CSIR NET Life Sciences Inheritance Biology Syllabus

Inheritance Biology syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Inheritance Biology in CSIR NET Life Sciences, not a summary of it.

1. 1

   Mendelian principles

   3 topics

   • Dominance
   • Segregation
   • Independent assortment
2. 2

   Concept of gene

   4 topics

   • Allele
   • Multiple alleles
   • Pseudoallele
   • Complementation tests
3. 3

   Extensions of Mendelian principles

   10 topics

   • Codominance
   • Incomplete dominance
   • Gene interactions
   • Pleiotropy
   • Genomic imprinting
   • Penetrance and expressivity
   • Phenocopy
   • Linkage and crossing over
   • Sex linkage
   • Sex limited and sex influenced characters
4. 4

   Gene mapping methods

   5 topics

   • Linkage maps
   • Tetrad analysis
   • Mapping with molecular markers
   • Mapping by using somatic cell hybrids
   • Development of mapping population in plants
5. 5

   Extra chromosomal inheritance

   2 topics

   • Inheritance of Mitochondrial and chloroplast genes
   • Maternal inheritance
6. 6

   Microbial genetics

   3 topics

   • Methods of genetic transfers
     • transformation
     • conjugation
     • transduction
     • sex-duction
   • Mapping genes by interrupted mating
   • Fine structure analysis of genes
7. 7

   Human genetics

   4 topics

   • Pedigree analysis
   • Lod score for linkage testing
   • Karyotypes
   • Genetic disorders
8. 8

   Quantitative genetics

   3 topics

   • Polygenic inheritance
   • Heritability and its measurements
   • QTL mapping
9. 9

   Mutation

   4 topics

   • Types, causes and detection
   • Mutant types
     • lethal
     • conditional
     • biochemical
     • loss of function
     • gain of function
   • Germinal verses somatic mutants
   • Insertional mutagenesis
10. 10

    Structural and numerical alterations of chromosomes

    5 topics

    • Deletion
    • Duplication
    • Inversion
    • Translocation
    • Ploidy and their genetic implications
11. 11

    Recombination

    2 topics

    • Homologous recombination
    • Non-homologous recombination including transposition

Inheritance Biology flashcards for CSIR NET Life Sciences

23 of 61 cards from the Inheritance Biology deck — real questions with worked answers.

1. State Mendel's Law of Dominance.

   In a heterozygote (Aa), one allele (the dominant one) masks the phenotypic expression of the other (the recessive allele); the recessive trait reappears only in homozygous recessive individuals.

2. State Mendel's Law of Segregation (Mendel's First Law).

   The two alleles of a gene separate (segregate) from each other during gamete formation, so each gamete carries only one allele; they reunite randomly at fertilization.

3. State Mendel's Law of Independent Assortment (Mendel's Second Law).

   Alleles of different genes assort independently of one another during gamete formation, giving all possible allele combinations equal probability — valid only for genes on different chromosomes or far apart on the same chromosome.

4. What is an allele?

   An allele is one of two or more alternative forms of a gene that occupy the same locus on homologous chromosomes and produce variation in a trait.

5. What are multiple alleles? Give a classic example.

   Multiple alleles are three or more alternative forms of a gene existing in a population (though any diploid carries only two). Example: the human ABO blood group (I^A, I^B, i) and the Drosophila white-eye allelic series.

6. What is a pseudoallele?

   Pseudoalleles are closely linked genes that behave like alleles of a single locus (failing to recombine in cis/trans tests) but are actually separate, functionally distinct genes separable by rare recombination.

7. What is the purpose of a complementation (cis-trans) test?

   To determine whether two recessive mutations causing the same phenotype lie in the same gene or different genes: if the trans-heterozygote shows wild-type (complementation), the mutations are in different genes; if mutant, they are in the same gene (cistron).

8. Define codominance and give an example.

   Codominance is when both alleles in a heterozygote are fully and simultaneously expressed, producing a phenotype showing both. Example: AB blood group (both A and B antigens) and MN blood group.

9. Define incomplete dominance and give an example.

   Incomplete dominance is when the heterozygote shows an intermediate phenotype between the two homozygotes. Example: pink flowers (Rr) from red (RR) x white (rr) in snapdragon/4 o'clock plant.

10. What is the F2 phenotypic ratio under incomplete dominance for a monohybrid cross?

    1:2:1, which equals the genotypic ratio because each genotype has a distinct phenotype (e.g., 1 red : 2 pink : 1 white).

11. What is epistasis (gene interaction)?

    Epistasis is an interaction in which an allele at one gene locus masks or modifies the phenotypic expression of alleles at a different (non-allelic) gene.

12. What modified dihybrid ratio results from recessive epistasis, and from dominant epistasis?

    Recessive epistasis: 9:3:4; Dominant epistasis: 12:3:1 (from the standard 9:3:3:1).

13. List the modified F2 dihybrid ratios for duplicate dominant, duplicate recessive, and dominant-recessive (inhibitory) epistasis.

    Duplicate dominant genes: 15:1; Duplicate recessive (complementary) genes: 9:7; Dominant-recessive (inhibitory) epistasis: 13:3.

14. What is pleiotropy?

    Pleiotropy is the phenomenon in which a single gene affects multiple, seemingly unrelated phenotypic traits. Example: sickle-cell allele affecting anemia, malaria resistance, and organ damage.

15. What is genomic imprinting?

    Genomic imprinting is parent-of-origin-dependent gene expression in which a gene is silenced (via DNA methylation) depending on whether it was inherited from the mother or father, so only one parental allele is expressed.

16. Name two human disorders caused by genomic imprinting at chromosome 15q11-q13.

    Prader-Willi syndrome (loss of paternal expression) and Angelman syndrome (loss of maternal expression).

17. Define penetrance.

    Penetrance is the proportion of individuals with a given genotype that actually express the associated phenotype (e.g., 80% penetrance = 80% of carriers show the trait).

18. Define expressivity.

    Expressivity is the degree or intensity to which a given genotype is phenotypically expressed in individuals who do show the trait (variable expressivity = trait varies in severity).

19. What is a phenocopy?

    A phenocopy is an environmentally induced phenotype that mimics a phenotype normally produced by a specific genotype, but is not heritable. Example: rickets (vitamin D deficiency) mimicking genetic vitamin-D-resistant rickets.

20. What is genetic linkage?

    Linkage is the tendency of genes located close together on the same chromosome to be inherited together because they do not assort independently, producing more parental than recombinant gametes.

21. What is crossing over and when does it occur?

    Crossing over is the reciprocal exchange of genetic material between non-sister chromatids of homologous chromosomes at chiasmata during pachytene of prophase I of meiosis, producing recombinant chromosomes.

22. How is recombination frequency related to genetic map distance?

    1% recombination frequency = 1 map unit = 1 centimorgan (cM). Map distance (cM) = (number of recombinant offspring / total offspring) x 100, valid for closely linked genes.

23. Why does recombination frequency saturate at 50% for distant genes?

    With multiple crossovers between far-apart loci, even and odd numbers of exchanges cancel out, so the genes assort as if unlinked; observed recombination cannot exceed 50%, underestimating true map distance.

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