Intro to Cytology

Genetics

the scientific study of genes and heredity. How a certain qualities or taits are passed from parents to offspring as a result of changes in DNA sequences.

genetic information

directs cellular function, determines an organism's external apperance, and serves as the link between generation in every species.

Prehistoric Times

this was when archeological evidence provides an insight of the successful domestication of animals and cultivation of plants thousand of years ago.

8000-1000 B.C.

when was the prehistoric times

Prehistoric Times

• represents the artificial selection of genetic variants within the populations

• desirable and undesirable traits are passed to successive generations.

• human awareness of heredity is apparent

The Greek Influence

during (500-300 BC)

On The Seed

Hippocrates treatise name

On the Seed

argued that the active "humors" resided in various parts of the body, serving as the bearers of hereditary traits. Drawn from the various parts of the male body to the semen.

Aristotle

proposed hat the generative power of male semen resided in a “vital heat" that it contained. This vital heat had the capacity to produce offspring of the same "form" as the parent.

The Dawn of Modern Biology

during (1600-1850)

Charles Darwin

a british naturalist coined the term "pangenesis"

Pangenesis

suggests that all parts of the parents could contribute to the evolution and development of the offspring.

Gregor Mendel

deduced that the genes come in pairs and are inherited as distinc units, one from each parent. He tracked the segragation of parental genes and their apperance in the offspring as dominant or recessive.

• William Harvey (1578-1657)

English anatomist. He was credited for the earliest statement of the theory epigenesis.

Epigenesis

term that an organism is derived from substances present in the egg that differentiate into adult structures during embryo development.

Theory of Preformation

theory states that sex cells contain a complete miniature adult.

Homunculus

Theory tells that sex cells contain a complete miniature adult called…?

Casper Wolff (1733-1794)

He disproved the theory of preformation, thus favoring the epigenesis.

John Dalton in 1808

He expounded his atomic theory.

Atomic Theory

This theory states that all matter is composed of small invisible units called atoms.

Matthias Schleiden and Theodor Schwann around 1830

 They proposed the cell theory.

cell theory

all organisms are composed of basic visible units called cells, derived from preexisting structures.

Spontaneous generation

term: the creation of living organism from nonliving components, has been disproved.

Fixity of species

this was also popular at that time, stating that animals and plant remained unchanged in form from the moment it appears on earth.

Carolus Linnaeus (1707-1778)

Fixity of Species was popularized by Swidish physician, known for binomial system of classification. Who is he?

Joseph Gottlieb Kolreuter (1733-1806)

German plant breeder, who formed a hybrid of tobacco.

He observed sgregation of traits in carnation.

Charles Darwin

Published the The Origin of Species in 1859 after his voyage on HMS Beagle.

He Formulated the theory of natural selection, a theory that attempts to explain the causes of evolutionary change.

The lack of understanding of the genetic basis of variation and inheritance left a gap to his theory.

He later published the book, Variation in Animals and Plants under Domestication

natural selection

A theory that attempts to explain the causes of evolutionary change.

Variation in Animals and Plants under Domestication

Books Charles Darwin later published

Gregor Johann Mendel

conducted an experiments between 1856 and 1863 and published his paper in 1866.

Gregor Johann Mendel

He demonstrated a number of statistical patterns underlying inheritance and developed a theory involving hereditary factors in the germ cells in explaining the patterns.

By the early part of the twentieth century

On what timeline was when chromosomes were discovered and supports the epigenetic interpretation of development.

gametes to each individual.

heredity and development were dependent on " information" contained in chromosomes, which were contributed by what?

Cytogenetics

the study of the structure and proprties of chromosomes, their behaviour during during somatic cell division during growth and development, and the germ cell division during reproduction, as well as their influence on phenotype.

Cytology

a branch of biology concerned with the structure and function of plant and animal cells.

Genetics

the study of genes, genetic variation, and heredity in an organism

Walther Flemming

• an Austrian cytologist and professor of anatomy

• published the first illustration of human chromosomes in 1882.

• He termed the stainable portion of the nucleus as chromatin and first to use the term mitosis

Heinrich Willhelm Gottfried von Waldeyer-Hartz

coined the term chromosome, a Greek word for "colored body" in 1888.

chromosome

a Greek word for "colored body" in 1888.

Walter Sutton and Theodor Boveri 1900

-Formally developed the "chromosome theory of inheritance"

it states that "chromosomes are the vehicles of genetic heredity."

"chromosome theory of inheritance"

it states that "chromosomes are the vehicles of genetic heredity."

Walter Sutton

Later, he combined the disciplines of cytology and genetics when he referred to the study of chromosomes as cytogenetics.

Allele

a specific copy of a gene found at a locus

Gene

a DNA segment that codes for a function or trait

Chromosome

an organized package of DNA in the nucleus

Genotype

an organism's allelic composition for a trait

Phenotype

the observable expression of a trait

Grigorii Andreevich Levitsky (1878)

First studies on cytology dealt with mitochondria in 1922-1923, he worked on the book "The Material Basis of Heredity".

He introduced to karyology the term karyotype, which is fundamental for cytogenetics.

Gregor Johann Mendel (1822- 1884)

Modern genetics began in 1900 with the rediscovery of studies of the monk.

• He was known as "father of genetics" who formulated laws of inheritance by experimenting garden pea.

• Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits.

Phoebus Levene (1863-1940)

He made the initialsteps towards discovering the components of genetic material. He is credited for discovering the carbohydrate component of both DNA and RNA and how their components are connected, as well as the structure of nucleotides in 1919

Oswald Avery (1877-1955)

He devised an ingenious experiment to find out that it was DNA that carried the vital information needed for protein expression in the next generation of cells.

Francis Crick and his colleague James Watson 1953

In 1953, they came up with a model for the structure of DNA (Deoxyribonucleic acid) based off of X-ray diffraction images.

1842

Wilhelm von Nageli, a Swiss botanist, observed the plant cell.

1866

Mendel's research work published under the title of "experiments on plant hybridization."

1869

Friedrich Miescher discovered nucleic acid

1888

Waldeyer identified the chromosome present in the cell.

1889

Richard Altmann purified DNA from the protein.

1905

William Bateson coined the term
"genetics"

1908

discovery of Hardy-Weinberg's law.

1910

Morgan T, explained that the genes are located on the chromosomes. Also, they experimented on Drosophila

Melanogaster and determined the nature of sex-linked traits.

1923

Griffith F, experimented on bacteria and postulated that DNA is the genetic material.

1953

Watson and Crick given the structure of DNA.

HUMAN GENETICS

• - The branch of genetics comprises the study of genetic alterations and its role in the development of disease especially in humans.

• - Using the cytogenetic, molecular genetics, phylogenetic, population genetics, and clinical

• genetic methods, any mutation can be characterized which are involved in the development of the disease.

• - We can study.

The inheritance pattern of disease.

The severity of the disease.

/ Possibility of inheritance in the consecutive generation

PREIMPLANTATION GENETICS

• It is characterizing or profiling the genetic composition of the embryo before implantation.

• Preimplantation genetic techniques are powerful enough to screen the genetic profile of oocyte or sperm cells before fertilization.

• The major application of preimplantation genetic is to screen high-risk pregnancies.

Clinical Genetics



• It involves the study of disease, finding the root of the disease, its adverse effects, and its inheritance pattern.

• Plant Genetics

• The branch of genetics deals with the study of genetic variations and chromosomal abnormalities in plants.

• It includes the study of plant genomes and genetically modified plant species using the techniques such as karyotyping, PCR, and DNA sequencing. Genetically modified plant species have tremendous economical value.

• Microbial Genetics

• It is an applied branch of genetics includes the study of the genes, genotypes ad gene expression of microorganism for various genetic engineering applications. The study includes genetic analysis of bacteria, viruses, archaea, protozoa and some fungi.

• The Novel coronavirus COVID-19 infecting people in recent times and causing respiratory problems is detected accurately using the RT-PCR technique.

• Metagenomics

• The branch of genetics that deals with the study and identification of different microorganisms by processing the environmental samples using modern genetics techniques.

• Shotgun sequencing and PCR direct sequencing are commonly used for metagenomic analysis.

Shotgun sequencing

• is a method that involves breaking the genome into a collection of small
  DNA fragments that are sequenced individually.

• A powerful sequencing tool can even identify any unknown organism or new microbe or strains of microorganisms.

• Population Genetics

• It includes the study of genetic differences within and between the population or individual.

• By doing mathematical calculations, statistical analysis, fieldwork and genetic analysis one can calculate the genetic frequency, allelic frequency, and other factors with respect to the population.

• We can also determine how natural selection, mutation, genetic drift, and gene flow can influence the phenotype and genotype in the population.

• Epigenetics

is the study of gene expression.

• It investigates gene expression profiles but not gene mutations.

• Biochemical Genetics

• The branch of genetics studying the chemistry of DNA, gene, chromosome, RNA and related biomolecules.

• Physiological Genetics

• Deals with the study of physiological characteristics such as sex differentiation and sex determination, blood group factor and sickle cell anemia like physiological conditions.

• Quantitative Genetics

• It is actually a branch of population genetics that studies the continuously varying phenotypes.

• Conservation genetics

• It is a subfield of population genetics in which, using the genetic tools and by understanding the dynamics of genes and their expression profile, researchers study the endangered species of plants, animals and other organisms.

Behavioral Genetics

• Studying the behavioral phenotypes of an organism at the genetic level is conducted in behavioral genetics. The behavior of an organism is influenced by the interaction between the environment and genetic composition.

• Karyotyping

identifies numerical and structural chromosomal abnormalities

Chromosomal staining and banding

improve chromosome visualization

Fluorescent in situ hybridization (FISH)

locates specific DNA sequences

PCR and RT-PCR

amplify and detect target genetic material

• Preimplantation genetic testing

screens embryos or gametes before implantation or fertilization