Genetics and Heredity Overview

Genetics and Heredity Overview

• Genetics is the study of heredity and the variation of inherited characteristics.
• Heredity is the passing of traits from parents to offspring.
• Traits are characteristics that are passed down, such as eye color, height, and blood type.
• Genes are segments of DNA that code for specific traits.
• Alleles are different versions of a gene.
• Dominant alleles express their trait even if there is a recessive allele present.
• Recessive alleles only express their trait if two copies are present.
• Genotype is the genetic makeup of an organism.
• Phenotype is the physical expression of the genotype.
• Homozygous means having two identical alleles for a trait.
• Heterozygous means having two different alleles for a trait.

Punnett Squares

• Punnett squares are diagrams used to predict the genotypes and phenotypes of offspring.
• They show all possible combinations of alleles from parents.
• They help determine probabilities of specific phenotypes or genotypes.
• A Punnett square is used to predict the outcome of a genetic cross.
• The alleles from each parent are shown on the top and side of the square.
• The possible combinations of alleles are entered into the squares.
• Phenotype probabilities can be determined based on dominant and recessive characteristics.

DNA Structure

• DNA is a double helix structure.
• It's composed of nucleotides.
• Nucleotides consist of a sugar, a phosphate group, and a nitrogenous base.
• The four nitrogenous bases are adenine (A), thymine (T), guanine (G), and cytosine (C).
• A always pairs with T, and G always pairs with C.
• The sequence of bases determines the genetic information.

Chromosomes

• Chromosomes are structures that contain DNA organized into genes.
• Humans typically have 23 pairs of chromosomes.
• Chromosomes are tightly coiled strands of DNA and protein.
• They are essential for cell division and carrying genetic information.
• Chromosomes replicate before cell division to ensure each daughter cell receives a complete set of genetic material.

DNA Replication

• DNA replication is the process of making a copy of DNA.
• It's essential for cell division and passing genetic information to daughter cells.
• The process involves unwinding the DNA double helix.
• Complementary base pairing allows for the creation of two identical DNA molecules from one original molecule.
• Enzymes are vital to this process to separate, copy, and reconnect the DNA.

Gene Expression

• Gene expression is the process by which information from a gene is used to synthesize a functional gene product.
• This typically results in a protein.
• The process involves transcription and translation.
• Transcription is the process where DNA is copied into mRNA.
• Translation is the process where mRNA is used to synthesize a protein with the help of ribosomes.
• The specific amino acid sequence of the protein depends on the sequence of the mRNA bases.

Mutations

• Mutations are changes in the DNA sequence.
• They can be caused by mistakes during DNA replication or environmental factors.
• Mutations can be beneficial, harmful, or neutral.
• Some mutations result in genetic disorders or diseases.
• Types of mutations include substitutions, insertions, and deletions.

Mendelian Genetics

• Mendelian genetics deals with the transmission of traits from parent to offspring.
• It focuses on the patterns of inheritance established by Gregor Mendel.
• These patterns can be predicted by using Punnett squares and other methods.
• Mendelian genetics illustrates dominant and recessive patterns of inheritance in organisms. Basic inheritance patterns like monohybrid and dihybrid crosses are included.

Additional Important Concepts

• Incomplete dominance: One allele isn't completely dominant over another, leading to a blended phenotype.
• Codominance: Both alleles are fully expressed, resulting in both traits appearing in the phenotype.
• Sex-linked traits: Traits located on sex chromosomes (often X chromosomes). Punnett squares can analyze sex-linked inheritance patterns.