NEET Biology Principles of Inheritance and Variation
Principles of Inheritance and Variation PDF Notes, Important Questions and Synopsis
- Heredity is the transmission of characters from one generation to another through direct genetic descendants.
- Mendel’s Laws of Inheritance:
- Punnett square is a graphical representation to calculate the probability of all possible genotypes of offspring in a genetic cross.
- Test cross is a cross between the F1 hybrid and its recessive parent. It confirms the purity of the F1 hybrid, whether it is homozygous or heterozygous.
- Back cross is a cross between the F1 hybrid and one of its parents, which may be dominant or recessive.
- Incomplete dominance occurs when two parents are intercrossed with each other, and the hybrid produced does not resemble either of its parents but is mid-way between the parents.
- Multiple allelism occurs when more than two alleles exist at a given locus of a chromosome. In a given individual, only two of these alleles occur, one derived from each parent.
- Co-dominance is the phenomenon when both alleles of a pair are fully expressed in a heterozygote, so the genes and traits are said to be co-dominant.
- Linkage is the tendency of the genes to remain together during the process of inheritance.
- Differences between complete linkage and incomplete linkage:
- Crossing over is the mutual exchange of segments of non-sister chromatids of homologous chromosomes during the process of meiosis.
- Chromosomal Theory of Inheritance was proposed by Walter Sutton and Theodor Boveri. Sutton combined the knowledge of chromosomal segregation with Mendelian principles and called it the chromosomal theory of inheritance.
- Sex Determination in Humans:
- Mutation is an abrupt and discontinuous process where a gene or a chromosome undergoes heritable change in its structure or number.
- Ways of Chromosomal Mutation:
- Mendelian disorders are determined by alteration or mutation in a single gene.
- Aneuploidy is a condition where an organism possesses fewer or extra chromosomes than the normal genome number of the species; e.g. (2N – 1) or (2N + 1), where N is the haploid chromosome number.
- Chromosomal disorders are caused by the absence or excess or abnormal arrangement of one or more chromosomes.
- What does the phrase 'unviable in the later stage of life' mean?
- Who gave Agarose gel electrophoresis method?
- Please explain this answer in detail and also tell that how will we know that what are non allelic gene referred in this question.
- What proportion of the offsprings obtained from cross AABBCC X AaBbCc will be completely heterozygous for all the genes segreated independently?(Please explain in detail with the cross) (a)1/8 (b)1/4 (c)1/2 (d)1/16
- Probability of four sons to a couple is [explain in detail]: (a)1/4 (b)1/8 (c)1/16 (d)1/32
- In a cross between AABB X aabb , the ratio of F2 genotype between AABB,AaBB,Aabb and aabb would be [I have read this chapter in detail, but still I am not able to solve these type of questions, so please tell me how should I improve myself to master this chapter.Also please explain this question in detail.] (a)9:3:3:1 (b)2:1:1:2 (c)1:2:2:1 (d)7:5:3:1
- Two linked genes a and b show 20% recombination.The individual of a dihybrid cross between ++/++ x ab/ab shall show gametes: [I was not able to understand this question what examiner exactly wants to ask here, '++' signifies what ?SO,i request to the expert please explain this question in detail(also tell which concept should be used to answer this question)] (a)++80:ab:20 (b)++50:ab:50 (c)++40:ab 40 : + a 10 : +b:10
- On selfing a plant of F1- generation with genotype "AABbCC", the genotypic ratio in F2- generation will be:[Please explain the cross in detail] (a)3:1 (b)1:1 (c)9:3:3:1 (d)27:9:9:9:3:3:3:1
- One of the parent of a cross has a mutation in its mitochondria. In that cross , that parent is taken as a male. During segregation of F2 progenies that mutation is found in [Its answer is (b) , but my question is that why mutation is not transferred to progeny .As mitochondria also carry its own genetic material ]: (a)one- third of the progenies (b) none of the progenies (c)all the progenies (d) 50% of the progenies
- In humans the number of chromosomes is 46 i.e (22+XX/XY),then what would be the chromosome number in (both male and female ,autosome and allosome): (a)Drosophilla (b)Grasshopper (c)Hen (d)Butterfly
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