Unit 4, Concept 1

DNA Structure and Replication

What are nucleic acids?

This is a macromolecule that carries our genetic information (DNA). Has the blueprint/instructions for making proteins.

\*\*What are two types of nucleic acids?

DNA and RNA are these two types

What does DNA stand for?

Deoxyribonucleic acid is what this stands for.

What does RNA stand for?

Ribonucleic acid is what this stands for.

What are nucleotides?

These make up nucleic acids. They are monomers of DNA.

What 3 parts do nucleotides have?

These have sugar, phosphate, and nitrogen base for their 3 parts.

What are examples of sugar?

Deoxyribose and Ribose are examples of this

What are nitrogen bases?

Adenine, Guanine, Cytosine, Thymine (DNA only), and Uracil (RNA only) are these.

What shape is DNA in?

This item’s shape is a double helix (a twisted ladder)

What two bonds bond things together in DNA?

Strong covalent bonds and weak hydrogen bonds are these two bonds.

What does Adenine and Cytosine bond with in DNA?

Thymine and Guanine bond with these in DNA.

What is it called when the nitrogen bases can only bond with certain others?

This is called the “complementary base pairing rules“.

What are Purines?

*(small word, big base*) These are big bases that have the nitrogen bases Adenine and Guanine.

What are Pyrimidines?

(big word, small base) These are big bases with Cytosine and Thymine.

What is the difference between Purines and Pyrimidines?

Purines are big bases with nitrogen bases Adenine and Guanine, while Pyrimidines are small bases with nitrogen bases Thymine and Cytosine.

What are Chargaff’s rules?

These rules state that A=T and C=G.

What do weak hydrogen bonds do?

These bonds hold the nitrogen pairs together

How many bonds do Adenine and Thymine share?

These two nitrogen bases share double bonds (2 bonds)

How many bonds do Cytosine and Guanine share?

These two bases share triple bonds (3 bonds).

What does antiparallel mean?

This term means the strands run in opposite (or antiparallel) directions.

How is DNA antiparallel?

DNA has two strands that run, and one starts with a phosphate and runs in the 5’ to 3’ direction. The other strand starts with deoxyribose (sugar) and runs in the 3’ to 5’ direction. Since these strands will always alternate and go in different directions, they are antiparallel.

What is the 5’ (5 prime) end?

This end is the phosphate end (“fa” sound - phosphate and five make the “fa” sound).

What is the 3’ (3 prime) end

This end is the sugar (deoxyribose) end.

Where are the weak hydrogen bonds in a DNA molecule?

These bonds are found in the middle of the DNA molecule. These bond the nitrogen bases together.

Where are the strong covalent bonds in a DNA molecule?

These bonds are found on the outside of a DNA molecule. These bond the phosphates and sugars together (nucleotide).

Draw a nucleotide (What does it look like/have?)

A nucleotide has a phosphate bonded (covalently) with sugar (deoxyribose). That sugar is also being bonded to a nitrogen base, which is also bonding (hydrogen bond) with another nitrogen base.

\
*Tip: When we were having to cut out little pieces of DNA and put them together with the phosphates, sugars, and bases (Adenine, Thymine, etc.), those were nucleotides. When we put them all together in class, those all together made a DNA molecule, or nucleic acid.*

What is the structure of a DNA molecule (in detail)?

For its structure, it has:

* Double Helix - sugar and phosphate form “sugar phosphate backbone", nitrogen bases bond in the middle.
* Nitrogen bases paired complementary with hydrogen bonds.
* It is antiparallel and runs in opposite directions (one strand runs in 5’ to 3’, the other runs in 3’ to 5’).

What’s the difference between a strand of DNA, genes, and a chromosome?

Genes are pieces/sections of DNA, chromosomes are long strands of DNA bunched up and coiled, and a strand is a long molecule with nucleotides/nitrogen bases.

Summarize the process of DNA Replication.

During DNA Replication, DNA is unzipped by Polymerase. Enzymes help find the complementary bases (basically match them up) according to the rules - A=T, C=G. Two identical DNA molecules are made, one “new” strand and one “old” strand.

What is the difference between the leading strand and the lagging strand in DNA replication?

* The leading strand needs 1 RNA primer but the lagging needs many.
* The leading strand is made continuously but the lagging strand is discontinuously.
* The lagging strand creates Okazaki fragments and the leading doesn’t.

Explain the function of each enzyme in the process of DNA Replication

* The enzyme Helicase unzips DNA into 2 strands.
* Enzyme DNA Polymerase adds complementary nucleotides to the template strands.
* Enzyme primase makes short RNA primers.
* DNA ligase seals DNA gaps, connects DNA pieces by making bonds.

What is RNA primer?

This is the RNA that initiates DNA synthesis.

What are Okazaki fragments?

These fragments are short sequences of DNA nucleotides that are made and later linked by DNA ligase to make the lagging strand.

What is the Semi-Conservative Model?

In this model, DNA’s 2 strands unwind and each help create a new, complementary strand.

What is Semi-Conservative Replication?

This is where DNA’s old (original) strands unzip and help create new strands that complement them. There one **new** strand and one **old** one, which is the original.