Variations on a Theme
Species
Characteristics
What
characteristics
are
Shared by each
of these
Species?
Individual
characteristicsmake a person
unique
Although your genes carry your
master plan there are
other factors
that
make
you
YOU!
Like What?
Environment
Spiritual life
GeneticsThe Study of Heredity
Genes
A section of DNA that codes for
a particular trait
(the recipe for
a protein)
Chromosomes
Threadlike structures composed of DNA
and proteins found in the nucleus of the
cell.
• Chromatid- one of the
identical halves of the
chromosome
• Centromereconstricted area
where chromatids are
joined
Homologous Pairs and
Homologues
MITOSIS
MEIOSIS
• Diploid- has two of
each chromosome2n- product of mitosis
• Haploid- 1 of each
chromosome- 1nproduct of meiosis
Humans have 46 chromosomes
or 23 pairs of chromosomes
Fruit Flies
8 chromosomes or 4
pairs
Goldfish
• 100
chromosomes
or 50 pair
Crayfish
• 200
chromosomes
or 100 pair
Lilies, Tomatoes, White Pines
• All have 24
chromosomes or 12
pair
• It’s not the
chromosome number
that determines the
species but the genes
on the chromosomes
What is a Karyotype?
•
• A photograph or
stained,
separated and
sorted
chromosomes
How many chromosomes would there be in
a human diploid cell? A haploid cell?
Haploid cells are for
reproduction
What is the difference between a
gene and a chromosome?
Cell Division
And the Cell Cycle
What is the cell cycle?
The life cycle of a cell
Interphase
Mitosis
Cytokinesis
Mitosis
• The division of a cell
to produce two
identical daughter
cells
Interphase
•Chromosomes are copied
•Appear as “threadlike”coils
(chromatin)at the start, but
each chromosome and its
copy (sister chromosome)
change to sister
chromatids at end of
this phase.
•Chromatid
Prophase
•Mitosis begins
•Centrioles appear
•Spindle fibers
form between
the poles
Metaphase
•Chromatids attach
to spindle fibers in
center
Anaphase
•Chromatids separate
and begin to move to
opposite sides of the
cell
Telophase
•Two nuclei form
•Chromosomes appear as
chromatin (threads rather
than rods
•Mitosis ends
Cytokinesis
•Membrane moves inward to create
two daughter cells with identical
chromosomes
Uses of Mitosis
• Growth
• Repair and replace old or damaged cells
• Asexual reproduction
Forming Gametes for Sexual Reproduction
MEIOSIS
Who discovered mitosis?
Van Beneden
Studying Ascaris
Meiosis Vocabulary
• Zygote- a diploid cell
formed by the union
of a haploid sperm
and egg
• Meiosis- the forming
of sexual gametes by
reducing the number
of chromosomes from
diploid to haploid
through two divisions.
Meiosis- two divisions
• 1st division reduces
the # of
chromosomes from
diploid to haploid
• 2nd division doubles
the number of cells
Meiosis
Comparison of Mitosis and Meiosis
Compare:
Mitosis Metaphase
Meiosis I Metaphase
Compare
Mitosis Anaphase
Meiosis I Anaphase
Compare:
Mitosis
Meiosis
Purpose of Meiosis
• To form gametes
for sexual
reproduction
Meiosis Vocabulary
• Gameteshaploid cells
that, when
united, form a
diploid zygoteex. sperm, eg
Meiosis Vocabulary
• Fertilization- the process of forming a
zygote
Meiosis Vocabulary
• Spermmale
gamete
• Eggfemale
gamete
Meiosis Vocabulary
Forming of Sperm
Forming of Eggs
Meiosis Vocabulary
• Sexual
Reproduction-The
fertilization (union)
of haploid gametes
to produce
offspring that are
not genetically
identical to either
parent