This document summarizes the packaging of DNA in the cell nucleus. It describes the four orders of DNA packaging: nucleosomes, solenoid fibers, chromatids, and chromosomes. DNA is wrapped around histone proteins to form nucleosomes, which coil to form solenoid fibers. Further coiling of fibers forms chromatids, which condense and loop to form fully packaged chromosomes. This packaging allows the long DNA molecule to tightly fit within the nucleus.

1. SHRI SHANKARACHARYA
MAHAVIDAYALAYA
JUNWANI,BHILAI
SEMINAR ON
DNA PACKAGING
Dr.Rachana choudhary
Astt.Professor-

2. SYNOPSIS
 INTRODUCTION
 NEED FOR PACKAGING
 PACKAGINGOF DNA INTO NUCLEUS
 ORDER OF PACKAGING
 1ST ORDER- NUCLEOSOME
proteins involved in packaging
components of nucleosome
 2ND ORDER-SOLENOID FIBER
 3RD ORDER-CHROMATIDS
 4TH ORDER-CHROMOSOME
 CONCLUSION
 REFERENCE

3. INTRODUCTION
 DNA is the only components of
chromosome which acts as a
heredity materials.
 The most important property
of DNA is super coiling .
 DNA is condensed in to a
complex structure with Histone
& Non-histone proteins .
 DNA is wrapped around a core
of histone molecule and non-
histone are some how
associated with that complex.

4. NEED FOR PACKAGING
 Packaging here refers to the condensing of
DNA to fit easily into the nucleus.
 Process of packaging differs in prokaryotes
and eukaryotes.
 In prokaryotes the chromosomes are present
freely in the cytoplasm hence packaging is
not required.
 in eukaryotes DNA is packaged as follows:-

5. PACKAGING OF DNA INTO NUCLEUS
 The length of DNA in the nucleus is far
greater than the size of the compartment in
which it is contained
 Condensation of DNA is necessary to fit into
the nuclear compartment.

6. ORDERS OF PACKAGING
 There are various order
of packaging:
 1ST order of packaging-
Nucleosome
 2ND order of packaging-
Solenoid fiber
 3RD order of packaging-
Chromatid
 4TH order of packaging-
Chromosome

7. NUCLEOSOME
 It is the fundamental
repeating subunit of
Eukaryotic chromatin.
 Made up of chromosomal
proteins, histones & non
histones

8. CHROMOSOMAL PROTIENS

10. COMPONENTS OF NUCLEOSOME
 CORE PARTICALS –It is consist
of 146 base pair of DNA wrapped 1.8 times
in left handed helix .
 CHROMATOSOME-The core
particle interact with one molecule of
histone H1 to from a particle containing
approx 166 base pair of DNA called
chromatosome.
 NUCLEOSOME-links with
the linker DNA forming a nucleosome
containing approx 200 base pair of DNA.

11. SOLENOID FIBER
 The coiling of beads in helical structure is
called 30 nm fiber. found in inter phase
chromatin & mitotic chromosome.
 Inter phase chromosome have a diameter of
300 nm coiled metaphase chromosome have
diameter of 700 nm.

12. CHROMATID
 The condensed piece of chromatin has a
characteristic scaffolding structure that can
be detected in metaphase chromosome.
 Chromatid forms as a result of extensive
looping of the DNA in the chromosome.

13. CHROMOSOME
 Final packaging of chromosomes occurs by
looping & scaffolding.
 Chromatid fibers condensed & gets packaged
& forms chromosome.
 Final packaging ratio is 1000 nm in inter
phase & 10000 nm in mitotic chromosome.

15. ROLE OF SMC PROTIENS
 Condensin helps in
condensation of DNA
in metaphase when
DNA enters
metaphase.

16. CONCLUSION
 Packaging is a characterstic feature of
Eukaryotic chromosomal organization.it
involves various orders like formation of
nucleosome, solenoid fiber & then
chromosomes.

17. REFERENCE
PRINCIPLES OF BIOCHEMISTRY BY-NELSON
and COX.
MOLECUCLAR BIOLOGY BY – KARP.
MOLECULAR BIOLOGY BY-B.D.SINGH.

18. THANKS