INTRODUCTION TO

CYTOGENETICS
LEARNING OBJECTIVES:
• Explain the general concept and principles relaited to cytogenetics
• Differentiate terms commonly employed in the study of genes.
• Identify the pioneers in Cytogenetics and their contribution.
• Enumerate the three main areas in the study of genetics and their
areas/ field.
CYTOGENETICS
• A branch of genetics that deals with the study of inheritance in
relation to the structure and function of chromosomes.
CYTOGENETICS
• NUCLEIC ACID
• CHROMOSOME AND GENES
• CELL CYCLE
• MENDELIAN PATTERNS OF INHERITANCE
• CHROMOSOMAL ABNORMALITIES AND DISEASES
• CYTOGENETIC TECHNIQUES
DEFINITION OF TERMS
• Character - heritable feature that varies among individual.
• Trait- pertains to each variant for a character (Ex: flower color: purple
or white)
• True Breeding- parents would produce an offspring that would carry
same phenotype.
• Hybridization- mating or crossing of two varries.
• Genotype- genetic composition of an organism
• Phenotype- the visible expression of information contained in a gene.
DEFINITION OF TERMS
• Locus- specific, fixed position on a chromosome where particular
gene is located.
• Allele- alternative form of a gene.
• Homozygous- an organism having a pair of identical allele at a given
locus at a given chromosome.
• Heterozygous- an organism having two different allels at a given locis
• Genes- A nucleotide sequence coding a polypeptide sequence which
makes an enzyme or structural protein.
OVERVIEW OF THE HISTORY OF
GENETICS/CYTOGENETICS
BEFORE 1860 - Discovery of the Cell and the Nucleus.
§ General beliefs of the Hippocratic school persisted ( gametes of the
organism would assemble into the individual)
§ Nicolas Hartsoeker (1694) - Homonculus: A miniature human carried
in the head of a sperm.
§ William Harvey- Theory of epigenesis
§ Robert Hooke (1165)- observed the cell structure under the light
microscope.
§ Anton van Leeuenhoek (1674-1683) - Master lens maker; Single lens
microscope.
OVERVIEW OF THE HISTORY OF
GENETICS/CYTOGENETICS
BEFORE 1860 - Discovery of the Cell and the Nucleus.
§ Jan Purkinje 1830- first described the nucleus within the cell.
§ Robert Brown (1831)- Botanist; coined the term nucleus; Brownian
motion of microscopic particles; gymnosperms vs. angiosperms.
§ Hugo von Mohl (1835-1839) - mitossis in cell.
§ Rudolf Virchow (1858)- summarized the concept of the cell theory
(“Omnis cellula”: all cells come from preexisting cells)
OVERVIEW OF THE HISTORY OF
GENETICS/CYTOGENETICS
1860-1900 Mendelian traits and Observation of Chromosomes
§ Gregor Mendel (1856-1863) - Austrian Monk; Classical hybridization
experiments with pea plants: Statical patterns of heritable phenotypes.
§ Oscar Hertwig (1875)- German embryologist; Fusion of sperm and egg-zygote
§ Walter Flemming (1879-1885)- Physician ; newly synthesized aniline dyes to
view and describe chromosomes and the way they moved during mitosis.
§ Heinrich Waldeyer (1888)- first used the term chromosome.
§ Theodore Boveri, Karl Rabi and Eduard van Beneden (1880)-= hypothesized that
chromosomes are individual structures with continuity from one generation.
§ August Weismann (1885)- inheritance of traits is based exclusively in the
nucleus; meiosis (1887).
OVERVIEW OF THE HISTORY OF
GENETICS/CYTOGENETICS
1900-1944 Chromosome Theory and Sex Linkage
§ Thomas Hunt Morgan (1900)- Introduced Drosophilia melanogasteras a model
genetic system, (1911)- genes producing white eyes, yellow body, and
miniature wings in Drosophila are located on the X chromosome.
§ Walter Sutton (1902)- explained Mendel’s rules of inheritance.
§ Nettie Maria stevens (1905)- investigated sex determinaution in a
maealworms: X and Y chromosome.
§ Alfred Sturtevant (1913)- used Drosophila to create the first genetic map.
§ Calvin Bridges(1914)- working with Morgan: described nondisjunction of
Drosophila sex chromosomes.
OVERVIEW OF THE HISTORY OF
GENETICS/CYTOGENETICS
1900-1944 Chromosome Theory and Sex Linkage
§ Lewis Stadler and Herman Muller- (1927)- genes can be mutated
artificially by X-rays.
§ William Bateson (1902)- terms f1,f2, homozygote, heterozygote, and
allelomorph; created the term genetics (1905).
§ Wilhelm Johannsen (1909)- phenotype, genotype, and gene.
§ Ronald A. Fisher, Sewall Wright, and John B.S. Haldane (1930-1932)-
algebraic foundations for our understanding of the process and
evolution.
§ Salvador Luria and Max Delbruck (1943)- demonstarted that bacteria
have gentic systems and phenotype that could be studied.
OVERVIEW OF THE HISTORY OF
GENETICS/CYTOGENETICS
1944 DNA and RNA and Molecular Genetics
GENERAL AREAS OF CYTOGENS
• CLASSICAL
• MOLECULAR
• EVOLUTION
CLASSICAL GENETICS
CLASSICAL GENETICS
MOLECULAR GENETICS
MOLECULAR GENETICS
MOLECULAR GENETICS
MOLECULAR GENETICS
MOLECULAR GENETICS
EVOLUTIONARY GENETICS