ICSE-X-Biology
02 Genetic: Some Basic Fundamentals
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- #Section : AA. Multiple Choice Type:
(Select the most appropriate option)
- Qstn #1Which one of the following has the smallest number of chromosomes? (a) Onion (b) Mouse (c) Monkey (d) AscarisAns : (d) Ascaris
- #2-a3:1 (b) 1:2:1 (c) 2:2 (d) 1:3Ans : 3:1
- #Section : BB: Very Short
- Qstn #1Match the terms in column I with their explanations in column II.
Ans : (a) genetics - (iii) Study of laws of inheritance of characters
(b) Autosomes - (v) Chromosomes other than the pair of sex chromosomes
(c) Recessive - (iv) A gene that can express when only in a similar pair
(d) Allele - (ii) The alternative forms of a gene
(e) Homologous chromosomes - (i) Chromosomes similar in size and shape
- Qstn #2Name two animals which have nineteen pairs of chromosomes.Ans : Lion, tiger, domestic cat (Any two)
- Qstn #3Name any two genetic in humans.Ans : Colour-blindness, Thalassaemia, Sickle cell anaemia and Haemophilia (Any two)
- Qstn #4Which one of the following genotypes is homozygous dominant and which one homozygous recessive in regards to tongue rolling:
Rr, rr, RRAns : Homozygous dominant - RR
Homozygous recessive - rr
- #Section : CShort
- Qstn #1Differentiate between: (a) genotype and phenotype. (b) character and trait. (c) monohybrid and dihybrid cross (phenotypic ratio)Ans :
Phenotype Genotype The observable characteristics which is genetically controlled is called Phenotype. The set of genes present in the cells of an organism is called genotype. Character Trait Any heritable feature is called a character. The alternative form a character is called trait. Monohybrid cross Dihybrid cross It is a cross between two pure breeding parent organisms with different varieties taking into consideration the alternative trait only one character. It is a cross between two pure breeding parent organisms with different varieties taking into consideration the alternative trait of two characters.
- Qstn #2Among lion, tiger and domestic cat, al the three have the same number of 38 chromosomes, yet they have different appearances. How do you account for such differences?Ans : The characteristics of a species such as physical appearance, body functions and behavior are not only the outcome of chromosome number, but these depend on the genotype of every organism. That means the set of genes present in the organisms may vary and therefore lion, tiger and domestic cat have the same number of 38 chromosomes, their characteristics (like different appearances) are the result of the genes located on the chromosomes.
- Qstn #3List any three features of garden pea with their dominant and recessive traits.Ans :
Character Dominant trait Recessive trait Flower colour Purple White Seed Yellow Green Seed Shape Round Wrinkled Pod Shape Inflated Constricted Flower Shape Axial Terminal
- Qstn #4Explain why generally only the male child suffers from colour blindness and not the female?Ans : Colour-blindness is caused due to recessive genes which occur on the X chromosome.
Males have only one X chromosome. If there is recessive gene present on X chromosome, then the male will suffer from colour-blindness.
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Females have two X chromosomes. It is highly impossible that both the X chromosomes carry abnormal gene. Hence, if one gene is abnormal and since it is recessive, its expression will be masked by the normal gene present on the other X chromosome. Females are unlikely to suffer from colour-blindness.