DNA Replication

​DNA REPLICATION

BIOLOGY I ​

​**you also have access to an annotated version of these slides on Canvas!

What is replication?

•Replication = making a copy, duplicating, doubling

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Why do we need replication in relation to DNA?

•DNA has to be duplicated in order for cell division to occur properly

•We want to make sure that the new cells have all of the necessary genetic information!

DNA REPLICATION

• ​​The process of copying DNA prior to cell division

• Replication happens in the cell cycle before cell division – more specifically, it occurs in the S phase!

​BIOLOGY I

​DNA Replication

Draw

Circle the letter on the image that represents S (synthesis) in the cell cycle!

​This is an example of the replication fork. We will look at more examples of it later. You will need to be able to label the parts of this!

​So, how does it happen?

• First, the two strands of DNA are separated

• Two new complimentary strands are synthesized, following the base pairing rules

  • Each original strand serves as a template, or model, for a new strand

• Replication is semi-conservative – each DNA molecule that results from replication has one of the two original strands and one new strand

BIOLOGY I

DNA Replication

Multiple Choice

DNA replication is run by a group of enzymes. What group of biomolecules do enzymes belong to?

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

• Two coiled strands called a double helix

• Sides made of a pentose sugar (Deoxyribose) bonded to phosphate (PO4) groups by phosphodiester bonds

• Center made of nitrogen bases bonded together by weak hydrogen bonds

​BIOLOGY I - DNA REPLICATION

​DNA Structure

• ​Nucleic Acids (DNA & RNA) are made up of nucleotides

  • nucleotides are the monomers of DNA & RNA

• Nucleotides differ by their nitrogenous bases

  • 4 in DNA: A, T, C, G​

BIOLOGY I - DNA REPLICATION

​Biomolecule Review

​

Match

Match the following nucleotide parts to their correct labels (on the image shown)

• Nitrogenous Base

• 5-carbon sugar

• Phosphate Group

C

A

B

• C

• A

• B

• We say DNA is antiparallel because one strand of DNA goes from 5’ to 3’ (carbon # on sugars), while the other strand is opposite in direction going 3’ to 5’

• See the next slide for images that explain this numbering!

BIOLOGY I - DNA REPLICATION

​Antiparallel

Multiple Choice

In a molecule of DNA, the strands run opposite of each other (one side goes from 5' to 3' and the other goes from 3' to 5'). What is the name for this relationship?

• Antagonal

• Antiparallel

• Anticipatory

• Opposatory

​keep this in mind for the next question!

Multiple Choice

A molecule of DNA has 10 cytosine bases (C) and 40 adenine bases (A). Based on Chargaff's Rule, how many guanine bases (G) are there in this molecule of DNA?

• 10

• 20

• 30

• 40

Multiple Choice

A molecule of DNA consists of 30% adenine (A) bases. Using Chargaff's Rule, what percent of the bases are guanine (G)?

• 15%

• 20%

• 30%

• 70%

​If the last question confused you, here's how it worked:

Chargaff's Rule states that A=T and C=G.

We know that 30% of this DNA molecule is adenine (A).

​

If A=T, and A=30%, then T=30% too.

​

The percentages of A+T+C+G must equal 100%.

​

Now we know A and T are both equal to 30%, which gives us:

30%+30%+C+G=100% --> 60%+C+G=100% --> C+G=40%

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Because of Chargaff's Rule, we know that C=G, so we can substitute and get 2G=40% --> G=(40%)/2 --> G=20%​.

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• Begins at the Origin of Replication

• Two strands separate, forming a Replication Fork (Y-shaped region)

• The new strands grow at the fork

• 3’ to 5’ is the leading strand

​BIOLOGY I - DNA REPLICATI​ON

​Replication - How do we start?

Multiple Choice

DNA Replication begins at the Origin of Replication. What is the name for the point at which the two strands separate?

• Replication Split

• Replication Knife

• Replication Fork

• Replication Division

​Replication Structures & Functions

The next FOUR slides will show you important structures in the replication process. It will also include helpful information about the FUNCTION of these structures!

Look through these carefully. You will be answering some questions about this material soon!​

DNA REPLICATION

BIOLOGY I

Multiple Choice

Which of the following functions to "unzip" or unwind the original DNA strand?

• Ligase

• Topoisomerase

• Polymerase

• Helicase

Multiple Choice

Which of the following functions to add new nucleotides?

• Ligase

• Topoisomerase

• Polymerase

• Helicase

Multiple Choice

TRUE OR FALSE: DNA Replication is semi-conservative, meaning that the new strands of DNA consist of 1 parental (original) strand and 1 new strand.

• TRUE

• FALSE

​Watch it happen!

The next slide will show a video representation of DNA Replication. Watch carefully to observe what you have already learned!

BIOLOGY I

DNA Replication

Poll

How do you feel about DNA Replication?

• Good, I'm pretty confident in this.

• Okay. It's starting to make sense.

• Eh. I don't really know much about this still.

• No clue. I know nothing.

​Congrats! You've completed this lesson.

Remember that you have access to all of these slides on Canvas to review later.

This Quizizz should have given you a decent idea of what you need to review about replication. ​

BIOLOGY I

DNA REPLICATION