DNA Replication: S-Phase Guided Notes | Study notes Cell Biology

DIRECTIONS: You will completethe guided notes using the Video found on BLEND. You also have access to the Google Slides and PDF version of the lesson. You can print

these notes and hand write on them, you can create a copy of this document and type intoit, or you can hand write your own notes in a notebook. Make sure to keep

your notes organized in a physical folder or in a folder on your google drive. You will want to be able to access them quickly for assignments!It is highly suggested to

highlight or mark your vocabulary terms as you go through a lesson and fill in your notes.

3.7 S-Phase (DNA Replication) Guided Notes Name: Date: 1/12/21

Recall: The Eukaryotic Cell Cycle

●Two main phases:

○1. Interphase: phases of growth and DNA replication

■G1 phase: 1st Cell Growth Phase

●Cells do most of their growing during this phase. Cells increase in size and synthesize

new proteins and organelles

■S phase: Synthesis Phase (DNA replication)

●S Phase: stage of interphase in which DNA is replicated

●New DNA is synthesized when the chromosomes are replicated.

●At the end of this stage, the cell contains twice as much DNA as it did as it did at the

beginning

■G2 phase: 2nd Cell Growth Phase

●Once DNA replication is completed, the cell enters the G2 phase. Many of the organelles

and molecules required for cell division are produced.

○2. M (Mitotic) Phase: division phases

■Mitosis – nuclear division

■Cytokinesis – cell division

S-Phase: DNA Replication

●Before a cell divides, it duplicates its DNA in a copying process called replication.

●Ensures that each resulting cell has the same complete set of DNA molecules.

○Overview of process:

■The two strands of the double helix separate, allowing two replication forks to form

■As each new strand is synthesized, new bases are added using the base pairing rules.

■The result is two DNA molecules identical to each other and the original DNA molecule

■Replication is semi-conservative: each new DNA molecule resulting from replication has one

original strand and one new strand

Check for Understanding

1. What type of bonds hold the nitrogenous base pairs together in a DNA molecule?

Hydrogen bonds

2. What does it mean that DNA is antiparallel?

Allowing the nitrogenous bases to connect in the middle

3. What were the two main phases of the cell cycle?

Interphase and Mitosis

4. What stage of the cell cycle does DNA replication occur?

S phase

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DIRECTIONS: You will complete the guided notes using the Video found on BLEND. You also have access to the Google Slides and PDF version of the lesson. You can print these notes and hand write on them, you can create a copy of this document and type into it, or you can hand write your own notes in a notebook. Make sure to keep your notes organized in a physical folder or in a folder on your google drive. You will want to be able to access them quickly for assignments! It is highly suggested to highlight or mark your vocabulary terms as you go through a lesson and fill in your notes. 3.7 S-Phase (DNA Replication) Guided Notes Name: Date: 1/12/ Recall: The Eukaryotic Cell Cycle ● Two main phases: ○ 1. Interphase: phases of growth and DNA replication ■ G1 phase: 1st Cell Growth Phase ● Cells do most of their growing during this phase. Cells increase in size and synthesize new proteins and organelles ■ S phase: Synthesis Phase (DNA replication) ● S Phase: stage of interphase in which DNA is replicated ● New DNA is synthesized when the chromosomes are replicated. ● At the end of this stage, the cell contains twice as much DNA as it did as it did at the beginning ■ G2 phase: 2nd Cell Growth Phase ● Once DNA replication is completed, the cell enters the G2 phase. Many of the organelles and molecules required for cell division are produced. ○ 2. M (Mitotic) Phase: division phases ■ Mitosis – nuclear division ■ Cytokinesis – cell division S-Phase: DNA Replication ● Before a cell divides, it duplicates its DNA in a copying process called replication. ● Ensures that each resulting cell has the same complete set of DNA molecules. ○ Overview of process: ■ The two strands of the double helix separate, allowing two replication forks to form ■ As each new strand is synthesized, new bases are added using the base pairing rules. ■ The result is two DNA molecules identical to each other and the original DNA molecule ■ Replication is semi-conservative: each new DNA molecule resulting from replication has one original strand and one new strand Check for Understanding

What type of bonds hold the nitrogenous base pairs together in a DNA molecule? Hydrogen bonds
What does it mean that DNA is antiparallel? Allowing the nitrogenous bases to connect in the middle
What were the two main phases of the cell cycle? Interphase and Mitosis
What stage of the cell cycle does DNA replication occur? S phase

What does it mean that DNA replication is semi-conservative? each DNA molecule has one original strand and one new strand
A DNA strand with the sequence: 3’-A-G-C-T-T-A-C-T-G-G-5’ is replicated. Write out the complementary strand. 5’ -T-C-G-A-A-T-G-A-C-C-3’ The Role of Enzymes Cells need to copy their DNA very quickly, and with very few errors (or risk problems such as cancer). To do so, they use a variety of enzymes and proteins, which work together to make sure DNA replication is performed accurately. ● Replication is carried out by several enzymes ● DNA Helicase: Unzips a molecule of DNA by breaking hydrogen bonds between the base pairs ● DNA Polymerase: joins nucleotides to synthesize a new complementary strand of DNA and proofreads the strand to ensure accuracy in replication DNA Replication: ● DNA polymerase can only synthesize DNA in the 5’ to 3’ direction. ○ Remember a DNA double helix is always anti-parallel, so one strand runs 5’ to 3’, and the other strand runs 3’ to 5’. ● Leading Strand: The DNA strand that is replicated continuously in the 5’ to the 3’ direction. It is continuous because it is moving towards the replication fork. ● Lagging Strand: The DNA strand that is replicated discontinuously in the 5’ to the 3’ direction. It is discontinuous because as the polymerase moves forward, away from the replication fork, it has to come off and attach. ○ Okazaki Fragment: Fragments of DNA replicated on the lagging strand.

Eukaryotic DNA Replication: ● In eukaryotic cells, replication may begin at dozens or even hundreds of places on the DNA molecule, proceeding in both directions until each chromosome is completely copied. ● Many proteins check DNA for damage or mismatches, but damaged regions of DNA are still sometimes replicated. Prokaryotic DNA Replication: ● Replication in most prokaryotic cells starts from a single point and proceeds in two directions until the entire chromosome is copied. ○ Recall: The Prokaryotic Cell Cycle ○ The process of cell division in prokaryotes is a form of asexual reproduction known as binary fission ■ Once the chromosome has been replicated, the two DNA molecules attach to different regions of the cell membrane ■ Binary fission results in the production of two genetically identical daughter cells. Exit Ticket

Identify the enzyme responsible for addition of new nucleotides to a lengthening strand of DNA. DNA Polymerase
Identify the enzyme responsible for separation of the double helix. DNA Helicase
DNA Polymerase synthesizes DNA in the 5’ to the 3’ direction.
Segments of DNA replicated on the lagging strand are called Okazaki Fragments.
These organisms have a single, circular chromosome. Prokaryotes

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