How do we repair?
How do we grow?
If “all” human cells have 46 chromosomes,
what must happen to those chromosomes
before the cell divides, in order for the
next two cells to each have 46
Start notes here Cell Cycle & Chromosomes
- 2 trillion cells reproduced daily by our
- 25 million cells reproduced per second
- new cells are reproduced when older
Intro to Cell Cycle
See Board (compare human cycle to cell cycle)
Text book page 204 & 206
In your notes copy the image on page 206 in your text. The image should
take up half of your paper. (Be sure to include the outside label)
Now, in each section (G1, S, G2, Mit, Cyto) list what happens in that phase
Below the image, in your notes, write and answer the following questions:
Where are there checkpoints?
What are checkpoints?
What happens if check points don’t exist?
2 You tube videos
Why Cells Reproduce (end of cycle cycle)
Grow and develop
Heal a wound
To produce gametes (sperm or egg)
Two types of Cell Reproduction:
1. Asexual Reproduction
- In bacteria this is called binary
fission, which creates identical offspring
Both mitosis and binary fission have two stages
1. DNA is copied
2. The cell divides
Chromosome # stays the SAME!!!!
Two types of Cell Reproduction cont.:
2. Sexual Reproduction
- to make sperm and egg (great
detail of this will come soon)
How many copies of
DNA do you want your
sperm or egg to have? is cut in half!!!
This page all side notes, you decide what you NEED to write . . .
Now we know cells divide, in order to go into
depth on the topic, we need to get some
terminology for what is inside the cell.
What is the control center?
Inside the control center are _________.
Terminology Check to Dive Deeper into Cell Cycle:
Get text book, open to page 205
Chromosomes: Remember are DNA, made of nucleotides
Chromosomes are made of segments called genes
Genes code for our characteristics
Most of a cells life, chromosomes in the nucleus are
spread out as chromatin while they are being read
Think of an extension cord, how is it when being used?
Right before they’re ready to divide a chromosome
makes a copy,
These copies coil up and are called chromatids
Chromatids are attached at the centromere
At this point, I would copy figure 8.10 from text into my notes
Types of Cells and Chromosome Number
Somatic cell (any cell except sperm and egg)
Have two pair of chromosomes
Each pair are called homologous chromosomes
Are called diploid
2n (n = number of chroms in one set, 23 in humans so 2n =
Mitosis creates these cells
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Types of Cells and Chromosome Number
Sex cells (sperm and egg)
Have one copy of each chromosome
Are called haploid
n (n = 23 in human cells)
Meiosis creates these cells
Types of Cells and Chromosome # Cont.
Fertilization – fusion (coming together) of
two haploid (sperm and egg) cells, this a
zygote or a fertilized egg cell.
First cell of many new organism
Used for growth, healing, cancer when out
Things that happen in stage
HW Draw and label 3 times. Time 1, use
your notes, time 2 peek at your notes
when you need to, time 3 complete
without notes (keep repeating until can
draw and label accurately without looking
at your notes and your book.
- View Meiosis on PP
- Meiosis on Elmo and on your own sheet
- Meiosis with straws
Go back and look at karyotype to see differences in sex chromosomes
Notice I did not have an actual
picture of meiosis
Following slides must be covered in
Notice I do not have a REAL picture
Causes of variation in gametes (good,
- crossing over
- random assortment of chromosomes
Types of Chromosomes and Sex determination
Autosomes – chromosomes not involved in
determining if an organism (you) are
going to be a male or female
Sex Chromosomes – one chromosome of
our 23 ( or 2 of our 46)
Female is XX (X from mom and X from dad)
Male XY – (x from mom and Y from dad)
Only chromosome not “identical” to its pair (see Figure 6.5 in
Male gamete determines sex of fertilized egg
Types of Mutation
These occur in metaphase I, why?
Name of Mutation Description Sketch
Deletion A piece of a chromosome
breaks off; a piece is
Duplication A chromosome fragment
breaks off and attaches to
its homologous chrom-
osome; now it carries 2
copies of same gene
Inversion The chromosome piece breaks
off reattaches to the
original chromosome in a
Translocation The piece reattaches to a
A A A A
B B B B
C C C C
D deletion D Inversion
E E E E
F F F D
A A A A
B B B B
C C C
D D D D
E E E E A A
F F F F B B
D Z D
Abnormalities in Chromosome Number
Karyotype – a photo of the chromosomes in a
dividing cell (See p.329)
Abnormalities in Chromosome Number, happen
in anaphase I, as a result of non-disjunction
Trisomy – an extra chromosome, 3 instead of two in
a pair, 47 instead of 46 in a human karyotype
Down syndrome – Trisomy 21, an extra 21st chromosome
Klinefelter’s syndrome – Male with XXY
Monosomy – missing a chromosome, havine 1 instead
of 2 in a pair, 45 instead of 46 in a human karyotype
Turner’s syndrome – Female with only 1 sex chromosome, or
missing part of one (XO)
The end . . . for now!!
Ready for the test?????
Nash – go over Go in cell cycle, as check points.
11/14 Cell Cycle
What are the stages to the cell cycle
(remember the image you drew
yesterday). What can you remember
happens in each piece of the pie?
Homework the night before this started
was to take notes on 6.1 using the topics
given to them
Therefore in class, they would just be
following along in there notes, adding and
11/12 Cell Division
How do you think a cell divides. There
is tons of information inside the nucleus,
and when the cell divides, that same
information must be in the new cell and
the old cell. What methods do you think,
or do you remember, will a cell go
through to replicate? If you have no
idea, be creative.