Download DNA cr.eu updated plg latest

The Presentation of Group 3…
Title:
Members of the group:
Muhammad Jefri bin Mohd Yusof (A 127205)
Noor Khairatul Azni binti Mat (A 127222)
Chai Lee Chin (A 129966)
Yosmetha Mayalvanan (A 126816)
Syamimi binti Haslan (A127285)
Nucleoid Structure of
Prokaryote….
• the chromosome also called
nucleoid
• lacks of a membrane enclosure
• supercoiling
• associated simple basic amino
acids influence the folding of DNA
molecule
Location of Nucleosome.
DNA
HISTONES
What is Nucleosome?
• The fundamental repeating units of
eukaryotic chromatin.
• It is used to pack the large eukaryotic
genomes into the nucleus.
• It is contain of
– DNA (strongly alkaline protein)
– Histone (nucleic acid that contains the
genetic instructions)
EUCHROMATIN
WHAT IS EUCHROMATIN?
• Euchromatin is a lightly packed
form of chromatin (DNA, RNA
and protein) that is rich in gene
concentration, and is often under
active transcription.
• Unlike heterochromatin, it is
found in both cells with nuclei
(eukaryotes) and cells without
nuclei (prokaryotes).
• Euchromatin comprises the most
active portion of the genome
within the cell nucleus
STRUCTURES OF EUCHROMATIN
• The structure of euchromatin is reminiscent of an
unfolded set of beads along a string, where in those
beads represent nucleosomes.
• Nucleosomes consist of eight proteins known as histone
with approximately 147 base pairs of DNA wound
around them; in euchromatin, this wrapping is loose so
that the raw DNA may be accessed.
• Each core histone possesses a `tail' structure, which
can vary in several ways; it is thought that these
variations act as "master control switches," which
determine the overall arrangement of the chromatin.
• In particular, it is believed that the presence of
methylated lysine 4 on the histone tails acts as a
general marker for euchromatin.
Another structure of the
Eukaryotic Chromosome…
• When the chromosomes of an organism such as wheat
or pine is dissected at the molecular level, stretches of
nucleotide sequence that occur once or only a few
times - including the genes - represent as little as 5% of
the DNA.
• Most plant and animal genomes consist largely of
repetitive DNA - perhaps 30 sequence motifs, typically
one to 10 000 nucleotides long, present many hundreds
or thousands of times in the genome, which may be
located at a few defined chromosomal sites or widely
dispersed.
• A major distinction between eukaryotic and prokaryotic
chromosomes is that eukaryotic chromosomes
contain vast amounts of DNA between the genes.
• Repetitive DNA, with different selective
pressures from those acting on genes and
evolutionarily successful multigene
modules, may show extensive differences
in sequence motifs and abundance even
between closely related species.
• The repetitive DNA in the genome is also
important for evolutionary, genetic,
taxonomic and applied studies.
• .
REPETITIVE DNA
FUNCTIONS
• A few repetitive sequences are known to have well
defined functions.
• The telomeric sequences, added at the ends of most
plant and animal chromosomes, allow a linear
replication unit to be maintained, protect
chromosome ends and overcome the 'end
replication problem'.
• Mobile DNA sequences - such as transposons and
retrotransposons - make up a high proportion of
most plant and animal genomes.
• A major class, the retroelements, encode the
proteins necessary for their own reverse
transcription and integration, and sometimes
represent 50% of the genome.
L1 Elements & Pseudogenes in
Mammalian DNA
• The two most abundant and best-characterized
middle-repetitive sequence families in
mammalian DNA are the short, interspersed
Alu1 repeats and the long, interspersed
repeated elements referred to as LINE or L1
elements.
• Alu-repeats. The majority of the middlerepetitive DNA in mammalian genomes
consists of numerous families of repeated
sequences that are only a few hundred base
pairs in length.
• One family of short, interspersed repeated
elements dominates this reiterated DNA
function.
• L1 elements : believed to be the only major
family of long, interspersed repeated
elements in primate DNA.
• The L1 family of dispersed repeated
sequences consists of largely of incomplete,
probably non-functional, processed
pseudogene-like copies together with a small
number transcriptionally-active elements.
• References:
‘Structure and function of repetitive DNA in
Eukaryotes’, article by Norman Hardman,
Department of Biochemistry, University of
Aberdeen.
Biochem J. (1986) 234, 1-11
Wikipedia.com