Write down and complete the data
table below
Types of
Reproduction
Sexual
Asexual
Advantages
•Allows for
genetic variation
•Can result in
better species
Disadvantages
•Requires partner
•Does not require
partner
•Does not allow for
•Generally faster
genetic variation
Through asexual
reproduction a
clone is produced.
Asexual
reproduction is
usually derived
by mitosis.
Parthenogenisis
Asexual Reproduction where the female
produces offspring from unfertilized eggs.
WHAT IS SEXUAL
REPRODUCTION?
TWO PARENTS GIVING RISE TO AN
OFFSPRING THAT IS A GENETIC MIX
OF THE PARENTS.
HUMAN LIFE CYCLE
The only
haploid cells
in humans
are the
gametes.
Angiosperm Life Cycle
Fungi Life Cycle
Union of the cytoplasm of the 2 parent mycelia
Haploid nuclei
contributed by the 2
parents fuse, producing
diploid cells
THREE TYPES OF LIFE CYCLES
Haploid and diploid cells may undergo mitosis but
only diploid cells will undergo meiosis
Each cycle of chromosome halving and doubling
contributes to genetic variation among offspring
Meiosis
A reduction division, followed by
fertilization ensures genetic diversity
in sexually reproducing organisms
Meiosis
• Makes gametes
• Reduces a diploid cell to form multiple haploid
cells.
– Each haploid cell is genetically different from the
other cells.
– Each haploid cell contains a mix of half of the
genetic information of the parent cell.
• Meiosis is divided into 2 divisions:
– Meiosis I and Meiosis II
Phases of Meiosis
• Step by step process where a diploid reproductive
cell produces 4 haploid daughter cells.
• First up is Interphase
– Same as the cell cycle
• Cell must divide 2 times in order to produce 4
haploid cells.
– The 1st meiotic division makes 2 cells & then each of
these cells divides during the 2nd meiotic division
producing the 4 cells total.
Meiosis 1
Homologous chromosomes
They are similar in shape & size
and the 2 chromosomes carry the
same genes.
n represents the number of
chromosomes in a haploid cell & 2n
for diploid cells.
Prophase I
=recombinant
chromosome
Homologous chromosomes cross overbreak & twist around each other; then
connect at each other’s initial position
Can occur 2 to 3 times between a pair of
homologous chromosomes depending on size
of chromosomes & position of centromeres
Metaphase I
WHAT’S DIFFERENT IN
THIS METAPHASE
COMPARED TO THE ONE
DURING MITOSIS?
WHAT DOES INDEPENDENT
ASSORTMENT MEAN?
Anaphase I
WHAT’S DIFFERENT IN
THIS ANAPHASE
COMPARED TO THE ONE
DURING MITOSIS?
Telophase I
AFTER CYTOKINESIS, WILL
THESE CELLS BE HAPLOID
OR DIPLOID? EXPLAIN
QUICK RE-CAP OF MEIOSIS I
Takes place in order to produce two cells
with a single set of chromosomes each.
Why don’t the cells go through interphase again before entering prophase II ?
Random Fertilization
• Adds to genetic variation arising from meiosis
– In humans, the fusion of a sperm and egg will produce
a zygote with any of about 64 trillion diploid
combinations.
WHERE IN MEIOSIS DOES GENETIC DIVERSITY OCCUR?
Sometimes chromosomes don’t separate the
way they are suppose to = non-disjunction
PLAY VIDEO
Nondisjunction (Trisomy 21) - An Animated Tutorial
Ex: Down’s Syndrome (aka Trisomy 21
Most common chromosome anomaly.
Affects 1 in 800 births
Non-disjunction can
happen with other
chromosomes & all
having a major impact
on a child’s
development
Other non-disjunction disorders
Patau’s Syndrome- Trisomy 13
Edward’s Syndrome – Trisomy 18
Turner’s SyndromeMonsomy X
Karyotypes
• A photograph of chromosomes found in a cell
(during metaphase of mitosis) arranged according
to size and shape.
• The shape depends largely on the location of
the centromere.
• The homologous pairs are place together.
• These are usually done on unborn fetuses to
determine any chromosomal anomalies.
Methods of obtaining cells for karyotyping
Amniocentesis
Chorionic villus sampling
Were these chromosomes taken from a male or female?
Is there any non-disjunction? Explain your answers
Were these chromosomes taken from a male or female?
Is there any non-disjunction? Explain your answers
Were these chromosomes taken from a male or female?
Is there any non-disjunction? Explain your answers
Were these chromosomes taken from a male or female?
Is there any non-disjunction? Explain your answers