In humans, the
diploid (2n)
number of
chromosomes
is…
46 chromosomes:
23 from dad, 23
from mom.
Electron Micrograph of Chromosomes taken from a somatic cell.
Karyotype – a picture of all
the chromosomes in a cell
of an organism
Single-stranded
chromosomes… What
stage of mitosis was this
cell in?
Anaphase or telophase
Homologous pairs are
arranged by size and
banding pattern;
Pairs 1  22 are
autosomes;
Pair #23
Only males have a Y chromosomes. Who
determines baby’s gender?
Pair 23 = sex chromosomes
Dad does!
(XX = female, XY = male) (sperm can have X or Y, egg can only have X)
The Making of a Karyotype
We Start Here
Karyotype Practice
Learn Genetics – University of Utah (in class)
The Biology Project Karyotype Activity (homework)
Answer on a separate sheet of paper:
Patient karyotypes and diagnoses (Qs #1 & 2);
Add brief description of genetic disorder/syndrome
(research)
A1, A2
B1, B2
C1, C2
TH
RA
I
P
P
LL
OO
II
DD
Add the term Homologous / Homologue
N or 1N, 1 of a kind
2N, 2 of a kind, A homologous pair
Egg cell or Sperm Cell
Body Cell
A term used to decribe if the cell is
Haploid or if the cell is Diploid
46
2
Female
Male
Mom or Dad
Dad
Autosomes
Autosomes
44
22
1
Chromosome #1 is the largest and gets
smaller as you progress to Chromosome
#22………………………………………..
therefore Chromosomes #1 has more DNA
and Chromosome #22 has the least amount
of DNA
Cell A
Cell B
Cell B
Cell A
Somatic Cells have a full set of DNA, 46
chromosomes
2n = 46
Gametes have a ½ set of DNA, only 23 chromosomes
because the other half of genetic material comes from
the other parent during fertilization
Meiosis…
Keeps the species’ number of chromosomes constant
from one generation to the next by creating haploid
gametes
↓
Creates genetic diversity in gametes through crossingover and random assortment of chromosomes
↓
Allows for the sexual recombination of genetically
diverse gametes (during fertilization), creates genetically
different individuals
Meiosis Movie Time! 
1. Focus on finding differences between meiosis and mitosis –
when you see something different, tell Mrs. Nordstrom
“STOP!”
2. Keep your meiosis w.s. on your desk during the movie so you
can identify the stages.
3. Complete your meiosis w.s. (due tomorrow, section 8.3 in
text)
*Leave ppt*
*During the movie,
just refer to the diagrams.*
*Complete the meiosis w.s. by labeling the phases and
sorting the stages into the blanks.*
Meiosis & Sexual Reproduction
In most sexually reproducing species, organisms
have two sets of chromosomes (2n, diploid),
one from each parent…
Being diploid
is awesome
because…
…you get a
backup copy
of each
gene!!!
Sexual reproduction is awesome because…
… it creates genetic diversity in a
population…
… which increases the chances that at least
some will survive challenging
environmental conditions.