PPT_10_Bio_Heredity important ppt for exam.pptx

ppt

1. Heredity INTRODUCTION…

2. Contents Heredity DNA copying- Importance Rules for the inheritance of traits – Mendel’s contributions Monohybrid cross Dihybrid cross Expression of traits Sex Determination

3. DNA copying DNA copying: The process of making a copy of DNA by itself along with its cellular apparatus. Impotance : It consists the information of protein synthesis which make the basic body design. It consists the hereditary information which transfer the parental characters to young ones . During DNA copying if any error occur, it leads to altered body design . Without DNA copying the reproduction process will not complete .

4. DNA copying

5. Variations The changes or differences among two individuals of the same species are called variations. Ex. Skin colour , Height, etc..

6. Blood Grouping

7. Inheritance of Blood Groups A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits-blood group A or O- is dominant? Why or why not? No, the information is not enough because the blood group is determined by a pair of gene. One inherited from mother and other from father. In this case, the child inherited gene for O blood group from mother as well as father. The genotype of the father (Whether homozygous or heterozygous) and the number of children in the family is not given here. In the case given, Father’s Genotype may be I A I A or I A I O Mother’s Genotype should be I O I O

8. Blood Groups- Genotypes

9. Genetics - Terminology Genetics: The study of genes. Heredity/ Inheritance: The process of passing the traits from parents to parents to off springs through genes. Variations: The changes or differences among the individuals of the same species. Chromosomes: Rod shaped, specialised constricted region of a chromatid. DNA: Deoxy ribo Nucleic Acid. Carries traits in a coded form. Gene: It is the basic unit of inheritance. It is the segment of DNA. Alleles: The alternative forms of genes.

10. Genetics - Terminology Homologous chromosomes: Chromosomes that are similar in morphology (Shape and form)and genetic constitution. Heterologous chromosomes: Chromosomes that are different in morphology (Shape and form)and genetic constitution . Dominant trait: The character which expresses itself in (F1) generation is a dominant trait. Ex. Tallness in pea plant. Recessive trait: The character which does not express itself but present in a generation is called recessive trait. Ex. Dwarfism in pea plant.

11. Genetics - Terminology Homozygous: A condition in which both the genes of same type are present. Ex. TT- Tallness; tt – Dwarfness Heterozygous: A condition in which both the genes of different type are present . Ex. Tt – Tallness ( T-gene of tallness, t- the gene of dwarfness. But the character tall only expressed. Dominant gene: The gene that controls the appearance of an organism even in the presence of an alternative gene. Ex . TT- Tallness; Tt – Tallness ( T-gene of tallness, t- the gene of dwarfness. But the character tall only expressed . So T is dominant. Recessive gene: The gene that controls the appearance of an organism only in the presence of an identical gene. Ex. tt – Dwarfness

12. Genetics - Terminology Parent generation (P): The generation that supplies gametes to the filial generation. Filial generation (F): The generation that receives gametes from the parental generation . Phenotype: The physical or chemical expression of an individual. Genotype: The Genetic make-up (combination of alleles) of an individual . Carrier: A heterozygous individual not expressing a recessive trait but capable of passing it on to its off spring.

13. Genetics - Terminology Hybrid: An off spring resulting from the matting between individuals of two different genetic constitutions. Monohybrid cross: It is the cross between two plants which have one pair of contrasting characters. Di hybrid cross: It is the cross between two plants which have two pairs of contrasting characters .

14. Laws of Inheritance Law of dominance: When two dissimilar factors of a character are present in an organism only one expresses itself (dominant factor) while other remain unexpressed (recessive factor ) Law of segregation: Two factors of a character is separated at the time of gamete formation and each gamete gets only one factor for that character . Law of Independent Assortment : During the inheritance of two or more characters, the assortment of individual traits takes place independently during gamete formation. Thus each allele of a pair segregates independently and each gamete formed contains one allele of that trait. This law is inapplicable for linked genes. 

15. Contrasting Characters in Pea plant

16. Monohybrid cross

17. Monohybrid cross

18. Dihybrid Cross

19. Dihybrid Cross In dihybrid cross, Mendel crossed two pea plants with two pairs of contrasting characteristics, for example- the seed colour and the seed shape. He crossed a pea plant with round, green seeds ( RRyy ) with one having yellow, wrinkled seeds ( rrYY ). In F1 generation the plants obtained all are round and yellow seeded plants. When he self-pollinated the F1 plants ( RrYy ), in F2 generation Round yellow ; Round green ; wrinkled yellow and wrinkled green plants were obtained in the ratio of 9:3:3:1 . This is due to law of independent Assortment.

20. Traits may be inherited But may NOT be Expressed Mendel took pea plants with contrasting characteristics, tall plant (TT) and dwarf plant ( tt ). On cross pollination, he got all tall plants ( Tt ) in F 1 generation. Here the allele which is responsible for dwarfness (t) , is inherited but not expressed. Because is a recessive allele it can express only in the presence of same identical allele.

21. Sex Determination

22. Sex Determination(Genetically) Humans have 46 chromosomes and are present in 23 pairs. Out of these 23 pairs, 22 pairs are autosomes and 1 pair is sex chromosome. Male consist XY chromosome whereas the female consist XX chromosome. Half of the male gametes (sperms) carry X chromosomes and other half carry Y chromosomes. All the female gametes (ovum) carry only X chromosomes. A child who inherits X chromosome from the father will be a girl; and one who inherits Y chromosome from the father will be a boy. (Hence the sex of the new born is determined by the father. Thus there bare 50-50 chances of a male or female child and none of the parents may be considered responsible for sex determination. Hence it is a matter of chance.

23. Sex Determination (Environmentally ) (a) In some animals, the temperature at which fertilized eggs are kept determines whether the developing animal in the egg is male or female. Ex- lizard. (b) In some animals like the snail, an individual can change sex under stress and different environmental conditions.

24. Sum Based Questions Two pea plants - one with round yellow seeds (RRYY) and another with wrinkled green ( rryy ) seeds produce F1 progeny that have round, yellow ( RrYy ) seeds. When F1 plants are self-pollinated, which new combination of characters is expected in F2 progeny? How many seeds with these new combinations of characters will be produced when a total 160 seeds are produced in F2 generation? Explain with reason. Total no.of plants produced=160 Dihybrid cross ratio=9:3:3:1 9X+3X+3X+1X=16 16X=160 X=160/16; X=10 Round, yellow: Round , green: wrinkled yellow: wrinkled green 9: 3 : 3 : 1 Round green (3x10)=30 Wrinkled yellow (3x10)=30 New combinations are produced because of the independent inheritance of seed shape and seed colour trait.

25. Sum Based Questions Sahil performed an experiment to study the inheritance pattern of genes. He crossed tall pea plants (TT) with short pea plants ( tt ) and obtained all tall plants in F1 generation. a. What will be set of genes present in the F1 generation? Tt b. Give reason why only tall plants are observed in F1 progeny. Traits like ‘T’ are called dominant traits, while those that behave like ‘t’ are called recessive traits. c. When F1 plants were self - pollinated, a total of 800 plants were produced. How many of these would be tall, medium height or short plants? Give the genotype of F 2 generation. Tall : Short 3 : 1 3X+1X=800 4X=800 X=800/4 X=200 Tall=3x200=600 Short=1x200=200 Out of 800 plants 600 plants will be tall and 200 plants will be small (1 mark), 1 TT: 2Tt: 1tt

26. Inherited traits Vs Acquired Traits

27. References: NCERT text book for class 10 S. Chand Publications – Lakmir Singh ISC BIOLOGY – Dr. P. S. Verma Dr. B. P. Pandey

28. THANK YOU! - V.Manivannan , M.sc( Bot ),M.sc(Biotech ),M.Ed ., Department of Biological Sciences…