Genetics: Heredity and Genes

• Genetics is the study of heredity and genes, serving as a central pillar of biology and overlapping with fields like agriculture, medicine, and biotechnology.

Historical Context

• Greek philosophers pondered human inheritance around 1600 years after 5000 BC.

• Aristotle proposed that lifetime-acquired traits could be passed on.

• Aristotle's theory of pangenesis described traits being passed via gemmules (sex cells), with each organ sending a copy to gametes for transmission to reproductive cells.

• August Weismann rejected Aristotle's theory, proposing the Germ Plasm Theory in 1883.

• Germ plasm, independent of all other cells of the body (somatoplasm or somatic cells).

• Germ cells are the hereditary material passed from generation to generation.

• Gregor Mendel, known as the Father of Genetics, conducted pea plant experiments in 1857.

• Mendel studied specific pea plant traits like height, seed texture and color, and flower color.

• Mendel repeated experiments over two generations, obtaining consistent ratios of traits.

• Mendel deduced four inheritance principles:

  • Hereditary determinants are called genes.
  • Genes exist in pairs called alleles (variations), which may be dominant or recessive.
  • Genes are segregated in gametes, which carry only one gene pair.
  • Fertilization, where two gametes fuse, is random.

• Swiss physician Friedrich Miescher discovered nuclein in 1869.

• Miescher isolated samples of nuclein from salmon sperm.

• Richard Altmann, Miescher's pupil, renamed nuclein to nucleic acid in 1889.

• Nucleic acid exists only in the chromosomes.

• Walter Flemming described the appearance and behavior of chromosomes in 1882.

• Theodor Boveri and Walter Sutton suggested in 1902 that chromosomes carry hereditary units.

• Different chromosome locations (gene loci) corresponded to specific hereditary traits.

• Chromosomes not only carry but also encode different traits.

• Boveri examined chromosomal behavior during cell division and gamete formation.

• This laid the groundwork for cytogenetics, describing chromosome structure, function, and inheritance.

DNA Components

• In 1929, Phoebus Levene at the Rockefeller Institute identified DNA molecule components:
  • Four bases: Adenine, Cytosine, Guanine, Thymine Sugar (Deoxyribose, Ribose) Phosphate
• Levene showed DNA components linked in a phosphate-sugar-base order.
• Levene distinguished deoxyribose and robose subtypes and coined the term nucleotide.
• In 1949, Andre Boivin and his students found that the nuclei of germ cells contained half the amount of DNA than that of somatic cells.
• In the 1940s, Erwin Chargaff found that the base composition (ACTG) varied between species.
• Chargaff stated that Ratios between bases were invariable.
• The quantity of adenine was equal to thyamine this became known as Chargaff's rule.
• In 1952, British researcher Rosalind Franklin crystallized a molecule of DNA.
• From Franklin's x-ray diffraction images, she demonstrated DNA contained repeating helical structure, allowing calculation of molecular spacing in DNA.
• Building on Franklin's work, James Watson and Francis Crick modeled DNA as a double helix in 1953.
• The double helix consists of evenly spaced pairs of bases connecting two strands, enabling prediction of measurements and strict base-pairing rules.
• Thymine could only pair with Adenine and Guanine with Cytosine, concurring with Chargaff's rule.
• Chargaff's rules indicate a 1:1 ratio (base pair rule) of pyrimidine and purine bases in any cell DNA.
• The amount of guanine is equal to cytosine and the amount of adenine is equal to thymine.

Discoveries

• Robert W. Holley, Har Gobind Khorana, and Marshall W. Nirenberg won a Nobel Prize for deciphering how DNA relates to protein synthesis, establishing the central dogma: DNA to RNA to protein.
• In 1977, Frederick Sanger, Allan Maxam, Walter Gilbert developed DNA sequencing methods.
• In 1983, Kary Mullis invented the polymerase chain reaction (PCR) to amplify DNA.
• These methods paved the way for sequencing the human genome, initiated in 1990 and completed 13 years later.
• DNA research expanded to "editing" the genome using novel methods to specifically change encoded information.
• The field of epigenomics rapidly expands, aiding understanding of genome behavior differences.
• Genetic engineering.

Cell Composition

• The cell is the fundamental unit of life.
• The human body is made up of billions and trillions of cells
• Cells of various organs vary according to their function.
• Each cell contains the hereditary material and can make copies of itself by reproducing and multiplying until they die.

Kinds of Cells

• Prokaryotic cells lack a defined nucleus with genetic material dispersed in the cytoplasm.
• Eukaryotic cells have a defined nucleus.
• Plant cells have a cellulose cell wall and contain chloroplasts and vacuoles.
• Animal cells may have flagella.
• Protist cells can have a cell wall without differentiated tissues.
• Fungal cells possess a chitin cell wall and are heterotrophs.

Cell Functions

• Cellular components maintain homeostasis and perform essential life activities.
• Cells are composed of several fundamental components:
  • Cell membrane (cell/plasma membrane) surrounds the cell and acts as barrier
  • Regulates passage of nutrients and waste materials.
  • Specialized proteins facilitate molecular transport and communication.
  • Phospholipid bilayer; hydrophilic

2. Cell nucleus

• Stores genetic information, and controls DNA replication
• Nucleolus inside the nucleus is involved in synthesis

Cytoplasm

• Gel-like matrix containing water, salts, proteins, and other molecules.
• Occupies space between the cell membrane and the nucleus.
• Plays role in biochemical reactions, energy production, and substance transport.
• Supports the cell.

Protein Synthesis

• Building and repairing cellular structures, regulating biological processes, and expressing specific characteristics
• Ribosomes
• Essential for cellular functioning and survival,
• Synthesize proteins using mRNA, which is crucial for structure, function, and regulation.
• Located in the cytoplasm and rough endoplasmic reticulum

Endoplasmic Reticulum

• A network extending from the nuclear membrane to the cell membrane.
• Plays role in the transport, processing, and distribution of proteins and lipids.
  • The Rough Endoplasmic Reticulum (RER) is with ribosomes and involved in the modification and synthesis of proteins.
  • The Smooth Endoplasmic Reticulum (SER) specializes in carbohydrate metabolism, lipid synthesis and detoxification.
• Golgi Apparatus - Processes, modifies, and packages proteins and lipids. Lipoproteins and Carbohydrates which help maintain cells internal balance.

Energy Supply

• Processes are essential for the proper function of the cell.
• Mitochondria are present in eukaryotic animal and plant cells.
• They produce electricity, using cellular respiration to generate energy

Cell Nutrition

• Involves molecules and recycling nutrients. Lysosomes contain enzymes that break down waste cellular components. Peroxisomes degrades hydrogen peroxide and protects cells from oxidative damage.

DNA Composition and Synthesis

• Cytoskeleton: maintains the cell's shape, with protein filaments that enable support and movement in eukaryotic cells.
• Flagella and Cilia specialize in movement which allow relocation.

Storage

• Storage or transportation regulate material, waste, and metabolism cycles..
• Vacuoles are used in plant cells water, and waste.
• Defensive against toxins
• Vesicles and Endosomes transport things between cells.

Genetic Makeup

• DNA strands form of the chromosome form from the genetic makeup of the cell.

• Chromosomes and hereditary traits.

• Typical humans have twenty-three pairs.

• The twenty third pair is referred to as sex chromosomes, the females have XX, and males XY.

• With research techniques DNA structure has made advances.

• Genes are the hereditary composition of the cell, that allows functions to carry out

• DNA consists of two base pairs: Adenine and Thymine

• Human Genomes consists of an estimated thirty-thousand genes.

• Karyotype of complete structures.

• Cytology - determine physical information regarding a gene or chromosome structure.

Cell Division: Mitosis and Meiosis

• Mitosis separates copied chromosomes into different cells.
• Unregulated separation can case complications or illness.
• Cancer of tumor formations
• Genes are for genetic heredity for traits
• Locus specifies a gene on a chromosome
• Gametes are reproductive, all body cells are reproductive cells, sperm and eggs
• Diploid refers to conditions where cells are reproduced.
• Haploid is when cells have new genetic material that's unique to the cell division cycle
• Each stage has different DNA qualities.
• The stages also has qualities that contribute to cancer and issues

Mitosis Structure and cycle

• DNA and protein, all packaged tightly
• Actively dividing cells cycle collectively
• Two phases: synthesis, and synthesis
• Chromosomes 1 and 2 are homologous
• Chromosomes 3 and 4 came from the mom and dad

Mitosis

• Cellular division produces daughters, with the same genetic structure.
• Processes usually take an hour.
• Metaphase is the alignments of chromosomes along the metaphase of the spindle
• Teleophase is that of many reactions occurring.
• Cytokenis is the stage where the final formation occurs, new cells.
• Interphase is the interval between mitotic divisions.

Mitosis and Meiosis Additional INformation

• Ensures the cells have the same genetic makeup and stability throughout stages.
• Anaphase and Metaphase - Ensures the correct distribution amount of chromosomes.
• Ensures balance and structure and prevents errors
• Mitosis maintains correct number
• Cells can also turn into cancer if unregulated.
• The mitosis can occur and effect tissues which impacts the body.
• Specialized cells can arise after differentiation.

Genetics is the study of heredity and genes and is a central pillar of biology. Greek philosophers pondered human inheritance around 1600 years after 5000 BC, with Aristotle proposing that lifetime-acquired traits could be passed on. Gregor Mendel, known as the Father of Genetics, conducted pea plant experiments in 1857.