Download Chromosomes

http://www.alumni.ca/~laue
d3e/chromosome.jpg
Chromosomes and Cell Division
New Cells Are Formed by Cell
Division
• About 2 trillion cells are produced by an
adult human body every day.
• This is about 25 million new cells per
second.
• Why would cells divide or reproduce?
Different Types of Cell Division
• 1. Bacteria reproduce by binary fission.
– Binary Fission= a form of asexual
reproduction that produces identical offspring
– If the offspring are identical, what is true about
the DNA?
• 2. Eukaryotic organisms undergoing
growth, development, repair or asexual
reproduction
• 3. The formation of gametes or sex cells
Rod-shaped Bacteria Dividing by
Binary Fission
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookmito.html
Binary Fission Video Clips
• http://www.youtube.com/watch?v=gEwzDy
dciWc&feature=related
• http://www.youtube.com/watch?v=3cD3U2
pgb5w&playnext_from=PL&feature=PlayLi
st&p=91845E3E72841AFE&playnext=1&in
dex=7
• http://www.youtube.com/watch?v=K0ZP8V
txUZ0&playnext_from=PL&feature=PlayLi
st&p=91845E3E72841AFE&index=8
Eukaryotic cells form chromosomes
before cell division
• gene = a segment of DNA that codes for a
protein or RNA molecule
• As a eukaryotic cell prepares to divide the
DNA and proteins associated with the DNA
coil into a structure called a chromosome.
• Before DNA coils, the DNA is copied.
• The two exact copies of DNA that make up
the chromosome are called chromatids.
• Genes are found on
chromosomes
• They are sections of
DNA
• Here is the gene for
Parkinson’s Disease.
• The chromatids attach at a point called the
centromere.
http://www.ams.org/
new-inmath/cover/images/
chromosome.gif
• Homologous Chromosomes =
chromosomes that are similar in size,
shape, and genetic content
• Each homologue in a pair of homologous
chromosomes comes from one of the two
parents.
• There are 46 chromosomes in human
somatic or body cells or 2 sets of 23
chromosomes.
• Diploid= two sets of chromosomes
• Haploid= one set of chromosomes
• Zygote= a fertilized egg cell, the fusion of
two haploid gametes
• autosomes= chromosomes that are not
directly involved in determining sex
– 22 pairs
• Sex chromosomes= determine sex
– XX=female
XY=male
chromatids
http://www.genomesize.com/rgreg
ory/Chromosome.JPG
• Karyotype = a photo of the chromosomes
in a dividing cell that shows the
chromosomes arranged by size.
Is this a karyotype of a male or
female?
Do you notice anything about this
karyotype?
• Down’s
syndrome
http://www.ucl.ac.uk/~ucbhjow/bmsi/lec7_images/47_xx_21.gif
What do you notice about this
karyotype?
• Turner Syndrome
http://www.antenataltesting.info/images/karyotypeTurners.jpg
• 1. Why is cell division important?
• 2. What are chromosomes made up of?
• 3. Where are genes found?
Homework
Directed Reading 6-1