercase letters represent recessive alleles (e.g., short = t).

Thomas Hunt Morgan's Work

• Morgan's fruit fly studies confirmed genes reside within chromosomes in cell nuclei.
• He was awarded a Nobel Prize in Medicine in 1933.

Chromosome Numbers

• Diploid (2n): Organisms with two sets of chromosomes (e.g., humans with 23 pairs).
• Haploid (n): Organisms with one set of chromosomes.

Meiosis and Mitosis

• Meiosis produces cells with half the number of chromosomes of the parent cell
• Mitosis produces cells with the same number of chromosomes as the parent cell.

Crossover and Independent Assortment

• Crossover occurs during meiosis when homologous chromosomes exchange segments.
• Independent assortment describes how allele pairs sort independently during meiosis.

Griffith's Findings

• Griffith's experiments suggested bacteria can transfer genetic information (a process called transformation).

Transcription and Translation

• Transcription is the process of copying DNA into RNA (mRNA).
• Codons on mRNA encode specific amino acids.
• There are 61 codons.

Gene Mutations

• Gene mutations are permanent changes in DNA sequences.
• These changes arise naturally or from environmental factors.

Regulatory Proteins

• Lac repressor controls genes related to lactose.
• Hox genes control cell and tissue differentiation in embryos.

Breeding Techniques

• Selective breeding: Choosing organisms with desired traits for reproduction.
• Genetic engineering: Modifying genes with technology.
• Hybridization: Crossing dissimilar organisms to combine their best traits.
• Inbreeding: Breeding similar organisms (e.g., purebred dogs)

Polyploidy

• Polyploidy is the condition of having more than two complete sets of chromosomes.

DNA Analysis Techniques

• Gel electrophoresis separates DNA fragments by size.
• DNA cloning replicates genes, such as in Dolly the sheep.

Other Key Concepts

• Ribosomal DNA is involved in protein synthesis.
• Genetic markers are DNA sequences at specific locations on chromosomes.
• A pedigree chart displays family history.

This quiz covers the fundamental concepts of genotype and phenotype, focusing on Mendel's principles of inheritance. Understand how true breeding parents and generations play a crucial role in determining inherited traits. Test your knowledge on dominant and recessive alleles, along with codominance.