Download DNA, Mitosis & Meiosis

DNA, Mitosis and Meiosis
Lindsey Bily
Anatomy & Physiology
Austin High School
History of DNA
Frederick Griffith
-1928 experimented
with Strep bacteria
and was able to
transform them from
one form to another.
Found a “
transforming factor”.
History of DNA
• Rosalind Franklin
– 1952: took a picture of DNA by X-ray diffraction
which was used to determine the double helical
structure of DNA
History of DNA
• Watson & Crick
– 1953: Used the
image of DNA
by Rosalind
Franklin to
determine that
the structure of
DNA is in a
double helix.
DNA
• Deoxyribonucleic Acid: a
HUGE molecule and the most
important molecule in the
world!
DNA Structure
• DNA is a polymer made up of millions of
nucleotides. (phosphate, sugar, and base)
DNA Structure
• Nucleotides differ in their
nitrogenous base component.
Purines: Adenine and guanine
Pyrimidines: Cytosine and thymine
DNA Structure
• Obligatory
Base Pairing
– A binds T
– C binds G
ALWAYS!!
DNA Structure
• Guanine pairs
with Cytosine
via 3 Hydrogen
bonds (lit area)
DNA Structure
• Adenine pairs
with Thymine via
2 Hydrogen
bonds (lit area).
DNA Structure
• Sugar
Phosphate
backbone.
• Base pairings
are the rungs
of the “ladder”.
Genes
• Genes are a segment of
DNA that code for
proteins.
Transcription
• DNA cannot exist outside of the nucleus. It
will be degraded by enzymes in the cytosol.
• DNA’s “message” has to get out to the
cytoplasm where proteins are made.
• mRNA is used to transcribe DNA’s message.
Transcription
• DNA unzips at the gene where the DNA is to
be transcribed.
• RNA nucleotides attach to the DNA strand.
• Complimentary Base Pairing
A binds with U (uracil, no thymine)
G binds with C
Transcription
• The mRNA has to be edited before it can
leave the nucleus.
• Introns are areas of noncoding DNA. These
are removed from the mRNA.
• The coding parts (exons) are kept on the
mRNA and spliced or joined together.
We can now leave the nucleus!
Transcription
Transcription
• Animation (click on website)
http://content.dnalc.org/content/c15
/15510/transcription_basic.mp4
Translation
• The mRNA moves into the cytoplasm and it
attracts lots of ribosomes.
• Let’s translate the DNA code!
Ribosomes on mRNA
Translation
• tRNA (transfer RNA)
molecules carry amino
acids.
– Each tRNA carries 1
amino acid
– The tRNA’s anticodon
binds to the codon on the
mRNA strand
Translation Animation
• http://content.dnalc.org/content/c15/15501/tra
nslation_basic.mp4
Translation to Protein
• Once the
polypeptide chain
has been formed,
the enzymes in the
Rough ER, Golgi,
and cytoplasm help
them to fold in their
1, 2, 3, or 4
structure.
Cell Growth and Reproduction
• Cell Growth: using
the DNA to make
the proteins needed
for survival.
• Cell Reproduction: DNA
is passed from one
generation of cells to
the next and from one
generation of
organisms to the next.
Cell Growth
• The cell produces
new structural
proteins and all the
enzymes needed to
make lipids,
carbohydrates, and
other substances.
Cell Growth
• The cell must make additional cytoplasm and
plasma membrane as the cell grows.
• Membranous organelles (ER, Golgi, lysosomes,
peroxisomes) are made up of the same material
as the plasma membrane and must also be
made as the cell grows.
• Mitochondria have their own DNA
and replicate themselves.
DNA Replication
• As a cell becomes
larger, this triggers
the replication of
DNA.
• Replication of DNA
is very similar to the
formation of mRNA
(transcription)
DNA Replication
1. DNA uncoils or “unzips”
except for small
segments.
DNA Replication
2. Nucleotides floating in the nucleus
pair with the unzipped bases in the DNA
strands.
DNA Replication
3. DNA Polymerase causes the new
nucleotides to bind with the unzipped
DNA strands.
DNA Replication
4. As nucleotides bind
to the DNA strands,
two new, identical
DNA molecules are
formed. These are
called chromatids.
Practice
The original DNA strand is shown below.
Please write down the sequence of the
complimentary strand that forms during DNA
Replication.
ATTCGTAGGCC
TAAGCATCCGG
DNA Replication
• Click on the website for animation.
http://www.dnalc.org/resources/3d/03mechanism-of-replication-basic.html
Cell Reproduction: Mitosis
• One parent cell
becomes 2
daughter cells.
• The plasma
membrane splits
into two via
cytokinesis (“cell
movement”).
Cell Reproduction: Mitosis
• Phase 1: Interphase
The cell is not growing, but is not reproducing
either. It is PREPARING for reproduction. DNA is
being replicated.
Cell Reproduction: Mitosis
Phase 2: Prophase
The nuclear envelope falls apart. The paired
chromatids form chromosomes. The centrioles
move towards the “poles” of the cell. Spindle fibers
are formed between them.
Cell Reproduction: Mitosis
• Phase 3:
Metaphase
“Position changing
phase”. Chromosomes
are no longer in the
nucleus and line up at
the “equator” of the cell.
One chromatid faces
one pole, the sister
chromatid faces the
other pole and become
attached to spindle
fibers.
Cell Reproduction: Mitosis
• Phase 4: Anaphase
“Apart Phase”. The
spindle fibers pull the
sister chromatids apart
from each other towards
the opposite poles of the
cell.
Cell Reproduction: Mitosis
• Phase 5: Telophase
“End Phase”. DNA is
returned to its original
form. The nuclear
envelope rebuilds.
Chromosomes elongate
into chromatin again.
Spindle fibers disappear.
Cytokinesis happens.
Mitosis Animation
• Click on the website for Mitosis
animation.
• http://vimeo.com/8333643
Cell Reproduction: Meiosis
• Cell division that occurs in the sex
cells ONLY.
• Primitive sex cells (spermatogonia
and oogonia) become mature
gametes (sperm and an ovum).
Cell Reproduction: Meiosis
• DIPLOID: All somatic
(body) cells have 46
chromosomes that are
in 23 pairs.
• HAPLOID: Meiosis
reduces the number of
chromosomes in the
primitive sex cells by
half. 23 total
chromosomes.
Two Phases:
Meiosis I
And Meiosis II
Cell Reproduction: Meiosis