Human genetics
• Lectures – 17x2 (Med); 17x1 (Stom);
• Seminars – 17x3 (Med); 17x2 (Stom);
–3 concluding tests (tests + practical part)
–Final examination (tests + practical part)
–Consultations
–www.biologiemoleculara.usmf.md
–http://e.usmf.md
–Passkey – bmgu
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Average mark
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•
•
•
•
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Written test 1 (max. 10)
Computer test 1 (max. 10)
Written test 2 (max. 10)
Computer test 2 (max. 10)
Computer test 3 (max. 10)
Attendance in lectures (max. 10)
Scientific report (max. 10, for Med only)
Final grade
• Average per semester – 50%
• Written (practical) part – 30%
• Multiple choice test – 20%
Agricultural revolution – XVII-XVIII century
Industrial revolution – XIX century
Informational revolution – XX century
Genetic revolution – XXI century
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Development
of Human and Medical genetics
• 1956 – identification of number of human
chromosomes (46,XX; 46,XY);
• 1961- relationship between chromosomal
aberrations and human diseases;
• 1966 – decoding of genetic code, description of
inherited metabolic diseases; prenatal diagnosis
via amniocentesis.
• 1980 – cloning of first human gene.
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• 1981 - molecular methods used for location of
genes in chromosomes.
• 1985 - PCR used for identification of mutations.
• 1991 – cloning of genes involved in many
human diseases: Dushenne muscle distrophy,
cystic fibrosis, neurofibromatosis, retinita
pigmentosum, Marfan sdr.
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• 1994 – McKusick published „Mendelian
Inheritance in Man; A Catalog of Human
Genes and Genetic Disorders”. On-line
version OMIM
http://www.ncbi.nlm.nih.gov/omim/
• 1996 – preimplantation diagnostic of
embryos obtained by in vitro fertilisation.
• 1996 - 2001 more then 1000 genes involved
in human pathology were described.
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In 2001 „Human genome project” starts.
During 2001-2003 many visions were changed:
– From structure – to function of genes;
– From location of genes in chromosomes – to
sequencing of DNA;
– From diagnostic of genetic diseases – to
calculation of predisposition to genetic diseases;
– From etiology – to mechanisms;
– From analysis of monogenic traits – to analysis of
polygenic traits;
– From genome – to proteome;
– From medical genetics – to genetic medicine;
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Cell
Chromosomes
Organism
Nucleus
Protein
Amino acids
DNA
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The “omics” cascade
DNA
• Genome
RNA
• Transcriptome
Proteins
• Proteome
Amino acids
Lipids
ATP
etc.
• Metabolome
Nervous system,
Cardio-vascular system
Muscular system, etc.
• Phenome
CLASSIC VISION
GENETIC VISION
Why this patient has this
disease now?
What is the
problem?
What to do in
order to solve
this problem?
What possibilities are for
prevention or reducing of
effect of disease for patient
or/and his family?
Which is the prognostic and
prophylaxis of complications
in this patient?
What is the risk for this
disease for other members of
the family?
Prenatal diagnostic
Prognosis of disease
evolution
Preimplantation
diagnostic
New methods of
diagnostic
Understanding of
etiopathology
How does
genetics benefit
medicine?
Family planning
Cell therapy
New etiopathological
drugs
Gene therapy
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Compartments of genetics
Human genetics –
Fundamental and applicative science
Genetics is fundamental science because it is studying:
• structure,
• main mechanisms,
• main principles,
- which ensure keeping, transmission and expression of
human traits,
- which ensure formation, development and functions of
human organism.
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Genetics is a clinic science
Which study relationships between heredity and diseases:
- mutations (monogenic, polygenic or chrs) determine
* a disease or
* a predisposition for a genetic disease.
- Genetic diseases are:
* numerous - 9000;
* frequent - 5-8% in newborns.
- Genetic diseases are present in all medical fields.
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Lymphocytes – 374
Endothelial cells – 1031
Salivary glands – 17
Thyroid gland – 584
Parathyroid glands – 46
Smooth muscle – 127
Skeletal muscle – 735
Brain – 3195 genes
Eye – 547 genes
Bons – 904 genes
Adipose tissue – 581 genes
Thymus – 261 genes
Esophagus – 76 genes
Lungs – 1887 genes
Genes involved in human
development and functions of
tissues and organs
Mammal glands – 696
Pancreas – 1094
Spleen – 1094
Adrenal glands – 658
Gallbladder – 788
Small intestine – 297
Heart – 1195 genes
Liver – 2091 genes
Erythrocyte – 8 genes
Trombocytes – 22 genes
Large intestine – 874 genes
Kidney – 712 genes
Placenta – 1290
Ovary – 504 genes
Testis – 370 genes
Prostate – 1283
Uterus – 1859 genes
Leucocytes – 2164
Embryo – 1989 genes
Skin – 620
Synovial membrane – 813 genes 17
Genetics is a science which study:
- heredity and
- variability of human organism.
Substrate of heredity and variability:
Molecular
Morphologic
Cellular
DNA
Chromosomes
Genetic
apparatus
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Heredity
• Heredity is the passing of traits to offspring
(from its parent or ancestors). This is the process
by which an offspring cell or organism acquires
or becomes predisposed to the characteristics of
its parent cell or organism.
Heredity is based on
Keeping of genetic
information (GI) in
DNA
• Genetic code is
universal
• There are systems for
DNA repair in case of
errors
• GI is stored as
chromatin or
chromosomes.
Expression of GI
• DNA → RNA →
polypeptide →
protein →
phenotype
• Based on the
principles of genetic
code
• Programmed in time
and space
• Modified by
environment
• 1 gene controls one
or several traits
• 1 trait is determined
by one or several
genes
Passing of GI
• Determined by
semiconservative
replication of the
DNA
• Equal distribution of
chromosomes during
cell division
• Combination of
maternal and paternal
genomes during
fecundation
Importance of heredity
Biological importance
• Keeping of family traits
• Keeping of population
peculiarities
• Species conservation
Medical importance
• Familial aggregation of genetic
diseases, genetic predisposition
to diseases
• Establishing of groups of high
risk for some genetic disorders
• Prenatal or pre-symptomatic
genetic testing
• Prevention of diseases in
relatives in families with high
risk
• High susceptibility to infectious
agents in particular families
• Characteristic population
frequency for genetic diseases
Variability
Genetic variability is a measure of
the tendency of
individual genotypes in
a population to vary from one another.
• Could be hereditary or non-hereditary.
• Could be induced by modifications in genetic
material  modification of phenotype.
Importance of variability:
Biological importance
• Each person is unique;
• Natural selection during
permanent interaction with
environment;
Medical importance
• Different response to
environment (food,
toxins...);
• Predisposition to some
diseases (cancer, diabetes,
hypertension...);
• Different manifestation of
disease in different patients;
• Different response to drugs
in different patients with the
same disease.
• !!! Individual medicine
Human organism
Modifications in genetic
material
Gene / chromosomal /
genomic mutations
Intra- / inter-chromosomal /
genomic recombination +
migration
Modification of traits only
Ontogenetic / adaptive /
destructive changes
Mutations
Mutations
• Unexpected, accidental, permanent changes which
occur in the structure of the genetic material of an
organism
May affect
• Nuclear genome
• Mitochondrial genome
May alter
• The whole genome (polyploidy or aneuploidy),
• One or several chromosomes (balanced or
unbalanced chromosomal aberrations);
• One or several nucleotides (gene, point mutations)
All pathologies have a genetic
component
Mutations (modifications of genetic material)
Responsible for a disease / syndrome
Responsible for predisposition to a
disease
Change resistance against infectious
agents
Change the metabolism of drugs
Influence the regeneration of tissues
Etc.
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• Genetic diseases are numerous.
• There are known over 10.000 of disease determined
or conditioned by genetic factors.
• Are highly diverse.
• May appear at any age.
• May affect any organ  present in all fields of
medicine.
• Present in 5-8% of newborns.
• Genetic factors may be responsible for reproductive
disorders (sterility, miscarriage).
• Genetic diseases responsible for infantile mortality
and morbidity.
• Genetic diseases are chronic diseases and produce
physical or mental disorders.
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Causes of mutations
Types of mutations
Genomic
Polyploidies (3n)
Aneuploidies
(2n±1)
Chromosomal
Deletions
Duplications
Inversions
Translocations
Iso-chromosomes
Gene
Substitutions
Deletions
Duplications
Insertions
Frequency of genetic
disorders
Polygenic
diseases
10%
Monogenic
diseases
2%
Chromosomal
syndromes
0,7%
0%
2%
4%
6%
8%
10%
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Genetic
diseases
Types
Aneuploidies
47, XX, +21 – (Down sdr.);
47, XXY – (Klinefelter sdr.);
45,X – (Turner sdr.);
Chromosomal
aberrations
Del, dup, izo, r;
ex: cri du chat sdr.; Wolf-Hirschhorn sdr.; DiGeorge sdr.;
Williams sdr.
Chromosomal
syndromes

> 1000
Autosomal
dominante
Monogenic
diseases

> 9000
Examples
Autosomal
recesive
X-linked
Mitochondrial
FH, ADPKD, neurofibromatosis 1, Marfan sdr., Huntington
disease, breast cancer, colon cancer
Phenylketonuria, cystic fibrosis, sickle cell anemia, albinism
Hemophilia, muscle dystrophy, color blindness
Leber neuropathy
Diabetes, hypertension, obesity, cancers
Adult diseases
Polygenic
diseases

> 100
Isolated
malformations
in children
Defects of neural tube, cleft lips, heart congenital
malformations
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Types of mutations
Generative
Somatic
• Homogeneous – alter all cells in the body
• Are inherited via gametes
• May be expressed by offspring
•
•
•
•
In mosaic – alter just groups of cells, a mutant cell clone will appear
Are produced after fecundation
May be expressed by holder
Cannot be inherited
Expression of mutations
in phenotype
Gene
Intra-chromosomal
• Crossing-over
• Prophase I
Recombination
of genetic
material
Inter-chromosomal
Genomic
• Independent segregation
of chromosomes
• Anaphase I
• During fecundation
Migration
Movement of genes from one
population to another
Modification of gene pool
Modification of frequency of some
normal genes vs. pathologic
Modification of frequency of some
genetic diseases ↑or↓
Phenotype variability
Ontogenic modifications
Adaptive modifications in the
limit of norm of reaction
Pathologic modifications out of
norm of reaction
Acquired modifications
Phenocopies
Adaptive modifications in
the limit of norm of reaction
• Norm of reaction is under control of genotype
• Under the pressure of environment gene
expression changes to ensure optimal activity
of organism
– Short-time adaptations
– Long-time adaptations
Spontaneous abnormalities
induced by environment
• Abnormalities produced during development
caused by destructive factors
• Congenital abnormalities
– Determined by teratogen factors
– Mime genetic disorders  PHENOCOPIES
• Postnatal abnormalities
Genetic apparatus of human cell
Genetic
material
46 mol.
DNA
Chrs
2-10
mol.
mtDNA
Cell components which
ensure activity
Realization of GI
Apparatus of
transcription
Apparatus of
translation
Transmission of
GI
Apparatus of
replication
Apparatus of
mitosis
Levels of organization of genetic material
I. Genome – complement of cell DNA
(nuclear + mitochondrial)
II. Chromosome – a linkage group of genes
III. Gene – elementary unit responsible for
synthesis of a protein and expression of a
trait
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Non-coding
sequences
Regulatory
sequences
GENOTYPE
~30000 pairs of genes
Coding
sequences
HUMAN GENOME
Peculiarities of the human genome
Haploid nuclear genome
Mitochondrial genome
3,2 x 109 bp
16,6 kb
~ 30000 genes
37 genes
Gene DNA
Extra-gene DNA
25%
75%
Coding
DNA
10%
Non-coding
DNA
90%
Single copy or
low number
copies sequences
Moderate or
highly repetitive
sequences
60%
40%
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Chromosome
No. of genes
Length, Mb
1
3511
250
2
2368
243
3
1926
198
4
1444
191
5
1633
181
6
2057
171
7
1882
159
8
1315
146
Chromosome
No. of genes
Length, Mb
9
1534
141
10
1391
136
11
2168
135
12
1714
134
13
720
115
14
1532
107
15
1249
103
16
1326
90
Chromosome
No. of genes
Length, Mb
17
1773
81
18
557
78
19
2066
59
20
857
63
21
450
40
22
855
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X
1672
155
Y
429
59
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Sequences of the Human genome
• Structural genes
• rRNA genes
• tRNA genes
• microRNA genes
• Transposons
• Retrotranspososns
• Viral DNA
• Pseudogenes
• Enhancers
• Silancers
CODING
REGULATORY
FACULTATIVE
NON-CODING
OBLIGATORY
NON-CODING
• ARS (ORI)
• Centromere DNA
• Telomere DNA
• Palindromes
• Spacers
Alternation of genome elements
•
•
•
•
•
•
•
•
•
•
Structural genes
Coding sequence in tandem (e.g., Nucleolar organizer)
Spacers
Satellite DNA (e.g., centromeric DNA)
LINEs (Long Interspersed Repeated Elements) – 16%
SINEs (Short Interspersed Repeated Elements) – 11%
LTRs (Long Terminal Repeats)
VNTRs (Variable Number Tandem Repeats)
SSRs (Simple Sequence Repeats)
etc.
Repetitive elements in human gene
HGO (homogentisate 1,2-dioxygenase)
Deficiency of enzyme encoded by HGO leads to alkaptonuria
Human chromosomes
• morphologic substrate of H and V;
• supramolecular level of organization of genetic material (DNA +
histones + non-histones + RNA)
• dynamic structures with different shape, level of condensation,
gene activity:
• single-chromatid or two-chromatid;
• chromatin or chromosome;
• transcriptional active or inactive.
47
• self-reproduction of chromosomes takes place during S phase
of interphase (replication).
• chromosomes represent linkage groups of genes:
- each chrs contains a specific number of genes;
- each gene has a specific place in chrs - locus;
- genes of one chromosome are inherited together
• a diploid set of chromosomes is called karyotype:
23 pairs: 22 pairs of autosomes +
1 pair of gonosomes (XX or XY).
Pair of chromosomes = homolougus chromosomes
48
Origin of gonosomes
49
• landmarks of karyotype:
relative and absolute length of chrs,
position of centromere = primary constriction - c,
presence of secondary constrictions - h,
presence of satellites - s
• chromosomes may be analyzed during:
• metaphase (homogenous painting or banding)
• prometaphase (banding)
• interphase (hybridization with fluorescent probes)
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• chromosomes have heterogeneous structure:
- Coding and non-coding sequences;
- euchromatin and heterochromatin,
- single copy and repetitive sequence;
-GC and AT reach sequences;
- transcribed and non-transcribed sequences;
- sequences associated with basic and basic proteins.
!!! This explains origin of chromosomal bands
• Chromosomal number and structural abnormalities induce
developmental abnormalities - sundromes
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Structure of metaphase chromosomes.
Rchromosomal landmarks
Satellite
Secondary
constriction
Centromere
Primary
constriction
Sister
chromatids
The shape of chromosome depends on position of
centromere
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p x100
Ic  p 
q
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Human karyotype
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Classification of chromosomes
By length:
By shape:
By type:
-Large
-Metacentric
-Autosomes
-Medium
-Submetacentric
-Gonosomes
-Small
-Acrocentric
By presence of
other landmarks:
Groups:
A 1-3
E 16-18
-h on p arm
B 4,5
F 19,20
-h on q arm
C X, 6-12
G 21, 22, Y
-satellites
D 13-15
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Human karyotype and chromosomal
formula
46,XX
46,XY
47,XXY
45,X
47,XY,+21
45,XY,-21
46,XX,5p-
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