Notes, summaries, assignments, exams, and exercises for Biology for Baccalaureate

Unit 10: The Basis of Heredity - Molecular Genetics

Basics of Genetics

• Gene: Each piece of DNA containing information for one character.
• Alleles: Each form a gene can have.
• Locus: The physical location a gene occupies on a chromosome.
• Loci: The place occupied by several genes.
• Diploid Organisms: Individuals who have two alleles for each gene, one from the mother and one from the father. This is represented as 2n.
• Haploid Organisms: Individuals that have only one gene for each character. This is represented by n.
• Gamete: A sexual reproductive cell, haploid (n), produced by meiosis.
• Genotype: The set of alleles of an individual for one or more characters.
• Phenotype: Each of the aspects or observable manifestations of a character.
• Phenotype = Genotype +

Understanding Viral Structure

Viruses are microscopic particles that are structurally very simple. They lack a cellular structure, cytoplasm, and the enzymes necessary for metabolism.

Viruses are classified by the host they parasitize, their type of genetic material, or the form of their protein capsule.

Structure of a Virus

Viruses consist of three primary elements:

• Viral Genome: Composed of one or more DNA or RNA molecules, but never both simultaneously. Viral genomes can be open-chain or circular, and single-stranded or double-stranded.
• Capsid: The protein coat that surrounds and protects the viral genome. In enveloped viruses, it helps recognize membrane receptors in host cells. Types include:
  • Icosahedral Capsid: A multifaceted structure formed

Viruses

• YF: icosahedral capsid, RNA and lipid envelope; vector: mosquito saliva. Causes infections in the liver, kidney and other organs. No vaccine.
• FLU: (airborne) enveloped virus with eight nucleocapsids and helical RNA; causes respiratory tract infections and sometimes lung involvement.
• HEPATITIS B: double-stranded DNA, enveloped; causes general weakness, nausea, vomiting. Can be transmitted through the blood. No vaccine.
• GENITAL HERPES: double-stranded DNA, icosahedral capsid and envelope; causes infections and blisters around the anus and urethra. Incurable, but acyclovir is often given.
• MUMPS: transmitted through the air; causes upper respiratory tract infection and inflamed glands; treated with vaccine.
• POLIOMYELITIS: (vehicle: water &

Role of Evolutionary Mutations

Mutations themselves are not evolutionary necessities; they must be favored by natural selection to persist. Predispositions occur by chance, not necessity, and can be:

• Advantageous: Selected and allowed to spread.
• Unfavorable: Eliminated by natural selection.
• Neutral: The majority; their persistence depends on random chance.

Gene or Allelic Frequency

This is the proportion of a specific gene within the overall population.

Allele Frequency Calculation: (Number of subjects with AA × 2 + Number of individuals with Aa) / (Total number of alleles).

Genotype Frequency

This is the proportion of a population exhibiting a particular genotype.

Frequency Calculation for AA Genotype: (Number of AA individuals) / (Total number of...

The Human Genome Project

The human body consists of approximately 10 trillion cells. Each cell contains 46 chromosomes (23 pairs), and each chromosome holds a specific number of genes. The Human Genome Project is a national scientific research initiative focused on determining the sequence of chemical base pairs that constitute human DNA and identifying all genes within the human genome.

Launched in 1990 by a U.S. government agency, this project was technically and scientifically challenging, involving the development of cutting-edge technologies. Its success signaled the commercial and scientific superiority of the country. In 1996, the project evolved into a public consortium. This phase focused on highly accurate sequencing: chromosomes were...

Initiation Phase: Unwinding the Double Helix

The initiation phase involves the unwinding and opening of the double helix. This process initiates in a region of DNA called the origin of replication (oriC point). Helicases break the hydrogen bonds of the nitrogenous bases, and as the double helix unwinding occurs, it creates tensions that could lead to more coiling. Therefore, topoisomerases break and rejoin strands, while SSB proteins (Single-Strand Binding proteins) bind to the template strands to prevent any recurrence of winding. A replication bubble is formed, containing two Y-shaped areas called replication forks, where new DNA strands will be synthesized.

Elongation: Synthesizing New DNA Strands

During elongation, a new strand of DNA is synthesized...

Population Genetics and Genetic Drift

When a small group founds the next generation, fewer individuals represent the genetic diversity of the original population. This situation can lead to the founder effect, where the founders' different characteristics are disproportionately represented in their progeny. Likewise, populations that suffer drastic reductions due to drought, pests, or catastrophic incidents undergo a bottleneck effect.

Natural Selection

Natural selection is the elimination of less fit individuals: organisms with lower biological efficiency contribute fewer genes to the next generation. Selection acts on phenotypes and thereby produces changes in genotypic frequencies and adaptations. Selection and mutation have antagonistic actions;...

Mitosis: Process and Purpose

Mitosis is a process of asexual cell division in which a diploid stem cell produces two cells equal to each other and identical to the mother cell. The two daughter cells have the same number of chromosomes as the parent cell and identical genetic information. The only difference is that their chromosomes are single (one chromatid) instead of the double chromosomes from the mother cell.

Function in Organisms

Mitosis in unicellular organisms serves to increase the number of individuals. In multicellular organisms, it serves for individual growth, regeneration of lost cells, and repair of damaged structures. Mitosis is divided into four stages which are not always sharply defined. Distinguish between mitosis (nuclear...

Genes and DNA

Genes are segments of DNA found in chromosomes. DNA is a molecule that stores genetic information.

DNA Replication

The process of copying the double helix of DNA. The helix opens like a zipper, and each strand is used as a template to create a complementary chain.

Genetic Function and Protein Synthesis

Genes serve to transmit genetic information. The genetic code provides instructions for making proteins from the nucleotide sequence of DNA. Nucleotides include: A, T, C, and G.

Understanding Mutations

A mutation is an error in the copying of DNA or RNA, or a protein involved in nucleotide exchange. Mutations can be:

• Neutral: No change in the protein; does not affect the individual.
• Beneficial: Changes the protein and provides a positive

Muscle Tissue Physiology

Muscle tissue consists of elongated cells capable of contracting and relaxing, performing mechanical work that facilitates the movement of bones. The cytoplasm is immersed in a multitude of myofibrils composed of actin and myosin.

Types of Muscle Tissue

• Smooth Muscle Tissue: Characterized by slow, involuntary contractions. These cells are spindle-shaped and contain a single nucleus. This musculature is found around the endothelium.
• Striated Muscle Tissue: Features cross-banded cells. There are two primary types:

Striated Skeletal Muscle

This tissue accompanies the movement of vertebrate bones and is composed of large cells. Due to high energy demands, these cells contain large numbers of mitochondria. They perform fast, voluntary...