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

Soma Cells: These cells comprise the whole body, excluding the germ cells.

Germ Line: Specialized cells in reproductive organs responsible for producing gametes.

Karyogamy: The fusion of cell nuclei.

Sexual Dimorphism: Morphological differences between males and females of a species.

Fecundity: The ability to produce offspring.

Withers: When two hermaphroditic individuals mate and fertilize each other.

Parthenogenesis: A phenomenon where an unfertilized egg develops into a normal adult.

Receptaculum Seminis: A storage location for sperm after mating.

Spermatophores: Packets containing sperm that are transferred to females.

Segmentation: A series of rapid cell divisions during early embryonic development.

Morula: A solid ball of cells in the early embryo.... Continue reading "Key Concepts in Reproduction and Embryonic Development" »

Chromosomes and the Cell Cycle

Chromosomes undergo distinct changes throughout the cell cycle. Here's a summary of their states:

• Invisible Chromosomes (Chromatin) with One Chromatid: Initially, chromosomes exist as invisible chromatin fibers, each with a single chromatid.
• Formation of a Second Chromatid: A second chromatid is formed, creating a mirror image.
• Invisible Chromosomes (Chromatin) with Two Chromatids: Chromosomes remain as invisible chromatin but now consist of two chromatids.
• Condensation and Visibility: Condensation of the chromatids occurs, making the chromosomes visible.
• Visible Chromosomes with Two Chromatids: Chromosomes are now clearly visible, each composed of two chromatids.
• Separation of Chromatids: The two chromatids separate

Mendel's Laws

Mendel explained the observations made during years of crossing different types of peas in the gardens of a monastery. He collected the general laws of inheritance that later became known as Mendel's laws.

Double Helix DNA

DNA carries the genetic information. DNA is a molecule composed of four simple units, repeated often and combined in different ways (called nucleotides). There are four types of DNA nucleotides: cytosine, guanine, thymine, and adenine. A single DNA molecule is formed by two chains of nucleotides linked and facing each other, with a structure that forms a spiral staircase: a double helix.

Replication of DNA

DNA contains genetic information. When the cell divides, it is capable of making an exact copy of the entire... Continue reading "Mendel's Laws, DNA, Genes, and the Genetic Code" »

Biomolecules and Genetic Information

Biomolecules form long chains, such as in genetic information storage. These chains consist of repeating nucleotides. A nucleotide is composed of a nitrogenous base, a pentose sugar (like am5C), and a phosphate group. A nucleoside is simply a base plus a pentose sugar.

Nitrogenous bases include adenine (A), thymine (T), uracil (U), and guanine (G). Purine bases (A and G) have a two-ring structure, while pyrimidine bases (C, T, and U) have a single-ring structure. These bases contain the genetic code necessary for protein synthesis. Approximately 3000 base pairs are needed to code for a single protein. The human genome contains 46 chromosomes (23 pairs), with 22 pairs being autosomes and one pair being sex... Continue reading "Biomolecules, Genetics, and Chromosomal Variations" »

Fertilization Process

Ovulation occurs about fourteen days before menstruation. The egg released from the Graafian follicle is propelled along the fallopian tube to the uterus, taking over a week for this journey.

The egg can be fertilized for only 24 hours after ovulation while traveling along the fallopian tube.

Intercourse, or the sexual act, is the introduction of the penis into the vagina. At ejaculation, sperm are released inside the vagina.

Unlike the egg, sperm are very fast. They ascend through the vagina, traverse the cervix and uterus, and reach both fallopian tubes in a few hours. They can also survive for three to five days, so if intercourse occurs in the days before ovulation, the probability of pregnancy is very high.

If the egg... Continue reading "Fertilization and Early Pregnancy Stages" »

DNA Replication

DNA replication begins with the double helix unwinding, separating like a zipper. Each strand serves as a template for creating a new complementary strand. DNA polymerase enzymes add nucleotides one by one, matching adenine with thymine and guanine with cytosine. This process creates two identical DNA molecules, each with one original and one new strand. Errors during replication can lead to mutations, which can be harmless, cause diseases, or contribute to evolution.

The Importance of Base Complementarity

Base complementarity is crucial for accurate DNA replication, ensuring that genetic information is passed correctly from parent to daughter cells. It also forms the basis of many molecular biology techniques.

Gene Expression:

Antibiotics

They test substances for chemical, biological, or synthetic origin that kill bacteria or prevent their multiplication. After years of research, we succeeded in isolating the substance that prevented the development of bacteria. It was the first antibiotic known as penicillin, discovered by Alexander Fleming. Other antibiotics have been discovered and manufactured in the laboratory; these synthetic antibiotics have a similar effect.

Antiviral

Antivirals act on bacteria; however, they have no effect on other infectious agents. For bacterial infectious diseases, other drugs should not be used.

The importance of certain viral diseases (such as AIDS) has forced pharmaceutical companies to put their efforts into development. It is not easy... Continue reading "Understanding Antibiotics and Antivirals: Key Insights" »

1. Health and Disease

1.1. Definitions

Health: A state of complete physical, mental, and social well-being, not merely the absence of disease.

Disease: A change in health status, i.e., a temporary or permanent loss of physical, mental, and social well-being.

Quality of Life: The comfort level, happiness, and satisfaction in a person that allows them to act and feel positively about their lives. This depends on their physical and mental health, their level of independence, and social relationships. One of the main indicators is life expectancy at birth.

1.3. Genes, Lifestyle, and Health

There are genetic diseases due to alterations in the genome (e.g., Down syndrome, hemophilia, or certain types of diabetes).

In other cases, the genotype determines... Continue reading "Health, Disease, and Infectious Diseases: A Comprehensive Overview" »

Uric Acid Stones: Causes, Treatment, and Diet

Uric acid stones are associated with the production of acidic urine.

Treatment for Uric Acid Stones

• Increase fluid intake.
• Increase urine pH to 6.0-6.5.
• Adopt a diet rich in alkaline-forming foods, supplemented with citrate or bicarbonate.

Dietary Considerations for Uric Acid Stones

Acid-Forming Foods (Potentially Acidic Residue)

• Meat: Beef, fish, game, seafood.
• Dairy: Eggs, cheese.
• Fats: Bacon, walnuts, Brazil nuts, hazelnuts.
• Grains & Baked Goods: Flour, bread (especially whole wheat), cereal, biscuits, pasta, rice, cakes.
• Vegetables: Corn, lentils.
• Fruits: Blueberries, plums.

Alkaline-Forming Foods (Potentially Basic Residue)

• Dairy: Milk and milk products, cream, whey.
• Fats: Almonds, chestnuts, coconut.
• Vegetables:

Types of Illness

There are several types of illness:

• Physical illness: Caused by injury, infection, or a degenerative process of the organism.
• Mental illness: May result from a malfunction of the brain.
• Social diseases: Can be caused by the existence of a violent social environment.

Defining Health and Illness

Health is a state of complete physical, mental, and social well-being. Illness is the state in which a person's health is disturbed.

Violence: Impact on Health and Society

Violence is a detrimental social issue, often originating in childhood. It negatively influences health, potentially harming or causing the death of loved ones, family members, or neighbors.

Understanding Infectious Diseases

Infectious diseases are caused by pathogens (such as... Continue reading "Foundations of Health: Diseases, Risks, and Well-being" »