Warm-Up / EOC Prep
1. The triplet code of bases for RNA may be
represented by all of the following except —
A. CGG
B. CGT
C. CGU
D. CGA
2. Which of these will complete the mRNA
strand matched to DNA?
A. AUG
B. CAG
C. GUC
D. UAC
Announcements
• Today & Tomorrow- Review
• Wednesday- EXAM 2
Mitosis vs. Meiosis Review Notes
• The cell cycle is a series of cellular growth and
division in the life of the cell.
• Stages:
• 1. G1-first growth, cell undergoes normal
activities and grows fast
• 2. S-Synthesis-DNA is copied (replicated)
• 3. G2-second growth, prepare for mitosis
• 4. M-Mitosis-division of the nucleus
• 5. Cytokinesis-division of the cytoplasm
• The cell cycle is regulated by proteins. W/o
this regulation it may result in cancer, the
uncontrolled growth of cells
• Mitosis is a form of asexual reproduction.
Mitosis includes one division that produces
two cells that are identical to one another and
to the parent. There is no crossing over and
no variation created because the cells are
identical.
• Mitosis includes four phases:
• 1. Prophase-chromosomes become visible and
the spindle forms
• 2. Metaphase-chromosomes move to the
center of the cell and line up along the
equator
• 3. Anaphase-centromeres divide and the two
chromatids move to opposite poles attached
to spindle fibers
• 4. Telophase-nuclear envelope forms around
the chromosomes at each pole, the
chromosomes uncoil, and the spindle
dissolves
• Meiosis is a form of sexual reproduction.
Meiosis includes two divisions that produce
four cells that are different from one another
and to the parent. There is crossing over and
variation created because the cells are
different.
• MEIOSIS CUTS THE CHROMOSOME NUMBER
IN HALF!
• Meiosis includes eight phases:
• Prophase I-crossing over occurs-chromosomes
become visible and the spindle forms
• Metaphase I-chromosomes move to the center of
the cell and line up along the equator
• Anaphase I-centromeres divide and the two
chomosomes move to opposite poles attached to
spindle fibers
• Telophase I-nuclear envelope forms around the
chromosomes at each pole, the chromosomes
uncoil, and the spindle dissolves
•
•
•
•
Prophase II
Metaphse II
Anaphse II
Telophase II
• The spindle fibers are the hairs that pull the
chromosomes apart. These spindle fibers are
made by organelles called centrioles.
Chromosomes (DNA wrapped in proteins) are
made up of two identical sister chromatids.
These chromatids are held together at the
center by the centromere.
• Cytokinesis, or the division of cytoplasm,
follows mitosis to split the cells in half.
Cytokinesis in animals occurs by pinching the
cytoplasm, while cytokinesis in plants occurs
by forming a cell plate between the two
nuclei. This cells plate will later become the
cell wall.
Mitosis
Meiosis
Asexual or Sexual?
Asexual
Sexual
Number of divisions
1
2
Number of cells formed
2
4
Identical or different from
parent
Crossing over?
Identical
different
No
Yes
Genetic variation?
No
Yes
• Combining the sperm and egg together is
called fertilization. A fertilized egg is called a
zygote.
• Fertilization: Sperm+Egg = zygote
• The gametes (reproductive cells-sperm and
egg) are formed during gametogenesis.
• Four sperm are produced during
spermatogenesis and one egg and three polar
bodies are produced during oogenesis.
• Write:
• Gametogenesis: forms gametes (egg/sperm)
– Spermatogenesis-> 4 sperm
– Oogenesis-> 1 egg + 3 polar bodies
• The chromosome number must be cut in half
to make the sperm and egg haploid (N) cells.
All other body cells are diploid (2N) because
they contain a full set of chromosomes.
• Haploid (N) half the chromosome #, sex cells
• Diploid (2N) full chromosome #, body cells
• There are 23 pairs of chromosomes-46 in
total. Each pair is made up of one
chromosome from mom and one from dad.
• Examples:
• a frog cell starts meiosis with 30
chromosomes, how many will be in the
gametes? 15
• A liver cell starts mitosis with 40
chromosomes, how many will be in each of
the daughter cells? 40
Review
• When does crossing over occur?
• Prophase I of meiosis
• In which stage of mitosis do the chromosomes
line up at the equator?
• Metaphase
• How many cell divisions and cells are
produced in meiosis?
• 2 cell divisions-four cells produced
• If an organisms has 40 chromosomes in their
body, how many are found in the gametes?
• 20
• If 10 chromosomes are found in the body
cells, how many are found in the gametes?
• 5
• Mit/Mei/CC Worksheet
Genetics Review Questions
• 10 minutes- complete them on your own first
• 10 minutes- discuss with your table partner
and decide on an answer
• 5 minutes- which ones were hard and why?
• BINGO
• Clean-up
• Cool-Down
• Study hard tonight