Transcript Chapter 4 Heredity and Evolution

Chapter 4
Heredity and Evolution
Review…
DNA


DNA is found in the
nucleus of cells,
organized into singlestranded chromosomes,
and tells the cell how to
function and what type
of cell it’s supposed to
be (i.e. liver cell, hair cell,
skin cell, bone cell, etc.)
DNA is made of
nucleotides (a sugar, a
phosphate and one of
four nitrogenous bases)
Review…
How DNA gets copied
Every cell must contain
the genetic information
and the DNA is therefore
duplicated before a cell
divides (replication)
 After the DNA replicates
inside the cell’s nucleus,
it must get it’s message
outside the nucleus…
…through the goopy
cytoplasm of the cell…
…and into the Ribosomes!
 RNA

Cytoplasm
Nucleus
DNA
Ribosomes
Review…
Genes and Chromosomes


A chromosome is
composed of a DNA
molecule and
associated proteins.
A gene is the entire
sequence of DNA
bases responsible for
the synthesis of a
protein.
Review…
Genes


Exons are the only
parts of genes that are
expressed in an
individual.
People also have
Introns in their genes,
copied faithfully
copied by the mRNA
that are later clipped
out and not expressed
for some reason not
yet known.
Review…
Chromosome Structure
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During normal cell
functions, chromosomes
exist as single-stranded
structures.
During cell division,
chromosomes consist of
two strands of DNA
joined at the
centromere.
Since the DNA
molecules have
replicated, one strand
of a chromosome is an
exact copy of the
other.
Review…
Mitosis
 Mitosis
is cell division in somatic cells.
 Mitosis occurs during growth and
repair/replacement of tissues.
 The result of mitosis is two identical
daughter cells that are genetically
identical to the original cell.
 Here’s the steps…
Review…
Mitosis
 The
cell is involved in
metabolic activities.
 DNA replication
occurs, but
chromosomes are not
visible.
Review…
Mitosis
 The
nuclear
membrane
disappears, and
double-stranded
chromosomes are
visible.
Review…
Mitosis
 The
chromosomes
align themselves at
the center of the
cell.
Review…
Mitosis
 The
chromosomes
split at the
centromere, and
the strands
separate and
move to opposite
ends of the
dividing cell.
Review…
Mitosis
 The
cell membrane
pinches in as the cell
continues to divide.
 The chromosomes
begin to uncoil
(below).
Review…
Mitosis
 After
mitosis is
complete, there are
two identical
daughter cells.
 The nuclear
membrane is
present, and
chromosomes are
no longer visible.
Review…
Meiosis
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Cell division in
specialized cells in
ovaries and testes.
Meiosis involves two
divisions and results in
four daughter cells,
each containing only
half the original
number of
chromosomes.
These cells can
develop into
gametes.