Principle Basis of Inheritance NCERT Flashcards by Ketan Kansal

___________ is the process by which characters are passed on from parent to progeny; it is the basis of heredity.

Inheritance

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Is inheritance the basis of ______

Heredity

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The degree by which progeny differ from their parents

Variation

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Since when did humans know that one of the causes of variation was hidden in sexual reproduction?

as early as 8000-1000 B.C

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One of the causes of variation was hidden in

Sexual reproduction

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Through artificial selection and domestication from ancestral wild cows, we have Indian breeds like ___ in Punjab.

Sahiwal cows

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Who proposed the laws of inheritance in living organisms?

Gregor Mendel

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Gregor Mendel, conducted ____ on garden peas.

Hybridization experiments

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For how many years Gregor Mendel conducted hybridization experiments on garden peas?

Seven years

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In which years did Mendel perform the experiments on garden pea?

1856-1863

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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

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What was there in Mendel’s experiments that gave greater credibility to the data he collected?

Large sampling size

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Mendel conducted such artificial pollination/cross-pollination experiments using

Several true-breeding pea lines

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One that has undergone continuous self-pollination shows the stable trait inheritance and expression for several generations called

True breeding line

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Mendel selected ___ true-breeding pea plant varieties as pairs which were similar except for one character with contrasting traits.

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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

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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

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Mendel called them ‘factors’ but now we call them as

Genes

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The units of inheritance are

Genes

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Genes contain the information that is required to express a _____ in an organism

Particular trait

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Genes which code for a pair of contrasting traits are known as

Alleles

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In case of the character of height, T is used for the _______ trait and t for the _______

T- Tall (dominant)
t - Dwarf ( recessive)

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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

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TT and tt are called ___ of the plant

Genotype

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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 ___

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,