Download Unit 6 Cell Cycle

UNIT V – GENETICS & HEREDITY
CELL CYCLE & MITOSIS
The Cell Cycle & DNA
The Story of the Nucleus
Introduction to Cell
Division
 Why do we need more cells?
 Recall: can’t have bigger cells…need more cells)
 To grow, repair, develop, reproduce
Introduction to Cell
Division
 How do we get more cells?
 Recall: “cells come from pre-existing cells”
 Cells divide into two
Introduction to Cell Division
 Before cells can divide, what must they do to
prepare?
 Grow larger
 Grow more organelles
 Double their DNA
The Cell Cycle
The Life Cycle of a Cell
 Interphase
 This is where cells grow and copy their DNA
(chromosomes)
 Has 3 parts:
 G1 (growth)
 S (doubling chromosomes)
 G2 (growth)
Note: in this phase, DNA is in the form
of very thin strands called
chromatin…hard to see
The Life Cycle of a Cell
 Mitosis
 Phase responsible for splitting cell into 2 exact copies
(new cells)
The Life Cycle of a Cell
 Interphase
 Nucleus visible w/ nucleolus
 can’t see chromosomes
 DNA doubles; cell grows
 Prophase
 Chromosomes form (coil)
 Nuclear membrane disappears
 Metaphase
 Chromosomes line up in the
middle (equator) of cell
The Life Cycle of a Cell
 Anaphase
 Sister chromatids
separate & migrate
away from each other
 Telophase
 Cell “furrow” or
cell plate appears
 Nuclei reappear in
each new cell
 Cytokinesis
 Cytoplasm splits to
separate cells
The Life Cycle
of a Cell
Name the phase:
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Quiz
 1. Why are the events of Interphase important?
 2. In which phase of mitosis do the sister
chromatids separate?
 3. Why can’t chromosomes be seen in the cell
during Interphase?
 4. In which phase of mitosis is the nucleus
broken down?
 5. Why is mitosis needed? (What is its purpose?)
Quiz
 6. Where in the cell does photosynthesis take
place?
 7. What is the purpose of photosynthesis?
 8. Where in the cell does cellular respiration
occur?
 9. What is the purpose of cell respiration?
 10. On the cellular level, why do we need to
breathe?
DNA Structure
 What is the difference between
chromosomes, genes, and DNA?
 Chromosomes are coiled up rods of DNA
 Genes are sections of DNA that code for traits
DNA Structure
 What does DNA look like?
 Double helix…2 strands coiled around each other
 Backbone is made up of alternating sugar and phosphate
groups
Deoxyribose
(sugar)
Phosphate
DNA Structure
 What does DNA look like?
 Connection points are pairs
of bases
 Adenine (A), guanine (G),
cytosine (C), thymine (T)
 A always pairs with T
 C always pairs with G
DNA Structure
How does DNA “control”?
 The order of bases spells out the plans for “how
to build you”.
 The bases work in groups of three.
 This group is called a “DNA triplet”
How does DNA “control”?
 How can 4 bases control everything in our cells
(and thus everything in an organism?)
 The 4 DNA bases are like
 letters in the alphabet
 The DNA triplets are like
 words
 The entire gene is like
 a sentence
How does DNA get copied?
 DNA Replication
 DNA unwinds
 New nucleotides bind to old strands
 The strands coil back up forming 2 instead of 1
DNA Quiz
 1. If the green base is adenine
(A), which base is the red?
 2. What structure is represented
by the blue section?
 3. Which structure is represented
by the teal section?
DNA Quiz
 4. Which part of DNA actually holds the code?
 5. During which phase of the cell cycle does DNA
copy itself?
 6. Describe how DNA is able to copy itself. Be
specific!
 7. What is the difference between a chromosome
and a gene?
Unit IV – Cell Function
Part 3 – Protein Synthesis
The Story of the Ribosome
How do we get actual traits from
DNA?
 Our heritable traits are determined by the proteins
that we make (including our enzymes)
 Example: a gene in DNA has directions for how to build
melanin…melanin gives you your skin coloration
gene

protein

trait
Rules for Building a Protein
1) DNA cannot leave the nucleus
2) Must have a messenger to get code from DNA &
take it to ribosome
3) Proteins are made from amino acids (AA’s)
Both DNA & RNA are needed to
build a protein
Although they are similar there are some important differences:
 DNA
 2 strands
 Deoxyribose sugar
 Thymine (T) binds with A
 RNA
 1 strand
 Ribose sugar
 Uracil (U) binds with A
RNA
 How does RNA
differ from
DNA?
 1 strand
 U not T
 ribose
What types of RNA are there?
 mRNA (messenger RNA) - copies the directions
from DNA & takes them to the ribosomes
 tRNA (transfer RNA) - picks up certain AA’s &
brings them to the ribosome for assembly
How does mRNA know how to
copy DNA?
 DNA triplets match up with sets of 3 mRNA
bases…called codons
 If DNA says this…what will mRNA be?
 TAC – GGA – CTT – GAT – ACA – ATT
 AUG – CCU – GAA – CUA – UGU – UAA
How does mRNA know which
AA’s to assemble?
 tRNA carries a code of 3 letters called an anticodon
that pairs up with the codons of mRNA
 If mRNA says this…what will the tRNA’s be?
 AUG – CCU – GAA – CUA – UGU – UAA
 UAC – GGA – CUU – GAU – ACA - AUU
How does mRNA know which
AA’s to assemble?
 Each tRNA can only pick up one specific AA
 When it matches up with the anticodon, it brings
along its AA
 If mRNA says this…what will the AA’s be?
 AUG – CCU – GAA – CUA – UGU – UAA
 Met – Pro – Glu – Leu – Cys - Stop
Use a chart to find order of
AA’s:
 Which AA is:
 CGU
 Arg
 AUC
 Iso
Use a chart to find order of
AA’s:
 Which AA is:
 UCA
 Ser
 GAG
 Glu
Protein Synthesis
 Transcription (“to copy”)
 mRNA goes to nucleus & copies DNA code for one
gene
 mRNA takes the copy to the ribosome in the
cytoplasm
Protein Synthesis
 Translation (“DNA” to “protein”)
 Ribosome uses mRNA copy
to look for certain tRNA’s
(ones with correct anticodon)
 tRNA’s pick up specific AA’s &
bring them to ribosome
when they are needed
 AA’s are pulled off tRNA’s &
attached to the growing
protein chain
Protein Synthesis
 Name the process:
Transcription
Translation
Protein Synthesis
 Name the parts:
DNA
mRNA
tRNA
Amino Acid
Protein
Ribosome
Gene Mutations
 Sometimes mutations (errors) occur
 Changes in DNA code may be harmful, helpful, or
have no effect
 If instructions for cell division affected, can lead to
cancer (uncontrolled cell growth)
Gene Mutations
 May occur in reproductive
cells
 Affects offspring, not you
 …Or in “body cells”
 Affects you, not offspring
Gene Mutations
 Point Mutations
 A change in a single DNA base
 THE DOG BIT THE CAT
 THE DOG BIT THE CAR
 This may or may not change the protein that is
made (some AA’s have more than one code)
Gene Mutations
 Point Mutations
Gene Mutations
 Frameshift Mutations
 AA’s shift when a single base is inserted or deleted
 THE DOG BIT THE CAT
 THE DOB ITT HEC AT
 THE DOQ GBI TTH ECA
(deletion)
(insertion)
Gene Mutations
 Frameshift Mutations
The End