Principle Basis of Inheritance NCERT Flashcards
___________ is the process by which characters are passed on from parent to progeny; it is the basis of heredity.
Inheritance
Is inheritance the basis of ______
Heredity
The degree by which progeny differ from their parents
Variation
Since when did humans know that one of the causes of variation was hidden in sexual reproduction?
as early as 8000-1000 B.C
One of the causes of variation was hidden in
Sexual reproduction
Through artificial selection and domestication from ancestral wild cows, we have Indian breeds like ___ in Punjab.
Sahiwal cows
Who proposed the laws of inheritance in living organisms?
Gregor Mendel
Gregor Mendel, conducted ____ on garden peas.
Hybridization experiments
For how many years Gregor Mendel conducted hybridization experiments on garden peas?
Seven years
In which years did Mendel perform the experiments on garden pea?
1856-1863
During Mendel’s investigations into inheritance patterns, what two things were applied to problems in biology for the first time?
Statistical analysis and mathematical logic
What was there in Mendel’s experiments that gave greater credibility to the data he collected?
Large sampling size
Mendel conducted such artificial pollination/cross-pollination experiments using
Several true-breeding pea lines
One that has undergone continuous self-pollination shows the stable trait inheritance and expression for several generations called
True breeding line
Mendel selected ___ true-breeding pea plant varieties as pairs which were similar except for one character with contrasting traits.
14
Contrasting Traits of these Characters are:-
Stem height -
Flower colour -
Flower position -
Pod shape -
Pod colour -
Seed shape -
Seed colour -
Stem height - Tall/dwarf
Flower colour - Violet/white
Flower position - Axial/terminal
Pod shape - Inflated/constricted
Pod colour - Green/yellow
Seed shape - Round/wrinkled
Seed colour - Yellow/green
Mendel proposed that something was being stably passed down, unchanged, from parent to offspring through the gametes, over successive generations and called it as
Factors
Mendel called them ‘factors’ but now we call them as
Genes
The units of inheritance are
Genes
Genes contain the information that is required to express a _____ in an organism
Particular trait
Genes which code for a pair of contrasting traits are known as
Alleles
In case of the character of height, T is used for the _______ trait and t for the _______
T- Tall (dominant)
t - Dwarf ( recessive)
Mendel also proposed that in a true-breeding, tall or dwarf pea variety, the allelic pair of genes for height are ________ or ___________, TT and tt, respectively.
Identical/homozygous
TT and tt are called ___ of the plant
Genotype
The descriptive terms tall and dwarf are the ____
Phenotype
In a pair of dissimilar factors, one dominates the other (as in the F1) and hence is called
Dominant factor
In a pair of dissimilar factors, one is the dominant factor, while the other factor is called
Recessive
Tt are called
Heterozygotes
Tt plant is heterozygous for genes controlling one character (height). It is a
Monohybrid
The cross between ‘TT’ and ‘tt’ is a
Monohybrid cross
The tall and dwarf plant produces gametes by the process of
Meiosis
When the tall and dwarf plant produces gametes, the alleles of the parental pair separate or ____ from each other.
Segregate
Segregation of alleles is a ____ process.
Random
How much percent chance is there of a gamete containing either allele?
50 per cent
The hybrids contain alleles which express contrasting traits, the plants are ____
Heterozygous
The three things which can be understood from a Punnett Square is
Production of gametes by the parents, the formation of the zygotes, and the F1 and F2 plants
Who developed Punnett square?
A British geneticist, Reginald C- Punnett
A graphical representation to calculate the probability of all possible genotypes of offspring in a genetic cross called
Punnett Square
Crossing of the tall plant from F2 with a dwarf plant is called a
Test cross
The progenies of test cross can easily be analyzed to predict the ____of the test organism.
Genotype
Characters are controlled by discrete units called
Factors
_____ is based on the fact that the alleles do not show any blending.
Law of Segregation
A good example to understand incomplete dominance.
Inheritance of flower colour in the dog flower
Dog flower is also known as
Snapdragon
Genus of dog flower is known as
Antirrhinum
In the case of _____, the F1 generation resembles both parents.
Co-dominance
ABO blood groups are controlled by the
Gene I
The plasma membrane of the red blood cells has
Sugar polymers
Which allele of a gene (I) does not produce sugar?
Allele i
More than two alleles governing the same character are called _________ alleles.
multiple
____ in pea seeds is controlled by one gene.
Starch synthesis
Dominance is not an ______ feature of a gene or the product that it has information for.
Autonomous
Dominance depends on the _______ and the production of ________ from this product.
Gene product; particular phenotype
Which law states that ‘when two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters.
Law of Independent Assortment
Mendel published his work on inheritance of characters in ____
1865
Mendel’s work on inheritance of characters remained unrecognized till
1900
Name three Scientists who independently rediscovered Mendel’s results on the inheritance of characters
de Vries, Correns and von Tschermak
By which year the chromosome movement during meiosis had been worked out?
1902
Which two scientists noted that the behavior of chromosomes was parallel to the behavior of genes and used chromosome movement to explain Mendel’s laws?
Walter Sutton and Theodore Boveri
The two alleles of a gene pair are located on homologous sites on _____
Homologous chromosomes
During ________ the two chromosome pairs can align at the metaphase plate independently of each other
Anaphase of meiosis I
Which two scientists argued that the pairing and separation of a pair of chromosomes would lead to the segregation of a pair of factors they carried?
Sutton and Boveri
Sutton united the knowledge of chromosomal segregation with Mendelian principles and called it the ______
Chromosomal theory of inheritance
Which scientist with his colleagues did experimental verification of the chromosomal theory of inheritance?
Thomas Hunt Morgan
Which scientist with his colleagues led to discovering the basis for the variation that sexual reproduction produced?
Thomas Hunt Morgan
Morgan worked with the tiny fruit flies, ____, which were found very suitable for such studies.
Drosophila melanogaster
Drosophila melanogaster complete their life cycle in about
Two weeks
In Drosophila melanogaster, a ___ could produce a large number of progeny flies
Single mating
Drosophila melanogaster has many types of hereditary variations that can be seen with _____
Low power microscopes
The term which describes the physical association of genes on a chromosome called
Linkage
The term which describes the generation of non-parental gene combinations called
Recombination
Which scientist used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes and ‘mapped’ their position on the chromosome?
Alfred Sturtevant
____ are extensively used as a starting point in the sequencing of whole genomes
Genetic maps
Traits that are generally controlled by three or more genes are called as
Polygenic traits
A single gene, which can exhibit multiple phenotypic expressions is called a
Pleiotropic gene
An example of pleiotropy is the disease ___which occurs in humans.
Phenylketonuria
Phenylketonuria is caused by a mutation in the gene that codes for the enzyme ___
Phenyl alanine hydroxylase
Which mutation caused the disease phenylketonuria?
Single gene mutation
Name the scientist who discovered X body but could not explain its significance.
Henking
In a large number of insects, the mechanism of sex determination is of the ______
XO type
Due to the involvement of the X-chromosome in the determination of sex, it was designated to be the ____and the rest of the chromosomes were named as
Sex chromosome; autosomes
_____ is an example of XO type of sex determination.
Grasshopper
XO type and XY type of sex determination mechanism is designated to be the example of ____
Male heterogamety
Two different types of gametes in terms of the sex chromosomes are produced by females which are called as
Female heterogamety
The sex-determining mechanism in case of humans is
XY type
The _________ of the sperm determines the sex of the child
Genetic makeup
An offspring formed from the union of a sperm and an egg develops as a female and an unfertilized egg develops as a male by means of ___
Parthenogenesis
In honeybees, the females are ____ and have ___chromosomes.
Diploid; 32
In honeybees, the males are ____ and have ___chromosomes
Haploid; 16
A phenomenon which results in alteration of DNA sequences and consequently results in changes in the genotype and the phenotype of an organism called
Mutation
Mutation is a phenomenon that leads to ___ in DNA
Variation
One DNA helix runs continuously from one end to the other in each chromatid, in a highly _____
Supercoiled form
Loss (deletions) or gain (insertion/duplication) of a segment of DNA result in
Alteration in chromosomes
Genes are known to be located on chromosomes, alteration in chromosomes results in
Abnormalities or aberrations
Chromosomal aberrations are commonly observed in
Cancer cells
Mutation which arises due to change in a single base pair of DNA is known as
Point mutation
A classical example of point mutation is ____
Sickle cell anemia
Deletions and insertions of base pairs of DNA, causes _____
Frame-shift mutations
There are many chemical and physical factors that induce mutations which are referred to as
Mutagens
Example of mutagen
UV radiations
An analysis of traits in several generations of a family is called the ______.
pedigree analysis
Genetic disorders may be grouped into two categories-
Mendelian disorders and Chromosomal disorders
Which disorders are mainly determined by alteration or mutation in a single gene?
Mendelian disorders
Name the six most common and prevalent Mendelian disorders
Haemophilia, Cystic fibrosis, Sickle cell anaemia, Colour blindness, Phenylketonuria and Thalassemia
Colour Blindness is a ____disorder
Sex-linked recessive
Colour Blindness occurs in about _____ of males and only about ____ of females-
8 per cent, 0.4 per cent
With which disease, a single protein that is a part of the cascade of proteins involved in the clotting of blood is affected
Haemophilia
Sickle-cell anaemia is an ____trait
Autosome linked recessive
Sickle cell anemia is caused by the substitution of Glutamic acid by ___at the sixth position of the ___ of the hemoglobin molecule
Valine, beta globin chain
Phenylketonuria affected individual lacks an enzyme that converts the amino acid ___ into ___
Phenylalanine into tyrosine
In Phenylketonuria, phenylalanine is accumulated and converted into ____
Phenylpyruvic acid
Thalassemia could be due to either mutation or deletion, which ultimately results in a reduced rate of synthesis of one of the __ that makeup hemoglobin-
Globin chains (alpha and beta chains)
Alpha thalassemia is controlled by two closely linked genes ___ and ___, on chromosome ___ of each parent
HBA1 and HBA2 ; 16
Beta Thalassemia is controlled by a single gene ___ on chromosome ___of each parent
HBB; 11
Failure of segregation of chromatids during cell division cycle results in the gain or loss of a chromosome(s) called
Aneuploidy
Failure of cytokinesis after telophase stage of cell division results in an increase in a whole set of chromosomes in an organism and, this phenomenon is known as
Polyploidy
An additional copy of a chromosome may be included in an individual & is known as
Trisomy
An individual may lack one of any one pair of chromosomes & is known as
Monosomy
Down’s Syndrome is caused by the presence of an additional copy of chromosome number ___
21
Down’s Syndrome was first described by ___ in ___
Langdon Down in 1866
Klinefelter’s Syndrome is caused due to the presence of an additional copy of the X-chromosome, resulting in a ___
Karyotype of 47, XXY
Development of breasts in males is called.
Gynaecomastia
Turner’s Syndrome is caused due to the absence of one of the X chromosomes, i-e-, ___
45 with X0,
