5. What is the difference between
fraternal and identical twins?
6. Do Now
What is mitosis?
What is meiosis?
List 2 differences between the two?
7. Let’s define the following
words…
Meiosis:
Sexual
Gamete:
Sex
reproduction-production of gametes
Cells (egg and sperm) haploid
Somatic Cells:
Body
Cells - diploid
8.
Haploid:
Half
the chromosome number (n)
1 of each pair of chromosomes (23)
Diploid:
2
of each type of chromosome (2n)
Twice the haploid number
Fertilization:
Sperm
enters egg
Zygote:
Fertilized
egg (diploid)
9. Chromosomes and Chromosome
Number
Human body cells have 46 chromosomes
Each parent contributes 23 chromosomes
Homologous chromosomes —one of
two paired chromosomes, one from each
parent
13. Meiosis
The sexual life cycle
in animals involves
meiosis
Meiosis produces
gametes.
When gametes
combine in
fertilization, the
number of
chromosomes is
restored.
19. Prophase I
Pairing of homologous chromosomes
occurs. (Synapsis)
Each chromosome consists of two
chromatids.
The nuclear envelope breaks down.
Spindles form
20. Prophase I (cont.)
Crossing over produces exchange
of genetic information.
Crossing over —chromosomal
segments are exchanged between
a pair of homologous
chromosomes.
32. Genetic Variability
Depending on how the
chromosomes line up at the
equator, four gametes with
four different combinations of
chromosomes can result
(independent assortment).
Genetic variation also is
produced during crossing
over
Random fertilization.
37.
Think – Pair - Share
Draw out the stages of meiosis using the
following cell. Make sure you draw the cell with
crossing over of only one pair of homologous
chromosomes! (use colored pencils)
38. Do Now – Period 3
How many
autosomes?
How many sex
chromosomes?
What is the sex of
this patient?
Monosomy,
Trisomy?
Is this individual
normal?
39. Do Now
Match the description to the phase of meiosis.
1. Sister Chromatids are pulled
apart. _____
A. Prophase I
2. Homologous chromosomes line
up in the middle of the cell._____
B. Metaphase I
3. 2 daughter cells are formed ____ C. Telophase I
4. Nuclear membrane disappears__ D. Anaphase II
5. Nuclear membrane reforms
around 4 cells ____
E. Anaphase I
6. Homologous chromosomes are
pulled apart ____
F. Telophase II
41. THINK – PAIR - SHARE
If a hamster has 44 chromosomes in G1
phase of the cell cycle, then…
How
many chromatids are in G2 Phase?
How many chromosomes are in the G2
Phase?
How many chromosomes will be in each cell
after it has gone through mitosis?
42. Do Now
What two divisions do your cells undergo?
What are the differences between the
two?