Cyto Trans Prelim

OUR LADY OF FATIMA UNIVERSITY
MEDICAL LABORATORY SCIENCE BATCH 2024

CYTOGENETICS
MS. KEITH ARLEIGH JOSON, RMT
ADAPTED FROM: POWERPOINT/LECTURE
TRANSCRIBED BY: TUASON, MLYL
COURSE OUTLINE: PRELIMS

1. Definition of terms The RNAs
2. Describe the relationship of Cytogenetics to
other sciences like Cytology and Genetics
• Messenger RNA (mRNA) – carries the instructions for protein
3. History and branches of Genetics synthesis to the sites of protein synthesis
4. Different parts of the cell • Ribosomal RNA (rRNA) – combines with proteins to form
5. Functions of the parts of the cells
6. Types of cells: somatic from gametic cells ribosomes
7. Different cell stages • Transfer RNA (tRNA) – RNA that delivers amino acids to the
REFERENCE BOOKS sites of protein synthesis
Klug, W., and Cummings, M. (2020) Essentials of
Genetics. 10th Edition, New Jersey: Pearson
Education, Inc.
REVIEW OF RELATED GENES, CHROMOSOMES AND GENOMES
TERMINOLOGIES • Genome – it is the complete set of genetic instructions

characteristic of an organism, including protein-encoding genes
and other DNA sequences
GENETICS AND GENES
• Chromosomes – structures that are a product of DNA coiling in
• Genetics - the study of inherited traits and their variation association with proteins
• Heredity - the sum of all biological processes by which Genes, the segment of DNA strand that encodes for the
particular characteristics are transmitted from parents to their production of different proteins, may have different variants.
offspring. These are called alleles.
• Genes - the units of heredity, which is the transmission of
inherited traits. Genes can be found on the nucleic acid DNA MUTATIONS, PHENOTYPE, AND GENOTYPE
• Alleles are products of mutations.
THE NUCLEIC ACIDS
• Mutations - defined as any heritable change in the DNA
• DNA – a molecule whose function is to store and transfer sequence and are the source of all genetic variation
genetic information • Phenotype – observable traits or features of an organism
• RNA – important molecule in protein synthesis (alleles that are expressed)
Both DNA and RNA are polymers of repeating called nucleotides • Genotype – set of alleles for a given trait carried by an
organism (alleles that are present)
MITOSIS AND MEIOSIS

• Mitosis – a type of cell division in which one somatic cell give
rise to two new ones
• Meiosis – cell division involved in the production of gametes
THE NUCLEIC ACIDS

• There are four different nucleotides present in a DNA molecule.
The various sequence combinations of these bases ultimately
encode genetic information.
CYTOGENETICS
of a gene pair separate from each other during gamete formation

INTRODUCTION TO
(the formation of egg cells and sperm)
CYTOGENETICS
CHROMOSOME THEORY OF INHERITANCE
• Heredity is dependent on the genes contained in the structures
BRANCHES OF GENETICS
called chromosomes. The chromosomes were contributed to the
• Classical genetics - refers to the study of the laws of hereditary
individual by the gametes.
transmission in living organisms. It began with Mendel’s study of
• Diploid number (2n) – the characteristic number of
inheritance in garden peas.
chromosomes a eukaryote has in most of its cells
• Population genetics - The study of genes in populations of
• Chromosomes in diploid cells exist in pairs called
animals, plants, and microbes provides information on past
homologous chromosomes
migrations, evolutionary relationships and extents of mixing
among different varieties and species, and methods of
adaptation to the environment.
• Cytogenetics – branch of genetics that studies the structure of
the DNA within the cell nucleus. It studies the number and
morphology of the chromosomes.
• Molecular genetics - the study of the molecular structure of
DNA, its cellular activities (including its replication), and its
influence in determining the overall makeup of an organism.
EARLY HISTORY OF GENETICS AND THEORIES OF

INHERITANCE
• Aristotle – proposed that ―humors‖ served as bearers of traits
• William Harvey – proposed the theory of epigenesis
• Preformationism – states that the fertilized egg contains a
complete miniature adult called a homunculus
• Cell theory vs Spontaneous Generation
• Chromosomes behave differently during the two forms of cell
CHARLES DARWIN division, mitosis and meiosis.
• Proposed that existing species arose by descent with • In mitosis, the chromosomes are copied and distributed to each
modification from ancestral species daughter cell. Both cells obtain a diploid set of chromosomes.
• Formulated the theory of Natural Selection • In meiosis, the cells receive only one chromosome from each
• Natural selection states that individuals with heritable traits that chromosome pair, and the resulting number of chromosome is
allow them to adapt to their environment are better able to called the haploid number (n).
survive and reproduce than those with less adaptive traits. • Finally, the chromosomal theory of inheritance states that
―inherited traits are controlled by genes residing on
chromosomes faithfully transmitted through gametes,
maintaining genetic continuity from generation to generation.‖
GREGOR MENDEL
• Published a paper describing how traits are passed from one CHEMICAL NATURE OF GENES
generation to the other, utilizing pea plants as models • Scientists tried to identify which component of the
• Proposed that traits are passed from parents to offspring in a chromosomes carries genetic information
predictable manner • The major chemical component of chromosomes were DNA
• He further concluded that each trait in pea plants is controlled and proteins.
by a pair of factors (which we now call genes) and that members
CYTOGENETICS
STRUCTURE OF DNA AND RNA • Other types are critical components of cells and organisms
• DNA is a long, ladder-like macromolecule that twists to form a • Some carry essential molecules (hemoglobin), regulate body
double helix. processes (protein hormones e.g. insulin), take part in muscle
• Each strand of the molecule is made up of nucleotides. (actin and myosin) and connective tissue (collagen)
• The four types of nucleotides found in DNA are: A (adenine), G • A protein’s shape and chemical behavior are determined by its
(guanine), C (cytosine), T (thymine) linear sequence of amino acids, which in turn is dictated by the
• The DNA ladder are exact complements of each other, so that stored information in the DNA of a gene that is transferred to
the double helix consist of A=T and G=C base pairs. RNA, which then directs the protein’s synthesis.
• The RNA is also made up of nucleotides but contains a • Once a protein is made, its biochemical or structural properties
different sugar than DNA. play a role in producing a phenotype.
• It is a single-stranded molecule that contains uracil • When mutation alters a gene, it may modify or even eliminate
(U) in place of thymine. the encoded protein’s usual function and cause an altered
phenotype.
RECOMBINANT DNA TECHNOLOGY

• Researchers discovered restriction enzymes that could be used
to cut any organism’s DNA at specific nucleotide sequences,
therefore producing a reproducible set of DNA fragments.
• Soon researchers discovered ways on how to insert the DNA
fragments into carrier DNA molecules (vectors) to form
recombinant DNA molecules.
• The recombinant DNA will be transferred into bacterial cells to
produce thousand of copies, or clones.
• The cloned DNA fragments can be isolated from the bacterial
GENE EXPRESSION: FROM DNA TO PHENOTYPE
host cells.
• The genetic information in the DNA is expressed to form a
• Such fragments can be used to isolate genes, study their
functional gene product, which in most cases, a protein.
organization and expression, and to study their nucleotide
• In eukaryotic cells, the process begin in the nucleus with
sequence and evolution.
transcription.
• The mRNA produced then moves to the cytoplasm and
migrates to the ribosomes.
• The synthesis of protein under the direction of the mRNA is
called translation.
• Information encoded in mRNA (the genetic code) consists of
linear series of nucleotide triplets (codon).
• Each codon is complementary to the information stored in DNA
and specifies the insertion of a specific amino acid into a protein.
• Protein assemble is accomplished with the aid of tRNAs.
PROTEINS AND BIOLOGICAL FUNCTION

• Proteins perform diverse biological functions
• Enzymes, the largest category of proteins, serve as biological
catalysts
CYTOGENETICS
• There are many genetics related issues, including concerns

BIOTECHNOLOGY about prenatal testing, genetic discrimination, ownership of
• The use of recombinant DNA technology and other molecular genes, access to and safety of gene therapy, and genetic
techniques to make products is called biotechnology. privacy.
• The use of recombinant DNA technology to genetically modify

crop plants has revolutionized agriculture.
• Biotechnology has also changed the way human proteins for
medical use are produced.
• Biotechnology-derived genetic testing is now available to
perform prenatal diagnosis of heritable disorders and to test
parents for their status as heterozygous carriers of more than
100 inherited disorders.
GENOMICS, PROTEOMICS AND BIOINFORMATICS

• There have been efforts to decode each gene in the genome
and establish its function
• Genomics – study of genome. It studies the structure, function,
and evolution of genes and genomes
• Proteomics – identifies the et of proteins present in a cell under
a given set of conditions, and studies their functions and
interactions
• Bioinformatics – subfield of information technology used to
store, retrieve and analyze the massive amount of data
generated by genomics and proteomics
MODEL ORGANISMS IN GENETIC STUDIES

• Principles of inheritance described by Mendel were universal
among plants and animals
• Geneticists gradually came to focus attention on small number
of organisms, including the fruit fly (Drosophila melanogaster)
and the mouse (Mus musculus)
• Reasons for using small number of organism: (1) genetic
mechanisms were the same in most organisms and (2) these
organisms had characteristics that made them especially
suitable for genetic research.
• They were easy to grow, had relatively short life cycles,
produced many offspring, and their genetic analysis was fairly
straightforward.
• They were called model organisms
GENETICS, ETHICS AND SOCIETY

• Genetics and its applications in biotechnology are developing
much faster than the social conventions, public policies, and
laws required to regulate their use.
CYTOGENETICS
CELLS  During mitosis and meiosis, chromatin fibers coil and

condense into chromosomes
 Cells are highly varied and highly organized structures
 The nucleolus, present inside the nucleus, is where ribosomal
 Their forms and functions are dependent on the genetic
RNA is synthesized
expression by each cell type
 The remainder of the cell within the plasma membrane,
 Bone, blood, nerve and muscle cells are somatic cells, also
excluding the nucleus, is called as the cytoplasm and
called as body cells
includes a variety of organelles
 Somatic cells have two copies of the genome and are said to
 The endoplasmic reticulum appears smooth in places where
be diploid
it serves as site for synthesis of fatty acids and phospholipids,
 Sperm and egg cells have only one copy of the genome and
and in other places, appears rough as it is studded with
are said to be haploid
ribosomes
 Ribosomes are sites of protein synthesis, guided by the
PROKARYOTES VS. EUKARYOTES information contained in the mRNA
 Prokaryotes lack nucleus as opposed to the nucleated cells of  The mitochondria provide energy by breaking down nutrients
the eukaryotes from food. The energy liberated from food is captured and
 Specialized organelles are also present in eukaryotic cells stored in the bonds present in a molecule called adenosine
triphosphate (ATP)
CHEMICAL CONSTITUENTS OF CELLS  The centrioles are a pair of complex structure that are located
 Cells are composed of macromolecules important in biological in a specialized region called the centrosome.
processes. The major groups of these substances are:  These are associated with the organization of spindle fibers
carbohydrates, lipids, proteins and nucleic acids. that function in mitosis and meiosis.
 Carbohydrates provide energy  The organization of spindle fibers by the centrioles plays an
 Lipids form membranes and hormones, provide insulation and important role in the movement of chromosomes during cell
store energy division
 Proteins have many diverse functions in the body, and are
important in blood clotting, nerve transmission, muscle Cytoskeleton
contraction, and immunity, while others serve and catalysts  The cytoskeleton is a meshwork of protein rods and tubules
 Most important in genetics are the nucleic acids DNA and RNA that molds the distinctive structures of a cell, positioning
organelles and providing three-dimensional shape.
 The cytoskeleton includes three major types of elements—
microtubules, microfilaments, and intermediate filaments.
 They are distinguished by protein type, diameter, and how
they aggregate into larger structures
MICROTUBULES
 Microtubules are long and hollow
 It provide many cellular movements
 Composed of a pair of protein called tubulin
 They form the cilia, which are hair-like structures
MICROFILAMENTS
 These are long, thin rods composed of many molecules of the
protein actin
 Solid and narrower than microtubules, they enable cells to
CELL STRUCTURES AND ORGANELLES withstand stretching and compression
 All cells are surrounded by a plasma membrane, a covering  They also help anchor one cell to another
that defines cell boundary
 The plasma membrane actively controls the movement of INTERMEDIATE FILAMENTS
materials in and out of the cell
 They have diameters intermediate between those of
 Most animal cells have glycocalyx or cell coat
microtubules and microfilaments
 The glycocalyx provides biochemical identity at the surface of
 They are abundant in skin and nerve cells
cells, and the components of the coat that establish cellular
 In actively dividing skin cells, it forms a strong inner framework
identity are under genetic control
that firmly attaches cells to each other and to the underlying
 The nucleus is a membrane bound structure that houses the
tissue
DNA, which is complex with protein into thin fibers
 During the nondivisional phases of the cell cycle, the fibers are
uncoiled and dispersed into chromatin
CYTOGENETICS
MITOSIS
DNA, GENES AND CHROMOSOMES

 An organism’s DNA, containing arrays of genes, is organized
into structures called chromosomes
 Chromosomes serve as vehicles for transmitting genetic
information
 There are two major processes involved in the genetic
continuity of nucleated cells: mitosis and meiosis
MITOSIS AND MEIOSIS

 Mitosis leads to production of two cells with the same number
of chromosomes as the parent cell
 Meiosis reduces the genetic content and the number of
chromosomes by half
 This reduction in the number of chromosomes is important in
the production of sex cells or gametes
REMEMBER: All somatic cells derived from members of the
CHROMOSOMES same species contain an identical number of chromosomes.
 Chromosomes are visible only during mitosis and meiosis  This is referred to as the diploid number (2n)
 When the cell is not undergoing division, the genetic material  With the exception of sex chromosomes, chromosomes exist
making up chromosomes unfolds and uncoils into diffuse in pairs (called homologous chromosomes)
network within the nucleus, generally referred to as  The homologs exhibit the same length and centromere
chromatin. placement
 Meaning, for each chromosome exhibiting a specific length
and centromere placement, another exists with identical
features
HUMAN MALE KARYOTYPE
 The chromosomes contains a constricted region called the

centromere, whose location establishes the general  Note that each chromosomes in the karyotype is clearly a
appearance of each chromosome double structure consisting of two parallel sister chromatids
 Depending on the position of the centromere, different arm connected by a common centromere.
ratios are produced.  The sister chromatids are replicas of one another and would
 Chromosomes are classified as metacentric, submetacentric, separate into two new cells during cell division
acrocentric or telocentric based on centromere location  The haploid number (n) of chromosomes is equal to one- half
 The short are is called the p arm, and the longer arm is called of the diploid number
the q arm.
CYTOGENETICS
 The genetic information contained in a haploid set of STAGES OF THE CELL CYCLE
chromosomes constitute the genome of the species.  Interphase
 Homologous chromosomes have genetic similarities o G1
 They contain identical gene sites along their lengths. Each site o S phase
is called a locus (pl. loci) o G2
 Therefore, homologous chromosomes are identical in the traits  Mitosis
that they influence and in their genetic potential. o Prophase
 In sexually reproducing organisms, one member of each pair o Prometaphase
is derived from the mother (though the ovum) and the other o Metaphase
from the father (through the sperm). o Anaphase
 THEREFORE, each diploid organisms contain two copies of o Telophase
each gene as a consequence of biparental inheritance, or
inheritance from two parents
 The members of each pair of genes, while influencing the
same characteristic or trait, need not be identical.
 In a population of members of same species, many different
forms of the same gene, called alleles, can exist.
INTERPHASE
 The interphase is note devoted solely to cell’s growth and
normal function. It is also when the cell replicates the DNA on
each chromosome
 DNA synthesis occurs before the cell enters mitosis. This
period is called the S phase
 There are two periods during interphase in which there is NO
synthesis of DNA.
 There is one important exception to the concept of  One occurs before and one after the S phase (G1/gap1 and
homologous pairs of chromosomes G2/gap 2, respectively)
 In many species, one pair, consisting of the sex-determining  During G1, S phase, and G2, intensive metabolic activity, cell
chromosomes, is often not homologous in size, centromere growth and cell differentiation are evident.
placement, arm ratio, or genetic content.  By the end of G2, DNA has been replicated and the cell
 In humans, while females carry two homologous X volume has doubled.
chromosomes,  The cell enters mitosis (M).
 males carry one Y chromosome in addition to one X  Following mitosis, continuously dividing cells repeat this cycle
chromosome (G1, S, G2 then M) over and over
 These X and Y chromosomes are not strictly homologous. The  At a point during G1, all cell follow one of two paths
Y is smaller and lacks most of the gene loci contained in the X.  They either (1) withdraw from the cycle, become quiescent,
and enter the G0 stage, or (2) become committed to proceed
CELL DIVISION through G1 and complete the cycle.
The process of mitosis is important in all eukaryotic organisms  Cells that enter the G0 remain viable and metabolically active
The genetic material is partitioned into daughter cells during but are not proliferative
nuclear division (karyokinesis)  The chromosomes are not visible during the interphase
The chromosomes must be replicated and then accurately  Instead, the nucleus is filled with chromatin fibers formed from
partitioned the uncoiling and dispersal of the chromosomes after the
This is followed by cytoplasmic division (cytokinesis) previous mitosis
It partitions the cell volume inti two parts and then encloses each
new cell in a distinct plasma membrane PROPHASE
 The chromosomes appear as a double structure split
THE CELL CYCLE longitudinally except at a single point of constriction, the
 Many cell divisions transform a fertilized egg into a full-grown centromere.
adult  The two parts of each chromosome are called sister
 The cell cycle is a series of events that describe the sequence chromatids because the DNA contained in each of them is
of activities a cell prepares for division and then divides genetically identical
 The sister chromatids are held together by protein complexes
called cohesin
CYTOGENETICS
IMPORTANT: Even though one cannot see the chromatids in the  The process takes the form of one DNA replication followed by
interphase because the chromatin is uncoiled and dispersed in two successive nuclear and cellular divisions (Meiosis I and
the nucleus, the chromosomes are already double structures, Meiosis II).
which becomes apparent in late prophase.  In these species, the reproductive cycle ends when a sperm
and egg fuse to form a diploid zygote, which has the potential
PROMETAPHASE AND METAPHASE to form a new individual.
 Migration is made possible by the binding of spindle fibers to
the chromosome’s kinetochore, an assemble of multilayered
plates of proteins associated with the centromere.
 This structure forms on opposite sides of each paired
centromere, in intimate association with the two sister
chromatids.
 At the completion of metaphase, each centromere is aligned at
the metaphase plate with the chromosome arms extending
outward in a random array.
ANAPHASE
 The shortest stage of mitosis, the anaphase, whose events
are critical to the chromosome distribution during mitosis
 During this phase, the sister chromatids of each chromosome,
separate from one another (an event described as disjunction),
and pulled to opposite ends of the cell.
 As these events proceed, each migrating chromatid is now
referred to as a daughter chromosome
 The steps that occur during anaphase are critical in providing
each subsequent daughter cell with an identical set of
chromosomes.
TELOPHASE
 At the beginning of telophase, two complete sets of
chromosomes are present, one on each pole
 Cytokinesis then occur, partitioning the cytoplasm in order to
produce two new cells from one
 Animal cells undergo constriction of the cytoplasm, producing
the cell furrow that is characteristic of newly divided cells.
 In each new cell, the chromosomes begin to uncoil
 In each new cell, the chromosomes begin to uncoil and
become diffuse chromatin once again
 The nuclear envelope reforms, and the spindle fibers
disappear
 The nucleolus re-forms and become visible THE KEY FEATURES OF MEIOSIS ARE AS FOLLOWS:
 At the completion of telophase, the cell enters the interphase  Meiosis involves two sequential cycles of nuclear and cell
division called meiosis I and meiosis II but only a single cycle
of DNA replication.
 Meiosis I is initiated after the parental chromosomes have
MEIOSIS & CHROMOSOME replicated to produce identical sister chromatids at the S
MORPHOLOGY phase.
 Meiosis involves pairing of homologous chromosomes and
MEIOSIS recombination between them.
 Four haploid cells are formed at the end of meiosis II. Meiotic
 As in mitosis, meiosis is preceded by a process of DNA
events can be grouped under the following phases:
replication that converts each chromosome into two sister
chromatids.
 Meiosis is the form of eukaryotic cell division that produces
haploid sex cells or gametes (which contain a single copy of
each chromosome) from diploid cells (which contain two
copies of each chromosome).
CYTOGENETICS
MEIOSIS INCLUDES TWO ROUNDS OF  Diplotene: the disassembly of the synaptonemal complexes
CHROMOSOME SEGREGATION and the concomitant condensation and shortening of the
 The first of these divisions (meiosis I) segregates the chromosomes
homologs.  crossover events between nonsister chromatids can be seen
 The duplicated paternal and maternal homologs pair up as inter-homolog connections called chiasmata (singular
alongside each other and become physically linked by the chiasma)
process of genetic recombination.
 In the first meiotic anaphase, duplicated homologs are pulled
apart and segregated into the two daughter nuclei.
 Only in the second division (meiosis II) are the sister
chromatids pulled apart and segregated (as in mitosis) to
produce haploid daughter nuclei.
 produces four haploid nuclei, each of which contains either the
maternal or paternal copy of each chromosome, but not both
PROPHASE I:
CROSSING OVER
 subdivided into the following five phases based on
 Crossing over is the exchange of genetic material between two
chromosomal behaviour
homologous chromosomes.
 Leptotene, Zygotene, Pachytene, Diplotene and
 Crossing over is also an enzyme-mediated process and the
Diakinesis.
enzyme involved is called recombinase.
 take hours in yeasts, days in mice, and weeks in higher plants
 Recombination between homologous chromosomes is
 It is during early prophase I that the homologs begin to
completed by the end of pachytene, leaving the chromosomes
associate along their length in a process called pairing
linked at the sites of crossing over.
 As prophase progresses, the homologs become more closely
juxtaposed, forming a four-chromatid structure called a Metaphase I: The bivalent chromosomes align on the
bivalent
equatorial plate
 DNA double-strand breaks are formed at several locations in
 The microtubules from the opposite poles of the spindle
each sister chromatid, resulting in large numbers of DNA
attach to the pair of homologous chromosomes.
recombination events between the homologs Anaphase I: The homologous chromosomes separate, while
 lead to reciprocal DNA exchanges called crossovers, where sister chromatids remain associated at their centromeres
the DNA of a chromatid crosses over to become continuous Telophase I: The nuclear membrane and nucleolus
with the DNA of a homologous chromatid reappear, cytokinesis follows and this is called as diad of cells .
 The stage between the two meiotic divisions is called
interkinesis and is generally short lived.
 Interkinesis is followed by prophase II, a much simpler
prophase than prophase I.
 Leptotene: the homologs condense and pair

 Zygotene: the synaptonemal complex begins to assemble at
sites where the homologs are closely associated and
MEIOSIS II
recombination events are occurring
 Prophase II: Meiosis II is initiated immediately after
 The complex formed by a pair of synapsed homologous
cytokinesis
chromosomes is called a bivalent or a tetrad.
 meiosis II resembles a normal mitosis
 Pachytene: the assembly process is complete, and the
homologs are synapsed along their entire lengths. During  The nuclear membrane disappears by the end of prophase II .
this stage bivalent chromosomes now clearly appears as  The chromosomes again become compact.
tetrads.
CYTOGENETICS
 Metaphase II: At this stage the chromosomes align at the MITOSIS – VS – MEIOSIS SUMMARY DETAILS
equator and the microtubules from opposite poles of the
spindle get attached to the kinetochores of sister chromatids.
 Anaphase II: It begins with the simultaneous splitting of
the centromere of each chromosome (which was holding
the sister chromatids together), allowing them to move toward
opposite poles of the cell
 Telophase II: Meiosis ends with telophase II, in which the
two groups of chromosomes once again get enclosed by a
nuclear envelope; cytokinesis follows resulting in the formation
of tetrad of cells i.e., four haploid daughter cells.
CHROMOSOME MORPHOLOGY
SIGNIFICANCE OF MEIOSIS
Meiosis is the mechanism by which conservation of specific
chromosome number of each species is achieved across
generations in sexually reproducing organisms, even though the
process, per se, paradoxically, results in reduction of
chromosome number by half. It also increases the genetic
variability in the population of organisms from one
generation to the next. Variations are very important for the
process of evolution.
CYTOGENETICS
CHROMOSOMES 3. Acrocentric
 There are 46 chromosomes in every somatic cell of a human  In this type of chromosome the centromere is located closer
being. Of which 22 pairs (44) are autosomes 23rd pair (XX or to one end of chromatid therefore the chromatids on
XY) are sex chromosomes. opposite side are very long.
 The DNA molecule may be circular or linear, and can be  A small round structure, attached by a very thin thread is
composed of 100,000 to 10,000,000,000 nucleotides in a observed on the side of shorter chromatid.
long chain.  The small round structure that is a part of the chromatid is
 Typically, eukaryotic cells (cells with nuclei) have large linear termed as satellite.
chromosomes and
 prokaryotic cells (cells without defined nuclei) have smaller
circular chromosomes, although there are many exceptions
to this rule.
CHROMOSOME NOMENCLATURE
 International System for Human Cytogenetic Nomenclature
(ISHCN) has been developed by the Standing Committee on
Human Cytogenetic Nomenclature
 The pair of non-sex chromosomes (autosomes) are serially
numbered, 1 to 22, as nearly as possible in descending order
of length. Identification of the chromosomes is based on
size, position of centromere and other morphological
features.
 Chromosome short arms are called p (petit) and long arms q
(queue).
4. Telocentric
THERE ARE FOUR TYPES OF CHROMOSOMES In this type of chromosome the centromere is placed
BASED UPON THE POSITION OF THE CENTROMERE At one end of the chromatid and hence only one arm.
1. Metacentric Such telocentric chromosomes are not seen in human
In this type of chromosome the centromere occurs in the center cells.
and all the four chromatids are of equal length.
2. Submetacentric
In this type of chromosome the centromere is a little away
from the center and therefore chromatids of one side are
slightly longer than the other side.
* Telomeres: long regions of repetitive non-coding DNA that cap

chromosomes to stop replication; undergo partial degradation
(i.e., become shorter) each time a cell undergoes division
CYTOGENETICS
TWO WAYS IN REPRESENTING CHROMOSOMES
SEM: Chromosomes
(uncondensed in nucleus, upper right)

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OUR LADY OF FATIMA UNIVERSITY

MEDICAL LABORATORY SCIENCE BATCH 2024

COURSE OUTLINE: PRELIMS

REVIEW OF RELATED GENES, CHROMOSOMES AND GENOMES

TERMINOLOGIES • Genome – it is the complete set of genetic instructions

MITOSIS AND MEIOSIS

THE NUCLEIC ACIDS

of a gene pair separate from each other during gamete formation

EARLY HISTORY OF GENETICS AND THEORIES OF

different sugar than DNA. play a role in producing a phenotype.

RECOMBINANT DNA TECHNOLOGY

PROTEINS AND BIOLOGICAL FUNCTION

• There are many genetics related issues, including concerns

techniques to make products is called biotechnology. privacy.

• The use of recombinant DNA technology to genetically modify

GENOMICS, PROTEOMICS AND BIOINFORMATICS

MODEL ORGANISMS IN GENETIC STUDIES

GENETICS, ETHICS AND SOCIETY

CELLS  During mitosis and meiosis, chromatin fibers coil and

DNA, GENES AND CHROMOSOMES

MITOSIS AND MEIOSIS

HUMAN MALE KARYOTYPE

 The chromosomes contains a constricted region called the

 Leptotene: the homologs condense and pair

* Telomeres: long regions of repetitive non-coding DNA that cap

TWO WAYS IN REPRESENTING CHROMOSOMES

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