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All Cells Come From Cells
Why do cells reproduce?
– Growth/ Development
– Repair
How often will a cell divide?
– Size
• In order to be efficient, cells must be
small!
– Type of cell/ Location of the cell
• Epithelial cells divide often
• Mature muscle cells and nerve cells don’t
divide at all
– Some cell division eventually stops.
• The cell deteriorates and dies, causing the
body to age.
– Cancer cells, on the other hand, are
"immortal.“
The Cell Cycle
Interphase (majority of the life of a
cell)
• Growth 1- growth, Protein
Synthesis
• Synthesis- DNA Replication
(making a second copy of DNA)
• Growth 2- growth, replicating
organelles
Mitotic Phase
• Mitosis- division of the DNA in
the nucleus
• Cytokinesis- division of the
cytoplasm and organelles
In order to enter the S
phase, there needs to be….
• Sufficient growth
• No damage to DNA
• Need for new cells
G1 Growth and Protein Synthesis
If DNA cannot leave the
nucleus and proteins are
made at the ribosomes,
how can this be possible?
DNA
How are DNA and RNA Different?
Deoxyribonucleic Acid
double helix
deoxyribose sugar
thymine
Ribonucleic Acid
single helix
ribose sugar
uracil replaces thymine
Ribonucleic Acid
3 Types
– mRNA (Messenger)
• Contains the
complementary code of
DNA
– tRNA (Transfer)
• Transfers amino acids
from the cytoplasm to
the ribosomes
– rRNA (Ribosomal)
• Builds the ribosomal
subunits
How does DNA code for proteins?
• mRNA contains the
complementary code of DNA
• Each amino acid is coded by
triplet combinations of bases
• tRNA transfers the amino
acids to the ribosome
The Genetic Code
Codon- triplet combinations of
bases on mRNA that code for a
specific amino acid
– More than one codon codes
for the same amino acid
– Start codon = AUG
– Stop codons = UAA, UAG,
UGA
Anticodon- triplet combinations
of bases on tRNA that are
complementary to the codon
How does this all fit together?
DNA
TAC ATA CAG CGA
↓
mRNA AUG UAU GUC GCU
↓
tRNA
UAC AUA CAG CGA
↓
AA
start-tyrosine-val-alanine
Coding Practice
DNA
TAC ACG GAC GGC TAT
↓
mRNA AUG UGC CUG CCG AUA
↓
tRNA UAC ACG GAC GGC UAU
↓
AA
start-cysteine-leucine-proline-isoleucine
Coding Practice
DNA
TAC CAT TAG GTA ATA
↓
mRNA AUG GUA AUC CAU UAU
↓
tRNA UAC CAU UAG GUA AUA
↓
AA start-valine-isoleucine-histadine-tyrosine
Protein Synthesis
Stages:
• Transcription of DNA
• RNA Processing
• Translation of mRNA
Transcription
• Occurs in the nucleus
• RNA Polymerase creates a complementary strand of RNA alongside the
coding segment of DNA
– A binds with U (Uracil)
– C binds with G
Editing the RNA Transcript
• DNA contains both
coding (exons) and
noncoding
(introns) segments
• Introns are
removed
• Exons are spliced
together
Translation
• At the ribosomes
• tRNA carrying a Methionine
attaches at the A-site where the
“start” (AUG) codon is read.
• The ribosome then moves along
the mRNA transcript accepting
new amino acids at the A-site
and holding the polypeptide
chain at the P-site
• The polypeptide is released when
the ribosome arrives at a “stop”
codon
Online activity 11.5
https://www.pearsonsuccessnet.com/snpap
p/iText/products/0-13-115075-8/index.html
Mutations can change the meaning of Genes
Mutagen
-mutation causing agent
Mutation- any change in the nucleotide
sequence of DNA
2 General Categories
– Base Substitutions
• Less hazardous- affects a single amino
acid
– Silent Mutation- substitution
coded for the same amino acid
– Base Insertion or Deletion
– Causes a frame-shift in the
coding of the rest of the strand
S DNA Replication
What is Semi- Conservative Replication?
• Newly created DNA contains 1
original and 1 new strand
What is the benefit?
• Each parent strand acts as a
template to create a new
complementary strand
• Complementary base pairing
ensures identical copies
How is our DNA read?
• DNA backbones run antiparallel (parallel, but in
opposite directions) to one
another
• DNA is read in the 3’ Carbon to
5’ Carbon direction
DNA Replication
• Begins at origins of replication or
replication forks
• Multiple origins = faster replication
• Reads 3' to 5' on each parent strand
• Creates new strands 5' to 3'
• Leading strand continuously
• Lagging strand in Okazaki fragments
• Dozens of enzymes are involved
• DNA Gyrase (unwinds DNA)
• DNA Helicase (breaks Hydrogen bonds)
• DNA Primase (stabilizes parent
strands)
• DNA Polymerase (adds new nucleotides
and checks for errors)
• DNA Ligase (seals breaks in strands)
animation
DNA Structure
DNA
Chromatin Duplicated Chromatin Sister Chromatids
Mitotic Phase- Mitosis and Cytokinesis
DNA exists as chromatin in Interphase
• allows access for protein synthesis and DNA
replication
DNA exists as chromosomes in Mitosis
• organized for division of the nucleus
Mitosis is the division of the nucleus
Cytokinesis is the division of the remainder of the
cell (occurs simultaneously with telophase)
http://www.learningliftoff.com/high-school-science-mitosis/#.VjJOXLerQdU
Chromosomes line
up perpendicular
to the poles so
each new nucleus
will get a complete
chromatid
https://www.youtube.com/watch?v=Vc1UqeHhjeo
Animal Cell vs. Plant Cell Cytokinesis
Onion Root Tip Cells
https://www.youtube.com/watch?v=Vc1UqeHhjeo
Benign vs. Malignant Tumors
• Both are the result of uncontrolled cell division
Cancer Treatment
Radiation
– Disrupts cell division by
destroying the cell
– Minimal damage to
normal cells
Chemotherapy
– Antimitotic drugs
• Prevents cell division
by interfering with
the spindle formation
• Intestinal or hair
follicle cells can be
affected by
chemotherapy,
leading to nausea or
hair loss
Homologous Chromosomes
• Pairs of chromosomes.
– One inherited from mother.
– One inherited from father.
• Identical in size, centromere
position, and the traits they code
for
Karyotype
• Visual display of an individual’s
chromosome pairs
• Pairs 1-22 are autosomes (code for
most body traits)
• 23rd pair are sex chromosomes
(determines the sex of the
individual)
What’s the difference between Mitosis and Meiosis?
Mitosis is the nuclear division of
Somatic Cells/ Body Cells
• 2 cells genetically identical to
parent cell
• Same number of chromosomes
(2n=diploid)
Meiosis is the nuclear division of
cells in your sex organs to
produce Gametes /Sex Cells
• 4 cells genetically different
than the parent cell (Why is
this important? DIVERSITY!)
• Half the number of
chromosomes (n=haploid)
(Why is this important?
Maintains chromosome
number!)
Meiotic Cell Division
Crossing Over increases variation
– Occurs during Prophase I only (the only prophase when pairs are together)
– Exchange of DNA segments between homologous chromosomes
– May occur at 1 or more sites
Independent Assortment increases variation
– Occurs during Metaphase I only (the only metaphase when pairs are together)
– Homologous pairs line up independently of one another
Meiosis I produces 2 haploid (with DNA existing as sister chromatids) cells
Meiosis II produces 4 haploid cells
http://www.learningliftoff.com/high-school-sciencemeiosis/#.VjJOrLerQdU
Alternation of Generations
Topic of the
EXTRA CREDIT
QUESTION!!!