Digestive System Explained

• The digestive system, also known as the gastrointestinal (GI) tract, breaks down food into smaller molecules for absorption, utilizing nutrients for energy, growth, and repair, while eliminating waste.

Organs of the Digestive System

• The mouth initiates digestion by mechanically breaking down food through chewing and mixing it with saliva.
• Amylase in the mouth breaks down complex carbohydrates into monosaccharides like glucose.
• The esophagus transports food and liquids from the mouth to the stomach through peristalsis.
• The stomach is a J-shaped structure that further breaks down food.
• The small intestine absorbs nutrients.
• The large intestine absorbs water and forms stool from undigested food material.
• The rectum, the final section of the large intestine, stores stool before it's passed out of the body.
• The anus is the external opening of the digestive tract, through which stool is expelled.
• Accessory digestive organs, including the liver, pancreas, and gallbladder, work together to break down food.
• The liver is the largest internal organ in the human body.
• Doctors advise patients with acid reflux to avoid lying down immediately after eating; standing helps keep stomach contents from flowing back into the esophagus.

Cellular Reproduction

• Cellular reproduction is the process where a parent cell divides into two daughter cells, vital for growth, repair, and maintenance of tissues.
• Cellular reproduction occurs through mitosis (for somatic cells) or meiosis (for germ cells).

Mitosis vs. Meiosis

• Mitosis makes body cells (somatic cells), resulting in 2 identical daughter cells.
• Meiosis makes gametes (sex cells) essential for sexual reproduction, resulting in 4 non-identical daughter cells.
• Meiosis ensures that chromosome number remains constant across generations by reducing the chromosome number in gametes and also ensures genetic diversity.

Stages of Cellular Reproduction

• Interphase includes G1 (growth and development), S (DNA replication), and G2 (final checking).
• Cell division includes PMAT: prophase, metaphase, anaphase, and telophase
• Prophase: chromatin condenses into chromosomes.
• Metaphase: chromosomes align at the middle of the cell.
• Anaphase: sister chromatids move to the different poles of the cells.
• Telophase: nuclear membrane formed and cell divides into two daughter cells (2n).

Spermatogenesis and Oogenesis

• Spermatogenesis and oogenesis are the processes that produce male and female gametes (sperm and ova) respectively, both involving meiosis but with key differences in the number and type of cells produced.
• Spermatogenesis produces 4 sperm, while oogenesis produces only 1 egg/ovum.

Mendelian Genetics

• Gregor Mendel is the Father of Genetics
• Pisum sativum is the scientific name of the pea plant used by Gregor Mendel in his genetic experiments.
• The Law of Segregation: gametes receive one allele for each gene from each parent.
• The Law of Dominance: one allele is dominant, and the other is recessive; the dominant allele masks the recessive trait.
• The Law of Independent Assortment: alleles of different genes assort independently of one another, meaning the inheritance of one trait doesn't influence the inheritance of another.
• Klinefelter Syndrome (XXY) is a condition in which a male has an extra X chromosome due to a failure of chromosome separation during meiosis.
• Patau syndrome, also called trisomy 13, occurs when all or some cells of the body contain an extra copy of chromosome 13, due to nondisjunction in one of the gametes.
• Cri-du-chat syndrome, also known as “Cat’s Cry Syndrome,” is a rare genetic disorder caused by a deletion in chromosome 5.
• Dominant alleles are represented as AA or Aa.
• Recessive alleles are represented as aa.
• A recessive allele trait is only expressed when paired with another identical recessive allele, meaning two copies are needed for the trait to be visible, while a dominant allele's trait will be expressed even with only one copy.
• Homozygous is represented as AA or aa.
• Heterozygous is represented as Aa.
• Genotype refers to the genetic makeup.
• Phenotype refers to the observable trait.
• Monohybrid investigates the inheritance of a single trait.
• Dihybrid examines the inheritance of two traits simultaneously.
• Blue eyes are possible in a child with brown-eyed parents if both parents are heterozygous (Bb), carrying the recessive allele for blue eyes (bb).