Topic 1_introduction to genetics

SBB 1054 Genetics
1
Prepared by Pratheep Sandrasaigaran
Lecturer at Manipal International University

GENETICS TEXTBOOKS
1. Concepts of Genetics, Klug, Cummings,
Spencer, Palladino, 2012
2. Human Genetics concepts and Application
9th ed.
3. Biology, 8th Edition, Campbell-Reece
4. Genetics for Dummies. Tara. R.R
5. The facts on file Illustrated guide to The
human: body Cells and Genetics
2

RATIONALE
1. The rationale to include this module in the academic
programme is because this module is the core and
major module in the academic programme.
2. The course is designed in developing an understanding
of Genetics theory and practical.
3

OBJECTIVES
This subject serves as a core for students to:
1. Understand the fundamental concepts in Genetics
2. Have in depth knowledge about chromosome structure
and genetic code
3. To understand the knowledge and steps on crossing
over during meiotic divisions, linkage
4. To understand the knowledge of genetic testing and
able to analyse as well construct the family pedigree
4

COURSE LEARNING OUTCOMES
• Demonstrate an understanding of fundamental concepts
in Genetics and justify the concepts.
• Develop an understanding that enables to illustrate the
chromosomal structure and genetic code.
• To know knowledge on crossing over during meiotic
divisions and able to measure the linkage percentage.
• To comprehend the knowledge of genetic testing and to
analyse as well to construct the family pedigree
5

Getting Registered in
www.edmodo.com
6
Group Code: te6gvr (Valid till 2nd March 2017 only!)
• Notes
• Assignment
• Lab manual
• Useful tips
• Guidance
• Forums
• Coursework marks
• Important announcements

IMPORTANT DATES..!
1. Test 1- Week 6 (20th – 24th MAC 2017)
2. Test 2- Week 11 ( 24th – 28th APR 2017)
3. Assignment 2- 3rd May 2017 (Week 12)
4. Study Break- Week 15 (22nd – 26th MAY
2017)
5. Exam- Week 16 & 17 (29th MAY – 9th JUN
2017)
Figure taken from Internet
7

Lecturer at Manipal International University
1.0 Introduction to
genetics
8

Figure taken from Internet
• Understand the concept of genetics in
brief
• History of genetics
• Define chromosomes and genes
• Knowing the different branches of
genetics
By the end of this chapter
you should be able to:
9

1.1 Introduction: What Is Genetics?
10

Genetics?
TRAITS OF AN
ORGANISM
INHERITED- PARENTS
VARIATIONS
BLUEPRINT
DNA
CHROMOSOME
EVOLUTIONS
MENDAL
AMAZING
UNIQ
UE
CODE
CLONING
FUNDAMENTALS
11

What Is Genetics?
• Genetics is the field of science that examines
how traits are passed from one generation to the
next.
• Blueprint of life.
• An organism’s genes, snippets of DNA that are
the fundamental units of heredity, control how it
looks, behaves, and reproduces.
12

The four major subdivisions Genetics
Classical
genetics
Population
genetics
Molecular
genetics
Quantitative
genetics
13

Four major subdivisions Genetics
• Classical genetics: Describes how traits (physical
characteristics) are passed along from one
generation to another.
• Molecular genetics: The study of the chemical
and physical structures of DNA, its cousin RNA,
and proteins.
14

Four major subdivisions Genetics
• Population genetics: Takes Mendelian genetics
(that is, the genetics of individual families) and
ramps it up to look at the genetic makeup of
larger groups.
• Quantitative genetics: A highly mathematical
field that examines the statistical relationships
between genes and the traits they encode
15

How different/similar are our DNA
sequences?
16
http://www.nature.com/scitable/knowledge/library/comparative-genomics-13239404
Organism
Estimated
size (bp)
Chromosome #
Estimated
gene #
Human (Homo sapiens) 3 billion 46 ≈ 25000
Mouse (Mus musculus) 2.9 billion 40 ≈ 25000
Fruit fly (Drosophila
melanogaster)
165 million 8 ≈ 13000
Plant (Arabidopsis thaliana)
157 million 10 ≈ 25000
Roundworm
(Caenorhabdtis elegans)
97 million 12 ≈ 19000
Yeast (Saccharomyces
cerevisiae)
12 million 32 ≈ 6000
Bacteria (Escherichia coli) 4.6 million 1 ≈ 3200

sequences?
• How different/similar are you compared to your siblings?
• How different/similar are you compared to your Gf/Bf?
• How different/similar are you compared to your
neighbor?
• How different/similar are you compared to Donald
Trump?
• How different/similar are you compared to your cat/ pet?
• How different/similar are you compared to Godzila/
Dinosaur?
• How different/similar are you compared to dust/
bacteria?
17

sequences?
• On average, you are 99.9%
identical to another human…
• What does it mean?: About 1
base in 1000 is different
• 1/1000 x 100% = ?
18

My hobby
My hobby is reading. I read story books, magazines, newspapers and any kind of
material that I find interesting. This hobby got started when I was a little boy. I had
always wanted my parents to read fairy tales and other stories to me. Soon they
got fed up and tired of having to read to me continually. So as soon as I could, I
learned to read. I started with simple ABC books. Soon read simple fairy tales and
other stories. Now I can fast going about anything that is available. Reading
enables me to learn about so many things that I would otherwise not know. I
learned about how people lived in bygone days of magic and mystery. I learned
about the wonders of the world, space travel, human achievements, gigantic
whales, tiny viruses and other fascinating things of our world. The wonderful thing
about reading is that I do not have to learn things the hard way. For example, I do
not have to catch a disease to know that it can kill me. Also I have to go into the
jungle to learn about tiger
19

My hobby
other stories. Now I can fast going about anything that is available. Reading
20

My hobby
other stories. Now I can fart going about anything that is available. Reading
21

Chromosome 3- locus XM_019023187
22
CTCCTCCTGTTCGACAGTCAGCCGCATCTTCTTTTGCATCGCCAGCCAAGCCACATCGCTGAGAC
ACCATGGGGAAGGTGAAGGTCGGAGTCAACGGATTTGGTCGTATTGGGCGCCTGGTCACCAG
GGCTGCTTTTAACTCTGGTAAAGTGGATATTGTTGCCATCAATGACCCCTTCATTGACCTCAACTA
CATGGTTTACATGTTCCAATATGATTCCACCCATGGCAAATTCCATGGCACCGTCAAGGCTGAGA
ACGGGAAGCTTGTCATCAATGGAAATCCCATCACCATCTTCCAGGAGCGAGATCCCTCCAAAAT
CAAGTGGGGCGATGCTGGTGCTGAGTACGTCGTGGAGTCCACTGGTGTCTTCACCACCATGGA
GAAGGCTGGGGCTCATTTGCAGGGGGGAGCCAAAAGGGTCATCATCTCTGCCCCCTCTGCTGA
CGCCCCCATGTTCGTCATGGGTGTGAACCATGAGAAGTATGACAACAGCCTCAAGATCATCAGC
AATGCCTCCTGCACCACCAACTGCTTAGCACCCCTGGCCAAGGTCATCCATGACAACTTTGGTAT
CGTGGAAGGACTCATGACCACGGTCCATGCCATCACTGCCACCCAGAAGACTGTGGATGGCCC
CTCCGGGAAACTGTGGCGTGATGGCCGCGGGGCTCTCCAGAACATCATCCCTGCCTCTACTGG
CGCTGCCAAGGCTGTGGGCAAGGTCATCCCTGAGCTGAACGGGAAGCTTACTGGCATGGCCTT
CCGTGTCCCCACTGCCAACGTGTCAGTGGTGGACCTGACCTGCCGTCTAGAAAAACCTGCCAAA
TATGATGACATCAAGAAGGTGGTGAAGCAGGCGTTGGAGGGCCCCCTCAAGGGCATCCTGGG
CTACACTGAGCACCAGGTGGTCTCCTCTGACTTCAATAGCGACACCCACTCCTCCACCTTCGACA
CTGGGGCTGGCATTGCCCTCAACGACCACTTTGTCAAGCTCAT

Chromosome 3- locus XM_019023187
23
CTCCTCCTGTTCGACAGTCAGCCGCATCTTCTTTTGCATCGCCAGCCAAGCCACATCGCTGAGAC
ACCATGGGGAAGGTGAAGGTCGGAGTCAACGGATTTGGTCGTATTGGGCGCCTGGTCACCAG
GGCTGCTTTTAACTCTGGTAAAGTGGATATTGTTGCCATCAATGACCCCTTCATTGACCTCAACTA
CATGGTTTACATGTTCCAATATGATTCCACCCATGGCAAATTCCATGGCACCGTCAAGGCTGAGA
ACGGGAAGCTTGTCATCAATGGAAATCCCATCACCATCTTCCAGGAGCGAGATCCCTCCAAAAT
CAAGTGGGGCGATGCTGGTGCTGAGTACGTCGTGGAGTCCACTGGTGTCTTCACCACCATGGA
GAAGGCTGGGGCTCATTTGCAGGGGGGAGCCAAAAGGGTCATCATCTCTGCCCCCTCTGCTGA
CGCCCCCATGTTCGTCATGGGTGTGAACCATGAGAACTATGACAACAGCCTCAAGATCATCAGC
AATGCCTCCTGCACCACCAACTGCTTAGCACCCCTGGCCAAGGTCATCCATGACAACTTTGGTAT
CGTGGAAGGACTCATGACCACGGTCCATGCCATCACTGCCACCCAGAAGACTGTGGATGGCCC
CTCCGGGAAACTGTGGCGTGATGGCCGCGGGGCTCTCCAGAACATCATCCCTGCCTCTACTGG
CGCTGCCAAGGCTGTGGGCAAGGTCATCCCTGAGCTGAACGGGAAGCTTACTGGCATGGCCTT
CCGTGTCCCCACTGCCAACGTGTCAGTGGTGGACCTGACCTGCCGTCTAGAAAAACCTGCCAAA
TATGATGACATCAAGAAGGTGGTGAAGCAGGCGTTGGAGGGCCCCCTCAAGGGCATCCTGGG
CTACACTGAGCACCAGGTGGTCTCCTCTGACTTCAATAGCGACACCCACTCCTCCACCTTCGACA
CTGGGGCTGGCATTGCCCTCAACGACCACTTTGTCAAGCTCAT

sequences?
• How different/similar are you compared to your
neighbor?
- 1 different per 1000 bases
- 3 000 000 000 bases per set
- 2 sets each person
- 6 000 000 differences
24

How much phenotypic differences do
these genotypic differences make?
• Most of 6 000 000 DNA differences don’t make any
detectable differences to phenotype.
• But the rest cause all the heritable differences between
people
• The same kinds of DNA differences cause the phenotypic
differences in all other species too..!
25

1.2 History of genetics
26

What principles of inheritance did Gregor Mendel
discover by breeding garden pea plants?
27

Advantages of pea plants for genetic
study
• There are many varieties with distinct heritable
features, or characters (such as flower colour).
• Mating can be controlled
• Each flower has sperm-producing organs (stamens) and
an egg-producing organ (carpel)
• Cross-pollination (fertilization between different plants)
involves dusting one plant with pollen from another
28

Parental
generation
(P) Stamens
Carpel
TECHNIQUE
2
1
3
4
29

Figure 14.2b
First filial
generation
offspring
(F1)
RESULTS
5
• Mendel chose to track only those characters that occurred in two distinct
alternative forms
• He also used varieties that were true-breeding (plants that produce
offspring of the same variety when they self-pollinate)
30

Mendal’s Experiment
• In a typical experiment, Mendel mated two contrasting,
true-breeding varieties, a process called hybridization
• The true-breeding parents are the P generation
• The hybrid offspring of the P generation are called the
F1 generation
• When F1 individuals self-pollinate or cross- pollinate
with other F1 hybrids, the F2 generation is produced
31

Mendal’s Experiment
The Law of
Segregation
The Law of
Independent
Assortment
1 2
32

Mendal’s Experiment: The Law of
Segregation
• Mendel identified his first law of inheritance by
following one characters at one time
• Crossing two true-breeding parents differing in one
characters produces monohybrid in the F1 generation,
heterozygous for both characters
• A dihybrid cross, a cross between F1 dihybrids, can
determine whether two characters are transmitted to
offspring as a package or independently
33

• Mendel observed the pattern six pea
plant characters, each represented by
two traits
• What Mendel called a “heritable factor”
is what we now call a gene
Mendal’s Experiment:
The Law of Segregation
34

Figure 14.4
Allele for purple flowers
Locus for flower-color gene
Allele for white flowers
Pair of
homologous
chromosomes
• A capital letter represents a dominant
allele, and a lowercase letter represents a
recessive allele
35

Phenotype
Purple
Purple
Purple
White
3
1
1
1
2
Ratio 3:1 Ratio 1:2:1
Genotype
PP
(homozygous)
Pp
(heterozygous)
Pp
(heterozygous)
pp
(homozygous)
Figure 14.6
36

Mendal’s Experiment: The law of
independent assortment
• Mendel identified his second law of inheritance by
following two characters at the same time
• Crossing two true-breeding parents differing in two
characters produces dihybrids in the F1 generation,
heterozygous for both characters
• A dihybrid cross, a cross between F1 dihybrids, can
determine whether two characters are transmitted to
offspring as a package or independently
37

Figure 14.8
P Generation
F1 Generation
Predictions
Gametes
EXPERIMENT
RESULTS
YYRR yyrr
yrYR
YyRr
Hypothesis of
dependent assortment
Hypothesis of
Predicted
offspring of
F2 generation
Sperm
Sperm
or
Eggs
Eggs
Phenotypic ratio 3:1
Phenotypic ratio 9:3:3:1
Phenotypic ratio approximately 9:3:3:1315 108 101 32
1/2
1/2
1/2
1/2
1/4
1/4
1/4
1/4
1/4
1/4
1/4
1/4
9/16
3/16
3/16
1/16
YR
YR
YR
YR
yr
yr
yr
yr
1/4
3/4
Yr
Yr
yR
yR
YYRR YyRr
YyRr yyrr
YYRR YYRr YyRR YyRr
YYRr YYrr YyRr Yyrr
YyRR YyRr yyRR yyRr
YyRr Yyrr yyRr yyrr
38

Mendal’s Experiment: The law of
• The law of independent assortment states that each
pair of alleles segregates independently of each other
pair of alleles during gamete formation
• Strictly speaking, this law applies only to genes on
different, nonhomologous chromosomes or those far
apart on the same chromosome
• Genes located near each other on the same
chromosome tend to be inherited together
39

Inheritance patterns are often more
complex than predicted by simple
Mendelian genetics
• The relationship between genotype and phenotype is
rarely as simple as in the pea plant characters Mendel
studied
• Many heritable characters are not determined by only
one gene with two alleles
• However, the basic principles of segregation and
independent assortment apply even to more complex
patterns of inheritance
40

Extending Mendelian Genetics for a Single
Gene
• Inheritance of characters by a single gene may deviate
from simple Mendelian patterns in the following
situations:
- When alleles are not completely dominant or
recessive
- When a gene has more than two alleles
- When a gene produces multiple phenotypes
41

Degrees of Dominance
• Complete dominance occurs when phenotypes of the
heterozygote and dominant homozygote are identical
• In incomplete dominance, the phenotype of F1 hybrids
is somewhere between the phenotypes of the two
parental varieties
• In codominance, two dominant alleles affect the
phenotype in separate, distinguishable ways
42

P Generation
Red White
Gametes
CWCW
CRCR
CR CW
43

P Generation
F1 Generation
1/2
1/2
Red White
Gametes
Pink
Gametes
CWCW
CRCR
CR CW
CRCW
CR
CW
44

P Generation
F1 Generation
F2 Generation
1/2
1/2
1/2
1/2
1/2
1/2
Red White
Gametes
Pink
Gametes
Sperm
Eggs
CWCW
CRCR
CR CW
CRCW
CR CW
CWCR
CR
CW
CRCR
CRCW
CRCW CWCW
45

Multiple Alleles
• Most genes exist in populations in more than two allelic
forms
• For example, the four phenotypes of the ABO blood
group in humans are determined by three alleles for
the enzyme (I) that attaches A or B carbohydrates to
red blood cells: IA, IB, and i.
• The enzyme encoded by the IA allele adds the A
carbohydrate, whereas the enzyme encoded by the IB
allele adds the B carbohydrate; the enzyme encoded by
the i allele adds neither
46

Carbohydrate
Allele
(a) The three alleles for the ABO blood groups and their
carbohydrates
(b) Blood group genotypes and phenotypes
Genotype
Red blood cell
appearance
Phenotype
(blood group)
A
A
B
B AB
none
O
IA IB i
iiIAIBIAIA or IAi IBIB or IBi
47

Is she having an affair? Think!
• A man divorced his wife immediately after the
blood group result of his son was revealed by
the doctor in HKL.
• The man is blood group A+ while his wife is
blood group B+.
• His newborn son is tested blood group O+.
Possible?
• The doctors were puzzled by the man’s impulsive
act!!!
48

Test Your Knowledge 1
49

1. There are 4 subdivision of genetics that you will be
studying for SBB 1054 Genetics.
2. Gregor Mandal is the father of genetics and DNA.
3. Two law introduced by Gregor Mandal is known as
Mendelian law.
4. Mendelian law can explain every phenotypes and
genotypes.
5. The secret of success of Gregor Mandal is the pea
plant itself.
50

1.3 Introductions to Chromosomes
and Genes
51

The Chromosome Theory of Inheritance
• Mendel conducted his experiments before the
structure and role of chromosomes were known.
• About 20 years after his work was published, advances
in microscopy allowed researchers to identify
chromosomes.
• What is chromosome?
• Chromosomes in diploid cells exist in pairs, called
homologous chromosomes (identical in size and
location of the centromere).
52

• In mitosis, chromosomes are copied and distributed so
that each daughter cell receives a diploid (2n) set of
chromosomes.
• Meiosis is associated with gamete formation.
• How many chromosome human have in general?
• How many chromosome do you see in human gamete?
53

• The chromosome theory of inheritance states:
- Mendelian genes have specific loci (positions) on
chromosomes
- Chromosomes undergo segregation and
54

P Generation Yellow-round
seeds (YYRR)
Green-wrinkled
seeds (yyrr)

Meiosis
Fertilization
Gametes
Y
Y
R R
YR
y
y
r
y r
r
55

F1 Generation
All F1 plants produce
yellow-round seeds (YyRr).
Meiosis
Metaphase I
Anaphase I
Metaphase
II
R R
R R
R R
R R
R R R R
r r
r r
r r
r r
r r r r
Y Y
Y Y
Y Y
Y Y
Y Y Y Y
y y
y y
y y
y y
y
y y y
Gametes
LAW OF SEGREGATION
The two alleles for each
gene separate during
gamete formation.
LAW OF INDEPENDENT
ASSORTMENT Alleles of
genes on nonhomologous
chromosomes assort
independently during gamete
formation.
1
2 2
1
1/4
1/4
1/4
1/4YR yr Yr yR
56

F2 Generation
3Fertilization
recombines the
R and r alleles
at random.
Fertilization results
in the 9:3:3:1
phenotypic ratio in
the F2 generation.
An F1  F1 cross-fertilization
9 : 3 : 3 : 1
LAW OF SEGREGATION LAW OF INDEPENDENT
ASSORTMENT
3
57

• Walter Sutton and Theodor Boveri noticed that
genes and chromosomes exist in pairs.
• They also notice that members of a gene pair and
members of a chromosome pair separate from
each other during gamete formation.
• Based on these parallels, Sutton and Boveri
independently proposed that genes are carried
on chromosomes
A drawing of chromosome
X of D. melanogaster
Adapted from Concepts of Genetics, Klug, Cummings, Spencer, Palladino, 2012
.58

Phenotype and Genotype
• Different alleles may produce differences in the
observable features, or phenotype, of an
organism.
• The set of alleles for a given trait carried by an
organism is called the genotype.
• Knowing gene control the phenotype and
genotype, what is the chemical nature of Genes?
• By the 1920s, scientists were aware that proteins
and DNA were the major chemical components
of chromosomes.
DNA
Protein
59

DNA is carrier of genetic: heritable factor
• When T. H. Morgan’s group showed
that genes are located on
chromosomes, the two components
of chromosomes; DNA or protein?
• The key factor in determining the
genetic material was choosing
appropriate experimental organisms
• The role of DNA in heredity was first
discovered by studying bacteria and
the viruses that infect them
An electron micrograph showing T phage infecting
a cell of the bacterium E. coli
Adapted from Concepts of Genetics, Klug,
Cummings, Spencer, Palladino, 2012
.
60

DNA is carrier of genetic: heritable factor
• In 1952, Alfred Hershey and Martha Chase
performed experiments showing that DNA is the
genetic material of a phage known as T2
• To determine this, they designed an experiment
showing that only one of the two components of T2
(DNA or protein) enters an E. coli cell during
infection
• They concluded that the injected DNA of the phage
provides the genetic information
61

Bacterial cell
Phage
Batch 1:
Radioactive
sulfur
(35S)
DNA
Batch 2:
Radioactive
phosphorus
(32P)
Radioactive
DNA
EXPERIMENT
Radioactive
protein
62

Bacterial cell
Phage
Batch 1:
Radioactive
sulfur
(35S)
Radioactive
protein
DNA
Batch 2:
Radioactive
phosphorus
(32P)
Radioactive
DNA
Empty
protein
shell
Phage
DNA
EXPERIMENT
63

Bacterial cell
Phage
Batch 1:
Radioactive
sulfur
(35S)
Radioactive
protein
DNA
Batch 2:
Radioactive
phosphorus
(32P)
Radioactive
DNA
Empty
protein
shell
Phage
DNA
Centrifuge
Centrifuge
Radioactivity
(phage protein)
in liquid
Pellet (bacterial
cells and contents)
Pellet
Radioactivity
(phage DNA)
in pellet
EXPERIMENT
64

Protein control the biological functions
• Lets do Maths..!
• Proteins are made from combinations of 20
different amino acids.
• Presume a protein is made of 3 bases of amino acid
polypeptide. How many different type of protein
can be derived?
• Now, if a Protein is made of 100 bases of amino
acid polypeptide. How many different type of
protein can be derived?
203 = 8000
20100 = ????
65

Timeline of genetics
timeline showing the development of genetics from Gregor Mendel’s work on pea plants to the current era of genomics
and its many applications in research, medicine, and society.
.
66

Central dogma
of genetics/
Molecular biology
Gene expression consists of transcription of DNA into mRNA
(top) and the translation (center) of mRNA (with the help of
a ribosome) into a protein (bottom).
.67

1.4 Different branches of genetics
68

Branches of genetics
• Behavioural genetics
• Developmental genetics
• Conservation genetics
• Ecological genetics
• Evolutionary genetics
• Genetic engineering
• Genomics
• Human genetics
• Microbial genetics
• Molecular genetics
• Population genetics
• Quantitative genetics
Dolly, a Finn Dorset sheep cloned from the genetic
material of an adult mammary cell, shown next to her
first-born lamb, Bonnie.
.69

Diagram of the human chromosome set, showing
the location of some genes whose mutant forms
cause hereditary diseases. Conditions that can be
diagnosed using DNA analysis are indicated by a
red dot
.
70

Topic 1_introduction to genetics

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