Principles Of Inheritance And Variation - Class 12 Medical Biology - Extra Questions

(a) Two pea plants with green pods, $${Gg \times GG}$$, were crossed. Complete the given Punnett square to show the results of this cross.

(b) What percentage of the offspring produced by this cross will most likely have green pods?


Explain how equal genetic contribution of male and female parents is ensured in the progeny.

A true-breeding tall, purple-flowered pea plant (TTPP) is crossed with a true-breeding dwarf, white-flowered plant (ttpp).
(a) What is the phenotype of the $${F_1}$$ generation?
(b) What is the genotype of the $${FI_1}$$ generation?
(c) What four type of gametes are formed by $${F_1}$$  plants?
(d) Fill in the given Punnett square to show the offspring of the$$ { F_2}$$  generation.
(e) List the phenotype and ratios found in the $${F_2}$$ generation.

Outline a project which aims to find the dominant coat colour in dogs.

"The chromosomes number of the sexually reproducing parents and their offspring is the same." Justify this statement.

Using a Punnett Square, workout the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus.

How is sex determined in human beings?

(a) Explain a monohybrid cross taking seed coat colour as a trait in Pisum sativum. Work out the cross up to $${F}_{2}$$ generation.
(b) State the laws of inheritance that can be derived from such a cross.
(c) How is the phenotypic ratio of $${F}_{2}$$ generation different in a dihybrid cross?

What is point mutation? Give one example.

Differentiate between male and female heterogamety.

What is pedigree analysis? Suggest how such an analysis can be useful.

In a cross between two tall pea plants some of the offsprings produced were dwarf. Show with the help of Punett square how this is possible.

In our society, women are often blamed for giving birth to daughters. Why is this not correct?

Who had proposed the chromosomal theory of the inheritance?

In a homozygous plant round seeds (R) are dominant over wrinkled seeds (r).
$$(i)$$Draw a Punnett square to show the gametes and offspring when both the plants have heterozygous round seeds (Rr).
$$(ii)$$ Mention the phenotype and genotype ratios of the offsprings in $${F}_{2}$$ generation.
$$(iii)$$ Name the sex chromosomes in human males and females.
$$(iv)$$ Briefly explain the term mutation.
$$(v)$$ What is the number of chromosomes in the gametes of human beings?

A homozygous plant having round (R) and yellow (Y) seed is crossed with the homozygous plant having wrinkled (r) and green (y) seeds. Answer the following questions based on observation.
i) Give the scientific name of the plant on which Mendel conducted his hybridization experiments.
ii) Give the genotype of the $$F_1$$ generation.
iii) Give the dihybrid phenotypic ratio and the phenotype of the offspring of the $$F_2$$ generation when two plants of $$F_1$$ generation are crossed.
iv) Name and state the law which explains the dihybrid ratio.
v) Give the possible combinations of gametes that can be obtained from $$F_1$$ hybrid.

What were the four different varieties of pea plants obtained by Mendel in his dihybrid cross experiment? Show their ratio with the help of a checker board.

Give the biological term for 'An alteration in the genetic material that can be inherited'.

Explain sex determination in humans with the help of flow-chart.

Mention the chromosomal abnormalities concerned with the following conditions in humans.
(i) Turner's syndrome
(ii) Klinefelter's Syndrome
(iii) Down's Syndrome

Write any two uses of pedigree study in human genetics.

Write the name of the theory of inheritance given by Walter Sutton.

Black coloured guinea pig (BB) is crossed with white coloured guinea pig (bb). Find out the ratio of the types of the offsprings produced in the $$F_2$$ generation with the help of a checker board.

Will it be  possible to judge the sex of the child by them?

Explain Mendel's Monohybrid cross. Give an example.

What makes the fertilized egg develop either into a boy or a girl?

Differentiate between aneuploidy and polyploidy.

What is aneuploidy? Write any four symptoms of Down's syndrome.

Foetal sex can be determined by a test based on the chromosomal pattern from the amniotic fluid.
(a) What is this test ?
(b) Revealing of sex determination through this test is banned. Is this ban necessary?
(c) Invitro fertilization followed by embryo transfer is known as

Identify the person who suffers fro, Klinefelter's syndrome. Write its symptoms.

It is evident that, it is the genetic make up of the sperm that determine the sex of the child in human beings. Substantiate.

In a homozygous pea plant, axial flowers $$(A)$$ are dominant over terminal flowers $$(a)$$.
Name two genetic disorders commonly seen in human males.

What is the basis of sex-determination in human beings? Explain.

What are polyploids? Write their limitations.

In a homozygous pea plant, axial flowers $$(A)$$ are dominant over terminal flowers $$(a)$$.
Draw a Punnet square board to show the gametes and offsprings when both the parent plants are heterozygous for axial flowers.

Write a note on the following :
(i) Genetic Code
(ii) Sex - determination in human.

What is mutation? Explain in detail.

A pea plant which is homozygous for Green pods which are inflated [GGII] is crossed with a homozygous plant for yellow pods which are constricted [ggii]. Answer the following question.
Write the phenotypic ratio of the $$F_2$$ generation.

Does the sex of the child depend on the father or it is just a matter of chance? Discuss.

Name the scientist associated with mutation theory.

In our society the women are often blamed for giving birth to daughters. Can you explain why this is not correct?

What is deoxyribose sugar? Give molecular structure of this sugar.

Short / Long answer type questions.
Explain a monohybrid cross taking seed Coat colour as a trait in Pisum sativum. Work out the cross up to F2 generation. (b) State the laws of inheritance that can be derived from such a cross. (c) How is the phenotypic ratio of F2 generation different in a dihybrid cross?

Who proposed the chromosome theory of inheritance? List the main points of this theory.

Differentiate between.
Monohybrid and dihybrid cross

Short / Long answer type questions.
A  dihybrid heterozygous round yellow seeded garden pea (Pisum sativum) offspring was crossed with a double recessive parent. 
(a) What type of a cross is this?  b) Work out the genotype and phenotype of the progeny. (c)What principle of Mendel is illustrated through the result of this cross?

How is an allopolyploid produced? Explain with an example.

Write short note on sex determination in humans.

What is mean by Mutation?

What is Pedigree analysis? Suggest how such analysis can be useful.

Name the event during cell division cycle that results in the gain or loss of chromosome.

Three Mark Questions :
Identify a, b, c, d, e, and f in the table
Down'sTrisomy of 21A-1, a-2b
(ii)cXXYOverall masculine developmentd
(iii)Turner's45 with XOe-1, e-2f

Three Mark Questions:
Haemophilia is sex-linked recessive disorder of humans. The pedigree chart given below shows the inheritance of haemophilia in one family. Study the pattern of inheritance and answer the questions given (a) Give all the possible genotypes of the members 4, 5 and 6 in the pedigree chart
(b) A blood test shows that the individual 14 is a carrier of haemophilia. The member numbered 15 has recently married numberedWhat is the probability that their first child will be haemophilic male.

Three Mark Questions :
Explain the mechanism of sex determination in insects like Drosophila and Grasshopper.

Three Mark Questions :
Women are often blamed for producing female children. Consequently they are ill treated and ostracized. How will you address this issue scientifically it you were to conduct an awareness programme to highlight the values involved?

Five Mark Questions :
(a) Explain the mechanism of sex determination in humans.
(b) Differentiate between male heterogamety and female heterogamety with the help of an example of each

Using a Punnett Square, work out the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus.

Three Mark Questions :
Who proposed chromosomal theory of inheritance? Point out any two similarities in the behaviour of chromosomes and genes.

Mohan has two daughters. He blames his wife for bearing only daughters and no son. How will you convince Mohan that his wife has no role in giving birth to daughters only so that she should not be blamed for it. Further, females are rather more important component of society, What values are involved in this advice?

Give the phenotype and genotype of the F2 generation in monohybrid cross

Explain the sex determination in baby?

How many different kinds of gametes will be produced by plant having the genotype $$AA \,Bb \,CC$$?

From the given pedigree:
(a) Predict the mode of inheritance.
(b) Write three points about the inheritance pattern with one example.

Write the mode of inheritance and give suitable example. 

In successive generations, individuals of the same species will have the same number of chromosomes was proposed by ..........

Is it right to consider the mother responsible for a girl child?

Identify the mode of Inheritance.

Give an example of a disease in humans that shows this pattern of inheritance.

Is the trait autosomal or sex-linked? Give reason.

Identify the pattern of Inheritance 

Make a punnett square for finding out the proportion of different genotypes in the progeny of a genetic cross between 
a) A pure tall (TT) pea plant with a pure dwarf (tt) pea plant.
b) Red flower variety of pea (RR) with white flower variety of pea (rr).

Explain the following terms:
(a) Heterozygous
(c)Pedigree chart

Give the genotype of the female parent in generation I.

What are offspring's?

Study the given pedigree chart and answer the question that follow.
Give the genotypes of the parents shown in generation I and their third child shown in generation II and the first grandchild shown in generation III.


Name the disorder, give its karyotype and write the symptoms a human suffers due to monosomy of sex chromosomes.

Define monohybrid ratio.

What is Punnets Square?

What will happen to the expression of a particular trait if a gene gets altered?

Study the given pedigree chart and answer the question that follow.
Is the trait recessive or dominant?


Study the given pedigree chart and answer the question that follow.
Is the trait sex-linked or autosomal?


(a)  Why did Mendel's work remain unrecognised from 1865 to 1900?
(b) What is a Punnett square?

Give diagram representation of mono hybrid cross

What is parental generation?

It is a matter of chance weather a couple will have male or female child Justify the statement

Why has T.H. Morgan selected fruit flies for his genetical experiments?

Mendel took tall pea plants and short pea plants and produced $$F_1$$ progeny through cross-fertilization. What did Mendel observe in the $$F_1$$ progeny?

What are the characters of Parental generation(P)?

Give scientific name of pea plant ?

Define aneuploidy . Name an allosomal hyperneuploidy condition and mention its characters.

Study the pedigree given and assign the type of inheritance of the trait.

How do mendel's experiments show that 
(a)traits may be dominant or recessive?
(b) inheritance of two traits is independent of each other

What is the phenotypic ratio of mendel's monohybrid cross?

Why are chromosomes called the hereditary vehicles?

Explain dihybrid cross with suitable example.

What is the term for addition or deletion of one or two chromosomes in diploid chromosome number?

Study the given pedigree chart and answer the questions that follow:
(a) Is the trait recessive or dominant?
(b) Is the trait sex-linked or autosomal?
(c) Give the genotypes of the parents shown in generation $$I$$ and their third child shown in generation $$II$$ and the first grandchild shown in generation $$III$$.

Describe chromosomal theory of sex determination.

Explain sex determination in humans with line diagram.

Who proposed the chromosomes theory of inheritance?

Compare in any three ways the chromosomal theory of inheritance as proposed by Sutton and Bovery with that of experimental results on pea plant presented by Mendel.

State the expected ratio of the genotypes BB and Bb in the $$F_2$$ progeny. 

Why do all the gametes formed in human females have an X chromosome? 

On the basis of the possibilities of combination of the sex chromosomes. what percentage probability does a couple have of having a son or a daughter? Show the same by making a cross.

Write the differences between the sex chromosomes of man and sex chromosomes of woman.

How does a mutagen induce mutation? Explain with example.

What is dihybrid cross?

Differentiate Glycosuria from Ketonuria.

What is the full name of Mendel?

 Green and red colour of seeds are the recessive and dominant traits respectively. Out of F1 and F2 generations, in which generation will, the green seed appear if both parents are homozygous for the traits?

Which law of Mendel cannot be explained by monohybrid cross?

Write a brief note. 

Sickle cell anaemia: symptoms and treatment 

Fill in the blank.

In humans, _____ chromosome is responsible for maleness.

Make a punnette square to show a cross between plants with yellow pod (Yy) and green pod (yy).

The pedigree chart given below shows a particular trait which is absent in parents but present in the next generation irrespective of sexes. Draw your conclusion on the basis of the pedigree.

Define point mutation.

It is said, that the harmful alleles get eliminated from the population over a period of time, yet sickle cell anaemia is persisting in human population. Why?

What is a silent mutation?

Describe the structural changes in chromosomal mutation.

In a Mendelian monohybrid cross, the $$F_2$$ generation shows identical genotypic and phenotypic ratios. What does it tell us about the nature of alleles involved? Justify your answer.

What is Euploidy?

"Gender of child is determined by the male partner of couple." 
Draw a diagram explaining the above statement.

If the D allele is completely dominant over the d allele, what percentage of the offspring will have the dominant phenotype when Dd and Dd individuals mate?

An angiosperm plant having red coloured flowers when crossed with the other having the same colour produced 40 progenies, out of which 30 plants were with red coloured flowers 10 plants were with white coloured flowers. Find out:
(a) What is the possible genotypic of parent plants?
(b) Which trait is dominant and recessive?
(c) What is this cross called as and what is its phenotypic ratio?

The genotype of green stemmed tomato plants is denoted as GG and that of purple stemmed tomato plants is denoted as gg. When these two are crossed with each other,
(a) What colour of stem would you expect in the $$F_1$$ progeny?

How is sex determined in humans?

What is meant by punnet square?

Give difference between-Homozygous and Heterozygous.?

(a) Select the homologous structures from the combinations given below:
(i) Forelimbs of whales and bats
(ii) Tuber of potato and sweet potato
(iii) Eyes of octopus and mammals
(iv) Thorns of Bougainvillea and tendrils of Cucurbita

If we cross pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant we will get Pea plant of $$F_1$$ generation, then we obtain Pea plants of $$F_2$$ generation.
(a) What do the plants of $$F_1$$ generation look like?
(b) State the ratio of tall plants to dwarf plants in $$F_2$$ generation.
(c) State the type of plants not found in $$F_1$$ generation but appeared in $$F_2$$ generation, mentioning the reason for the same.

During a monohybrid cross involving a tall pea plant with a dwarf pea plant, the offspring populations were tall and dwarf in equal ratio. Work out a cross to show how it is possible.

Given below is the representation of amino acid composition not the relevant translated portion of $$\beta$$-chain of haemoglobin, related to the shape of human red blood cells.
(a) Is this representation indicating a normal human or a sufferer from certain related genetic disease? Give reason in support of your answer.
(b) What difference would be noticed in the phenotype of the normal and the sufferer related to this gene?
(c) Who are likely to suffer more from the defect related to the gene represented the males, the females or both males and females equally? And why?

Why is pedigree analysis done in the study of human genetics? State the conclusions that can be drawn from it.

Briefly explain the following terms :
(i) monohybrid cross          (ii) Biomedical waste             (iii) Innate immunity.             
(iv) Diapedesis                   (v) Hormones.

State the cause of adenosine deaminase enzyme deficiency.

Explain the process to understand monohybrid cross of Mendel experiment with a checker board.

Differentiate between '$$ZZ$$' and '$$XY$$' type of sex-determination mechanisms.

Write the types of sex-determination mechanisms the following crosses show. Give an example of each type.
(i) Female XX with Male XO
(ii) Female ZW with Male ZZ

(a) If a sperm with 'X' chromosome fertilizes with an ovum with 'X' chromosome, what will be the gender of the baby?
(b) Who determines the sex/gender of the baby, mother or father?
(c) Is it correct to blame the mother for giving birth to a baby girl?
(d) Are all our characters resembles our parents?

Explain Mendel's monohybridization experiment. Write the rules proposed on the basis of this experiment. Draw its diagram using punnet square.

Short / Long answer type questions.
In human beings blue eye colour is recessive to brown eye colour. A brown-eyed man has a blue-eyed mother.
(a) What is the genotype of the man and his mother?,  (b) What are the possible genotypes of his father?,  (c) If the man marries a blue-eyed woman, what are the possible genotypes of their offspring? 

Application based questions.
A pea plant with purple flowers was crossed with white flowers, producing 50 plants with only purple flowers. On selfing, these plants produced 482 plants with purple flowers and 162 with white flowers. What genetic mechanism accounts for these results? Explain.

Define nucleotides and give their functions

Differentiate between.
Paracentric inversion and pericentric inversion

Mention the chromosomal abnormalities concerned with following conditions in humans
 (a) Turner's syndrome (b) Klinefelter's syndrome  (C) Down's syndrome

How many pairs of chromosomes does a male Drosophila fly have? Which one of these bears the gene for the eye colour?

Three Mark Questions :
(a) Name the kind of diseases/disorders that are likely to occur in human if,
(i) There's a mutation in the gene that codes for an enzyme phenylalanine hydrolase.
(ii) There is an extra copy of chromosome 21.
(iii) The karyotype is XXY.
(b) Mention any one symptom of the diseases/disorders named above.

Carry out a monohybrid cross between two individuals, one having black coloured hair and the other having brown coloured hair and also determine the genotype of the parent as well as children if three of their children are having black hair and one is having brown hair?

Five Mark Questions :
(a) How does a chromosomal disorder differ from a Mendelian disorder.
(b) Name any two chromosomal aberration associated disorders.
(c) List the chracteristics of the disorders mentioned above that help in their diagnosis.

Three Mark Questions :
Why is pedigree analysis done in the study of human genetics? State the conclusion that can be drawn from it.

Give a short description for homogametes and heterogametes with example.

How is chromosomes maintained by meiosis in sexual reproduction?

In one of the experiments with pea plants, Mendel observed that when a homozygous tall pea plant (TT) is crossed with a homozygous dwarf pea plant (tt), in the first generation, only tall plants appear. What happens to the traits of the dwarf plant in this case?

A breeder crossed a pure bred tall plant having white flowers to a pure bred short plant having blue flowers. He obtained $$202$$ $$F_1$$ progeny and found that they are all tall having white flowers. Upon selfing these $$F_1$$ plants, he obtained a progeny of $$2160$$plants. Approximately, how many of these are likely to be short and having blue flowers?

In one of his experiments with pea plants, Mendel observed that when a pure tall pea plant is crossed with a pure dwarf pea plant, in the first generation $$F_1$$ only tall plants appear.

(i)When the $$F_1$$ generation plants were self-fertilized, he observed that in the plants of second-generation $$F_2$$ both tall plants and dwarf plants were present. Why did it happen? Explain briefly. 
(ii)What happens to the traits of the dwarf plants in this case?

Name of the following:
Appearance of a trait due to the presence of an allele exclusively on either the X chromosome or on the Y chromosome. 

In the following human pedigree, the filled symbols represent the affected individuals. Identify the type of given pedigree.

Aneuploidy of chromosomes in human beings results in certain disorders. Draw out the possibilities of the karyotype in common disorders of this kind in human beings and its consequences in individuals.

What indication do we get by reappearance of dwarf plant in $$F_2$$ generation?

A sudden change in one or more genes, or in the number or in the structure of chromosomes is called _______.

Which of the two, sperm or egg cell (ovum), decides the sex of the child?

Explain sex determination in humans with a neat labelled diagram.

The term 'mutation was coined by whom?

What is Downs syndrome? Give its symptoms and cause. Why is it that the chances of having a child with Downs syndrome increases if the age of the mother exceeds forty years?

Filling the blank based on the given relationship.

$$44+X:$$ Turner syndrome $$: 44 +XXY:-$$ _____

Complete the illustration of the hybridisation experiment conducted by Mendel in Pea plants.
i. (refer image)
ii. Which are the characters expressed in second generation?

A tall plant with red flowers (TtRr) is self-pollinated. Represent the plants obtained in $$F_2$$ generation with the help of a checkerboard (punnet square). The traits which are not found in the parental plants are expressed in the offspring. Why?

Write possible genotypes Mendel got when he crossed $$F_1$$ tall plant with a dwarf pea plant.

Mendel crossed a pea plant having an inflated green pod with a constricted yellow pod.
a) What type of cross is it?
b) What types of plants are obtained in $$F_1$$ generation?
c) In $$F_2$$ generation the phenotype ratio is 9:3:3:State the rule for the inheritance of traits as observed by Mendel.

In a pea plant, the trait of flowers bearing purple colour (PP) is dominant over white colour (pp). Explain the inheritance pattern of $$F_1$$ and $$F_2$$ generations with the help of a cross following the rules of inheritance of traits. State the visible characters of $$F_1$$ and $$F_2$$ progenies.

A blue colour flower plant denoted by BB is crossbred with that of white colour flower denoted by bb.
a) State the colour of flower you would expect in their $$F_1$$ generation plants.
b) What must be the percentage of white flower plants in $$F_2$$ generation if flowers of $$F_1$$ plants are self-pollinated?
c) State the expected ratio of the genotypes BB and Bb in the $$F_2$$ progeny.

Define aneuploidy. How is it different from polyploidy? Describe the individuals having following chromosomal abnormalities.

(a) Trisomy of $$21^\text{st}$$ Chromosome
(b) XXY
(c) XO

a. A tall pea plant is crossed with a short pea plant. Draw the monohybrid cross to show $$F_1$$ and $$F_2$$ generation. Write the phenotypic and genotypic ratio.
b. The frequency of inherited traits changes over generations. What is the essence of this idea of evolution?

Green pod colour is dominant over yellow pod colour in pea plants. Fill in the Punnett square and determine the genotypic and phenotypic ratios from crossing two heterozygous parents. (Dominant gene to be represented by "G")
Genotypes -
Genotypic Ratio -
Phenotypic Ratio -


Class 12 Medical Biology Extra Questions