Maharashtra State Board Class 9 (SSC) Science & Technology Solutions Chapter 16 Heredity and Variation - Digest Answers | Maharashtra Board Solutions

Q: Question 1: How do specific traits or characteristics appear in organisms? (Can you tell; Textbook Page No. 180)

Step-by-step solution provided.

Q: Question 3: Why did the characteristic of the Rounded- Yellow seeds alone appear in the Fj generation but not the characteristic of the wrinkled- green seeds? (Use your brain power; Textbook P

Step-by-step solution provided.

Q: Question 4: Do all boys and girls of your class look alike? (Think about it; Textbook Page No. 179)

Step-by-step solution provided.

Q: Question 5: Carefully observe your classmate’s earlobes. (Observe; Textbook Page No. 179)

Step-by-step solution provided.

Q: Question 6: Irrespective of all of us being humans, what difference do you notice in our skin colour? (Observe; Textbook Page No. 179)

Step-by-step solution provided.

Maharashtra State Board Class 9 Science Solutions Chapter 16 Heredity and Variation

Class 9 Science Chapter 16 Heredity and Variation Textbook Questions and Answers

1. Complete the following sentences by choosing the appropriate words from the brackets.
(Inheritance, sexual reproduction, asexual reproduction, chromosomes, DNA, RNA, gene)

a. Hereditary characters are transferred from parents to offsprings by …………………………….., hence they are said to be structural and functional units of heredity.
b. Organisms produced by …………………………….. show minor variations.
c. The component which is in the nuclei of cells and carries the hereditary characteristics is called ……………………………..
d. Chromosomes are mainly made up of ……………………………..
e. Organisms produced through …………………………….. show major variations.

2. Explain the following.

a. Explain Mendel’s monohybrid progeny with the help of any one cross.
Answer:

b. Explain Mendel’s dihybrid ratio with the help of any one cross.
Answer:

c. Distinguish between monohybrid and dihybrid cross.
Answer:

Monohybrid cross	Dihybrid cross
(i) Cross involving a single pair of contrasting characters is called monohybrid cross.	(i) Cross involving two pairs of contrasting characters is called a dihybrid cross.
(ii) F₁plants of monohybrid cross produce two types of gametes.	(ii) F₁plants of dihybrid cross produce four types of gametes.
(iii) Monohybrid cross has a phenotypic ratio of 3 : 1 in F₂generation.	(iii) Dihybrid cross has a phenotypic ratio of 9 : 3 : 3 : 1 in F₂generation.

d. Is it right to avoid living with a person suffering from a genetic disorder?
Answer:

3. Answers the following questions in your own words.

a. What is meant by ‘chromosome’. Explain its types.
Answer:

(a) Metacentric: The centromere is exactly at the mid-point in this chromosome, and therefore, it looks like the English letter ‘V’. The arms of this chromosome are equal in length.

(b) Sub-metacentric: The centromere is somewhere near the mid-point in this chromosome which, therefore, looks like the English letter ‘U. One arm is slightly shorter than the other.

(c) Acrocentric: The centromere is near one end of this chromosome which therefore looks like the English letter One arm is much smaller than the other.

(d) Telocentric: The centromere is right at the end of this chromosome making the chromosome look like the English letter ‘i’. This chromosome consists of only one arm.

b. Describe the structure of the DNA molecule.
Answer:

c. Express your opinion about the use of DNA fingerprinting.
Answer:

d. Explain the structure, function and types of RNA.
Answer:

e. Why is it necessary for people to have their blood examined before marriage?
Answer:

4. Write a brief note on each.

a. Down syndrome
Answer:

b. Monogenic disorders
Answer:

c. Sickle cell anaemia: symptoms and treatment.
Answer:

5. How are the items in groups A, B and C inter-releated?

6. Filling the blanks based on the given relationship.
a. 44 + X : Turner syndrome : : 44 + XXY: – ……………………………..
b. 3:1 Monohybrid : : 9:3:3:1 : ……………………………..
c. Women : Turner syndrome : : Men : ……………………………..
Answer:
a. Klinefelter syndrome
b. Dihybrid
c. Klinefelter syndrome

7. Complete the tree diagram below based on types of hereditary disorders.

Answer:

Class 9 Science Chapter 12 Study of Sound Intext Questions and Answers

Question 1 Maharashtra Board Solution

How do specific traits or characteristics appear in organisms? (Can you tell; Textbook Page No. 180)

Solution & Step-by-Step Answer:

Question 2 Maharashtra Board Solution

Show the monohybrid cross between (RR) and (rr) and write the phenotypic and genotypic ratio of F2 generation. (Use your brain power; Textbook Page No. 187)

Solution & Step-by-Step Answer:

Parental Generation (P1) Phenotypic ratio : 3 Round : 1 Wrinkled Genotypic ratio : 1 RR : 2 Rr : 1 rr

Question 3 Maharashtra Board Solution

Why did the characteristic of the Rounded- Yellow seeds alone appear in the Fj generation but not the characteristic of the wrinkled- green seeds? (Use your brain power; Textbook Page No. 187)

Solution & Step-by-Step Answer:

Question 4 Maharashtra Board Solution

Do all boys and girls of your class look alike? (Think about it; Textbook Page No. 179)

Solution & Step-by-Step Answer:

Question 5 Maharashtra Board Solution

Carefully observe your classmate’s earlobes. (Observe; Textbook Page No. 179)

Solution & Step-by-Step Answer:

Question 6 Maharashtra Board Solution

Irrespective of all of us being humans, what difference do you notice in our skin colour? (Observe; Textbook Page No. 179)

Solution & Step-by-Step Answer:

Question 7 Maharashtra Board Solution

All of you are in std. IX. Why then are some students tall and some short? (Observe; Textbook Page No. 179)

Solution & Step-by-Step Answer:

Our height is decided by gene. People who are tall have genes for tallness whereas people who are short have genes for shortness and hence the variation.

Class 9 Science Chapter 12 Study of Sound Additional Important Questions and Answers

Choose and write the correct option:

Question 1 Maharashtra Board Solution

The similarities and differences are all the effect of (a) Heredity (b) Fertilization (c) Evolution (d) Natural selection

Solution & Step-by-Step Answer:

(a) Heredity

Question 2 Maharashtra Board Solution

Each chromosome appears midway during cell division. (a) Circular (b) Rod-shaped (c) Dumbbell-shaped (d) Bottle-shaped

Solution & Step-by-Step Answer:

Question 3 Maharashtra Board Solution

The chromosome in which the centromere is exactly at the mid-point is called chromosome. (a) sub-metacentric (b) metacentric (c) acrocentric (d) telocentric

Solution & Step-by-Step Answer:

(b) metacentric

Question 4 Maharashtra Board Solution

The chromosome in which the centromere is somewhere near the mid-point is called chromosome. (a) metacentric (b) acrocentric (c) sub-metacentric (d) telocentric

Solution & Step-by-Step Answer:

Question 5 Maharashtra Board Solution

The chromosome in which the centromere is near one end of the chromosome is called chromosome. (a) metacentric (b) acrocentric (c) sub-metacentric (d) telocentric

Solution & Step-by-Step Answer:

(d) telocentric

Question 6 Maharashtra Board Solution

Sex chromosomes are called (a) homologous chromosomes (b) autosomes (c) allosomes (d) metacentric chromosomes

Solution & Step-by-Step Answer:

Question 7 Maharashtra Board Solution

Which of the following is absent in RNA? (a) Adenine (b) Uracil (c) Cytosine (d) Thymine

Solution & Step-by-Step Answer:

(d) Thymine

Question 8 Maharashtra Board Solution

DNA was discovered by (a) Watson and Crick (b) Frederick Miescher (c) Gregor Johann Mendel (d) Robert Brown

Solution & Step-by-Step Answer:

(b) Frederick Miescher

Question 9 Maharashtra Board Solution

The double helix model of DNA was produced by (a) Watson and Crick (b) Frederick Miescher (c) Gregor Johann Mendel (d) Robert Hooke

Solution & Step-by-Step Answer:

(a) Watson and Crick

Question 10 Maharashtra Board Solution

The molecule of RNA which is a component of the ribosome organelle is called a (a) mRNA (b) tRNA (c) rRNA (d) DNA

Solution & Step-by-Step Answer:

Question 11 Maharashtra Board Solution

In a monohybrid cross, the phenotypic ratio of F, generation is (a) 1 tall: 3 dwarf (b) 2 tall: 2 dwarf (c) 3 tall: 1 dwarf (d) 3 tall: 2 dwarf

Solution & Step-by-Step Answer:

Question 12 Maharashtra Board Solution

arises due to either inheritance of only X chromosome from parents or due to inactivation of the gender-related part of X-chromosomes. (a) Down syndrome (b) Turner syndrome (c) Klinefelter syndrome (d) Albinism

Solution & Step-by-Step Answer:

(b) Turner syndrome

Question 13 Maharashtra Board Solution

Progenies of normal man and sufferer woman for sickle-cell anaemia will be (a) all normal (b) 25% normal and 75% sufferer (c) all carrier (d) all sufferer

Solution & Step-by-Step Answer:

Question 14 Maharashtra Board Solution

is a mitochondrial disorder. (a) Down syndrome (b) Cleft palate (c) Spina bifida (d) Leber hereditary optic neuropathy

Solution & Step-by-Step Answer:

(d) Leber hereditary optic neuropathy

Question 15 Maharashtra Board Solution

is a monogenic disorder. (a) Haemophilia (b) Cleft palate (c) Diabetes (d) Spina bifida

Solution & Step-by-Step Answer:

(a) Haemophilia

Question 16 Maharashtra Board Solution

is a recessive character of pea plant. (a) Round shape of seeds (b) White colour of flowers (c) Green colour of pods (d) Inflated shape of pods

Solution & Step-by-Step Answer:

(b) White colour of flowers

Question 17 Maharashtra Board Solution

is a dominant character of pea plant. (a) Dwarf height (b) Yellow colour of pod (c) Yellow colour of seeds (d) Terminal position of flower

Solution & Step-by-Step Answer:

Question 18 Maharashtra Board Solution

is a dominant character in human beings. (a) Non-rolling tongue (b) Attached ear lobe (c) Absence of hair on arms (d) Free ear lobe

Solution & Step-by-Step Answer:

(d) Free ear lobe

Question 19 Maharashtra Board Solution

is a recessive character in human beings. (a) Absence of hair on arms (b) Black and curly hair (c) Free earlobe (d) Presence of hair on arms

Solution & Step-by-Step Answer:

(a) Absence of hair on arms

Question 20 Maharashtra Board Solution

If one parent is normal and one parent is carrier of sickle-cell anaemia, then the progenies will be (a) all normal (b) 50% normal and 50% carrier (c) 50% carrier and 50% sufferer (d) all carrier

Solution & Step-by-Step Answer:

(b) 50% normal and 50% carrier

Question 21 Maharashtra Board Solution

If one parent is carrier and one parent is a sufferer of sickle-cell anaemia, then the progenies will be (a) 50% normal and 50% carrier (b) all sufferers (c) 50% carrier and 50% sufferer (d) all carrier

Solution & Step-by-Step Answer:

Find the odd man out:

Question 1 Maharashtra Board Solution

Adenine, thymine, cytosine, uracil

Solution & Step-by-Step Answer:

Adenine. It is a purine whereas the others are pyrimidines.

Question 2 Maharashtra Board Solution

Axillary flower, green pod, green seed, inflated pod

Solution & Step-by-Step Answer:

Green seed. It is a recessive character of pea plant whereas the others are dominant characters.

Question 3 Maharashtra Board Solution

Constricted pod, purple flower, axillary flower, yellow seeds.

Solution & Step-by-Step Answer:

Constricted pod. It is a recessive character of pea plant whereas the others are dominant characters.

Question 4 Maharashtra Board Solution

Green seeds, wrinkled seeds, terminal flower, green pod.

Solution & Step-by-Step Answer:

Green pod. It is a dominant character of pea plant whereas the others are recessive characters.

Question 5 Maharashtra Board Solution

Attached ear lobes, brown and straight hair, non-rolling tongue, presence of hair on arms.

Solution & Step-by-Step Answer:

Presence of hair on arms. It is a dominant characteristic of human beings whereas the others are recessive characters.

Question 6 Maharashtra Board Solution

Cystic fibrosis, albinism, spina bifida, sicklecell anaemia.

Solution & Step-by-Step Answer:

Spina bifida. It is a polygenic disorder whereas the others are monogenic disorders.

Question 7 Maharashtra Board Solution

Fiutchinson’s disease, phenylketonuria, nightblindness, leber hereditary optic neuropathy.

Solution & Step-by-Step Answer:

Leber hereditary optic neuropathy. It is a mitochondrial disorder whereas the others are monogenic disorders.

Complete the analogy:

a. Tall plant: Phenotype :: Tt:
b. Dominant trait : Axial position of flower :: Recessive trait:
c. Women : 44 + XX :: Men :
d. Adenine and Guanine : Purine :: Cytosine and Thymine :
Answer:
a. Genotype
b. Terminal position of flower
c. 44 + XY
d. Pyrimidine

Match the columns

Question 1 Maharashtra Board Solution

Column 1	Column 2	Column 3
(1) Leber hereditary optic neuropathy	(a) 44 + XXY	(i) Pale skin, white hairs.
(2) Diabetes	(b) 45 + X	(ii) Men are sterile.
(3) Albinism	(c) Mitochondrial disorder	(iii) Women are sterile.
(4) Turner syndrome	(d) Polygenic disorder	(iv) This disorder arises during development of zygote.
(5) Klinefelter Syndrome	(e) Monogenic disorder	(v) Effect on blood- glucose level.

Solution & Step-by-Step Answer:

(1 – c – iv),
(2 – d – v),
(3 – e – i),
(4-b- Hi),
(5 – a – ii)

Question 2 Maharashtra Board Solution

Column ‘A’	Column ‘B’
(1) Yellow and rinkled	(a) yyrr
(2) Green and round	(b) YyRr
(3) Yellow and round	(c) YYrr
(4) Green and wrinkled	(d) yyRr

Solution & Step-by-Step Answer:

(1 – c),
(2 – d),
(3 – b),
(4 – a)

Question 3 Maharashtra Board Solution

Column ‘A’	Column ‘B’
(1) Tay-Sachs disease	(a) Multifactorial disorder
(2) Diabetes	(b) Destruction of erythrocytes
(3) Sickle-cell anaemia	(c) Absence of melanin
(4) Albinism	(d) Monogenic disorder

Solution & Step-by-Step Answer:

(1 – d),
(2 – a),
(3 – b),
(4 – c)

State whether the following statements are true or false. Correct the false statement:

Question 1 Maharashtra Board Solution

Offsprings produced through asexual reproduction show greater variations as compared to those produced through sexual reproduction.

Solution & Step-by-Step Answer:

False. Offsprings produced through asexual reproduction show minor variations as compared to those produced through sexual reproduction.

Question 2 Maharashtra Board Solution

Information necessary for protein synthesis is stored in the RNA.

Solution & Step-by-Step Answer:

False. Information necessary for protein synthesis is stored in the DNA.

Question 3 Maharashtra Board Solution

The quantity of growth hormone produced by a plant depends upon the efficiency of the concerned enzyme.

Solution & Step-by-Step Answer:

True

Question 4 Maharashtra Board Solution

The chromosome in which the centromere is exactly at the mid-point is called telocentric chromosome.

Solution & Step-by-Step Answer:

False. The chromosome in which the centromere is exactly at the mid-point is called metacentric chromosome.

Question 5 Maharashtra Board Solution

RNA molecules are called master molecules.

Solution & Step-by-Step Answer:

False. DNA molecules are called master molecules.

Question 6 Maharashtra Board Solution

The pair of sex chromosomes are called autosomes.

Solution & Step-by-Step Answer:

False. The pair of sex chromosomes is called allosomes.

Question 7 Maharashtra Board Solution

In DNA, Adenine always pairs with thymine and cytosine always pairs with guanine.

Solution & Step-by-Step Answer:

True

Question 8 Maharashtra Board Solution

In humans there are 23 pairs of autosomes and one pair of allosomes.

Solution & Step-by-Step Answer:

False. In humans, there are 22 pairs of autosomes and one pair of allosomes.

Question 9 Maharashtra Board Solution

The phenotypic and genotypic ratios are not same.

Solution & Step-by-Step Answer:

True

Question 10 Maharashtra Board Solution

Phenotype means the pairs of genes responsible for the visible characteristics of organisms.

Solution & Step-by-Step Answer:

False. Phentotype means external appearance of visible characteristics of organisms.

Question 11 Maharashtra Board Solution

During gamete formation, in Pj generation the pair of gametes separate independently.

Solution & Step-by-Step Answer:

True

Question 12 Maharashtra Board Solution

Down syndrome is caused due to monosomy of X chromosome.

Solution & Step-by-Step Answer:

False. Down syndrome is caused due to trisomy of 21st chromosome.

Question 13 Maharashtra Board Solution

In Klinefelter syndrome, women are sterile.

Solution & Step-by-Step Answer:

False. In Klinefelter syndrome, men are sterile as this disorder arises in men due to abnormality in sex chromosome.

Question 14 Maharashtra Board Solution

If the father and mother are both sufferers or carriers of sickle-cell anaemia, their offsprings are likely to suffer from this disease.

Solution & Step-by-Step Answer:

True

Question 15 Maharashtra Board Solution

During fertilization, mitochondria is contributed by the sperm cell and egg cell(ovum).

Solution & Step-by-Step Answer:

False. During fertilization, mitochondria is contributed by the egg cell (ovum) alone.

Question 16 Maharashtra Board Solution

Polygenic disorders strictly follow Mendel’s principles of heredity.

Solution & Step-by-Step Answer:

False. Polygenic disorders do not strictly follow Mendel’s principles of heredity.

Question 17 Maharashtra Board Solution

Genetic material is transferred in equal quantity from parents to progeny.

Solution & Step-by-Step Answer:

True

Give scientific reasons:

Question 1 Maharashtra Board Solution

DNA molecules are called as ‘Master molecules’.

Solution & Step-by-Step Answer:

Question 2 Maharashtra Board Solution

Phenotypic and genotypic ratios are different.

Solution & Step-by-Step Answer:

Question 3 Maharashtra Board Solution

A carrier or sufferer of sickle-cell anaemia should avoid marriage with another carrier or sufferer.

Solution & Step-by-Step Answer:

Question 3 Maharashtra Board Solution

Mitochondrial disorders are inherited from the mother only.

Solution & Step-by-Step Answer:

Question 4 Maharashtra Board Solution

Tobacco smoking causes cancer.

Solution & Step-by-Step Answer:

Define the following terms:

Question 1 Maharashtra Board Solution

Gene

Solution & Step-by-Step Answer:

The segment of DNA which contains all the information for synthesis of a particular protein is called a ‘gene’.

Question 2 Maharashtra Board Solution

Chromosome

Solution & Step-by-Step Answer:

The structure in the nucleus of the cells that carries the hereditary characteristics is called chromosome.

Question 3 Maharashtra Board Solution

Genetics

Solution & Step-by-Step Answer:

The branch of biology which studies the transfer of characteristics of organism from one generation to the next and genes in particular, is called genetics.

Question 4 Maharashtra Board Solution

Heredity

Solution & Step-by-Step Answer:

Transfer of characteristics from parents to offsprings is called heredity.

Question 5 Maharashtra Board Solution

Homologous chromosomes

Solution & Step-by-Step Answer:

If the pair consists of chromosomes are similar in shape and organization, they are called homologous chromosomes.

Question 6 Maharashtra Board Solution

Heterologous chromosomes

Solution & Step-by-Step Answer:

If the pair which consists of chromosomes are not similar in shape and organization, they are called heterologous chromosomes.

Question 7 Maharashtra Board Solution

Genetic disorders

Solution & Step-by-Step Answer:

Diseases or disorders occuring due to abnormalities in chromosomes and mutations in genes are called genetic disorders.

Distinguish between:

Question 1 Maharashtra Board Solution

DNA and RNA

Solution & Step-by-Step Answer:

DNA	RNA
(i) In DNA, the sugar present is deoxyribose.	(i) In RNA, the sugar present is ribose.
(ii) In DNA, the nitrogen bases are adenine, guanine, cytosine and thymine.	(ii) In RNA, the nitrogen base thymine is replaced by uracil.
(iii) DNA is double stranded.	(iii) RNA is single-stranded.
(iv) DNA carries hereditary information	(iv) RNA helps in protein synthesis.

Question 2 Maharashtra Board Solution

Turner syndrome and Klinefelter syndrome.

Solution & Step-by-Step Answer:

Turner syndrome	Kline fater syndrome
(i) It is due to monosomy of sex chromosome.	(i) It is due to felter of sex chromosome.
(ii) Disorder in sex chromosome results in 44 + X condition.	(ii) Disorder in sex chromosome results is 44 + XY condition.
(iii) Seen in women.	(iii) Seen in men
(iv) Women suffering from this syndrome are sexually sterile.	(iv) Men suffering from this syndrome are sexually sterile.
(v) There is presence of total 45 chromosomes instead of 46.	(v) There is presence of total 47 chromosomes instead of 46.

Write short notes on:

Question 1 Maharashtra Board Solution

Albinism

Solution & Step-by-Step Answer:

Question 2 Maharashtra Board Solution

Polygenic disorders.

Solution & Step-by-Step Answer:

Question 3 Maharashtra Board Solution

Turner syndrome.

Solution & Step-by-Step Answer:

Answer the following questions:

Question 1 Maharashtra Board Solution

What are the main objectives of National Health Mission?

Solution & Step-by-Step Answer:

The main objectives of National Health Mission are:

Question 2 Maharashtra Board Solution

Which were the seven pairs of contrasting characteristics studied by Mendel in pea plant?

Solution & Step-by-Step Answer:

The seven pairs of contrasting characters studied by Mendel in pea plant were as follows:

Characters	Dominant	Recessive
Shape of the seed	Round(R)	Wrinkled (r)
Colour of the seed	Yellow (Y)	Green (y)
Colour of the flower	Purple (C)	White (c)
Shape of pod	Inflated (I)	Constricted (i)
Colour of pod	Green (G)	Yellow (g)
Position of flower	Axillary (A)	Terminal (a)
Height of the plant	Tall (T)	Dwarf (t)

Question 3 Maharashtra Board Solution

Name some dominant and recessive characteristics seen in human beings.

Solution & Step-by-Step Answer:

Some dominant and recessive characteristics of human beings.

Dominant	Recessive
Rolling tongue	Non-rolling tongue
Presence of hair on arms	Absence of hair on arms
Black and curly hair	Brown and straight hair
Free earlobe	Attached earlobe