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What is Genetics?

• Genetics is the study of heredity and genes.
• It is a pillar of biology, intersecting agriculture, medicine, and biotechnology.

Historical Context

• Greek philosophers explored human inheritance around 3400 years ago.
• Aristotle proposed traits acquired during life could be inherited; pangenesis describes how particles, called 'gemmules', transmit these traits via gametes.
• August Weismann rejected Aristotle's theory with the Germ Plasm Theory (1883), stating germ plasm is independent of body cells and is the hereditary material passed down.
• Gregor Mendel, the "Father of Genetics", experimented with pea plants in 1857.
• Mendel Studied plant height, seed texture/color, flower color, pea-pod size/color, and flower position.
• Mendel repeated experiments over generations, deducing four inheritance principles:
  • Hereditary determinants are called genes.
  • Genes exist in pairs (alleles), which may be dominant or recessive.
  • Genes segregate in gametes, each carrying one gene pair.
  • Fertilization is random, involving the fusion of two gametes.
• Swiss physician Friedrich Miescher discovered 'nuclein' in 1869 and isolated a purer sample from salmon sperm.
• In 1889, Richard Altmann (Miescher's pupil) renamed nuclein to 'nucleic acid', found exclusively in chromosomes.
• In 1882, Walter Flemming described chromosome appearance and behavior.
• Theodor Boveri and Walter Sutton independently postulated in 1902 that chromosomes carry hereditary units organized with specific gene loci; Boveri studied chromosomal behavior during cell division/gamete formation, forming the basis of cytogenetics.
• In 1929, Phoebus Levene at the Rockefeller Institute identified DNA components: four bases (adenine, cytosine, guanine, thymine), deoxyribose/ribose sugar, and phosphate.
• Levene determined components were linked as phosphate-sugar-base, distinguished ribose subtypes, and coined 'nucleotide' for the sugar, base, and phosphate arrangement.
• In 1949, André Boivin and Roger Vendrely found germ cell nuclei contain half the DNA of somatic cells.
• In the 1940s, Erwin Chargaff found base composition differed between species but ratios were invariable.
• Adenine equaled thymine, and cytosine equaled guanine, known as Chargaff's Rule.
• In 1952, Rosalind Franklin's X-ray diffraction images showed DNA has a regularly repeating helical structure, allowing calculation of molecular spacing.
• James Watson and Francis Crick built on Franklin's work to create a double helix model with evenly spaced base pairs.
• Thymine pairs with adenine, and guanine with cytosine, concurring with Chargaff's rule of a 1:1 ratio of pyrimidine and purine bases.

Notable Discoveries After the Double Helix

• Robert W. Holley, Har Gobind Khorana, and Marshall W. Nirenberg won a Nobel prize for deciphering the DNA-protein link, establishing the central dogma of DNA to RNA to protein.
• Frederick Sanger, Allan Maxam, and Walter Gilbert developed DNA sequencing methods in 1977.
• In 1983, Kary Mullis invented the polymerase chain reaction (PCR) to amplify DNA.
• These methods paved the way for sequencing the human genome, which began in 1990 and was completed 13 years later.

Today

• Focus has shifted to genome editing with methods to specifically alter encoded information.
• Epigenomics is rapidly expanding to understand individual genome behavior differences.

Cell Structure and Basic Funtions

• Cells are the basic structural unit of the body.
• The human body is composed of billions of cells.
• Cell structure and function varies based on organ.
• Cells contain hereditary material.
• Cells reproduce and multiply.
• Cells die off after a specific life span.
• Components work together to maintain homeostasis and perform essential life activities.
• Plasma membrane surrounds the cell.
• The plasma membrane is a selective barrier.
• Primary role is regulating passage of substance, including nutrients and waste materials. Specialized proteins assist the transport of materials through out cells.
• Cell nucleus houses DNA in eukaryotic cells.
• The primary function of the cell nucleus is storing/safeguarding genetic information.
• The cell nucleus controls gene expression and DNA replication.
• The cell nucleus contains the nucleolus which is involved in ribosome synthesis.
• Cytoplasm is a gel-like matrix containing water, salts, proteins, and other molecules.
• The cytoplasm is crucial for biochemical reactions, energy production, and substance transport.
• The cytoplasm provides structural support to the cell.
• Building and repairing cellular structures, regulating biological processes, and expressing specific characteristics of each organism.
• Ribosomes synthesize protein with genetic information from from mRNA.
• Ribosomes are essential for cellular functioning and survival.
• Ribosomes are located in the cytoplasm and the rough endoplasmic reticulum.
• Endoplasmic reticulum is a network of interconnected membranes, extends from nuclear membrane to cell.
• The endoplasmic reticulum plays a fundamental role in the transport, processing, and distribution of proteins and lipids within the cell.
• The Rough Endoplasmic Reticulum RER is studded with ribosomes and is involved in the synthesis and modification of proteins.
• The Smooth Endoplasmic Reticulum SER specializes in lipid synthesis, carbohydrate metabolism, and detoxification
• The Golgi apparatus is key in the processing and proteins of lipids produced in teh endoplasmic reticulum.
• Consists of flattened sacs called cisternae.
• The golgi apparatus synthesizes carbohydrates and lipoproteins.

Energy Supply

• To carry out vital functions and necessary metabolic processes essential for proper functioning of the cell.
• Mitochondria are in eukaryotic animal and plant cells.
• Mitochondria's primary function is energy generation through cellular respiration (ATP production.)
• Chloroplasts are exclusive to plant cells and photosynthetic organisms.
• Chloroplasts carry out photosynthesis, converting solar energy into chemical energy.
• Chloroplasts synthesize glucose and other organic compounds using carbon dioxide and water, releasing oxygen.

Cellular Digestion

• Cellular digestion involves breaking down molecules and unwanted materials, enabling the recycling of nutrients and cellular maintenance.
• Peroxisomes contain enzymes that degrade hydrogen peroxide and toxic compounds, protecting the cell from oxidative damage.
• Lysosomes contain digestive enzymes that breakdown molecules and unwanted cellular materials.

Support and Movement

• Maintaining cellular shape, enabling cellular movement and division, are essential for its functioning and survival.
• Cytoskeleton (microtubules, microfilaments, and intermediate filaments) provides support and enables movement in eukaryotic cells.
• Flagella and cilia have specialized structures for movement.

Storage and Transportation

• They manage nutrients, eliminate waste, and regulate metabolic processes.
• Vacuoles are membrane-bound organelles found in pant and some animal cells.
• Vaculoles store nutrients, water, ions and waste materials.
• Vesicles and endosomes are membranous vesicles that transport specific materials between the cell membrane.

DNA, Chromosomes, and Genes

• Within the nucleus, the DNA strands are tightly packed to form chromosomes.
• During the cell division, the chromosomes are visible.
• Each chromosome has a constriction point called the centromere from from where two arms are formed.
• The short arm is labelled "p arm".
• The long arm of the chromosome is labelled the "q arm".
• Humans typically have 23 pairs of chromosomes for a total of 46.
• 22 pairs of chromosomes are autosomes.
• The 23rd pair is called the sex chromosomes and differs between males and females.
• Females have two copies of the X chromosomes, while males have on X and one Y chromosome.
• DNA is responsible for building and maintaining your human structure.
• Genes are herefitary material that lies within thr cell nucleus.
• Genes are made up of DNA and act as instructions to make molecules called proteins.
• The Human Cenome Project estimates that humans have between 20,000 - 25,000 genes
• Every peson has two copies of each gene, one inherited from each parent.
• DNA or deoxyribonucelic acid, lies within the nucelus of all cells in humans or living organism.
• Adenine (A) and Guanine (G) Purine
• Cytosine (C) and Thymine (T) are Pyrimidine
• DNA bases pair with eachother
• Adenine-Thymine is held together by 2 hydrogen bonds
• Guanine-Cytosine is held together by 3 hydrogen bonds

Human Chromosomes

• There are 23 chromosomes that occur in pairs.
• 23 pairs consist of autosomes and allosomes
• The first 22 pairs are autosomes and the 23rd pair is the allosome.

Cell Cycle, Mitosis, Meiosis

• Gene is the basic unit of heredity; codes for a specific trait.
• Locus is the specific location of a gene on a chromosome (locus- plural loci)
• Genome is the total hereditary endowment of DNA of a cell or organism.
• Somatic cell are all body cells except for reproductive cells.
• Gamete are reproductive cells.

Types of Cells

• Diploid is the cellular condition where each chromosome type is the same and represented by two homologous chromosomes. Haploid on the other hand, the cellular condition where is each chromosome is represented by only one chromosome.

Chromosome Structure

• The regions of the chromosome are composed of DNA and protein that are all tightly wrapped in one package.
• Duplicated chromosomes are connected by a centromere.
• Chromosomes 1 and 2 are homologous chromosomes.
• Chromosomes 3 & 4 are homologous chromosomes.
• Chromosomes 1 and 3 came from the mother
• Chromosomes 2 & 4 came from the father.
• Actively dividing cells pass through a series of stages known collectively as the cell cycle: two gap phases (G1 and G2); an S (for synthesis) phase, in which the genetic material is duplicated; and an M phase, in which mitosis partitions the genetic material and the cell divides.

The Cell Cycle

• G1 phase: Metabolic changes prepare the cell for division.
• S Phase: DNA syntesizes replicates the genetic material.
• G2 Phase: Metabolic changes assenble cytoplasmic materials necessary for mitosis and cytokinesis.
• M Phase: A nuclear division (mitosis) followed by a cell division (cytokinesis).
• Mitosis is a form of eukaryotic cell division that produces two daughter cells with the same genetic component as the parent cell.
• In actively dividing animal cells, the whole proccess takes about one hour.
• Prometaphase: The chromosomes line up along the midline of the cell.
• Individual spindle fibers bind to a kinetochore structure on each side of the centromere the chromosomes continue to condense.

Additional Information to Review For Prelim Exam

• If spindle fibers fail to attach, most chromosomes may not align properly and there may be issues with the amount of chromosomes one cell could recieve over the other. Results could then show that one may recieve an extra chromosome, while the other is missing chromosomes - this is seen in diseases such as cancer.
• Apoptosis helps to remove damaged cells which is nessesary for mitosis where things grow in excess. The process helps prevent tumour formation and ensures tissue homeostasis.