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Introduction to the human
genome
The Human Genome
Humans are diploid- the genome sequence is divided into 23 pairs of
chromosomes
If the DNA in 1 cell is stretched out it would be 2m in length
Human Genome Packaging
Chromosomes packing in eukaryotic cells
DNA wraps around nucleosomes- they are primarily made of histones (2xH2A,
H2B, H3, and H4)
Nucleosomes coil further into a come compact fiber (-30 nm in diameter) (H1
stabilisation)
Looped domains coil and fold further, producing thicker chromatid fibres
Metaphase chromosomes in the highest level of condensation (during mitosis
or meiosis)
Introduction to the human genome 1
, DNA complexed with various proteins to form chromatin that undergoes
various levels of coiling and compaction
In interphase, chromosome can be in 2 states:
-Euchromatin: most chromosomes are uncoiled and highly extended and loose
in a state that allows gene expression
-Heterochromatin: Tightly packed transcriptionally silent form of chromatin
that often contains repetitive DNA elements including centromere and
telomere DNA
In cells about to undergo division, chromatid attached at centromeres, become
tightly condensed, and as a result genes cannot be expressed
Introduction to the human genome 2
Introduction to the human
genome
The Human Genome
Humans are diploid- the genome sequence is divided into 23 pairs of
chromosomes
If the DNA in 1 cell is stretched out it would be 2m in length
Human Genome Packaging
Chromosomes packing in eukaryotic cells
DNA wraps around nucleosomes- they are primarily made of histones (2xH2A,
H2B, H3, and H4)
Nucleosomes coil further into a come compact fiber (-30 nm in diameter) (H1
stabilisation)
Looped domains coil and fold further, producing thicker chromatid fibres
Metaphase chromosomes in the highest level of condensation (during mitosis
or meiosis)
Introduction to the human genome 1
, DNA complexed with various proteins to form chromatin that undergoes
various levels of coiling and compaction
In interphase, chromosome can be in 2 states:
-Euchromatin: most chromosomes are uncoiled and highly extended and loose
in a state that allows gene expression
-Heterochromatin: Tightly packed transcriptionally silent form of chromatin
that often contains repetitive DNA elements including centromere and
telomere DNA
In cells about to undergo division, chromatid attached at centromeres, become
tightly condensed, and as a result genes cannot be expressed
Introduction to the human genome 2
