Chromosomes and Cell DivisionNew Cells Are Formed by Cell

Division

http://www.alumni.ca/~laued3e/chromosome.jpg

• 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=gEwzDydciWc&feature=related

• http://www.youtube.com/watch?v=3cD3U2pgb5w&playnext_from=PL&feature=PlayList&p=91845E3E72841AFE&playnext=1&index=7

• http://www.youtube.com/watch?v=K0ZP8VtxUZ0&playnext_from=PL&feature=PlayList&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-in-math/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

http://www.genomesize.com/rgregory/Chromosome.JPG

chromatids

• 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?

HomeworkDirected Reading 6-1