Your “Do Now” 2/22

• Get out your lab from yesterday• Prepare to answer questions on the back side– (Make sure they are filled-in)

• Ask for yours back if you turned it in• Going over this in 5 minutes

Your “Do Now” 2/23

• Write down our 2 new learning targets:LT #2. I can explain the process of DNA replicationLT #3. I can explain the causes and effects of mutations on an organism

Agenda 2/23

• Notes on DNA replication• Replication activity

• Get missing work in!!!• Test retakes today too

Ch 12 Notes # 2 DNA Replication

• DNA replication: DNA making a copy of itself

• The process happens inside the cell’s nucleus

Why replicate DNA?• DNA needs to replicate before cells divide. So

each cell can have an exact copy of the DNA• Happens before mitosis/meiosis• Remember: 4 reasons for organisms’ cells to

divide:1. Growth 3. Reproduction2. Healing/Repairing 4. Replacing

DNA Replication: Basic Facts

• We call each side of DNA a strand• DNA is double-stranded (there are 2 sides of it)• It needs to be opened before it can be replicated!

DNA Replication: Basic Facts

• One side of a DNA molecule will become a template for making a new strand– Template = model to copy

Steps of Replication

1) Enzymes (chemicals) break the hydrogen bonds between bases, splitting the DNA in two (“unzipping” it)

2) Replication enzymes bring in complementary nucleotides (The matching base pair + sugar + phosphate)

3) Now there are 2 exact copies of the DNA-1/2 original strand-1/2 complementary strand

• We started with ____ molecule of DNA and ended with ____

• Each one is made of ____ strand of the original DNA molecule and ____ new strand

Video

• http://www.youtube.com/watch?v=zdDkiRw1PdU&feature=related

Accuracy is important in replication!

• Remember: the order of the bases in DNA is like the order of letters in a word

• This means each DNA strand has to be copied exactly or a mutation (error) could occur

3 main mutations • Substitution– One base replaces another

• Insertion– Extra bases are put

into the sequence• Deletion– Bases are removed

from the sequence

Original DNA:Mutated DNA:

Original DNA:Mutated DNA:

Original DNA:Mutated DNA:

What are some causes of mutations?

• Exposure to radiation

OR certain types of chemicals

• Mutations in a body cell are passed on to other new body cells

• Example: DNA in a bone cell gets mutated, now all bone cells made by that cell have the mutation

Mutations that happen in gametes get passed to offspring-Parents pass on the mutated DNA to offspring through their gametes

• Mutations could cause cancer(uncontrolled cell division)

Example: Mutation in skin cell could lead to skin cancer

• Mutations can be lethal if they affect an important gene

Example: Mutation in brain cell function could cause those cells not to work right

• Other times they may not affect an important gene, so they are not harmful

Not all mutations are bad• Remember: mutations lead to variation,

which is necessary for evolution