Presentation by Prof Eric Danquah, West African Centre for Crop Improvement, University of Ghana, Legon
Delivered at the B4FA Media Dialogue Workshop, Accra, Ghana - September 2012
For the IB DP Biology course, core unit: Genetics. To get the file, please make a donation to one of my preferred charities via Biology4Good. Find out more here: http://sciencevideos.wordpress.com/about/biology4good/
توضیح وراثت به طور کلی و گسترده در دهه 1800، و به طور مشخص فرضیه "مخلوط شدن" مورد پسند دانشمندان و زیست شناسان عصر خود بود. براساس این ایده، مواد ژنتیکی توسط والدین و درست همان طور که رنگ های آبی و زرد برای تبدیل شدن به رنگ سبز ترکیب میشوند، مخلوط میشدند. البته این فرضیه توضیح نمیداد که چگونه صفات پس از کنار رفتن یک نسل دوباره در نسل بعدی ظاهر میشوند. یک گزینه جایگزین برای مدل مخلوط شدن مواد ژنتیکی، فرضیه وراثت "ذرات معلق" است یا همان ایده ژن. در این مدل، والدین واحدهای موروثی به نام ژنها را که هویت جداگانه خود را در فرزندان حفظ می کنند، منتقل میکنند. گریگور مندل راهبی بود كه سازوكار ذرهای این نوع وارثت را با استفاده از گیاه نخود فرنگی به اثبات رساند.
The explanation of heredity most widely in favor during the 1800s was the “blending” hypothesis, the idea that genetic material contributed by the two parents, mixes just as blue and yellow paints blend to make green. The blending hypothesis failed to explain how traits can reappear after they’ve skipped a generation. An alternative to the blending model is a “particulate” hypothesis of inheritance: the gene idea. In this model, parents pass on discrete heritable units—genes— that retain their separate identities in offspring. Gregor Mendel was the monk who documented a particulate mechanism for this form of inheritance using pea plants.
For the IB DP Biology course, core unit: Genetics. To get the file, please make a donation to one of my preferred charities via Biology4Good. Find out more here: http://sciencevideos.wordpress.com/about/biology4good/
توضیح وراثت به طور کلی و گسترده در دهه 1800، و به طور مشخص فرضیه "مخلوط شدن" مورد پسند دانشمندان و زیست شناسان عصر خود بود. براساس این ایده، مواد ژنتیکی توسط والدین و درست همان طور که رنگ های آبی و زرد برای تبدیل شدن به رنگ سبز ترکیب میشوند، مخلوط میشدند. البته این فرضیه توضیح نمیداد که چگونه صفات پس از کنار رفتن یک نسل دوباره در نسل بعدی ظاهر میشوند. یک گزینه جایگزین برای مدل مخلوط شدن مواد ژنتیکی، فرضیه وراثت "ذرات معلق" است یا همان ایده ژن. در این مدل، والدین واحدهای موروثی به نام ژنها را که هویت جداگانه خود را در فرزندان حفظ می کنند، منتقل میکنند. گریگور مندل راهبی بود كه سازوكار ذرهای این نوع وارثت را با استفاده از گیاه نخود فرنگی به اثبات رساند.
The explanation of heredity most widely in favor during the 1800s was the “blending” hypothesis, the idea that genetic material contributed by the two parents, mixes just as blue and yellow paints blend to make green. The blending hypothesis failed to explain how traits can reappear after they’ve skipped a generation. An alternative to the blending model is a “particulate” hypothesis of inheritance: the gene idea. In this model, parents pass on discrete heritable units—genes— that retain their separate identities in offspring. Gregor Mendel was the monk who documented a particulate mechanism for this form of inheritance using pea plants.
As a periodontist, it is of utmost importance to understand the genetic basis of inheritance in periodontal diseases be able to relate to the various polymorphisms associated with periodontal diseases. This ppt presents the basics of genetics from the point of view of future understanding of polymorphisms related to periodontal diseases.
Structure of DNA. Coiling of DNA. Definitions about genetics. The Gene & The Genetic Code. Gene Mutation. Regulation of gene expression. DNA Functions. Patterns Of Inheritance
What Is Genetics and How different/similar are our DNA sequences? Understanding Mendal's genetics and physical genetics; genotype, phenotype, allele, gene, homozygous, heterozygous, dominant, recessive.
Life-Span Human Development 9th Edition Sigelman Solutions ManualTimothyPadilla
Full download : https://alibabadownload.com/product/life-span-human-development-9th-edition-sigelman-solutions-manual/
Life-Span Human Development 9th Edition Sigelman Solutions Manual
Chapter 3 The New GeneticsAlma Villanueva, MACalifornia S.docxwalterl4
Chapter 3:
The New Genetics
Alma Villanueva, MA
California State University, Los Angeles
Overview
Genetic Code
The Beginning of Life
Male & Female
Twins
Genotype & Phenotype
Disorders
Genetic Counseling
Genetic Code
Cells
Basic unit of life
Trillions!
Nucleus
Chromosomes
Thread– like structures made up of DNA & protein
23 pairs
DNA (Deoxyribonucleic acid)
2 strands twisted in a double helix
Chemical composition of molecules that contain the genes
Contains all of the information required to build/maintain the cell
3
Genes
Small section of the chromosome
18,000 – 23,000 genes
Each gene provides a unique recipe to make a protein
4 bases
Code for your traits
A - adenine
T - thymine
C - cytosine
G – guanine
Only 4 possible pairs
A-T; T-A; C-G; G-C
http://mybrainnotes.com/brain-dna-behavior.html
4
Allele
A variation of a gene
Example: the gene for eye color has several variations (alleles); an allele for blue eye color or an allele for brown eyes
Everyone inherits alleles from sperm & ovum
Genetic diversity
Distinguishes each person
Allows the human species to adapt to pressures of the environment
Genome
Full set of genes with instructions to make a living organism
Genomes exist for each species
Video about Genes
5
The Beginning of Life
Two Parents, Millions of Gametes
Gamete
Reproductive cell
Sperm or Ovum
Each contains 23 pairs
Zygote
Cell formed with union of Sperm & Ovum
Produce a new individual with 23 chromosomes from each parent
Conception
http://predictingbabygender.info/tag/intercourse-timing/
Matching genes
Genotype
Organism’s entire genetic inheritance, or genetic potential.
Homozygous (same zygote)
Two genes of one pair that are exactly the same in every letter of their code
Heterozygous
Two genes of one pair that differ in some way
Usually not an issue
Male of Female?
Humans usually possess
46 chromosomes
44 autosomes and 2 sex chromosomes
SEX chromosome = 23rd pair
Female – XX
Male – XY
Mother’s contain X
Father’s may have X or Y
X chrom. Is larger & more genes
Y contain SRY,
making male hormones & organs
It's a girl!
Uncertain Sex
“ambiguous genitals,” = child's sex is not abundantly clear
a quick analysis of the chromosomes is needed, to make sure there are exactly 46 and to see whether the 23rd pair is XY or XX
shown here a baby boy (left) and girl (right).
Too Many Boys?
Is sex selection the parents’ right or a social wrong?
Preference for boys in many areas of world
Ways to prevent female birth
Inactivating X sperm before conception
In vitro fertilization (IVF)
Aborting XX fetuses
My Strength, My Daughter
slogan these girls in New Delhi are shouting at a demonstration against abortion of female fetuses in India
The current sex ratio of children in India suggests that this campaign has not convinced every couple.
New Cells
Within hours of conception
23 pairs of chromosomes carrying all the genes duplicate, forming two complete sets of the genome
Two sets.
Chapter 3 The New GeneticsAlma Villanueva, MACalifornia S.docxketurahhazelhurst
Chapter 3:
The New Genetics
Alma Villanueva, MA
California State University, Los Angeles
Overview
Genetic Code
The Beginning of Life
Male & Female
Twins
Genotype & Phenotype
Disorders
Genetic Counseling
Genetic Code
Cells
Basic unit of life
Trillions!
Nucleus
Chromosomes
Thread– like structures made up of DNA & protein
23 pairs
DNA (Deoxyribonucleic acid)
2 strands twisted in a double helix
Chemical composition of molecules that contain the genes
Contains all of the information required to build/maintain the cell
3
Genes
Small section of the chromosome
18,000 – 23,000 genes
Each gene provides a unique recipe to make a protein
4 bases
Code for your traits
A - adenine
T - thymine
C - cytosine
G – guanine
Only 4 possible pairs
A-T; T-A; C-G; G-C
http://mybrainnotes.com/brain-dna-behavior.html
4
Allele
A variation of a gene
Example: the gene for eye color has several variations (alleles); an allele for blue eye color or an allele for brown eyes
Everyone inherits alleles from sperm & ovum
Genetic diversity
Distinguishes each person
Allows the human species to adapt to pressures of the environment
Genome
Full set of genes with instructions to make a living organism
Genomes exist for each species
Video about Genes
5
The Beginning of Life
Two Parents, Millions of Gametes
Gamete
Reproductive cell
Sperm or Ovum
Each contains 23 pairs
Zygote
Cell formed with union of Sperm & Ovum
Produce a new individual with 23 chromosomes from each parent
Conception
http://predictingbabygender.info/tag/intercourse-timing/
Matching genes
Genotype
Organism’s entire genetic inheritance, or genetic potential.
Homozygous (same zygote)
Two genes of one pair that are exactly the same in every letter of their code
Heterozygous
Two genes of one pair that differ in some way
Usually not an issue
Male of Female?
Humans usually possess
46 chromosomes
44 autosomes and 2 sex chromosomes
SEX chromosome = 23rd pair
Female – XX
Male – XY
Mother’s contain X
Father’s may have X or Y
X chrom. Is larger & more genes
Y contain SRY,
making male hormones & organs
It's a girl!
Uncertain Sex
“ambiguous genitals,” = child's sex is not abundantly clear
a quick analysis of the chromosomes is needed, to make sure there are exactly 46 and to see whether the 23rd pair is XY or XX
shown here a baby boy (left) and girl (right).
Too Many Boys?
Is sex selection the parents’ right or a social wrong?
Preference for boys in many areas of world
Ways to prevent female birth
Inactivating X sperm before conception
In vitro fertilization (IVF)
Aborting XX fetuses
My Strength, My Daughter
slogan these girls in New Delhi are shouting at a demonstration against abortion of female fetuses in India
The current sex ratio of children in India suggests that this campaign has not convinced every couple.
New Cells
Within hours of conception
23 pairs of chromosomes carrying all the genes duplicate, forming two complete sets of the genome
Two sets ...
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B4FA 2012 Ghana: Fundamentals of Genetics - Eric Danquah
1. Basic Genetics
Eric. Y. Danquah
West Africa Centre for Crop Improvement (WACCI)
University of Ghana
edanquah@wacci.edu.gh
Media Fellowship Programme, Biosciences for Farming in Africa
Accra, Ghana, September 19-22, 2012
2. Outline
• Genetics and the
Organism - Heredity and
Variation
• Mendelian Genetics
• Cells, Chromosomes, DNA,
and Genes
• Sexual/Asexual
reproduction in plants
• Backcrossing
• Mutation; Polyploidy
• Take-home message
Eggplant
Tomato
4. 4
First, we need to define what genetics is
• Study of heredity?
- ancient discipline (domestication
of plants and animals)
- inheritance of individuality in humans
(why children resemble their parents; how
various diseases run in families)
• Definition incorrect; ancient people not
geneticists. Genetics comes from the word
genes and genes provide the focus for the
subject.
7. Second, genetics is a crucial
component of medicine
A large proportion of
human ill health has a
genetic basis
•Inherited genetic
diseases
(Phenylketonuria)
•somatic genetic diseases
(Cancer)
•chromosomal
aberrations (Down
syndrome)
10. Model I:
Genetic determination
• Compare a maize plant to
say a cowpea plant
• The case of sickle cell
anaemia (caused by a variant
of haemoglobin, the oxygen-
transporting protein molecule
found in red blood cells)
- Normal people have a
type of haemoglobin
called haemoglobin A.
- Replacement of
glutamic acid for
valine in the ββββ
globin chain results in
the production of a
slightly changed
haemoglobin, termed
haemoglobin S.
10
11. Hybrid vrs Open pollinated maize
On the right a
new, hybrid
maize variety
developed by
CIMMYT
with PASS
funding.
On the left, a
local landrace
variety
12. Above are monozygotic twins raised in the same home but,
consider the case of monozygotic twins separated at birth
from peasant parents and adopted by foster parents from two
culturally diverse backgrounds
Model II:
Environmental determination
14. The Beauty of Diversity: A Result of Genes - Environment
Interaction
Two of the biggest
mysteries in biology
answered by Genetics
•What makes a species
what it is?
•What causes variation
within a species?
15. Heredity
•Heredity is the
passing of traits
to offspring
(from its parent
or ancestors).
Offspring resemble their parents more than they
resemble unrelated individuals (why is this so?)
16. What is a trait?
•A peculiar quality
or characteristic
exhibited by an
individual
organism.
Can you think of examples of identifiable traits?
Observable traits in pea
19. Gregor Johann Mendel,
(b. 22 July 1822; d. 6 January 1884)
Moravia, Austro-Hungarian Empire
Originator of the concept of the gene
(autosomal inheritance)
Birthplace of Modern Genetic Analysis
Augustinian monastry garden, St. Thomas,
Brünn, Austria
Brno (Czech Rep.)
Experimemts, 1856-1870
20. The idea of blending inheritance
Spermatozoon and egg
contained essences from
various parts of the body;
at conception, these
essences somehow
blended to form a pattern
for the new individual
Ideas in Science come in
fashions
called paradigms
21. Reasons for choosing to study garden pea
• No morals involved
• Can be grown in a small area
• Produce lots of offspring
• Easily identifiable traits
• Produce true-to-type when
allowed to self- pollinate
over several generations
• Can be artificially cross-
pollinated
24. Summary and conclusions of Mendel’s
experiments
•After crossing pure parental strains,
the F1 produced 100% of one
character.
•After self-pollinating the F1, both
characters showed up in a 3:1 ratio.
•Because the same types of ratio kept
coming up, Mendel believed that there
must be some mathematical formula or
explanation for the observed data
•The first assumption made by Mendel
was that there must be a ”pair of
factors” that controls the trait in pea
plant. This “pair of factors” idea helped
him formulate his principles
26. Punnet square of the predicted genotypic and phenotypic
constitution of the F2 generation from a dihybrid cross
27. Mendel’s Laws
• Law of equal segregation (First Law)
- The two members of a gene pair
segregate from each other into the
gametes; so that half the gametes carry
one member of the pair and the other
half of the gametes carry the other
member of the pair.
• Law of Independent Assortment (Second Law)
- different gene pairs assort
independently during gamete
formation
28. Organisms
• An organism is any
living thing:
– microbes
– plants
– insects
– birds
– mammals
– us
29. Cells
• Cells are the building blocks of
organisms
• Think of bricks making a building
• The type of brick determines what
the building will look like
30. Cells, cont.
• in the same way, the
type of cell
determines the type
of organ
• and, the type of organ
determines the type
of organism
Each time we scratch our
skin we scrape off
millions of cells
31. Cells, cont.
• Each cell is like a city
• It has a:
– transport system
– waste disposal system
– food delivery system
– water delivery system
– disease control system
– management centre
32. Cell management centres
• Cell management
centres contain all
the information
needed to keep the
cell running
• They also contain
all the information
needed to make the
whole organism
– a ‘blueprint’
34. Genes (Every organism carries inside
itself what are known as genes)
• The code on the
DNA is divided into
sections called
genes.
• Each gene codes for
a protein
• Each protein has a
function
– an action
– building block
35. DNA - the code for life
• The DNA code consists
of just 4 building
blocks:
– A, C, T and G.
• Whether we are
bacteria, fungi
earthworms, mushrooms
or humans our DNA has
the same building
blocks, just in a
different order.
A C T G ...GCCTTACG…
....ACTGCCTGGAAC….
….TGACGGACCTTG….
Source: Microsoft Encarta
Source: Microsoft Encarta
37. Genes, cont.
and …
• HIV has genes that
cause AIDS, while
• Chickenpox virus
has genes that
cause chicken pox
or shingles
38. Genes (The genes are codes or messages. They carry
information. The information they carry is used to tell
the organism what chemicals it needs to make in order
to survive, grow or reproduce )
• Genes make us who
we are
• We receive our
genes from our
parents
• The same is true for
all animals, plants
and microbes
39. The Cell
Cells are the basic functional unit of all life forms they hold all of the
biological equipment necessary to keep an organism alive Earth
45. Background to discovery of DNA
James Watson & Francis Crick – accurate model of DNA
Chargaff's realization that A = T and C = G, combined with the X-ray crystallography
work by Rosalind Franklin and Maurice Wilkins, contributed to Watson and Crick's
derivation of the three-dimensional, double-helical model for the structure of DNA.
http://www.nature.com/scitable/topicpage/discovery-of-dna-structure-and-function-watson-397
49. What is a gene?
• A hereditary unit that
occupies a certain
position on a
chromosome/DNA in
the nucleus of a cell.
This unit that has one
or more specific effects
on the physical
appearance of an
organism.
58. Backcrossing
• Backcrossing is done with the main
objective of incorporating a desired gene,
either dominant or recessive, from a wild
or non commercial variety to a highly
productive, commercially successful variety
which lacks that specific gene.
http://theagricos.com/plant-breeding/backcross-method/
59. Backcrossing……. cont’d
• This is a type of repeated selection where a specific gene can
be incorporated into otherwise superior cultivars.
• One of the parental varieties is highly productive and
commercially successful but lacks a specific gene (e.g. disease
resistance). This trait is usually present in the other parental
variety.
• After each back cross, hybrid plants are identified with the
gene under consideration and are back crossed again with
the recurrent parent.
• The rate at which undesired traits from the donor parent are
eliminated depends upon linkage with the desired gene.
62. Asexual Reproduction
• Asexual reproduction is
the formation of new
individuals from the
cell(s) of a single parent.
It is very common in
plants.
• All plant organs have
been used for asexual
reproduction, but stems
are the most common.
63. Mutations - accidental changes
in genomic sequence of DNA
• Can arise spontaneously (Naturally occurring
mutations) - Errors in DNA replication, Spontaneous
lesions (naturally occurring damage to the DNA) ,
Transposable genetic elements
• Can be induced: mutagens (physical - Ionizing
radiation e.g. X-rays and gamma rays, Non-ionizing
radiation e.g. ultraviolet rays, Heat is a significant
environmental mutagen; Chemical - Nitrous acid,
EMS, Benzene, Sodium Azide; Biological - viruses)
64.
65.
66. Colchicine added to mitotic cells during metaphase and anaphase
disrupts spindle fibre formation preventing the migration of chromatids
after the centromere is split. A single cell is created that contains pairs
of identical chromosomes that are homozygous at all loci
68. Epidermal leaf cells of tobacco plants,
showing an increase in cell size, particularly
evident in stoma size, with an increase in ploidy
Diploid
Tetraploid
Octoploid
Polyploidy
70. The origin of an amphidiploid (doubled diploid) -
Allopolyploid
Cabbage
Raddish
71. Three diploid species (blue boxes) of Brassica
and their allopolyploids (pink boxes)
72. The proposed evolutionary history of modern hexaploid wheat
in which amphidiploids are produced at two points. A, B, and
D are different chromosome sets
74. Take-home message
• Sexual reproduction and random mutations have
been used to change the characteristics of
individuals from time immemorial- this is
imprecise and more of an art than a science; it
also take a long time to develop plants of choice
and only sexually compatible species can be
crossed
• Genes govern the characteristics that are passed on
from parents to offspring
• If we can isolate specific genes and use them to
direct the evolution of plants and animals to our
benefit, why should we put the world at risk by
not taking advantage of science and technology