Download Making Genetically-Identical Cells The Somatic Cell Cycle

What is a clone?
Making Genetically-Identical Cells
A clone is a set of genetically identical individuals.
Cells reproduce by splitting in two.
Are clones unnatural?
! To make genetically-identical cells we have to:
No. Some organisms, like many microorganisms, naturally reproduce clonally.
Human clones are also naturally-occurring--we call them identical twins.
(1) Replicate the DNA How do we do this? DNA Replication
How long have humans been able to clone other organisms?
• We’ve been able to clone plants for thousands of years.
• We’ve been able to clone microorganisms for hundreds of years.
• We’ve been able to clone amphibians (frogs) for roughly 100 years.
• We’ve been able to clone mammals from adult cells since 1996.
(2) Separate the replica copies of DNA
correctly into the two new cells.
The Somatic Cell Cycle (Figure 2.14)
Preparation for division
MITOSIS
How do we do this?
Replicated Chromosome (Figure 2.15a)
Paternal
Brown Hair
Allele
Nuclear division
Maternal
Blonde Hair
Allele
One Chromosome
= one DNA molecule
DNA Replication
DNA Replication
Homologous Pair of
Chromosomes
Cell division
Cell growth and maturation
One Homologous Pair
Still
Chromosome
ofOne
Chromosomes
Centromere
Sister Chromatid Sister Chromatid
This specific
location on this
specific chromosome
is a hair color
GENE.
Prophase (Figure 2.16)
• Replicated chromosomes
condense.
• Microtubules organize
into a spindle
Metaphase (Figure 2.16)
•
Chromosomes line up on the
metaphase plate.
•
Spindle microtubules are
attached to centromeres of
chromosomes.
• Nuclear membrane
disintegrates.
Anaphase (Figure 2.16)
•
Centromeres of sister
chromatids separate
•
Chromosomes move to opposite
ends of the cell
Telophase (Figure 2.16)
•
Nuclear membranes form
•
Spindle disappears
•
Division of cytoplasm occurs
(cytokinesis)
Cytokinesis (Figure 2.16)
The Somatic Cell Cycle (Figure 2.14)
Nuclear division
Cytoplasmic division
occurs after nuclear
division is complete.
Preparation for
division
DNA Replication
Two cells are formed.
Cell growth and
maturation
How are genes inherited?
Each person has 46 chromosomes. Half of these (23) come from mom (in an
egg). The other half come from dad (in a sperm).
• Each parent provides a specific set of 23 chromosomes (not just any
random 23)--one Chr1, one Chr2, one Chr3, and so on.
The specialized nuclear and cell division that produces sperm and egg is called
MEIOSIS.
Meiosis I (Figure 3.4)
Cell division
Crossing-Over (Figure 3.5)
Meiosis II (Figure 3.4)
Occurs during Prophase I
Physical exchange of parts between
HOMOLOGOUS CHROMOSOMES.
Result: New combination of alleles along a
chromosome. So, if this occurs in the
production of a sperm, a baby born from
this sperm will have alleles FOR THIS
ONE CHROMOSOME from both paternal
grandparents.
Table 3.1
Male Reproductive System (Figure 3.1)
Spermatogenesis I (Figure 3.7)
Spermatogenesis II (Figure 3.8)
Spermatogenesis begins at puberty and continues throughout life.
Sperm Anatomy (Figure 3.9)
Not part of material
that fertilizes the
ovum.
Female Reproductive System (Figure 3.2)
Oogenesis I (Figure 3.11)
Oogenesis II (Figure 3.12)
Oogenesis begins during embryonic development and stops after Meiosis I. A girl is
born with about 250,000 primary oocytes. After puberty, one oocyte per month
typically erupts from the ovary. If this oocyte is fertilized, then Meiosis II will occur.
Fertilization (Figure 3.13a)
Initial Stages of Human Development (Figure 3.14)