1. Unit V – Genetics & Heredity Cell Cycle & Mitosis
The Cell Cycle & DNA
The Story of the Nucleus

2. Introduction to Cell Division
Why do we need more cells?
Recall: can’t have bigger cells…need more cells)
To grow, repair, develop, reproduce

3. Introduction to Cell Division
How do we get more cells?
Recall: “cells come from pre-existing cells”
Cells divide into two

4. Introduction to Cell Division
Before cells can divide, what must they do to prepare?
Grow larger
Grow more organelles
Double their DNA

5. The Cell Cycle

6. 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

7. The Life Cycle of a Cell Mitosis
Phase responsible for splitting cell into 2 exact copies (new cells)

8. The Life Cycle of a Cell Interphase Prophase Metaphase
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

9. The Life Cycle of a Cell Anaphase Telophase Cytokinesis
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

10. The Life Cycle of a Cell Name the phase: Interphase Prophase Metaphase
Anaphase
Telophase
Cytokinesis

11. 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?)

12. 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?

13. 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

14. 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

15. 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

16. DNA Structure

17. 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”

18. 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

19. 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

20. 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?

21. 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?

22. Part 3 – Protein Synthesis The Story of the Ribosome
Unit IV – Cell Function
Part 3 – Protein Synthesis
The Story of the Ribosome

23. 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

24. Rules for Building a Protein
DNA cannot leave the nucleus
Must have a messenger to get code from DNA & take it to ribosome
Proteins are made from amino acids (AA’s)

25. 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

26. RNA
How does RNA differ from DNA?
1 strand
U not T
ribose

27. 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

28. 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

29. 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

30. 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

31. Use a chart to find order of AA’s:
Which AA is:
CGU
Arg
AUC
Iso

32. Use a chart to find order of AA’s:
Which AA is:
UCA
Ser
GAG
Glu

33. 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

34. 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

35. Protein Synthesis
Name the process:
Transcription
Translation

36. Protein Synthesis Name the parts: DNA mRNA tRNA Amino Acid Protein
Ribosome

37. 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)

38. Gene Mutations May occur in reproductive cells …Or in “body cells”
Affects offspring, not you
…Or in “body cells”
Affects you, not offspring

39. Gene Mutations Point Mutations THE DOG BIT THE CAT THE DOG BIT THE CAR
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)

40. Gene Mutations
Point Mutations

41. 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 (deletion)
THE DOQ GBI TTH ECA (insertion)

42. Gene Mutations
Frameshift Mutations

43. The End