● The nucleus is surrounded by a double nuclear membrane that
contains pores, the pores form a passage between nucleus and
cytoplasm.
● The nucleus regulates structure and metabolism of the cell
● The nuclear membrane encloses the nucleoplasm
● The nucleolus is suspended in the nucleoplasm
● The mass of thread-like structures known as the chromatin network
can occur in the nucleus.
● When the cell divides, the chromatin network coils and thickens into
separate, shorter, thread like structures called chromosomes.
● Chromosomes are carriers of genetic information in the cell
, Nucleic acids
● Organic molecules that control the synthesis1 of proteins, by storing
and transferring genetic information.
● There are two types of Nucleic Acids that occur in living cells
1. DNA (deoxyribonucleic acid)
2. RNA (ribonucleic acid)
DNA
● Occurs mainly in the nucleus
● Forms part of chromatin network/chromosomes, this is known as
chromosomal DNA
● A small part of DNA occurs outside the nucleus, it's in the nucleus in
the mitochondria of plant and animal cells, as well as in the
chloroplasts for plants, this DNA is known as Extranuclear DNA, this
is DNA found outside the nucleus.
● DNA found in the mitochondria, is known as mitochondrial DNA, is
passed to child from mother, and thus used to trace maternal lines, it
also rarely goes under changes due to mutations. This is also known
as mtDNA.
1
the composition or combination of parts or elements so as to form a whole.
, Chromosomes and Genes
● Chromosomes are long thin structures that are made of DNA wrapped
around histones.
● A short segment of
DNA molecule that
Codes for a specific
Protein is called a
Gene
● Each gene carries a
Code for the synthesis of a specific protein.
● Proteins determine the structure and functioning of an organism
● thus a gene is a segment of DNA that controls an inherited
characteristic and determines the appearance and functioning of an
organism
● Chromosomes are only visible in a dividing cell 2
2
the division of a cell into two daughter cells with the same genetic material.
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