This document provides an introduction to genetics. It outlines the key topics to be covered, including Mendel and his experiments that established the laws of inheritance, sex-linked inheritance as demonstrated by Morgan's experiments with fruit flies, sex determination and differentiation in humans, and linked inheritance. It discusses genetics as a science, defining heredity and variability as its main subjects of study. It also introduces important figures in the history of genetics like Mendel, Morgan, and their classic experiments.

1. INTRODUCTION TO GENETICS
1

2. OUTLINE
1. Genetics as a science,
it’s subject-matter and main goals.
2. Mendel and his experiments.
3. Sex-linked inheritance.
4. Sex determination and
differentiation.
5. Linked inheritance.
2

3. GENETICS AS A SCIENCE
greek “genesis” – “descent”, “origin”
Genetics is a scientific study of
mechanisms of inheritance and causes
of variation in living organisms related
by descent.
The term “genetics” was used
in 1902 by W. Bateson
3

4. GENETICS AS A SCIENCE
Subject-matter of genetics???
HEREDITY
VARIABILITY
4

5. GENETICS AS A SCIENCE
 HEREDITY - the property of living
matter providing the transference of
parental signs in generations.
 VARIABILITY - the property of living
matter undergoing change the
characters in generations
5

6. GENETICS AS A SCIENCE
Main goals
1. Studying of laws, determining the gene inheritance.
2. Establishment of hereditary basis of variability.
3. Comprehension of species origin.
4. Studying of a gene distribution within the population.
5. Studying of a gene structure and functions;
6. Discovery of the factors, regulating gene activity
during embryogenesis in the norm and pathological
conditions.
6

7. GENETICS AS A SCIENCE
Methods
7
 Hybridological
 Biochemical
 Twin method
 Population method
 Cytogenetic
 Genealogycal
 Molecular-genetic
 Method of somatic cell

8. GENETICS AS A SCIENCE
History
8
I period - Before 1900
ORGANISM LEVEL
(G. Mendel, C. Correns, De Vries, R. Tschermak)
II period – 1900 – 1952 years
CELLULAR LEVEL
(G. Boveri, F.A. Janssen, W.S. Sutton, T.H. Morgan,
W.Bateson, W. Johansen H. J. Muller, G. Beadle,
E.Tatum, O. Avery and others)
III period – 1953 till Now
MOLECULAR LEVEL
(J. Watson, F. Crick, A. Kornberg, M. Nirenberg,
H. G. Khorana, N. Borlaug, H. Smith, K. Wilcox)

9. GENETICS AS A SCIENCE
Founder of Genetics
9
 Austrian monk with a
background in plant
breeding and
mathematics
 Discover
the Laws of inheritance
Gregor Mendel
(1822 –1884)

10. MENDEL EXPERIMENTS
Laws of inheritance
10
Characters of pea plant Pisum Sativum

11. MENDEL EXPERIMENTS
Laws of inheritance
REASONS TO USE
1. It is easy to cultivate.
2. It has a short life-cycle, the results can be had
within a year.
3. The pollination can easily be controlled in pea
plants, they have self-pollination and cross-
pollination.
4. It produces a larger number of seeds.
It helps in drawing correct conclusions.
5. They have varieties differing by observable
alternating characteristics.
11

12. MENDEL EXPERIMENTS
Laws of inheritance
Pure line – organism which is crossed with
genetic identical organism and does not give
rise the segregation in offspring
(AA or aa) (by Mendel).
Monohybrid cross - a cross between the
organisms which are different by one
character (a single gene pair) (by Mendel).
12

13. MENDEL EXPERIMENTS
Laws of inheritance. First
13
Parental lines:
yellow seeds x green seeds
Gametes:
F1 : all yellow
Aa
aa
A a
AA

14. MENDEL EXPERIMENTS
Laws of inheritance. First
14
Parental lines:
round seeds x wrinkled seeds
Gametes:
F1 : all round
Aa
A a
AA aa

15. MENDEL EXPERIMENTS
Laws of inheritance. First
Principle of Dominance
(Uniformity, definition)
The hybrids of cross between the
pure line organisms are uniformity in
genotype and phenotype.
15

16. MENDEL EXPERIMENTS
Laws of inheritance. Some terms
HYBRID, DOMINANT CHARACTER, RECESSIVE
CHARACTER
Hybrid – the organism which is produced in the
result of cross between the pure line organisms,
differed by alternative characters (by Mendel).
Dominant character – it has manifestation in the
presence of the other character (by Mendel).
Recessive character – it has no manifestation in the
presence of the dominant character (by Mendel).
16

17. MENDEL EXPERIMENTS
Laws of inheritance. Some terms
HOMOZYGOTE, HETEROZYGOTE
Homozygote (or pure line) is an organism, formed from a
zygote by the merging of two identical gametes and
produces one kind of gametes (example: AA or aa) (by
W.Bateson, 1902).
Heterozygote (or hybrid) - is organism formed from a
zygote by the merging of two different gametes according
to their hereditary features and produces more than one
kind of gametes (example: Aa) (by W. Bateson, 1902).
17

18. MENDEL EXPERIMENTS
Laws of inheritance. Some terms
PHENOTYPE, GENOTYPE
Phenotype is a combination of all characters
of an individual (by Johansen in 1909).
Genotype is a combination of all genes of
an individual (by Johansen in 1909).
18

19. MENDEL EXPERIMENTS
Laws of inheritance. Second
19
Parental lines:
yellow seeds x yellow seeds
Gametes:
F2: 3 yellow 1 green
Aa aa
A a
Aa Aa
a A
Aa Aa
А

20. MENDEL EXPERIMENTS
Laws of inheritance.
Second
MENDEL’S
MONOHYBRID
CROSS RESULTS
F2 plants showed
dominant-to-
recessive ratio that
averaged 3:1
20
787 tall
277 dwarf
651 long stem 207 at tip
705 purple 224 white
152 yellow
428 green
299 wrinkled
882 inflated
6,022 yellow 2,001 green
5,474 round 1,850 wrinkled

21. MENDEL EXPERIMENTS
Laws of inheritance. Second
Principle of Segregation (definition)
The segregation of characters of F2
hybrids in the complete dominant
inheritance is occurred in the definite
quantitative proportions (3:1 in
phenotype, 1:2:1 in genotype).
21

22. MENDEL EXPERIMENTS
Laws of inheritance. Third
DIHYBRID CROSS
Cross between two organisms that
differ by two characters.
22

23. MENDEL EXPERIMENTS
Laws of inheritance. Third
Segregation in color and
shape of seeds in pea plants:
12 yellow : 4 green
3 yellow : 1 green
12 round : 4 wrinkled
3 round : 1 wrinkled
CONCLUSION:
Each character is
inherited
independently from
the others.
23

24. MENDEL EXPERIMENTS
Laws of inheritance. Third
PRINCIPLE OF INDEPENDENT
ASSORTMENT
Inheritance of pairs of characters
located in the different chromosomes
is independently from each other.
24

25. MENDEL EXPERIMENTS
Laws of inheritance. Third
Cytological Basis of Independent Assortment
25
Metaphase I:
Metaphase II:
Gametes:
1/4 AB 1/4 ab 1/4 Ab 1/4 aB
A A A A
A A A A
A
A
A
A
B B
B B
B
B
B B
B
B
B
B
a a a a
a
a a
a
a
a
a
a
b
b b b
b
b b b
b b b b

26. MENDEL EXPERIMENTS
Molecular Basis: Chromosome behavior
1879: Walter Flemming discovers chromosomes
in living cells.
1900: De Vries, Correns, and Tschermak repeat,
rediscover Mendel.
1902: Sutton and Boveri and others link behavior
of chromosomes to Mendelian segregation and
independent assortment;
propose the chromosomal theory of heredity.
26

27. MENDEL EXPERIMENTS
Chromosome behavior
Correlation Between Unit Factors and Genes on
Chromosomes:
 unit factors in pairs ~ genes on homologous chromosomes in
pairs;
 segregation of unit factors during gamete formation ~ genes on
homologes segregate during meiosis;
 independent assortment of segregating unit factors ~ genes on
nonhomologous chromosomes assort independently;
Stronger evidence for the chromosomal theory of heredity came
from experiments of T.H. Morgan and others with fruit flies from
1909 onwards.
27

28. SEX-LINKED
INHERITANCE
T. H. Morgan
(1866 – 1945)
American biologist and
geneticist
28

29. SEX-LINKED
INHERITANCE
Drosophila
melanogaster
is an object of
Morgan’s experiments
29

30. SEX-LINKED
INHERITANCE
Morgan (1910) found a mutant white-eyed
male fly, and used it in a series of
experiments that showed a gene for eye
color located on the X-chromosome.
Character: Traits
Eye color: Red eye (wild type)
White eye (mutant)
30

31. SEX-LINKED INHERITANCE
Morgan’s experiment
Parental Phenotypes:
Red-eyed female x
White-eyed male
F1 Phenotypes: All red-eyed
Conclusion:
Red eye is dominant to white
eye
31

32. SEX-LINKED INHERITANCE
Morgan’s experiment
A cross between the F1
hybrids should give:
3 red eye : 1 white eye
An interesting observation:
no white-eyed female
Conclusion:
the white eye recessive
allele was present on
the X-chromosome.
32

33. SEX-LINKED INHERITANCE
Morgan’s experiment
33
Morgan tried the cross the
other way round:
white-eyed female x red-eyed
male
Result:
All red-eyed females and
all white-eyed males
(crisscross inheritance)
Conclusion:
only the X chromosome
carries the gene for eye color.
There is no gene locus for eye
color on the Y

34. SEX-LINKED INHERITANCE
Morgan’s experiment
A cross between the F1
hybrids should give:
2 red eye : 2 white eye
An interesting observation:
 25% white-eyed female
 25% white-eyed male
 25% red-eyed female
 25% red-eyed male
34

35. SEX DETERMINATION AND
DIFFERENTIATION
Types of Sex Determination
1. Progamic - before fertilization
2. Epigamic - after fertilization
3. Syngamic (chromosomal) - in the moment of
fertilization
4. Eusyngamic – with fertilization and without
fertilization
35

36. SEX DETERMINATION AND
DIFFERENTIATION
It is based on the presence of a Y chromosome in human:
XY chromosomes = male; XX chromosomes = female
36
XY XX
X
Y
X
XY
XX

37. SEX DETERMINATION AND
DIFFERENTIATION
EVOLUTION OF SEX CHROMOSOMES IN HUMAN
37

38. SEX DETERMINATION AND
DIFFERENTIATION
38

39. SEX DETERMINATION AND
DIFFERENTIATION
39
 Dosage compensation ensures an equal
expression of genes from the sex
chromosomes even though females have 2
X-chromosomes and males have only 1.
 In each female cell, 1 X chromosome is
inactivated and is highly condensed into a
Barr body.
 Females heterozygous for genes on the X-
chromosome are genetic mosaics.

40. SEX DETERMINATION AND
DIFFERENTIATION
40

41. SEX DETERMINATION AND
DIFFERENTIATION. Genetic mosaicism
41

42. LINKED-INHERITANCE.
Types of inheritance
42
Inheritance
Mongenic Polygenic
Autosomic Sex-linked
Dominant Recessive X-linked Y-linked
Dominant Recessive

43. LINKED-INHERITANCE.
Types of inheritance
LINKAGE - the tendency of genes on the same
chromosome to segregate together.
43
• the tendency, when genes closely located in
the chromosome and have no chance of
separating by crossing-over and are always
transmitted together to the same gamete and
the same offspring.
Complete
• the tendency, when genes distantly located
in the chromosome and have a chance of
separation by crossing-over and of going into
different gametes and offspring.
Incomplete

44. LINKED-INHERITANCE.
Morgan’s experiment
Parental Phenotypes
(pure lines):
Female with grey body
and long wings x
Male with black body
and vestigial wings
RESULT:
All (males and females)
are with grey body and
long wings
44

45. LINKED-INHERITANCE.
Morgan’s experiment
Test cross of F1 females (females
have crossing-over)
RESULT:
41,5% flies with grey body and long
wings
41,5% flies with black body and
vestigial wings
8,5% flies with grey body and
vestigial wings
8,5% flies with black body and long
wings
CONCLUSION:
Inheritance of genes may be
destroyed by crossing-over and
they show incomplete linkage.
45

46. LINKED INHERITANCE
Law of Linkage of Th. Morgan
Power of gene linkage is inversely
proportional to the distance
between them in a chromosome.
46

47. LINKED INHERITANCE
Morganid
Constancy of percentage of crossing over
between genes is used as index of relative
distance between.
It corresponds to the distance by which crossing over
takes place in 1% of gametes.
At the distance of 50 morganids and more over signs
are inherited independently in spite of localization of
genes in one chromosome.
47

48. EXTRACHROMOSOMAL
HEREDITY
1. Mitochondria and chloroplasts contain
genes.
2. Traits controlled by these genes do not
follow the chromosomal theory of
inheritance.
3. Genes from mitochondria and chloroplasts
are often passed to the offspring by only
one parent.
48

49. EXTRACHROMOSOMAL
HEREDITY
Maternal inheritance: uniparental (one-
parent) inheritance from the mother:
 the mitochondria in a zygote are from
the egg cell; no mitochondria come from
the sperm during fertilization;
 in plants, the chloroplasts are often
inherited from the mother, although this
is species dependent.
49

50. EXTRACHROMOSOMAL
HEREDITY
50

51. CHROMOSOMAL AND CYTOPLASMIC
HEREDITY. Resume
51
Characters
Prokaryotes Eukaryotes
Nucleus Cytoplasm Nucleus Cytoplasm
DNA Nucleoid Plasmids Nucleotype Cytotype
Obligatory
genetic
elements
Nucleoid genes Plasmids,
Episomes
Genes DNA Of
Mitochondria
and
Chloroplasts
Facultative
genetic
elements
1. Inseration
2. Transposons
3. Bacteriophagy
4. Bacteria
1. Symbiotic
bacteria,
2. Symbiotic algae
3. Tox+transposon
plasmids
1. Mobile gene
(MDG),
2. Viruses,
3. B-chromoso-
mes,
4. Amplificatory
copies of DNA
1. Spiroplasms,
2. Viruses,
3. Extra-
chromosomal
elements

52. HEREDITY. Chromosomal
Theory of Heredity. Resume
52
1. Genes are located in chromosomes; different chromosomes keep
different number of genes. The set of genes of every
nonhomologous chromosomes is unique.
2. Allele genes occupy appointed and identical loci of homologous
chromosomes.
3. Genes are localized in the chromosome in appointed sequence in
linear order.
4. Genes of one chromosome form group of linkage owing to which
linked inheritance of some signs takes place. The force of linkage
is in the inversely proportion to the distance between genes.
5. Every biological species is characterized by specific
chromosome set - karyotype.

53. HEREDITY
Thank you for your attention!
53

54. VARIABILITY

55. Variability
Phenotypic Genotypic
Modificational Accidental Combinative Mutational

56. Modificational variability
Hare Dandelion
WINTER SUMMER

57. Modificational variability
FEATURES:
1) is associated with a change in the
intensity of the enzymatic activity and
the metabolic reactions in the body
under the environmental factors;
2) non-hereditary, because it does not
involve a change genotype or
karyotype;
3) manifested by the interaction of the
genotype with the environment

58. Modificational variability
FEATURES:
4) changes are a group character;
5) modifications may disappear after caused
their factor will be terminate ;
6) modification changes the intensity
proportional to the strength and duration
of the factors that cause them.

59. Modificational variability.
Norm of reaction
Norm of reaction is a range of feature
changes that are incompatible with life.
Limits of variation of the character determining
by genotype

60. Mechanisms of Combinative
Variability
1. Independent divergence of chromosomes
during meiosis;
2. Crossing over;
3. Accidental combination of genes during
fertilization.

61. Classification of
mutations
I. According to the level of hereditary material:
a) genomic mutations;
b) chromosomal mutations;
c) gene mutations;
II. According to the cell type:
a) somatic;
b) germinal;
III. According to the origin:
a) spontaneous mutations;
b) induced mutations.

62. CHROMOSOMAL
MUTATIONS
1. DELETION – a segment of DNA containing one
or several genes is lost from a chromosome.
2. DUPLICATION – a segment of DNA containing
one or more genes is present more than once
in a set of chromosomes.
3. INVERSITION – the location of a block of
genes is inverted within a chromosome.

63. Chromosomal mutations

64. CHROMOSOMAL
MUTATIONS
4. INSERTION – the changes the number of
DNA bases in a gene by adding a piece of
DNA.
5. TRANSLOCATION - the location of a block
of genes is changed in the chromosomes.

65. CHROMOSOMAL MUTATIONS

66. GENOMIC MUTATIONS
1. FUSION - two
nonhomologous
chromosomes fuse into one.
This involves the loss of a
centromere.
2. FISSION - one chromosome
splits into two.

67. GENOMIC MUTATIONS
3. ANEUPLOIDY - one or more
chromosomes of the normal
set may be lacking or
present in excess.
4. HAPLOIDY AND
POLYPLOIDY - the number of
sets of chromosomes is other
than two.

68. GENOMIC MUTATIONS
Mechanisms of forming of genomic mutations

69. Gene mutations

70. Gene mutations
1. Transitions
2. Transversions
3. Deficiency or deletion
4. Duplication
5. Inversion
6. Insertion
7. Missense mutations.
8. Repeat expantion
mutations.
9. Nonsense mutations.
10. Frameshift mutations.

71. Gene mutations
Transitions -
replacements of a
purine by another
purine (A by G, or
vice versa), and of a
pyrimidine by another
pyrimidine (C by T, or
vice versa).
Transitions
А Т
T A
G C
C G

72. Gene mutations
Transversions -
replacements of a
purine by a pyrimidine,
and vice versa (C or T
by either G or A, and
vice versa).
Transvertions
А Т G C
T A C G

73. Gene mutations

74. A deletion changes the number of DNA bases by
removing a piece of DNA.
Gene mutations. Deletion

75. An insertion changes the number of DNA bases in
a gene by adding a piece of DNA.
Gene mutations. Insertion
As a result, the protein made by the gene may not function properly.

76. A duplication consists of a piece of DNA that is
abnormally copied one or more times.
Gene mutations.
Duplication

77. Gene mutations

78. This type of mutation is a change in one DNA base pair that
results in the substitution of one amino acid for another in the
protein made by a gene.
Gene mutations. Missense mutation

79. REPEAT EXPANSION MUTATION – nucleotide repeats are
short DNA sequences that are repeated a number of times in a
row.
Gene mutations

80. A nonsense mutation is
also a change in one DNA
base pair. Instead of
substituting one amino acid
for another, however, the
altered DNA sequence
prematurely signals the cell
to stop building a protein.
This type of mutation
results in a shortened
protein that may function
improperly or not at all.
Gene mutations. Nonsense
mutation

81. This type of mutation occurs when the addition or loss of
DNA bases changes a gene’s reading frame.
Gene mutations. Frameshift mutation.
Insertions, deletions, and duplications can all be frameshift
mutations.

82. 1. Phenotypic variability: modificational and accidental.
2. Genotypic variability: combinative and mutational.
3. Limits of variation of the character determining by
genetically.
4. Mechanisms of Combinative Variability: Independent
divergence of chromosomes during meiosis; Crossing over;
Accidental combination of genes during fertilization.
5. Classification of mutations: According to the level of
hereditary material; According to the cell type; According
to the origin.
VARIABILITY. Resume

83. VARIABILITY
Thank you for your attention!
83