Shirabh Botany classes

Correct for "Golden Rice" 🌾
A. Rice with B - carotene
B. Yellow in colour
C. It is GM rice

#PGT Biology
#assistant professor botany

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Shirabh Botany classes

In which era were gymnosperms dominant?

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Shirabh Botany classes

1 year ago | [YT] | 8

Shirabh Botany classes

The term biostystematics was introduced by

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Shirabh Botany classes

Traget CUET-PG Botany 2026
Agr aap log chahte ki sabhi unit channel per cover ki jaye ager yes to comment kre
‪@YouTube‬
‪@cuetPG‬

1 year ago (edited) | [YT] | 10

Shirabh Botany classes

Learn about Blue - White Screening

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Shirabh Botany classes

Name the enzyme of TCA cycle which uses FAD as a cofactor

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Shirabh Botany classes

Here are 25 important points on DNA replication, relevant for CUET PG Botany, Zoology, and Life Science:

Basic Concept

Definition: DNA replication is the process of making an identical copy of DNA before cell division.

Semi-Conservative: Each daughter DNA consists of one parental and one newly synthesized strand (proposed by Watson and Crick).

Experiment: Meselson and Stahl (1958) confirmed the semi-conservative nature using N¹⁵ and N¹⁴ isotopes of nitrogen.

Enzymes Involved

Helicase: Unwinds the DNA helix by breaking hydrogen bonds.

Topoisomerase (Gyrase in Prokaryotes): Relieves supercoiling tension ahead of the replication fork.

Single-Strand Binding Proteins (SSBs): Prevent reannealing of separated strands.

Primase: Synthesizes a short RNA primer for DNA polymerase to initiate replication.

DNA Polymerase: Adds nucleotides in a 5' → 3' direction.

Prokaryotes: DNA Polymerase I, II, III

Eukaryotes: DNA Polymerase α, β, δ, ε, γ

DNA Ligase: Joins Okazaki fragments on the lagging strand.

Telomerase: Extends the 3' overhang in eukaryotic chromosomes to prevent telomere shortening.

Replication Process

Origin of Replication (Ori site): Starting point of DNA replication.

Prokaryotes: One origin (OriC in E. coli).

Eukaryotes: Multiple origins per chromosome.

Replication Fork: Y-shaped structure formed during DNA synthesis.

Leading vs. Lagging Strand:

Leading Strand: Synthesized continuously (5' → 3').

Lagging Strand: Synthesized discontinuously in Okazaki fragments.

Okazaki Fragments: Short DNA segments (~1000–2000 bp in prokaryotes, ~100–200 bp in eukaryotes) on the lagging strand.

RNA Primer Removal:

Prokaryotes: DNA Polymerase I replaces RNA primers with DNA.

Eukaryotes: RNase H and DNA Polymerase δ.

Regulation & Proofreading

Proofreading by DNA Polymerase:

DNA Polymerase III (prokaryotes) and Polymerase δ/ε (eukaryotes) correct errors via 3' → 5' exonuclease activity.

Error Rate: DNA replication is highly accurate (~1 error per 10⁹ nucleotides).

Prokaryotic vs. Eukaryotic Replication

Speed: Prokaryotic replication is faster (~1000 nt/sec) than eukaryotic (~50 nt/sec).

Chromosomal Shape: Prokaryotic DNA is circular, eukaryotic DNA is linear.

Replication Time:

Prokaryotes: ~40 minutes (E. coli).

Eukaryotes: Several hours due to multiple origins.

Special Cases & Applications

Rolling Circle Replication: Used in plasmids and viruses (e.g., bacteriophage λ, F plasmid).

Mitochondrial DNA Replication: Uses DNA Polymerase γ (gamma).

End-Replication Problem: Telomere shortening in eukaryotic cells due to incomplete lagging strand replication.

Replication Blockers: Drugs like Aphidicolin (inhibits eukaryotic DNA polymerase α).

Clinical Relevance: Defects in DNA replication enzymes are linked to cancer (e.g., mutations in DNA Polymerase δ can cause genomic instability).

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Extensions to Mendelian principles

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Shirabh Botany classes

‍ Which of the following is regarded as the age of pteridophytes?

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