DNA: Structure and Replication

Nucleic Acids, 3 parts of a nucleotide, DNA Structure, DNA is Antiparallel, RNA Structure, Basics of Hereditary, DNA Replication

Nucleic Acids: What are macromolecules

They hold our genetic material (DNA)

Nucleic Acids: What do nucleic acids contain?

Genes

Nucleic Acids: What are genes?

They’re sections of DNA that are the blueprint/instructions for making proteins.

Nucleic Acids: Where are genes located?

At specific points on the chromosome

Nucleic Acids: What are the types of Nucleic Acids?

DNA and RNA

What are the 3 parts of a nucleotide

Phosphate group, pentose sugar, and nitrogenous base

DNA Structure: What is the structure of DNA?

Double helix

DNA Structure: What does the sugar and phosphate combined make?

The “phosphate sugar backbone”

DNA Structure: What bases bond in the middle and what do they use to bond in the middle?

Nitrogen bases bond in the middle using weak hydrogen bonds

DNA Structure: What are the rest of the bonds in DNA?

Covalent

DNA Structure: What base pairs do nitrogen bases bond with? Give an example:

They only bond with their complementary base pair (Adenine with Thymine or Uracil, depending on if it’s DNA or RNA, and Cytosine with Guanine)

DNA Structure: What is it called when Adenine and Thymine are bonded to each other?

That they are double bonded

DNA Structure: What is it called when Cytosine always bonds to Guanine?

Triple-Bonded

DNA Structure: What is Chargaff’s Rule?

That the amount of Adenine always equals to Thymine, and that the amount of Cytosine always equals to Guanine.

DNA is Antiparallel: What does it mean if DNA is antiparallel?

DNA strands run in opposite directions

DNA is Antiparallel: Give an example of DNA being antiparallel?

• One strand runs in the 5’ → 3’ direction

• The other strand runs in the 3’→5’ direction

• 5’=Phosphate end

• 3’=(Deoxyribose) sugar end

RNA Structure: What is RNA?

It’s a single strand of nucleotides with exposed bases

RNA Structure: What do RNA bases bind with?

DNA bases

Comparisons - DNA and RNA: What is the function of DNA?

Long term storage of genetic information

Comparisons - DNA and RNA: What is the function of RNA?

Used to transfer genetic information in organisms

Comparisons - DNA and RNA: What is the structure of DNA?

Double helix, Deoxyribose sugar used

Comparisons - DNA and RNA: What is the Structure of RNA?

It’s a single strand of Ribose Sugar used

Comparisons - DNA and RNA: What is the composition of DNA and RNA?

DNA: Adenine, Guanine, Cytosine and Thymine Bases

RNA: Adenine, Guanine, Cytosine, and Uracil Bases

Comparisons - DNA and RNA: What is the formation of DNA?

DNA is self-replicating

Comparisons - DNA and RNA: What is the formation of RNA?

It’s synthesized from DNA on an as-needed basis.

Basics of Hereditary: What are chromosomes?

Tightly coiled strands of DNA (different organisms have different amounts of chromosomes)

Basics of Hereditary: What is a gene? How many genes can one chromosome have?

-Section of DNA, has instructions to code for protein

-Thousands, potentially

Basics of Hereditary: What are the amount of chromosomes humans posses?

46 (23 pairs of chromosomes)

DNA Replication: What does a cell do when it’s ready to divide?

What is this called?

-It must first copy its DNA

-DNA Replication

DNA Replication: When does DNA Replication happen?

In the nucleus during S phase of Interphase

DNA Replication: What does DNA replication ensure/what is its purpose?

That each new cell has the same genetic information as the original one.

DNA Replication: Step 1 of Replication

-Helicase (enzyme) unzips DNA into 2 separate strands

-Several spots along double helix open at once

DNA Replication: Step 1 of Replication - What is the opening called?

“Origin of Replication”

DNA Replication: Step 2 - Which other enzyme is added and what does it do?

-DNA Polymerase adds complementary nucleotides to template strands

DNA Replication: Step 2 - What happens to nucleotides?

They are only added to the free 3’ end → new DNA strands are only formed in the 5’ 3’ direction

DNA Replication: Step 2 - What is the only thing that makes step 2 work?

Enzymes

DNA Replication: Step 2 - What is RNA Primase? What is it required for?

•  makes short RNA primers (short pieces of RNA to help get the DNA polymerase started)

• DNA synthesis

DNA Replication: Step 2 - What is DNA Polymerase

Adds nucleotides to the RNA primer

DNA Replication: Step 2 - How many functions does DNA polymerase completed in step 2 of replication

3

DNA Replication: Step 2 - What is the first function of DNA polymerase

Making polynucleotides

DNA Replication: Step 2 - What is the second function of DNA polymerase?

After all nucleotides are added to the strand, RNA is replaced with DNA

DNA Replication: Step 2 - What is the 3rd function of DNA polymerase?

Proofreads the strands

DNA Replication: Step 2 - What does DNA ligase do?

Seals the gaps in DNA

DNA Replication: Step 2 - How many new strands of DNA are being created? What’s the timeframe for them?

2 at the same time

DNA Replication: Step 2 - What is the leading strand?

The new strand made toward the replication fork

DNA Replication (Step 2): Leading Strand - What is the leading direction of the DNA strand? What is its original one?

Made in 5’→3’ (template is 3’→5’)

DNA Replication (Step 2): Leading Strand - What does the leading strand need?

ONE RNA primer made by primase

DNA Replication (Step 2): Leading Strand - How is the new leading strand being made?

Continuously

DNA Replication (Step 2): Lagging Strand - Which direction does the new strand synthesize too?

Away from the replication fork

DNA Replication (Step 2): Lagging Strand - How is the lagging strand being made? What does this create?

-Discontinuously

-Okazaki fragments (short pieces of DNA)

DNA Replication (Step 2): Lagging Strand - What happens to the okazaki fragments?

They’re stitched together by DNA ligase

DNA Replication: Lagging Strand - What does the lagging strand need?

MANY RNA primers made by primase

DNA Replication: Step 3 - What happens in step 3 of replication? What is this called?

-Two identical DNA molecules are formed, each containing HALF of the ORIGINAL/TEMPLATE STRAND

-Semi-conservative replication

DNA Replication: Step 3 - What is semi-conservative replication?

Each parent strand is now a template that determines which order nitrogen bases go in.

DNA Replication: Step 3 - What does semi-conservative replication form?

A “complimentary” strand to the original/parent strand (newly synthesized double helix)

DNA Replication: Step 3 - What is the newly synthesized double helix a combination of in semi-conservative replication?

-One strand of the old/original DNA

One strand of the new DNA

General overview of replication:

1. Unzip the DNA

2. Enzymes help find complementary bases, bind them according to complementary base pair rules

3. Two identical DNA molecules are formed, each with one “old” strand and one “new” strand