Gregor Mendel was an Austrian monk who experimented with pea plants in the mid-19th century and is considered the father of genetics. Through his experiments crossing thousands of pea plants, he discovered the basic principles of heredity, including dominance, segregation, and independent assortment. His work showed that traits are passed from parents to offspring through discrete units (now known as genes) that can be dominant or recessive.
Law of Dominance - Recessive alleles will always be masked by dominant alleles .
Law of Segregation - At the time of gametes formation the two copies of each hereditary factor segregates so that offspring get one factor from each parent .
Law of Independent Assortment - Genes for one trait are not inherited together with another trait .
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Law of Dominance - Recessive alleles will always be masked by dominant alleles .
Law of Segregation - At the time of gametes formation the two copies of each hereditary factor segregates so that offspring get one factor from each parent .
Law of Independent Assortment - Genes for one trait are not inherited together with another trait .
IF YOU ARE GOING TO DOWNLOAD THIS FILE, PLEASE NOTIFY me by sending a message via Facebook.
It's a pleasure to help you through my presentation. Thank you so much!
chromosomal aberrations
Variation in chromosomal structure or number
changes in the number of sets of chromosomes (ploidy), changes in the number of individual chromosomes (somy), or changes in appearance of individual chromosomes through mutation-induced rearrangements. They can be associated with genetic diseases or with species differences
Mujahid Hussain, Department of Botany, University of Sargodha, Sargodha, Punjab, Pakistan
A chromosome abnormality, disorder, anomaly, aberration, or mutation is a missing, extra, or irregular portion of chromosomal DNA. It can be from an atypical number of chromosomes or a structural abnormality in one or more chromosomes
This Power Point Presentation is designed to explain Mendel's experiment on hybridization and dihybrid cross which considers inheritance of two traits at a time and to know whether they are inherited independently or are influenced by each other and also about Law of Independent assortment
We could define Mendel´s laws as the basic laws that talks about the inheritance of biological features that every human being has. They were created by Gregor Johann Mendel in 1865. Mendel created three laws: The law of Segregation, the law of Independent Assortment and the law of Dominance.
The rules of Mendel's inheritance: In a cross between pure contrasting traits, the dominant trait will be observed in the phenotype of the organism whilst the recessive trait will be concealed. Only a single gene copy is allocated in a gamete cell and this is carried out in a random manner.
Mendel’s Procedure: (i) Mendel observed one trait at a time. For example, he crossed tall and dwarf pea plants to study the inheritance of one gene. (ii) He hybridised plants with alternate forms of a single trait (monohybrid cross). The seeds produced by this cross were grown to develop into plants of Fillial 1 progeny or F 1 -generation
Epistasis is a Greek word that means standing over .Bateson used it to describe the masking effect in 1909.
An interaction between a pair of loci in which the phenotype effect of one locus depends on the genotype at the second locus.
Genes whose phenotypes are ;
Expressed,epistatic.
Altered or suppressed hypostatic.
chromosomal aberrations
Variation in chromosomal structure or number
changes in the number of sets of chromosomes (ploidy), changes in the number of individual chromosomes (somy), or changes in appearance of individual chromosomes through mutation-induced rearrangements. They can be associated with genetic diseases or with species differences
Mujahid Hussain, Department of Botany, University of Sargodha, Sargodha, Punjab, Pakistan
A chromosome abnormality, disorder, anomaly, aberration, or mutation is a missing, extra, or irregular portion of chromosomal DNA. It can be from an atypical number of chromosomes or a structural abnormality in one or more chromosomes
This Power Point Presentation is designed to explain Mendel's experiment on hybridization and dihybrid cross which considers inheritance of two traits at a time and to know whether they are inherited independently or are influenced by each other and also about Law of Independent assortment
We could define Mendel´s laws as the basic laws that talks about the inheritance of biological features that every human being has. They were created by Gregor Johann Mendel in 1865. Mendel created three laws: The law of Segregation, the law of Independent Assortment and the law of Dominance.
The rules of Mendel's inheritance: In a cross between pure contrasting traits, the dominant trait will be observed in the phenotype of the organism whilst the recessive trait will be concealed. Only a single gene copy is allocated in a gamete cell and this is carried out in a random manner.
Mendel’s Procedure: (i) Mendel observed one trait at a time. For example, he crossed tall and dwarf pea plants to study the inheritance of one gene. (ii) He hybridised plants with alternate forms of a single trait (monohybrid cross). The seeds produced by this cross were grown to develop into plants of Fillial 1 progeny or F 1 -generation
Epistasis is a Greek word that means standing over .Bateson used it to describe the masking effect in 1909.
An interaction between a pair of loci in which the phenotype effect of one locus depends on the genotype at the second locus.
Genes whose phenotypes are ;
Expressed,epistatic.
Altered or suppressed hypostatic.
LIKE BEGETS LIKE, which means young one resemble their parents, (MONOHYBRID CROSS & DIHYBRID CROSS) is the well-known dogma associated with heredity. Each species has similarities among themselves due to the cause of heredity. W.Bateson was the first one to coin the term genetics in 1905. It is derived from the greek word “genesis” means to grow into or to become . in other word, genetics is the study of heredity and variation.
https://thegeneralscience.com/monohybrid-and-dihybrid-cross/
LIKE BEGETS LIKE, which means young one resemble their parents, (MONOHYBRID CROSS & DIHYBRID CROSS) is the well-known dogma associated with heredity. Each species has similarities among themselves due to the cause of heredity. W.Bateson was the first one to coin the term genetics in 1905. It is derived from the greek word “genesis” means to grow into or to become . in other word, genetics is the study of heredity and variation.
Biology 103 Laboratory Exercise – Genetic Problems
Introduction
Although the science of genetics has become a highly sophisticated discipline dealing
with the interactions of hereditary factors at the molecular level, it has its roots in the
basic laws of heredity initially discovered and presented by Gregor Mendel more than
one hundred years ago. Mendel's success in discovering these laws was due largely to his
application of the simple rules of mathematical probability - the laws of chance - to his
observations concerning the inheritance of certain characteristics in the garden pea plant.
Reginald Punnett and the Punnett Square
The Punnett square is a diagram used by biologists to determine genotypic probability
within the offspring from a particular genetic cross. The Punnett square shows every
possible genotypic combination of maternal alleles with the paternal alleles for a genetic
cross. Punnett squares only give probabilities for genotypes, not phenotypes. The square
diagram was designed by the British geneticist, Reginald Punnett (1865-1967) and first
presented to the science community in 1905. Punnett’s Mendelism (1905) is considered
the first popular science book to introduce genetics to the public.
Solving Genetic Problems
R
R'
R
RR RR'
R'
RR' R'R'
Maternal alleles
A
A
a
Aa
Aa
Paternal
Alleles
a
Aa
Aa
The first step in solving a genetic problem is to establish the genetic symbols you will use
in your problem solution. Stay consistent by using these same symbols throughout the
problem solving process.
Represent dominant and recessive alleles (different forms of a gene) using traditional
genetic symbols. Dominant alleles should be represented with the capital version of an
alphabetic letter while using the lower case version to show recessiveness. For example:
B = black color, b = white color.
Each individual gene or trait is diploid (2n) in nature and therefore, must be represented
with two alleles. Continuing with the alleles mentioned previously, an individual may
have the genetic makeup BB, Bb, or bb when using those alleles.
Remember that gametes (sperm and egg) are haploid (n) and can only provide one allele
per trait. For example: B or b
An individual’s genotype contains the possible gametes that can be expected to be
produced by that individual. Much of genetics revolves around the probability of the
makeup of gametes. If the individual is homozygous, all of the gametes produced will
possess the same kind of allele. For example, an individual with the genotype BB would
be expected to produce only B gametes and individuals with genotype bb would produce
only b gametes.
If the individual is heterozygous, that is the individual’s genotype contains one dominant
allele and one recessive allele (Bb), the gametes produced will possess one or the other of
the two forms of the gene – B or b. ...
Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms. Though heredity had been observed for millennia, Gregor Mendel, Moravian scientist and Augustinian friar working in the 19th century in Brno, was the first to study genetics scientifically. Mendel studied "trait inheritance", patterns in the way traits are handed down from parents to offspring over time. He observed that organisms (pea plants) inherit traits by way of discrete "units of inheritance". This term, still used today, is a somewhat ambiguous definition of what is referred to as a gene.
Trait inheritance and molecular inheritance mechanisms of genes are still primary principles of genetics in the 21st century, but modern genetics has expanded beyond inheritance to studying the function and behavior of genes. Gene structure and function, variation, and distribution are studied within the context of the cell, the organism (e.g. dominance), and within the context of a population. In science and especially in mathematical studies, a variational principle is one that enables a problem to be solved using calculus of variations, which concerns finding functions that optimize the values of quantities that depend on those functions.
Genetics- Chapter 5 - Principles of inheritance and variation.docxAjay Kumar Gautam
Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms. Though heredity had been observed for millennia, Gregor Mendel, Moravian scientist and Augustinian friar working in the 19th century in Brno, was the first to study genetics scientifically. Mendel studied "trait inheritance", patterns in the way traits are handed down from parents to offspring over time. He observed that organisms (pea plants) inherit traits by way of discrete "units of inheritance". This term, still used today, is a somewhat ambiguous definition of what is referred to as a gene.
Genetics- Chapter 5 - Principles of inheritance and variation.docx
Mendel's laws 31 1 2011
1.
2. GREGOR JOHANN MENDEL
•1822 - 1884
•Austrian monk
•Experimented with pea plants
•He thought that ‘heritable factors’
(genes) retained their individuality
generation after generation
•Principles of genetics were
developed in the mid 19th century
•Experimented with pea plants, by
crossing various strains and
observing the characteristics of their
offspring
•Gregor mendel is the father of
modern genetics.
3. •Gregor Mendel–studied inheritance of seven traits
in pea plants and first used the term dominance
and recessiveness
•Proposed similar but separate inheritable
characters, one from each parent, later to be called
genes.
4. INHERITANCE
Parents and offspring often share observable traits.
Mendelian inheritance (or Mendelian
genetics or Mendelism) is a set of primary tenets
relating to the transmission
of hereditary characteristics from parent organisms
to their offspring; it underlies much of genetics.
They were initially derived from the work of Gregor
Johann Mendel published in 1865 and 1866 which
was "re-discovered" in 1900, and were initially very
controversial..
5. THE UNITS OF INHERITANCE ARE ALLELES OF
GENES
Traits are controlled by alleles - alternate
forms of a gene
Found on homologous chromosomes at a
particular gene locus
The dominant allele masks the expression
of the other allele - the recessive allele
Genotype refers to the alleles an individual
receives at fertilization
Homozygous - an organism has two identical
alleles at a gene locus
Heterozygous - an organism has two different
alleles at a gene locus
Phenotype - the physical appearance of the
individual.
9-5
6. DOMINANT AND RECESSIVE
A dominant allele is represented by a
CAPITAL letter. It is always expressed
when present. (BB or Bb)
A recessive allele is represented by lower
case letter. It is only expressed when an
individual has 2, one from mom and one
from dad. (bb only)
7. GENOTYPE AND PHENOTYPE
A genotype is the genetic make-up of an
individual, expressed in letters. (BB, Bb, bb)
A phenotype is the physical appearance of
an individual, determined by his or her
genotype. (black, brown, short, tall, etc)
8. HOMOZYGOUS AND HETEROZYGOUS
Homozygous: when both alleles of a
genotype are the same (either both
dominant, BB, or both recessive, bb)
Heterozygous: when one allele is dominant
and one is recessive (Bb only)
9. PUNNETT SQUARES
Punnett Squares
are used to show
the mating of two
parents and the
possible offspring
they can produce.
10. MENDEL OBSERVED SEVEN PEA PLANT TRAITS
THAT ARE EASILY RECOGNIZED IN ONE OF TWO
FORMS:
1. Flower color : purple or white
2. Flower position : axial or terminal
3. Stem length : Tall or Dwarf
4. Seed shape : round or wrinkled
5. Seed color : yellow or green
6. Pod shape : inflated or constricted
7. Pod color : green or yellow
11. True-breeding plants
make offspring that
are the same as the
parents every time
From his
experimental data,
Mendel deduced that
an organism has two
genes (alleles) for
each inherited
characteristic
One characteristic
comes from each
parent!!!
FLOWER
COLOR
FLOWER
POSITION
SEED
COLOR
SEED
SHAPE
POD
SHAPE
POD
COLOR
STEM
LENGTH
Purple White
Axial Terminal
Yellow Green
Round Wrinkled
Inflated Constricted
Green Yellow
Tall Dwarf
Mendel’s seven pea
characteristics
12. MENDEL DEDUCED THE UNDERLYING PRINCIPLES OF GENETICS
FROM THESE PATTERNS
1. Dominance
2. Segregation
3. Independent
assortment
14. 1.MENDEL’S LAW OF DOMINANCE
If your two alleles are different (heterozygous,
e.g. Bb), the trait associated with only one of
these will be visible (dominant) while the other
will be hidden (recessive). E.g. B is dominant, b
is recessive.
B b
B BB Bb
b Bb bb
Eggs
Sperm
15. CONTD..
Law of dominance : In a hybrid union, the
allele which expresses itself phenotypically is
the dominant allele while the other allele
which fails to express itself phenotypically is
the recessive allele. The hybrid individual
shows phenotypically only the dominant
character.
The law of dominance is often described
as Mendel’s first law of inheritance.
16.
17.
18. 2.MENDEL’S LAW OF SEGREGATION
A normal (somatic) cell has two variants (alleles) for a
Mendelian trait.
A gamete (sperm, egg, pollen, ovule) contains one
allele, randomly chosen from the two somatic alleles.
E.g. if you have one allele for brown eyes (B) and one
for blue eyes (b), somatic cells have Bb and each
gamete will carry one of B or b chosen randomly.
Law of segregation – the separation of alleles into
separate gametes.
B b
B BB Bb
b Bb bb
Eggs
Sperm
19. CONTD..
The law of segregation states:
Each individual has two factors for each trait
The factors segregate (separate) during the
formation of the gametes
Each gamete contains only one factor from each
pair of factors
Fertilization gives each new individual two
factors for each trait
20.
21.
22. MONOHYBRID CROSS
What happens when
true breeding plants
with two distinct
forms of a trait are
crossed?
Progeny show only one form
of the trait.
The observed trait is called dominant.
The masked trait is called recessive.
Progeny- A genetic descendant or offspring
23. CONTD..
When we are looking at one trait (such as eye
color or height), we do a monohybrid cross.
Parents are called P(Parental Generation)
Children are called F1(First Fililal Generation)
Grandchildren are called F2(Second Filial
Generation)
24. CONTD..
Two heterozygous parents produce gametes
with T or t allele equally frequently.
Offspring genotypes 1/4 TT : 1/2 Tt : 1/4 tt
Offspring phenotypes 3/4 tall : 1/4 short
25. 3.LAW OF INDEPENDENT ASSORTMENT
"When a dihybrid (or a polyhybrid ) forms gametes,
(i) each gamete receives one allele from each allelic pair
and
(ii) the assortment of the alleles of different traits during the
gamete formation is totally independent of their original
combinations in the parents.
In other words, each allele of any one pair is free to
combine with any allele from each of the remaining
pairs during the formation for the gametes
This is known as the Law of Independent Assortment of
characters.
It is also referred to as Mendel’s third law of heredity.
26. EXPLANATION OF THE LAW OF INDEPENDENT ASSORTMENT:
The principle of independent assortment was
explained by Mendel with the help of a dihybrid
cross involving characters of cotyledon color
(yellow / round) and seed shape (round /
wrinkled).
Mendel crossed a true breeding variety of pea
having yellow cotyledons (YY) and round seeds
(RR) with another true breeding variety having
green cotyledons (yy) and wrinkled seeds (rr).
27. Thus, the yellow round parent has the genotype
(YYRR) and the green wrinkled parent (yyrr).
Since each parent is homozygous for both
characters (color and shape), each will produce
only one type of gametes.
The (YYRR) parent will produce all (YR) type
gametes and the (yyrr) will produce all (yr) type
gametes.
28. CONTD..
All F1 dihybrids resulting from the fusion of these
gametes would be double heterozygous with
(YyRr) genotype and appear yellow round.
This indicated that in the dihybrid cross also in
each pair, the alleles behaved exactly in the same
way as in the monohybrid cross.
Both the dominants (Y and R) expressed
themselves in F1while both the recessive alleles
(y and r ) remained hidden.
29. TYPES OF GAMETES FORMED BY F1DIHYBRID:
According to Mendel, during gamete
formation by the F1 dihybrid, the alleles in
both pairs Y-y and R-r first segregate from
each other (Law of segregation).
Each pair segregates independently of the
pair. Then the alleles enter the gametes. A
gamete can receive only one allele from
each pair, i.e. Y or y and R or r.
30. CONTD.,
Similarly, a gamete that receives a factor
(gene) for color must also receive factor for
shape (a factor for every character must be
present in each gamete).
Thus, a gamete that receives Y for color may
receive R or r for shape. This would result in
(YR) and (Yr) types of gametes. Similarly, a
gamete that receives y for color may receive
R or r for shape.
31. CONTD..
This would give (yR) and (yr) types of
gametes. In other words, the F1 dihybrid
would produce four types of gametes (YR),
(Yr), (yR) and (yr) in equal proportions. This
is the principle of independent assortment of
characters.
There will be four types of male gametes
and four types of female gametes formed by
the F1 dihybrid.
33. CONTD..
During self-fertilization or inbreeding of the
F1 dihybrids to produce an F2generation, these
male and female gametes can form maximum to
dihybrid unions as shown in the Punnet’s
Checker-board .
These can be grouped into four kinds on the basis
of phenotypic appearance. i.e. yellow
round, yellow wrinkled, green round and green
wrinkled in the ratio of 9:3:3:1 respectively.
This is called the Phenotypic dihybrid ratio.
34. CONTD..
The 16 squares of the checker board are
serially numbered for convenience.
The squares represent the 16 possible
combinations of the gametes which might result.
The genotypes and the phenotypes of the
F2 offspring are shown in the sixteen squares.
A count of these squares shows the four kinds
of phenotypes and their ratio in the
F2 generation.
35. MENDEL CAME TO FOUR IMPORTANT
CONCLUSIONS FROM THESE EXPERIMENTAL
RESULTS:
1. The inheritance of each trait is determined by
"units •" or "factors"• (now called genes) that are
passed on to descendents unchanged.
2. An individual inherits one such unit from each
parent for each trait.
3. A trait may not show up in an individual but can
still be passed on to the next generation.
4. The genes for each trait segregate themselves
during gamete production.