1. Agenda for 11/25- DNA Replication
Bellwork, Homework check (turn in lab, any work from yesterday)
New Information: review DNA structure, DNA replication
Lab: Extracting DNA from strawberries

2. Bellwork:
Scientists compared the DNA sequence of a gene in four mammals. A portion of the gene’s DNA sequence in each mammal is shown below.
Mammal DNA Sequence
1 TCTCAACTACAA
2 TCTCAGCTGCAA
3 ACTCAGCTACAA
4 TCTCAGCTGCAG
Based on the sequence data, which of the mammals are most closely related to each other?
A. mammals 1 and 2
B. mammals 1 and 3
C. mammals 2 and 4
D. mammals 3 and 4

3. DNA Structure Double Helix.
made up of millions of tiny subunits called Nucleotides.
Phosphate group
Pentose sugar
(deoxyribose)
Nitrogenous base
Phosphate
Nitrogenous
Base
Pentose
Sugar

4. Nucleotides Phosphate and sugar backbone
the nitrogen bases form the “rungs”.
There are four types of nitrogenous bases.

5. Nucleotides
Each base will only bond with one other specific base (Chargaff’s Rule, or Base-Pair Rule).
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Form a base pair.
Form a base pair.

6. Complementary base pairing:
the order of the bases in one strand determines the order of the bases in the other strand. C

7. DNA Replication
Enzymes “unzip” DNA (helicase)- breaks hydrogen bonds holding the two strands together.
DNA polymerase adds new nucleotides to the old strands, creating 2 new DNA molecules
Each new DNA molecule has an old strand and a new strand (semi-conservative)

8. DNA Replication (click title for a video clip)
Errors minimized by “proofreading” (DNA polymerase)
DNA replication precedes cell division (mitosis and meiosis)

9. DNA Replication Complete the worksheet in pairs.
Review your answers with the other pair at your table.
We will review as a class in 10 minutes.

10. DNA Extraction Lab We’ll read through the lab procedure together.
You can use this same procedure to extract DNA from any living thing (including your own DNA!)
Safety is critical! No gum, no food, no drinks. Always assume chemicals are dangerous! (even though these are relatively safe if you don’t consume them).