GATE Biotechnology Genetics, Cellular and Molecular Biology Syllabus

Genetics, Cellular and Molecular Biology syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Genetics, Cellular and Molecular Biology in GATE Biotechnology, not a summary of it.

1. 1

   Genetics and Evolutionary Biology

   14 topics

   • Mendelian inheritance
   • Gene interaction
   • Complementation
   • Linkage, recombination and chromosome mapping
   • Extra chromosomal inheritance
   • Microbial genetics
     • Transformation
     • Transduction
     • Conjugation
     • Horizontal gene transfer
     • Transposable elements
   • Chromosomal variation
   • Genetic disorders
   • Population genetics
   • Epigenetics
   • Selection and inheritance
   • Adaptive and neutral evolution
   • Genetic drift
   • Species and speciation
2. 2

   Cell Biology

   8 topics

   • Prokaryotic and eukaryotic cell structure
   • Cell cycle and cell growth control
   • Cell-cell communication
   • Cell signalling and signal transduction
   • Post-translational modifications
   • Protein trafficking
   • Cell death and autophagy
   • Extra-cellular matrix
3. 3

   Molecular Biology

   7 topics

   • Molecular structure of genes and chromosomes
   • Mutations and mutagenesis
   • Regulation of gene expression
   • Nucleic acid
     • Replication
     • Transcription
     • Splicing
     • Translation
     • Regulatory mechanisms
   • Non-coding and micro RNA
   • RNA interference
   • DNA damage and repair

Genetics, Cellular and Molecular Biology flashcards for GATE Biotechnology

25 of 50 cards from the Genetics, Cellular and Molecular Biology deck — real questions with worked answers.

1. State Mendel's Law of Segregation.

   Each diploid organism carries two alleles for a trait, and during gamete formation the two alleles separate (segregate) so that each gamete receives only one allele. The pair is restored at fertilization.

2. State Mendel's Law of Independent Assortment.

   Alleles of different genes assort independently of one another during gamete formation, producing all possible allele combinations in equal frequency. This holds only for genes on different chromosomes (or far apart on the same chromosome).

3. In a monohybrid cross ($Aa \times Aa$), what are the genotypic and phenotypic ratios in the $F_2$ generation?

   Genotypic ratio $1\,AA : 2\,Aa : 1\,aa$; phenotypic ratio $3$ dominant $: 1$ recessive.

4. In a dihybrid cross ($AaBb \times AaBb$), what is the classic $F_2$ phenotypic ratio?

   $9 : 3 : 3 : 1$ (9 both dominant : 3 dominant A/recessive b : 3 recessive a/dominant B : 1 both recessive).

5. What is a test cross and why is it used?

   A cross of an individual showing the dominant phenotype with a homozygous recessive ($aa$) individual. It reveals the unknown genotype: a $1:1$ ratio of offspring indicates heterozygosity ($Aa$), while uniform dominant offspring indicate homozygosity ($AA$).

6. Define incomplete dominance and give its $F_2$ ratio.

   Heterozygotes show an intermediate phenotype between the two homozygotes (e.g., red $\times$ white snapdragons giving pink). The $F_2$ phenotypic ratio is $1:2:1$, matching the genotypic ratio.

7. Define codominance with an example.

   Both alleles are fully and simultaneously expressed in the heterozygote, with neither masked. Example: the ABO blood group AB phenotype, where both $I^A$ and $I^B$ antigens appear; also the MN blood group.

8. What is epistasis?

   A form of gene interaction in which one gene (the epistatic gene) masks or modifies the phenotypic expression of another gene (the hypostatic gene) at a different locus.

9. What $F_2$ dihybrid ratio results from recessive epistasis, and give an example?

   $9:3:4$. Example: coat color in mice/Labrador retrievers where homozygous recessive at one locus ($cc$) masks the other gene, producing albino/yellow regardless of the second locus.

10. What $F_2$ dihybrid ratio characterizes dominant epistasis?

    $12:3:1$, where a dominant allele at one locus masks the expression of alleles at the second locus (e.g., fruit color in summer squash).

11. What $F_2$ ratio results from duplicate recessive epistasis (complementary gene action)?

    $9:7$ — both dominant alleles (one from each gene) are required to produce the phenotype; absence of either gives the recessive phenotype. Classic example: flower color in sweet peas.

12. What is the complementation test and what does it determine?

    A genetic test that crosses two recessive mutants showing the same phenotype to determine whether the mutations lie in the same gene or different genes. Wild-type offspring = complementation = mutations in different genes; mutant offspring = no complementation = same gene.

13. Why do two mutations in the same gene fail to complement?

    Because neither homologous chromosome carries a functional copy of that gene; both alleles are defective, so no functional product is made and the mutant phenotype persists in the heterozygote.

14. Define genetic linkage.

    The tendency of genes located close together on the same chromosome to be inherited together because crossing over rarely separates them, causing deviation from independent assortment.

15. What is recombination frequency and how is it calculated?

    The proportion of recombinant offspring among total offspring: $$RF = \frac{\text{number of recombinant offspring}}{\text{total offspring}} \times 100\%$$ It estimates the genetic distance between two loci.

16. What is a map unit (centimorgan) in chromosome mapping?

    One map unit (1 centimorgan, cM) equals a recombination frequency of $1\%$. It defines genetic distance between linked genes; $1\ \text{cM} = 1\%$ recombinants.

17. What is the maximum recombination frequency observed, and why?

    $50\%$. Genes that are very far apart on the same chromosome (or on different chromosomes) recombine so frequently they appear unlinked, behaving as if independently assorting; RF cannot exceed $50\%$.

18. In a three-point test cross, how do you identify the gene in the middle?

    Compare the parental (most frequent) class with the double-crossover (least frequent) class. The gene whose allele has switched position between these two classes is the middle gene.

19. What is interference and the coefficient of coincidence?

    Interference is the phenomenon where one crossover reduces the likelihood of a second nearby crossover. $$C.o.C. = \frac{\text{observed double crossovers}}{\text{expected double crossovers}}, \quad I = 1 - C.o.C.$$

20. Define extrachromosomal (cytoplasmic) inheritance.

    Inheritance of traits controlled by genes located outside the nucleus, in organelles such as mitochondria and chloroplasts. It shows non-Mendelian, typically maternal, inheritance patterns.

21. Why is mitochondrial inheritance typically maternal?

    The egg contributes nearly all the cytoplasm (and thus the mitochondria) to the zygote, while sperm mitochondria are usually excluded or degraded. Hence offspring inherit mtDNA from the mother only.

22. What is the classic example of chloroplast (plastid) inheritance studied by Carl Correns?

    Variegation (leaf color) in four-o'clock plant (Mirabilis jalapa), where green/white/variegated phenotypes are inherited maternally through the plastids of the egg cytoplasm.

23. What is bacterial transformation?

    The uptake of free (naked) DNA from the surrounding environment by a competent bacterial cell, leading to genetic change. Demonstrated by Griffith (1928) and confirmed as DNA by Avery, MacLeod, and McCarty (1944).

24. What is bacterial transduction?

    The transfer of bacterial DNA from a donor to a recipient cell via a bacteriophage (virus). It is divided into generalized and specialized transduction.

25. Distinguish generalized from specialized transduction.

    Generalized transduction: any bacterial gene can be transferred because random host DNA fragments are mistakenly packaged into phage during the lytic cycle. Specialized transduction: only genes adjacent to the prophage integration site are transferred, due to faulty excision of a lysogenic prophage.

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