2006-2007 Regents Biology
Biology is the only subject in which multiplication is the same thing as division…
2006-2007 Regents Biology
Making New CellsMaking New DNA
Regents Biology
Where it all began…
You started as a cell smaller than a period at the end of a sentence…
Regents Biology
And now look at you…
How did you get from there to
here?
Regents Biology
Going from egg to baby…. the original fertilized egg has to divide…
and divide…and divide…
and divide…
Getting from there to here…
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Why do cells divide… __________________________
one celled organisms (clones)
__________________________ from fertilized egg to multi-celled organism
__________________________ replace cells that die from
normal wear & tear or from injury
amoeba
starfish
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Dividing cells… What has to be copied
______________ ______________ ______________ ______________
______________ ______________
animal cellplant cell
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Copying DNA A dividing cell ______________________
creates 2 copies of all DNA separates the 2 copies to opposite ends
of the cell splits into 2 daughter cells
But the DNA starts loosely wound in the nucleus
If you tried to divide it like that, it could tangle & breaknucleus
cell
DNA
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Organizing & packaging DNA
nucleus
cell
DNA
nucleus
cell
4 chromosomesin this organism
DNA in chromosomes ineveryday “working” cell
DNA in chromosomes in cell getting ready to divide
DNA has been “wound up”
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Chromosomes of Human Female
46 chromosomes23 pairs
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Chromosomes of Human Male
46 chromosomes23 pairs
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Paired bases DNA structure
double helix 2 sides like a ladder
Bases match together ______________
______________ ______________
______________
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Watson and Crick
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Copying DNA Matching bases allows
DNA to be easily copied
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Making new DNA Copying DNA
______________DNA starts as a double-stranded
molecule matching bases (A:T, C:G)
then it unzips…
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DNA replication Strands “unzip” at the weak bonds
between bases
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DNA replication
DNA polymerase
Enzyme ______________ adds new bases
DNA basesin nucleus
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DNAPolymerase
Copying DNA Build daughter DNA strand
use original parent strand as “template”
add new matching bases _________________________
_____________
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New copies of DNA Get 2 exact copies of DNA to split
between new cells
DNA polymerase
DNA polymerase
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Copied & Paired Up Chromosomes
centromere
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Copying & packaging DNA
Copying DNA
Coil DNA into compact chromosomes
When cell is ready to divide… copy DNA first, then… coil up doubled chromosomes
like thread on a spool… now can move DNA around cell without having
it tangle & break
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double-strandedhuman chromosomesready for mitosis
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DNA must be duplicated…
nucleus
cell
DNA in chromosomes
nucleus
cell
duplicated chromosomes
chromosomes in cell
4 single-stranded chromosomes
duplicatedchromosomes
4 double-stranded chromosomes
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Mitosis: Dividing DNA & cells Stage 1: cell copies DNA
nucleus
cell
DNA _____________
(interphase)
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Mitosis: Dividing DNA & cells Stage 2: DNA winds into chromosomes
DNA is wound up into chromosomes to keep it organized
nucleus
cell
duplicated chromosomes
(prophase)
_____________
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Mitosis: Dividing DNA & cells Stage 3: Chromosomes line up
chromosomes line up in middle attached to protein “cables” that will
help them move
duplicated chromosomeslined up in middle of cell
(metaphase)
_____________
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Mitosis: Dividing DNA & cells Stage 4: Chromosomes separate
chromosomes split, separating pairs start moving to opposite ends
chromosomes split & move to opposite ends
(anaphase)
_____________
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Mitosis: Dividing DNA & cells Stage 5: Cell starts to divide
cells start to divide nucleus forms again
(telophase)
_____________
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Mitosis: Dividing DNA & cells Stage 6: DNA unwinds again
cells separate now they can do their every day jobs
(cytokinesis)
_____________
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New “daughter” cells Get __________ copies of original cells
________________ ________________
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Cell division in Animals
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Mitosis in whitefish embryo
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Mitosis in plant cell
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onion root tip
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Overview of mitosis
Copy DNA Wind Up
Line Up Separate Divide
Bye-Bye!
2006-2007 Regents Biology
Any Questions??
Any Questions??
Regents Biology
And now look at you…
How did you get from there to
here?