Download 4.1 Le Noyau

4.1 The nucleus
A trait- particular feature
The nucleus
• Responsible for heredity and for
controlling the functions of the cell.
• heredity = the process through which
patterns of traits are pased on from an
individual to it offspring
• Information in the nucleus determines your
traits
• This information also determines:
– The type of cell
– Its function
– Its growth
– When it will divide( reproduce)
– When it will die
DNA
• Deoxyribonucleic
acid
Made of 4 nitrogen
bases
Adenine(A)
Thymine (T)
and
Cytosine (C)
Guanine (G)
• Everything that occurs within a cell is the
result of how the bases on the DNA
molecule are arranged.
• A joins with T
• G joins with C
• But the order and number of these bases
can vary greatly within the DNA molecule
• When a cell is ready
to divide, each strand
of loosely coiled DNA
folds up further into a
very compact, xshaped structure
called a
chromosome.
• Each organism
has a specific
number of
chromosomes.
• Humans have
46
chromosomes
arranged in 23
pairs.
20
60
78
80
44
Genes are small
segments of
DNA located at
specific places
on the
chromosome.
The difference between a gene and
a chromosome?
• Genes can be composed of hundreds or
thousands nitrogen bases.
• Produces a particular trait.
• Each chromosome is made up of
thousands of genes.
• Therefore, can produce thousands of
traits.