Balbharti Maharashtra State Board Class 9 Science Solutions Chapter 16 Heredity and Variation Notes, Textbook Exercise Important Questions and Answers.
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) F1 plants of monohybrid cross produce two types of gametes. | (ii) F1 plants of dihybrid cross produce four types of gametes. |
| (iii) Monohybrid cross has a phenotypic ratio of 3 : 1 in F2 generation. | (iii) Dihybrid cross has a phenotypic ratio of 9 : 3 : 3 : 1 in F2 generation. |
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.
How do specific traits or characteristics appear in organisms? (Can you tell; Textbook Page No. 180)
Answer:
Question 2.
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)
Answer:
Parental Generation (P1)
Phenotypic ratio : 3 Round : 1 Wrinkled
Genotypic ratio : 1 RR : 2 Rr : 1 rr
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 Page No. 187)
Answer:
Question 4.
Do all boys and girls of your class look alike? (Think about it; Textbook Page No. 179)
Answer:
Question 5.
Carefully observe your classmate’s earlobes. (Observe; Textbook Page No. 179)
Answer:
Question 6.
Irrespective of all of us being humans, what difference do you notice in our skin colour? (Observe; Textbook Page No. 179)
Answer:
Question 7.
All of you are in std. IX. Why then are some students tall and some short? (Observe; Textbook Page No. 179)
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.
The similarities and differences are all the effect of
(a) Heredity
(b) Fertilization
(c) Evolution
(d) Natural selection
Answer:
(a) Heredity
Question 2.
Each chromosome appears midway during cell division.
(a) Circular
(b) Rod-shaped
(c) Dumbbell-shaped
(d) Bottle-shaped
Answer:
(c) dumbbell-shaped
Question 3.
The chromosome in which the centromere is exactly at the mid-point is called chromosome.
(a) sub-metacentric
(b) metacentric
(c) acrocentric
(d) telocentric
Answer:
(b) metacentric
Question 4.
The chromosome in which the centromere is somewhere near the mid-point is called chromosome.
(a) metacentric
(b) acrocentric
(c) sub-metacentric
(d) telocentric
Answer:
(c) sub-metacentric
Question 5.
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
Answer:
(d) telocentric
Question 6.
Sex chromosomes are called
(a) homologous chromosomes
(b) autosomes
(c) allosomes
(d) metacentric chromosomes
Answer:
(c) allosomes
Question 7.
Which of the following is absent in RNA?
(a) Adenine
(b) Uracil
(c) Cytosine
(d) Thymine
Answer:
(d) Thymine
Question 8.
DNA was discovered by
(a) Watson and Crick
(b) Frederick Miescher
(c) Gregor Johann Mendel
(d) Robert Brown
Answer:
(b) Frederick Miescher
Question 9.
The double helix model of DNA was produced by
(a) Watson and Crick
(b) Frederick Miescher
(c) Gregor Johann Mendel
(d) Robert Hooke
Answer:
(a) Watson and Crick
Question 10.
The molecule of RNA which is a component of the ribosome organelle is called a
(a) mRNA
(b) tRNA
(c) rRNA
(d) DNA
Answer:
(c) rRNA
Question 11.
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
Answer:
(c) 3 talhl dwarf
Question 12.
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
Answer:
(b) Turner syndrome
Question 13.
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
Answer:
(c) all carrier
Question 14.
is a mitochondrial disorder.
(a) Down syndrome
(b) Cleft palate
(c) Spina bifida
(d) Leber hereditary optic neuropathy
Answer:
(d) Leber hereditary optic neuropathy
Question 15.
is a monogenic disorder.
(a) Haemophilia
(b) Cleft palate
(c) Diabetes
(d) Spina bifida
Answer:
(a) Haemophilia
Question 16.
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
Answer:
(b) White colour of flowers
Question 17.
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
Answer:
(c) Yellow colour of seeds
Question 18.
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
Answer:
(d) Free ear lobe
Question 19.
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
Answer:
(a) Absence of hair on arms
Question 20.
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
Answer:
(b) 50% normal and 50% carrier
Question 21.
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
Answer:
(c) 50% carrier and 50% sufferer
Find the odd man out:
Question 1.
Adenine, thymine, cytosine, uracil
Answer:
Adenine. It is a purine whereas the others are pyrimidines.
Question 2.
Axillary flower, green pod, green seed, inflated pod
Answer:
Green seed. It is a recessive character of pea plant whereas the others are dominant characters.
Question 3.
Constricted pod, purple flower, axillary flower, yellow seeds.
Answer:
Constricted pod. It is a recessive character of pea plant whereas the others are dominant characters.
Question 4.
Green seeds, wrinkled seeds, terminal flower, green pod.
Answer:
Green pod. It is a dominant character of pea plant whereas the others are recessive characters.
Question 5.
Attached ear lobes, brown and straight hair, non-rolling tongue, presence of hair on arms.
Answer:
Presence of hair on arms. It is a dominant characteristic of human beings whereas the others are recessive characters.
Question 6.
Cystic fibrosis, albinism, spina bifida, sicklecell anaemia.
Answer:
Spina bifida. It is a polygenic disorder whereas the others are monogenic disorders.
Question 7.
Fiutchinson’s disease, phenylketonuria, nightblindness, leber hereditary optic neuropathy.
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.
| 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. |
Answer:
(1 – c – iv),
(2 – d – v),
(3 – e – i),
(4-b- Hi),
(5 – a – ii)
Question 2.
| 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 |
Answer:
(1 – c),
(2 – d),
(3 – b),
(4 – a)
Question 3.
| 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 |
Answer:
(1 – d),
(2 – a),
(3 – b),
(4 – c)
State whether the following statements are true or false. Correct the false statement:
Question 1.
Offsprings produced through asexual reproduction show greater variations as compared to those produced through sexual reproduction.
Answer:
False. Offsprings produced through asexual reproduction show minor variations as compared to those produced through sexual reproduction.
Question 2.
Information necessary for protein synthesis is stored in the RNA.
Answer:
False. Information necessary for protein synthesis is stored in the DNA.
Question 3.
The quantity of growth hormone produced by a plant depends upon the efficiency of the concerned enzyme.
Answer:
True
Question 4.
The chromosome in which the centromere is exactly at the mid-point is called telocentric chromosome.
Answer:
False. The chromosome in which the centromere is exactly at the mid-point is called metacentric chromosome.
Question 5.
RNA molecules are called master molecules.
Answer:
False. DNA molecules are called master molecules.
Question 6.
The pair of sex chromosomes are called autosomes.
Answer:
False. The pair of sex chromosomes is called allosomes.
Question 7.
In DNA, Adenine always pairs with thymine and cytosine always pairs with guanine.
Answer:
True
Question 8.
In humans there are 23 pairs of autosomes and one pair of allosomes.
Answer:
False. In humans, there are 22 pairs of autosomes and one pair of allosomes.
Question 9.
The phenotypic and genotypic ratios are not same.
Answer:
True
Question 10.
Phenotype means the pairs of genes responsible for the visible characteristics of organisms.
Answer:
False. Phentotype means external appearance of visible characteristics of organisms.
Question 11.
During gamete formation, in Pj generation the pair of gametes separate independently.
Answer:
True
Question 12.
Down syndrome is caused due to monosomy of X chromosome.
Answer:
False. Down syndrome is caused due to trisomy of 21st chromosome.
Question 13.
In Klinefelter syndrome, women are sterile.
Answer:
False. In Klinefelter syndrome, men are sterile as this disorder arises in men due to abnormality in sex chromosome.
Question 14.
If the father and mother are both sufferers or carriers of sickle-cell anaemia, their offsprings are likely to suffer from this disease.
Answer:
True
Question 15.
During fertilization, mitochondria is contributed by the sperm cell and egg cell(ovum).
Answer:
False. During fertilization, mitochondria is contributed by the egg cell (ovum) alone.
Question 16.
Polygenic disorders strictly follow Mendel’s principles of heredity.
Answer:
False. Polygenic disorders do not strictly follow Mendel’s principles of heredity.
Question 17.
Genetic material is transferred in equal quantity from parents to progeny.
Answer:
True
Give scientific reasons:
Question 1.
DNA molecules are called as ‘Master molecules’.
Answer:
Question 2.
Phenotypic and genotypic ratios are different.
Answer:
Question 3.
A carrier or sufferer of sickle-cell anaemia should avoid marriage with another carrier or sufferer.
Answer:
Question 3.
Mitochondrial disorders are inherited from the mother only.
Answer:
Question 4.
Tobacco smoking causes cancer.
Answer:
Define the following terms:
Question 1.
Gene
Answer:
The segment of DNA which contains all the information for synthesis of a particular protein is called a ‘gene’.
Question 2.
Chromosome
Answer:
The structure in the nucleus of the cells that carries the hereditary characteristics is called chromosome.
Question 3.
Genetics
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.
Heredity
Answer:
Transfer of characteristics from parents to offsprings is called heredity.
Question 5.
Homologous chromosomes
Answer:
If the pair consists of chromosomes are similar in shape and organization, they are called homologous chromosomes.
Question 6.
Heterologous chromosomes
Answer:
If the pair which consists of chromosomes are not similar in shape and organization, they are called heterologous chromosomes.
Question 7.
Genetic disorders
Answer:
Diseases or disorders occuring due to abnormalities in chromosomes and mutations in genes are called genetic disorders.
Distinguish between:
Question 1.
DNA and RNA
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.
Turner syndrome and Klinefelter syndrome.
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.
Albinism
Answer:
Question 2.
Polygenic disorders.
Answer:
Question 3.
Turner syndrome.
Answer:
Answer the following questions:
Question 1.
What are the main objectives of National Health Mission?
Answer:
The main objectives of National Health Mission are:
Question 2.
Which were the seven pairs of contrasting characteristics studied by Mendel in pea plant?
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.
Name some dominant and recessive characteristics seen in human beings.
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 |
Question 4.
What is Klinefelter syndrome?
Answer:
Question 5.
How is the diagnosis for sickle-cell anaemia made?
Answer:
Question 6.
Find out the Phenotypic ratio of the following:
(a) Round-Yellow
(b) Wrinkled-Yellow
(c) Round-Green
(d) Wrinkled-Green
Answer:
(a) Round-Yellow: 9
(b) Wrinkled-Yellow: 3
(c) Round-Green: 3
(d) Wrinkled-Green: 1
Phenotypic ratio: 9:3:3:1
Question 7.
Find out the Genotypic ratio of the following:
(a) RRYY
(b) RRYy
(c) RRyy
(d) RrYY
(e) RrYy
(f) Rryy
(g) rrYY
(h) rrYy
(i) rryy
Answer:
(a) RRYY -1
(b) RRYy-2
(c) RRyy-1
(d) RrYY-2
(e) RrYy-4
(f) Rryy-2
(g) rrYY – 1
(h) rrYy – 2
(i) rryy – 1
Genotypic ratio: 1:2:1:2:4:2:1:2:1
Draw neat and labelled diagrams of the following:
Question 1.
Structure of chromosome
Answer:
Question 2.
Types of RNA
Answer:
Answer the following questions:
Question 1.
What are the effects of tobacco consumption?
Answer:
Question 2.
Complete the table for number of chromosomes in different organisms.
Answer:
| Organism | No. of Chromosomes |
| Crab | 200 |
| Maize | 20 |
| Frog | 26 |
| Roundworm | 04 |
| Potato | 48 |
| Human | 46 |
| Dog | 78 |
| Elephant | 56 |
| Fruit fly | 08 |
| Mango | 40 |