Bellringer 10.15
1. Put the following phases of cell division in the
correct order:
anaphase
telophase
metaphase
G2
G1
cytokinesis
S
prophase
2. Describe what occurs in each of the phases
above.
Bellringer 4/29
1. Describe the phases of meiosis.
2. How does meiosis differ from mitosis?
G1  S  G2  P  M  A  T  Cytokinesis
Sexual Reproduction
Sexual reproduction
• Uses genetic information from
more than one source
• Offspring are different from
parents (lots of variation because
of genetic recombination)
• May use gametes (sex cells)
Advantages
• When an environment is changing an organism
group (species) may be able to adapt because so
much variation
Disadvantages
• When an environment is stable, variation is not
as necessary
• Reproduction cannot occur as quickly as asexual
How are gametes made? ...
MEIOSIS
• Cell division that reduces the number of
chromosomes in half
• Makes haploid cells from diploid cells
• Produces gametes (sperm and egg)
Interphase
• Period of cell growth and chromosome
replication
• Precedes meiosis
Steps of Meiosis
Meiosis I
• 4 phases: P I, M I, A I, T I
Prophase I:
• Nucleolus and nuclear membrane fade, chromatin
condenses and becomes chromosomes
• Homologous chromosomes pair up (called
synapsis).
▫ Homologous chromosomes = chromosomes that
have the same type of genes (one from each parent)
During synapsis,
CROSSING OVER occurs
• Homologous
chromosomes cross over
each other
▫ Exchange of genetic
information
▫ Produces genetic
recombination, which
increases variations in
offspring
Metaphase I:
• Homologous chromosomes line up in center of
the cell
Anaphase I:
• Homologous chromosomes separate
Telophase I:
• Nuclear membrane reforms
RESULT: TWO haploid cells
Meiosis II:
• Separates the copied chromosomes
• 4 phases: P II, M II, A II, T II
• RESULT: FOUR haploid cells
PROPHASE II:
• Nuclear membrane and nucleolus disappear,
chromatin condenses into chromosomes, centrioles
appear
METAPHASE II:
• Chromosomes line up at center of cell
ANAPHASE II:
• Centromeres break at center of chromosomes,
chromosomes are divided into two chromatids;
chromatids are pulled to opposite poles of cell
TELOPHASE II:
• Nuclear membrane and nucleolus reappear,
chromosomes uncoil into chromatin
Trait
Mitosis
Chromosome
Number
Same (diploid) Half (haploid)
Genetic
Similarities
Same
Diverse
Type of Cell
Somatic cells
(any cell other
than
sperm/egg)
Sex cells (egg
& sperm)
Number of
Divisions
1(one)
I and II (two)
Type of
Reproduction
Asexual
Sexual
Role/Function Produce cells
for growth &
repair
Meiosis
Produce sex
cells
April 28, 2015
• Bellringer:
1. List the phases of mitosis in the correct
order and describe what occurs in each
phase.
• Read section 10.2 (pg 263) in the blue Biology
book.
• Answer section questions 1-4 (pg 273)
• Define the review and new vocabulary (pg 263)
TO TURN IN! 
Mendel’s Pea Plant Experiment Questions
1. If the round seed shape is dominant to the
wrinkled seed shape, what would the genotype
be of the parent plants in the P generation of
the cross between pure round seeds vs pure
wrinkled seeds? What are the possibilities of
genotypes in the F1 generation? F2
generation?
2. Repeat #1 the green/yellow cross,
purple/white cross, and the tall/short cross.
3. What is the ratio of:
1.
2.
3.
4.
Round : wrinkled
green : yellow
Purple : white
Tall : short