Concepts of Mendelian genetics, molecular genetics, disorders, and mutations.

1. MENDELIAN
GENETICS

3. WHO WAS GREGOR MENDEL?
Heizendorf, Austria
July 22nd, 1822
Botanist and Scientist
University of Vienna
University of Olmütz
Father of Modern Genetics
Monk of Agustinian order at
St. Thomas Monastery, Brno

4. MENDEL’S EXPERIMENTS

5. MENDEL’S LAWS

6. MONOHYBRID CROSS

7. DIHYBRID CROSS

8. TRIHYBRID OR POLIHYBRID CROSS

9. Molecular
Genetics

10. Structure of a chromosome
Chromosomes are
made of very
tightly wound DNA
(Deoxyribonucleic
Acid). DNA carries
the genetic
material for all
living things.
Genes are portions
of DNA.

11. Structure of the DNA molecule

12. DNA Replication
◼Tsuneko and Reiji Okazaki studied the
process of replication of DNA during cell
division. They complemented the description
of the process by describing the Okazaki
fragments.

14. Protein Synthesis
◼Is the process in which DNA encodes to build
proteins.

15. RNA Structure

16. Transcription
Before the synthesis of a protein begins, the
corresponding RNA (Ribonucleic Acid)
molecule is produced by RNA transcription.
One strand of the DNA double helix is used as a
template by the RNA polymerase to synthesize
a messenger RNA (mRNA). This mRNA
migrates from the nucleus to the cytoplasm.

17. ◼During this step, mRNA goes through
different types of maturation including one
called splicing when the non-coding
sequences are eliminated. The coding mRNA
sequence can be described as a unit of three
nucleotides called a codon.

19. Translation
The ribosome binds to the mRNA at the start
codon (AUG) that is recognized only by the
initiator tRNA. The ribosome proceeds to the
elongation phase of protein synthesis. During
this stage, complexes, composed of an amino
acid linked to tRNA, sequentially bind to the
appropriate codon in mRNA by forming
complementary base pairs with the tRNA
anticodon.

20. ◼. The ribosome moves from codon to codon
along the mRNA. Amino acids are added one
by one, translated into polypeptidic
sequences dictated by DNA and represented
by mRNA. At the end, a release factor binds
to the stop codon, terminating translation
and releasing the complete polypeptide from
the ribosome.

21. EXAMPLE OF A PROTEIN
SYNTHESIS SEQUENCE
DNA GCT GCC GCA GCG
mRNA CGA CGG CGU CGC
tRNA GCU GCC GCA GCG

22. Mutations
The smallest change makes the difference.

23. What happens when a cell
divides?
Let’s remember cell division and chromosomes...

24. Copyright © 2011 Pearson Education Inc.Biology: Life on Earth, 9e
The Principal Features of a Eukaryotic Chromosome
During Cell Division
Fig. 9-5
gene loci
centromere
telomeres
(a) A eukaryotic chromosome before DNA replication
sister
chromatids
centromere
duplicated
chromosome
(two DNA double
helices)
(b) A eukaryotic chromosome after DNA replication
independent
daughter
chromosomes,
each with one
identical DNA
double helix
(c) Separated sister chromatids become independent
chromosomes

25. Copyright © 2011 Pearson Education Inc.Biology: Life on Earth, 9e
▪ Prior to cell division, the DNA is replicated
– A duplicated chromosome consists of two
identical DNA double helices, called sister
chromatids, which are attached to each other at
the centromere
– During mitotic cell division, the two sister
chromatids separate, each becoming an
independent chromosome that is delivered to
one of the two daughter cells

26. Copyright © 2011 Pearson Education Inc.Biology: Life on Earth, 9e
▪ Eukaryotic chromosomes usually occur in pairs
with similar genetic information
– When an entire set of stained chromosomes
from a single cell are examined (its karyotype),
we see that most cells contain pairs of
chromosomes
– Both members of each pair are the same length
and shape, and have the same staining pattern
– These similarities occur because each
chromosome in a pair carries the same genes
arranged in the same order

27. Copyright © 2011 Pearson Education Inc.Biology: Life on Earth, 9e
▪ Chromosomes that contain the same genes are
called homologous chromosomes, or
homologues
– Cells with pairs of homologous chromosomes
are called diploid, which means “double”

28. Copyright © 2011 Pearson Education Inc.Biology: Life on Earth, 9e
sex
chromosomes
The Karyotype of a Human Male
Fig. 9-6

29. Copyright © 2011 Pearson Education Inc.Biology: Life on Earth, 9e
The Eukaryotic Cell Cycle
Fig. 9-7
G2: cell
growth
and
preparation
for cell
division
S: synthesis
of DNA;
chromosomes
are duplicated
G1: cell growth
and
differentiation
cytokinesis

30. Copyright © 2011 Pearson Education Inc.Biology: Life on Earth, 9e
Homologous Chromosomes May Have the Same or
Different Alleles of Individual Genes
Fig. 9-12
gene 1 gene 2
same alleles different alleles

31. Copyright © 2011 Pearson Education Inc.Biology: Life on Earth, 9e
sister
chromatids
homologous
chromosomes
(c) After meiosis II(b) After meiosis I(a) Replicated
homologues
prior to
meiosis
Meiosis Is a Reduction Division That Halves the
Number of Chromosomes
Fig. 9-13

32. Copyright © 2011 Pearson Education Inc.Biology: Life on Earth, 9e
Meiotic Cell Division Is Essential for Sexual
Reproduction
Fig. 9-14
meiotic
cell division
fertilization
diploid
parental
cells
diploid
fertilized
egg
haploid
gametes
2n
2n
2n n
n

33. Copyright © 2011 Pearson Education Inc.Biology: Life on Earth, 9e
Crossing Over
Fig. 9-16

34. Copyright © 2011 Pearson Education Inc.Biology: Life on Earth, 9e
Random Separation of Homologous Pairs of
Chromosomes Produces Genetic Variability
Fig. 9-21

35. What is a mutation?
A mutation is a change on the nucleotide
sequence in a DNA chain.
Some mutations can be mild, some others can
be strong.
Mutations cause variety, evolution and in
some cases, they can be harmful.

36. How many kinds of mutations are
there?
Which of this mutations is
common in sexual reproduction?

37. Essential Amino acids

39. Nucleotide substitution
◼When a pair of bases
is occasionally
mismatched, and
the repairing
enzymes replace the
original nucleotide
instead of the
mismatched.

40. Insertion mutation
◼One or more
nucleotide pairs are
inserted into the
DNA double helix.

41. Deletion mutation
◼One or more
nucleotide pairs
are removed from
the double helix.

42. Inversion mutation
◼When a piece of
DNA is cut out of a
chromosome,
turned around, and
reinserted into the
gap.

43. Translocation mutation
◼When a chunk of DNA, often very large, is
removed from one chromosome and
attached to another one.

44. Exceptions to Mendel’s laws
Codominance: The two traits show
simultaneously.
Example: Spotted animals, multicolor flowers,
blood types

45. Incomplete dominance: The two traits are
expressed as an intermediate characteristic.
Examples: Intermediate color of the hair, skin,
eyes.

46. Linked Genes
“The material of inheritance is carried by the genes in chromosomes”
Walter S. Sutton (American Biologist. 1903)

47. Some alleles do not sort independently
as suggested by Mendel’s Law.
A chromosome has many genes.
When genes for two traits are
located in the same
chromosome, the two genes
travel together into the same
gamete, so they are inherited
together instead of sorting
independently.

48. Sex Linkage
Chromosomes are divided into sex
chromosomes (Those that define whether
the offspring are male or female) and
autosomes (non-sex chromosomes)
Humans and other mammals have two sex
chromosomes. XX for females and XY for
males.

49. X and Y chromosomes are not
homologous.
◼Genes found only in
the X chromosome
are X-linked genes,
and genes found only
in the Y chromosome
are Y-linked genes.

50. X and Y don’t match.
◼ X and Y chromosomes are plenty different.
They don’t recombine, so Y chromosome loses
genes. X chromosome has the opportunity to
show genes of the loosen parts of Y.

51. Sex linked disorders
When X can show what it has…

52. Color blindness
◼Abnormality in the cones that makes the
patient to perceive color in distorted ways.

53. How to represent a sex linked
disorder in a Punett square?
X’X= CARRIER XY=NORMAL
X’X’= COLORBLIND X’Y=COLORBLIND
A woman who is a carrier marries a normal
vision man.
X’ X
X X’X XX
Y X’Y XY

54. Androgenic alopecia
◼The loss of 70 to 90%
of the hair without
medical or stress
reasons. Women
rarely suffer
baldness. They may
experience diffuse
thinning of their hair.

55. Hemophylia
Recessive genetic disorder
that affects the ability of
the body to control blood
clotting or coagulation.

56. Duchenne’s muscular dystrophy
It is an X recessive gene
that causes a muscular
dystrophy characterized
by rapidly progressive
muscle weakness and
wasting due to
degeneration of skeletal,
smooth and cardiac
muscle.
(orpha.net)

57. Martin-Bell or X fragile
syndrome
It is a dominant trait that causes a range of
developmental problems including learning disabilities
and cognitive impairment. https://ghr.nlm.nih.gov/

58. Incontinentia Pigmenti
◼Refers to the loss of melanin
from cells in the epidermis.
▪ Typical neonatal rash
▪ Typical hyperpigmentation
▪ Linear, atrophic lesions.
▪ Lethal for males.

59. Chromosomal
abnormalities.
Genetic disorders due to cell division issues.

60. Monosomies or trisomies.
Non-disjunction: When homologous chromosomes
do not separate during metaphase I.

61. Turner’s Syndrome. XO women.
One of the two sex
chromosomes is missing
or defective. They are
usually sterile and short.

62. Triple X syndrome.
◼Taller than average.
◼Learning and
behavioral
difficulties.
◼Curved fingers.
◼Eyes more separated
than average.

63. Klinefelter Syndrome. XXY men.
◼also known as the
XXY condition, is a
term used to
describe males who
have an extra X
chromosome in
most of their cells.

64. Jacobs syndrome. XYY men.
◼High levels of testosterone.
◼Severe acne
◼Taller than average.
◼Learning and behavioral difficulties.
◼Curved fingers.
◼Eyes more separated than average.
◼Escoliosis

65. Trisomy 21 or Down Syndrome
◼ Extra copy of
chromosome 21
◼ Weak muscle tone
◼ Small mouth held
partially open
◼ Distinctively shaped
eyelids.
◼ Low resistance to
infectious diseases
◼ Heart malformations
◼ Varying degrees of
mental retardation

66. Trisomy 18. Edwards syndrome.
Individuals with this
syndrome can develop
abnormalities in their
body structures, renal,
cardiovascular and
nervous disorders. Life
span is of 1 year, but
with cases of teenagers
from 12 to 14 years.

67. Patau’s syndrome. Trisomy 13.
The individual presents
serious medical
conditions especially in
the heart and nervous
systems, so the life span
can be of 1 year. Still,
some people can
survive if the conditions
are not so serious.

68. HEREDITARY
DISORDERS
It is in your DNA…

69. Albinism
◼The lack of
producing
tyrosinase. The
enzyme to produce
melanin. The dark
pigment of the skin,
iris and hair.

70. Sickle-cell anemia
◼Mutation in the
hemoglobin gene.
◼Red blood cells are
weak and fragile.
◼Can cause anemia
because many red
blood cells are
destroyed.
◼There are less
oxygen in the blood.

71. Huntington disease
◼Dominant disorder
that causes a slow,
progressive
deterioration of parts
of the brain after the
30 to 50 years.
◼Loose of coordination.
◼Failing movements.
◼Personality
disturbances.

72. Cystic fibrosis
◼ Mutations in the CFTR
production (CFTR
hormone helps
reabsorbing salt
avoiding dehydration
of cells.)
◼ Mucus in the lungs is
dehydrated and thick.
◼ Cilia can’t move and
bacteria stay in the
lungs.

73. Tay-Sachs disease
◼Incapability to
metabolize a lipid
that stays in the
brain causing
blindness and brain
damages.

74. Phenylketonuria
◼ Lack of the enzyme to
break down the
aminoacid
phenylalanine.
◼ Accumulations of
phenylalanine can
cause damage in
nerve cells leading to
severe developmental
disabilities and death

75. Genetics environmental
affections
Watch your actions…

76. Smoking habits
◼Tobacco products are dangerous mutagens
that may produce serious damage in DNA
causing respiratory, cardiac, digestive or
nervous system diseases.
◼Pregnant women who smoke can cause their
babies growth and development problems,
mental retardation, or even death because of
spontaneous abortion.

77. Alcohol
◼Alcohol is an strong mutagen that can cause
liver damages, brain diseases, bloodstream
problems and so many other diseases.
◼Pregnant women can cause their babies Fetal
alcohol syndrome that includes physical,
mental and behavioral defects.

78. Psychotropic substances
◼They act as mutagens that affect the nervous
system, the endocrine and the cardiovascular
system.
◼Pregnant women can cause serious damage
to their babies as mental retardation, and
other mental diseases, addiction and even
malformations.
◼Psychotropic substances can cause abortions.

79. Radiation
◼Radiation is a very dangerous mutagen that
can cause translocations and other mutations
in cell DNA.
◼A pregnant woman exposed to radiation can
affect the baby in many ways: Malformations,
mental retardation or death.
◼UV rays are harmful to the skin cells.

80. Cancer
◼Cancer is uncontrolled, abnormal cell
division.
◼There are many different forms of cancer as
cells in our body.
◼Cancer cells can migrate from one part of an
organism to another part.
◼Cancer can result of genetic or environmental
factors.

81. Oncogenes
◼Is a gene that causes a cell to become
cancerous.
◼Some oncogenes in humans appear to be
mutated forms of genes that code for
proteins called growth factors that help cell
division and differentiation.
◼Some others result from changes in the
tumor suppressor genes.

82. Becoming an oncogene…
◼A mutation can occur in a growth factor gene
◼An error in DNA replication can result in
multiple copies of a single growth-factor
gene.
◼A change in a gene’s location can create an
oncogene (translocation)
◼Carcinogens as tobacco products, alcohol and
some other drugs can replace or change DNA
bases.

83. Healthy habits
◼ Have a diet low in fat and high in fiber and beta-
carotene.
◼ Have a diet rich in vitamins A, C, and E, and
omega-3. Avoid burned foods.
◼ Avoid smoking (even passive), alcohol and other
drugs.
◼ Protect yourself from the UV rays of the sun.
◼ Make exercise and remain calm and relaxed.
Stress is not good.
◼ Find out about your family history and talk to
your doctor.

84. DNA makes us what we are
and defines what we will be.
We’ve been walking on this planet from million
years. Our species had dramatically changed
since.