- Mendel conducted experiments with pea plants involving monohybrid and dihybrid crosses to study inheritance of traits.
- In monohybrid crosses, he studied inheritance of one trait (e.g. plant height) between pure-breeding tall and dwarf pea plants. His results supported laws of dominance, segregation, and independent assortment.
- In dihybrid crosses, he studied inheritance of two traits (e.g. seed shape and color) and found offspring exhibited four phenotypes in a 9:3:3:1 ratio, supporting independent assortment of genes.
- Mendel's experiments were pioneering in establishing basic principles of genetics and heredity.
MENDELE'S EXPERIMNENT AND TERMINOLOGY, BY MR. DINABANDHU BARAD, MSC TUTOR, DEPARTMENT OF PEDIATRIC, SUM NURSING COLLEGE, SIKSHA 'O' ANUSANDHAN DEEMED TO BE UNIVERSITY
This pdf comprises of Basic of Genetics: Purpose: To convey that “Genetics is to biology what Newton’s
laws are to Physical Sciences”. Mendel’s laws, Concept of segregation and
independent assortment. Concept of allele. Gene mapping, Gene
interaction, Epistasis. Meiosis and Mitosis be taught as a part of
genetics. Emphasis to be give not to the mechanics of cell division nor the
phases but how genetic material passes from parent to offspring. Concepts
of recessiveness and dominance. Concept of mapping of phenotype to
genes. Discuss about the single gene disorders in humans. Discuss the
concept of complementation using human genetics.
MENDELE'S EXPERIMNENT AND TERMINOLOGY, BY MR. DINABANDHU BARAD, MSC TUTOR, DEPARTMENT OF PEDIATRIC, SUM NURSING COLLEGE, SIKSHA 'O' ANUSANDHAN DEEMED TO BE UNIVERSITY
This pdf comprises of Basic of Genetics: Purpose: To convey that “Genetics is to biology what Newton’s
laws are to Physical Sciences”. Mendel’s laws, Concept of segregation and
independent assortment. Concept of allele. Gene mapping, Gene
interaction, Epistasis. Meiosis and Mitosis be taught as a part of
genetics. Emphasis to be give not to the mechanics of cell division nor the
phases but how genetic material passes from parent to offspring. Concepts
of recessiveness and dominance. Concept of mapping of phenotype to
genes. Discuss about the single gene disorders in humans. Discuss the
concept of complementation using human genetics.
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.
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Introduction to Genetics - Mendelism SMGsajigeorge64
Introduction to Genetics - Mendelism ; Genetics defenition- heridity and variation - heritable and non-heritable variations; Gregor Johann Mendel - rediscovery of Mendelism- Terminology and symbols; Mendel's experiments , laws
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.
Various waste products are formed in our body as a result of many
metabolic activities taking place inside the body. These waste substances if
accumulated would poison cells or slow down their metabolism. Hence, the body must
get rid of these unwanted substances.The metabolic wastes to be excreted include
CO2, H2O, fat, ammonia, urea and uric acid.
The nourishment coming from food that is simplified or processed by digestion is consumed by the blood and conveyed all through the body. When this absorbed food is broken down in the tissues and many toxic and poisonous substances are produced which should be removed as they may be fatal if present beyond a certain concentration. The removal of these substances is known as excretion. Excretion and osmoregulation, both are interconnected processes and occur side by side. in higher vertebrates like humans, kidneys perform both the functions, excretion as well as osmoregulation.The system responsible for these function is known as the excretory system or urinary system
Bacteria are the simplest ,most primitive and unicellular organisms without a true nucleus. That is why they are prokaryotic. they are placed under kingdom Monera. they are found everywhere in air,water,soil,food,inside our body etc. they lack nucleus and other cell organelles of complex cellslike plants,they possess a cell wall. each bacterial cell has its nuclear material in the form of a single chromosome which is not enclosed in a nuclear membrane.
https://thegeneralscience.com/bacteria-images/
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.
NCERT Books Class 12 Biology Chapter 5 Principles of InheritanceExplore Brain
NCERT Books Class 12 Biology Chapter 5
Principles of Inheritance
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Ncert Solutions for Class 12 bio,
ncert solutions for class 12 biology chapter 1,
ncert solutions bio class 12,
ncert solutions for class 12,
ncert solutions for class 12 bio pdf,
Introduction to Genetics - Mendelism SMGsajigeorge64
Introduction to Genetics - Mendelism ; Genetics defenition- heridity and variation - heritable and non-heritable variations; Gregor Johann Mendel - rediscovery of Mendelism- Terminology and symbols; Mendel's experiments , laws
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.
Various waste products are formed in our body as a result of many
metabolic activities taking place inside the body. These waste substances if
accumulated would poison cells or slow down their metabolism. Hence, the body must
get rid of these unwanted substances.The metabolic wastes to be excreted include
CO2, H2O, fat, ammonia, urea and uric acid.
The nourishment coming from food that is simplified or processed by digestion is consumed by the blood and conveyed all through the body. When this absorbed food is broken down in the tissues and many toxic and poisonous substances are produced which should be removed as they may be fatal if present beyond a certain concentration. The removal of these substances is known as excretion. Excretion and osmoregulation, both are interconnected processes and occur side by side. in higher vertebrates like humans, kidneys perform both the functions, excretion as well as osmoregulation.The system responsible for these function is known as the excretory system or urinary system
Bacteria are the simplest ,most primitive and unicellular organisms without a true nucleus. That is why they are prokaryotic. they are placed under kingdom Monera. they are found everywhere in air,water,soil,food,inside our body etc. they lack nucleus and other cell organelles of complex cellslike plants,they possess a cell wall. each bacterial cell has its nuclear material in the form of a single chromosome which is not enclosed in a nuclear membrane.
https://thegeneralscience.com/bacteria-images/
All matters are in nature is made up of only a few elements. The elements exist as atoms and/or molecules. Molecules of an atom are made up of atoms of the same type. Compounds contain two or more elements. Thus, the molecules of compounds contain atoms of different elements.
https://thegeneralscience.com/atomic-structure-pdf/
A tissue is a group of cells which have a common origin, similar shape, size and structure and perform the same function. Cells in a tissue are usually held together by a cementing substance and form a tissue system.
Different types of tissues are : Tissue present in plant and Tissue present in animal.
https://thegeneralscience.com/study-of-tissue/
If we look at the sky of the solar system drawing in a dark and clear night, we will notice that the entire sky dotted with countless stars, some bright and some not so bright . We must notice that the moon is the brightest objects in the night sky. The objects which twinkle are stars and the objects which twinkle are stars and the objects which do not twinkle are planets .
https://thegeneralscience.com/solar-system-darwing/
Transfer of pollen grain from another to the stigma of the same flower or another flower of the same plant, is called self-pollination. e.g. Apricot, Fig, Plum, Rose, Tomato, Sweet Pea.
https://thegeneralscience.com/plant-life/
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
1. MONOHYBRID AND DIHYBRID CROSS:
HOW TO DESCRIBE IT
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MONOHYBRID AND DIHYBRID CROSS
INTRODUCTION:
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.
SOME IMPORTANT TERMS RELATED TO
GENETICS ( MONOHYBRID CROSS & DIHYBRID
CROSS)
HEREDITY: It is the process to transmit characteristics from progeny to progeny.
GENES: Genes are units of heredity present on the chromosomes. Each gene is the specific segment of
DNA and, when activated, encodes specific characteristics of an organism.
GENETICS: It is the branch of biology, which deals with the study of the transmission of similarities and
differences from the parents to their offsprings.
ALLELES or ALLELOMORPHS: These are two alternative forms of same gene and occupy the
corresponding loci or position on the homologous chromosomes. T and t are alleles for tallness and
dwarfness of heights of the plant respectively.
HOMOZYGOUS: An organism having alleles for same phenotypic expression, e.g. TT are the
homozygous allele for tall plant; tt are the homozygous allele for the dwarf plant. It is genetically pure for
that character.
HETEROZYGOUS: An organism in which two alleles of a gene regulate different phenotypic expression
of same character is called heterozygous e.g. Tt condition for height of the plant. The organism is called
genetically hybrid for that characters.
DOMINANT: In heterozygous condition (Tt) the allele which masks the expression of other allele and
expresses itself, is called dominant. In Tt condition, T (allele for tallness) expresses itself.
RECESSIVE: In heterozygous condition, the allele whose expression is masked by dominant allele, is
called recessive e.g. in Tt condition, t (allele for dwarfness) is recessive.
PHENOTYPE: The physical expression of a character is called phenotype e.g. phenotypic expression of
allele T is tallness.
GENOTYPE: The genetic make up of a character is called its genotype e.g. TT for homozygous tallness
and Tt for heterozygous
GENE POOL: The genotype of all the organisms of of a species are collectively called gene pool of that
species.
MONOHYBRID CROSS : A cross-breeding experiment in which only one allelic pair of the parents is
considered, is called monohybrid cross g. a cross between pure tall (TT) and pure dwarf (tt) pea plant.
DIHYBRID CROSS: A cross-breeding experiment in which two alleleic pairs of the parents are
considered is called dihybrid cross. E.g. a cross between pure yellow and round seeded pea plant and
pure green and wrinklrd seeded pea plant.
P GENERATION: Individuals with which a cross-breeding experiment is started, collectively form P
generation.
F1GENERATION or FIRST FILIAL GENERATION: Offsprings of individuals of P generation collectively
form F1
F2GENERATION or SECOND FILIAL GENERATION: Offsprings produced by selfing or self-pollination
of F1 individuals collectively form F2
2. MUTATION: These are sudden and large inheritable changes in the genetic material. These produce
variations in the populations so help in evolution. Sickle cell anaemia (RBC is become sickle
shaped) is caused by recessive gene mutation.
VARIATION: The structural, functional and behavioural changes from the normal characters of the
organisms are called variations. These act as raw materials for evolution. Variations are commonly seen
in various races of human beings and even members of a population as well as a family.
MENDEL: THE FOUNDER OF GENETICS
Gregor Mendel was a monk in an Austrian monastery; he was not biologist by profession.Mendel was born
in 1802 to peasant parents and went to live in the Augustinian monastery ( now in Czechoslovakia) in 1843.
In 1851 knowing his abilities, he was sent to the University of Vienna for two years to study science and
mathematics. Mendel had choosen 7 different characters from various pea plants about 34 varietis of garden
pea ( Pisum sativum) . He experimented near about 7 years and published all his results in the Natural
History Society of Brumm of 1865: but it came in front of public in 1866 but not got popularity and attention
till 1900. His work got known after his death when three scientists, De Vries in Holland, Correns in Germany
and Tschermark in Austria, rediscovered his work and began to make use of his finding.
EXPERIMENTAL PLANT: Mendel did his experiments on garden pea plant (Pisum sativum), he choosen
the garden pea plant,due to following reasons:
DISTINCT VARIETIES: Pea plants have several distinct varieties which have sharp contrasting
characteristics such as colour and shape of seeds.
BISEXUAL FLOWERS: Pea plants bear bisexual flowers with each flower having both the male and
female parts.
PURE LINES FOR SEVERAL GENERATIONS: In pea plant due to self-fertilization, it is easy to get
pure lines of generation.
ANNUAL PLANT: Pea plants are annual plants so it is possible to study several generation within a
short span of time.
SIZE OF PEA FLOWERS: The flowers of pea plants are adequate in size and easy t to handle.
SEED PRODUCTION: Each plant can produce large number of seeds in a single generation.
SEVEN PAIRS OF CONTRASTING CHARACTERS ( MONOHYBRID CROSS &
DIHYBRID CROSS)
CHARACTERIS
TICS
DOMINANT EXPRESSION RECESSIVE EXPRESSION
(i)Plant size
TALL DWARF
(ii)Fruit / Pod
colour
GREEN YELLOW
3. (iii)Fruit/ Pod
shape
INFLATED WRINKLED (CONSTRICTED)
(iv) Shape of the
seed
ROUND (SMOOTH) WRINKLED (CONSTRICTED)
(v) Colour of the
seed
YELLOW COTYLEDON GREEN COTYLEDON
4. (vi) Flower colour
PURPLE (VIOLET) WHITE
(viii) Flower
position
AXIAL POSITION TERMINAL ON THE STEM
MENDEL’S MONOHYBRID CROSS: ( MONOHYBRID CROSS
& DIHYBRID CROSS)
This experiment was conducted in three stages.
5. He selected the pure breeding individuals for P generation which differed in only one phenotypic
expression.
He cross-bred the individuals of P generation and obtained F1 He counted the number of different
phenotypes observed in F1generation.
F1 plants were allowed to self-pollinate to produce F2 He counted the number of different phenotypes
observed in F2 generation.
P generation: Pure tall plant X Pure dwarf plant
Genotype: (TT) X (tt)
Gametes: (T) (T) X (t) (t)
F1 generation: (Tt)
Hybrid tall
self pollination of F1plants
Self-pollination: ( Tt) X (Tt)
Gamete: (T) (t) X (T) (t)
F2:
T t
T TT (PURE TALL) Tt( HYBRID TALL)
t Tt( HYBRID TALL) Tt (PURE TALL
F2 Genotypic ratio: 1 TT : 2 Tt : 1 tt
1:2:1
F2 Phenotypic ratio: tall : dwarf :: 3:1
CONCLUSION: Mendel proposed following three principles of inheritance after the analysis of monohybrid
cross.
Law of Dominance
Law of Segregation
Law of Independent Assortment
The law of Dominance: Various hereditary characteristics or traits are controlled by factors (gene)
which occurs in pairs. Out of these only one factors expresses itself in the F1 The character or factor
which is seen or expressed is called dominant and the character which one is hidden or latent
as recessive.
The law of segregation: It states that allelic pair (now genes) separate or segregrate individually
during formation of gametes and the paired structure is brought back by the fusion of gametes
randomly of gametes during fusion or
The law of Independent Assortment: It states that when a dihybrid organism forms gametes, each
gamete receives one allele from each allele pair ( or each characteristics) and the combination of alleles
(now genes) of various characteristics or speciality is completely independent or free their parental
combination during formation of gametes.
DIHYBRID CROSS
For example, two plants differing in two characters like seed shape ( round and wrinkled) and cotyledon
colour ( yellow and green) were crossed together.
Mendel selected a pure or homozygous dominant variety of pea plant for yellow round (YYRR) and
another homozygous recessive variety of green wrinkled (yyrr) He made cross between these plants
and observed that all F1 generation seeds had the features of only one type (yellow and round shape
seed). This result reveals that yellow seed colour was dominant over green colour of seed which is a
6. recessive or non-expressive characteristics and round shape of seed was dominant or expressable
over wrinkled seed shape.
Mendel did selfing or self-pollination of these F 1 hybrids . When these F1 generation seeds were cross-
bred to raise the F2generation, the F2 progeny showed four different kinds of phenotypes of seeds. It was
observed that not only both the parental types (round seeds of yellow colour and wrinkled seeds of
green colour) were present, but also new combination of traits ( round seeds of green colour and
wrinkled seeds of yellow colour) also appeared.
Thus, there were yellow round, yellow wrinkled, green round and green wrinkled seeds in the ratio
of 9:3:3:1 respectively, of these, two are of the parental (P) types and two are new combinations or
recombinants. Dihybrid cross is represented here.