GENETICS

**GENETICS**

* the scientific study of how physical, biochemical, and behavioral traits are transmitted from parents to their offspring.
* the science of heredity.
* It explains how genes bring about characteristics in living organisms and how those characteristics are transmitted from parents to offspring.
* It is at the center of all biology because gene activity underlies all biological processes!

1. **Molecular/cellular genetics** 
2. **Mendelian genetics** 
3. **Population genetics**

**THREE LEVELS OF GENETICS**

**Molecular/cellular genetics**

* what genes are, what they do
* Studies activities of gene (molecules that carry genetic information from generation to generation).
* Concerned with molecules that compose the genes, molecules that control genes & molecules that are the products of genes.

**MENDELIAN OR CLASSICAL GENETICS**

* **TRANSMISSION GENETICS**
* inheritance and expression of traits
* Explains patterns of transmission of traits from generation to generation
* Examines phenotypic characteristics & how they are transmitted

**POPULATION GENETICS**

* Studies variation of genes between & within populations.
* Aims to understand how the observed genetic variation evolved.
* The study of genetics at the population level.

**MENDELIAN POPULATION** 

* a group of sexually reproducing organisms with a close degree of genetic relationship.

**GENE POOL**

* a mixture of the genetic units (Genes or Gametes) produced by a Mendelian population from which the next generation arises. Alleles occur in this pool.
* **EVOLUTION:** Through events such as natural selection, migration, or mutation, the gene pool changes as new alleles enter or existing alleles exit the pool. These changes are the basis for evolution.

**GREGOR MENDEL**

* an Austrian monk
* He discovered important facts about heredity using garden peas.
* The father of genetics
* Grew pea plants, and observed the patterns of the baby pea plants he made and how they differed from their parents - heredity
* He discovered that hereditary characteristics were determined by genes that are transmitted between. generations in uniform predictable manner.

1. The gene is inherited from generation to generation in such a fashion that each progeny has a physical copy of this material.
2. It provides information regarding the structure, function & other biological properties of the characteristic or trait it controls.

**TWO IMPORTANT ATTRIBUTES OF THE GENE**

* Development & maintenance of the individual's unique inherent pattern in dynamic interplay with the environment.
* Deals with the ability of the species to transfer the system to the other generations (primary requirement for continued existence).
* Deals with the orderly variety of patterns among living forms & their changes with time on a geological scale (constitutes accomplishment of evolution).
* Deals with similarities & differences in the patterns encountered within human species.

**SCOPE OF GENETICS**

1. Field of Medicine
2. Agriculture/Food Production/Industry
3. Legal Application
4. Genetic Counseling
5. Genetic Code

**APPLICATION OF GENETICS**

**MEDICINE**

* Diseases & abnormalities that have genetic bases have been identified & appropriate preventive measures prescribed.

**GENE THERAPY**

Employed to prevent heritable diseases such as hemophilia, diabetes, hemoglobin abnormalities, some forms of mental disorders, blindness & deafness.

**AGRICULTURE**

* Plant, animal & microbial improvement.
* High yielding & pest resistant varieties of rice, corn, wheat.
* Advances in meat production of cattle, swine, poultry.
* Higher efficiency in fermentation that have increased productivity in fermented food & food products.

**LEGAL APPLICATION**

* Genetics has helped solve problems of disputed parentage in settling child support, estate claims or even baby mix up in hospitals.
* Traits commonly used are DNA "fingerprints" or profiles, ABO & MN blood types & some enzyme markers.
* DNA profiles of suspects have been found to be an accurate tool in identifying criminals.

**CELL**

basic unit of life.

330 years ago

When did the study of cells started?

microscope

the cell became visible because of this

* 1665: **Robert Hooke**

* English Scientist and Microscopist.
* Observed sliver of cork.
* Saw a row of empty boxes.
* Discovered and coined the term "cell".

1665: **Robert Hooke**

fatherof cytology

1670: **Antoine van Leeuwenhoek**

* Dutch Biologist and Microscopist.
* Described cells (bacteria) in a drop of pond water using a microscope.
* Father of Microbiology.
* Studied the structure of plants.

1831: **Robert Brown**

* English Botanist
* Discovered the nucleus in plant cells

1838: **Matthias Jakob Scleiden**

* German Botanist
* Described that the cell is the basic building block of all plants matter

1839: **Theodor Schwann**

* German Biologist
* Same idea as Scleiden
* Stated that "cell is the basic unit of life"

1851: **Hugo von Mohl**

* German Botanist
* First person to use the word "protoplasm" (living matter of the cell)

1855: **Rudolf Virchow**

* German Physiologist, physician, pathologist and anthropologist)
* Demonstrated the cell theory

1855: **Louis Pasteur**

* French Chemist
* Founder of medical microbiology For the causes and prevention of diseases

1855: **Jan Evangelista Purkinje**

* Czech Anatomist and Physiologist
* Named the cell contents as protoplasm

* All living things are made of cells (Theodor Schwann & Matthias Schleiden, 1839).
* Smallest living unit of structure and function of all organisms is the cell.
* All cells arise from pre-existing cells (Rudolf Virchow, 50 years later).

**PRINCIPLES OF CELL THEORY**

1. Multicellular
2. Unicellular

**CELL TYPES BASED ON THE NUMBER OF CELLS**

1. Prokaryotic
2. Eukaryotic

**BASIC CELL TYPES**

**PROKARYOTES**

* First cell type on earth
* Found only in Domain Bacteria
* bacteria


* Found also in Domain Archaeans
* archaeans


* Represent the most archaic lines of evolution
* with simpler forms
* no membrane bound nucleus
* no membrane Bound organelles
* __nucleoid__ - region of DNA concentration

* **BACTERIA**

* serve as decomposers
* agents of fermentation (wine and beer)
* play a role in our digestive system
* involve in many nutrient cycles

**EUKARYOTES**

* found in plants, animals, fungi, protists
* more complex
* with true-membrane-bounded nucleus
* with many organelles that allow them to be more diverse and complex, both morphologically and physiologically

**CELL WALL**

* provides structure, support and protection
* surrounds the plasma membrane
* composed of 60% cellulose
* three layers: middle lamella, primary cell wall and secondary cell wall

1. middle lamella,
2. primary cell wall
3. secondary cell wall

three layers of the cell wall

**MIDDLE LAMELA**

* cements cell walls of two adjoining cells together.
* pectin layer between cells.

**PRIMARY CELL WALL**

* relatively thin and flexible and extensible layer
* composed of cellulose, hemicellulose and pectin
* common in young cells and cells in actively growing areas

**SECONDARY CELL WALL**

* thick cell layer
* formed inside the primary cell wall
* more rigid than the primary cell wall
* with 25% lignin

**PLASMA MEMBRANE/CELL MEMBRANE**

* Plasmalemma
* Covers the surface of the protoplasm
* Selectively permeable
* Regulates the passage of substances in and out of the cell

* Lipid bilaver
* Phospholipid molecules
* Proteins

**COMPOSITION OF MEMBRANE**

**PROTOPLASM**

* Mass of proteins, lipids, nucleic acids, and water within a cell.
* Everything in the cell is protoplasm except for the cell wall.
* Cytoplasm and the nucleus.

Protoplast

the protoplasm of a single cell.

**NUCLEUS**

* Control center of the cell
* Permanent storage place of DNA
* Protein synthesis, cell division, growth and differentiation

**CENTRAL VACUOLE**

* with membrane or tonoplast
* the largest organelle
* stores both nutrient reserves, water products and wastes (membrane bound storage sac)
* provide structure and support for the growing plant

**MITOCHONDRIA**

* Powerhouse of the cell
* Break down fuel molecules (cellular respiration - glucose and fatty acids)
* Release energy (ATP)


* with own ribosomes (for protein synthesis) and DNA (for proteins and enzymes production)

**PLASTIDS**

chloroplast

**CHLOROPLAST**

* green due to chlorophyll bodies
* larger than mitochondria
* cell may contain 50 chloroplasts

\

**RIBOSOMES**

**ENDOPLASMIC RETICULUM (ER)**

* as manufacturing and packaging system
* rough ER (protein synthesis)
* smooth ER (for carbohydrate and lipid synthesis)

**DICTYOSOMES/GOLGI APPARATUS**

* Packaging and shipping station of cell.
* Two-sided.
* With membrane-bound vesicles.
* Cisternae


* Membrane bound vesicles (proteins, lipids and other substances)

**MICROBODIES**

* smallest membrane-bound organelle.
* associated with ER, chloroplasts and mitochondria.
* two kinds: peroxisomes and glyoxysomes

**PEROXISOMES**

* occur primarily in leaves
* break down some of the toxic products of cell

**GLYOXYSOMES**

* house the glyoxylic acid cycle

**CYTOSOL**

* the semi-fluid matrix between organelles
* intracellular fluid or the internal fluid of the cell.
* the main component is water
* large part of cell metabolism occurs here

\

**MICROTUBULES**

* fibrous, hollow rods
* help support and shape the cell
* serve as a transportation function
* one of the cytoskeletons (filaments) of the cell

**MICROFILAMENTS**

* thinnest filaments.
* help support the cell.
* function in cellular movement.
* also known as actin filaments.
* one of the cytoskeletons of the cell.

**PLASMODESMATA**

* bridges between two plant cells.
* allows molecules and substances to move back and forth.

**GENES**

* a unit of heredity.
* are carried on DNA

**DNA**

contained within __chromosomes__ as __chromatin__.

**CELL CYCLE (DIVISION)**

* This is the series of events that takes place in a cell leading to its division and duplication that produces 2 daughter cells.

1. INTERPHASE
2. M PHASE

**2 MAIN PHASES OF CELL CYCLE**

**INTERPHASE**

prepares cell for division.

**M PHASE**

where division actually takes place.

1. TELOMERE
2. CENTROMERES

**CHROMOSOME PARTS:**

**TELOMERE**

* chromosome tips


* Repeats
* Act as sort of biological clock
* Being whittled down at each Mitosis.

**CENTROMERES** 

* middle


* Highly condensed
* Also repetitive sequence
* Region where spindle fibers attach
* Pulling chromatids apart during Mitosis

CLASSIFICATION OF CHROMOSOME

MITOSIS OR SOMANTIC CELL DIVISION

\

1. REPRODUCTION
2. GROWTH
3. REPAIR & REPLACEMENT

IMPORTANCE OF CELL DIVISION

**CHARACTER**

a heritable feature that varies among individuals (such as flower color).

**TRAIT**

each variant for a character, such as purple, or white color for flowers:

**HOMOZYGOTE**

An organism with 2 identical alleles for a character. 

* it is said to be homozygous for the gene controlling that character.

**HETEROZYGOTE**

An organism with 2 different alleles for a gene.

* It is said to be heterozygous for the gene controlling that character.
* Unlike homozygotes, heterozygotes are nat true-breeding.

**TRUE BREEDING**

are plants that produce offspring of the same variety when they self-pollinate.

**MONOHYBRIDS**

are heterozygous for one character.

**DIHYBRIDS**

are heterozygous for 2 characters.

**PHENOTYPE**

 the physical appearance. (color, etc.)

**GENOTYPE**

the genetic makeup. (Ex. PP and Pp).

**HYBRIDIZATION**

mating 2 contrasting, true-breeding varieties.

**P GENERATION**

true-breeding parents (parental).

**F1 GENERATION**

hybrid offspring or the P generation (first generation after crossing 2 parents).

**F2 GENERATION**

produced when F1 individuals self-pollinate or cross-pollinate with other Fl hybrids.

**GENE**

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

**ALLELES**

* two forms of a gene dominant & recessive. A different form of the same gene.
* any 2 or more related genes of a trait