Notes, summaries, assignments, exams, and problems for Biology

Genetics: The Study of Gene Inheritance

Genes are transmitted according to defined rules or laws. Genes are located on chromosomes, which are cellular structures. Sex is determined by specific genes or chromosomes in most living organisms.

Key Genetic Terms

• Genotype: The genetic constitution of an individual, referring to a specific character or the entire set of genes.
• Phenotype: The external expression of the genotype; the observable characteristics of an individual.
• Alleles: Variants that a gene may present. For each gene, an individual has a pair of alleles, often represented by letters.
• Homozygous: An individual having two identical alleles for a specific gene.
• Heterozygous: An individual carrying two different alleles for a specific gene.

Mendelian

Acoustic and Articulatory Classification of Speech Sounds

Places of Articulation (Phonetic Classification)

Sounds are classified based on where the vocal tract is constricted:

• Labial (Lip): Severe and diffuse sound, articulated with the lips.
  • Voiced (Sonoro): (b, m)
  • Unvoiced (Sordo): (p, f)
• Dental: Acute and diffuse sound, articulated with the tongue on the teeth (anterior and coronal).
  • Voiced (Sonoro): (d)
  • Unvoiced (Sordo): (t, s [strident], c [mate])
• Velar (Soft Palate): Serious, thick sound, articulated by striking the tongue against the soft palate (velum).
  • Voiced (Sonoro): (g [as in 'gue'])
  • Unvoiced (Sordo): (k, x [j])
• Palatal: Acute and dense sound, articulated by rubbing the tongue against the hard palate (coronal).
  • Voiced (Sonoro): (ñ, y)
  • Unvoiced

Immunodeficiencies: Types and Causes

An individual suffers from an immunodeficiency when their immune system is unable to effectively combat or stop an infection. These conditions are broadly categorized into two main types: congenital and acquired.

Congenital Immunodeficiencies

Congenital immunodeficiencies are genetic and inherited conditions. They arise from failures in the synthesis of the complement system or from the abnormal development of lymphoid organs. These can manifest as:

• B Lymphocyte Defects

  These are due to defects in B lymphocytes, which are unable to produce normal antibodies or produce them in insufficient quantities. Symptoms typically do not appear until after 6 months of age.

• T Lymphocyte Defects

  Defects in T lymphocytes are

Fundamentals of Protein Synthesis

1. Information for Protein Synthesis

Question: Which part of the cell contains the information needed to synthesize a protein?

Answer: Deoxyribonucleic Acid (DNA), primarily located in the nucleus.

2. Cellular Organelles for Protein Production

Question: What are the cellular organelles responsible for making proteins, and where are they located in the cell?

Answer: Ribosomes, which are primarily located in the cytoplasm and on the endoplasmic reticulum.

3. Understanding RNA (Ribonucleic Acid)

Statement: RNA, or Ribonucleic Acid, plays a crucial role in gene expression and protein synthesis.

4. RNA Nucleobases

Question: Name the four nucleobases found in RNA.

Answer: Cytosine, Guanine, Adenine, and Uracil.

5. The Process

Fertilization

Fertilization is the fusion of male and female gametes, initiating the process of reproduction. It's important to note that fertilization of the egg is not immediate upon contact.

Human Fertilization

In humans, fertilization occurs when a sperm and egg unite in the fallopian tubes after sexual intercourse. Humans develop from the union of these two tiny cells. Mature eggs measure approximately 0.135 mm in diameter, while sperm are even smaller. Each ejaculation can contain between 120 and 600 million sperm. The union of these cells has the potential to create a new human being with extraordinary abilities.

Zygote

In biology, a zygote is the cell formed by the union of male and female gametes during sexual reproduction in organisms... Continue reading "Human Reproduction: From Fertilization to Embryonic Development" »

Fundamentals of Genetics and Heredity

Genes: Units of Heredity

Genes are the fundamental units of heredity.

Mendel's Experiments on Inheritance

To test his hypotheses, Mendel crossed pure strains differing in a single character (e.g., tall or dwarf plants, green or yellow seeds—up to seven different traits). He approached the problem quantitatively and with patience.

For each variety studied, he found, surprisingly, that the first generation (F1) were all identical. All offspring resembled one character from the father or the mother.

After crossing the F1 generation with each other, he found that the grandchildren (F2) were not all identical.

He also noted that if the parents differed by more than one character, each character is transmitted independently

Infectious Diseases

Definition

Temporary or permanent loss of health caused by microorganisms.

Types of Microorganisms

• Bacteria: Unicellular prokaryotic organisms that multiply and can destroy cells and tissues.
• Viruses: Not considered living organisms. They reproduce by entering cells and using their resources, causing damage.
• Protozoa: Single-celled eukaryotes. Some cause disease.
• Fungi: Unicellular and multicellular eukaryotes. Some can cause disease in weakened individuals.
• Parasites: Multicellular organisms that live at the expense of a host, weakening but not killing it.
• Prions: Misfolded proteins that accumulate and cause neuron degeneration.

Non-Infectious Diseases

Nonspecific Defenses

Mechanisms that prevent the entry of microorganisms:

• Skin: Acts

Definition of Infectious Diseases

An infectious disease occurs when a parasite develops and multiplies within a host. The causal agent of transmissible diseases is usually a living organism that moves from one individual to another by contagion. The set of elements that define a communicable disease consists of:

• Reservoir: Where infectious agents are usually found.
• Source of Infection: Animate or inanimate object from which the causative agent originates.
• Mechanism of Transmission: The pathways that allow the causal agent of a transmissible disease to contact the host.
• Host: A person susceptible to contracting a communicable disease upon contact with the source of infection.

Samples arriving at the laboratory for the diagnosis of causative agents... Continue reading "Infectious Diseases: Definition, Transmission, and Diagnosis" »

Genetics and Heredity

Genetics is the science that studies how traits are inherited. Besides hereditary traits, external factors, including the environment, cause changes. Species variation is the manifestation of differences between individuals of the same species. The main causes are genetic variations.

Continuous and Discontinuous Variation

Continuous variation occurs when a trait has slightly different manifestations, like hair or skin color. Discontinuous variation occurs when a trait is clearly expressed as different and is genetically determined, not changing during an individual's life.

Phenotypic and Genotypic Variations

Phenotypic variations are observable traits (weight, height, color) resulting from the environment and genotype. Genotypic

Main Characteristics of Mammals

In general, mammals are characterized by the following:

• They are warm-blooded; their body temperature is constant.
• Mothers have mammary glands that produce milk for their young.
• The mouth is surrounded by lips, allowing young to suckle.
• They have abundant glands (sebaceous, sweat, and odoriferous) and are generally covered in fur, which they shed periodically.
• They have teeth to chew food.
• They have pulmonary respiration.
• Circulation is double (pulmonary and general).
• Most are viviparous: The embryo develops inside the mother and is nourished through the placenta.

Mammals are among the most highly evolved animals. They can live on land, fly, or live in the water.

Here, we will examine in more detail some common characteristics... Continue reading "Key Characteristics and Evolution of Mammals" »