DNA, Chromosomes, and Cell Division - WEEK 4

Bonded from phosphate to sugar between 3’& 5’ carbons

How are nucleotide in DNA backbone bonded?

Replication

This is the synthesis of a new molecule of DNA

• DNA has to be copied before a cell divides

• New cells will need identical DNA strands

The the process of replication (synthesis of new DNA molecule), these must be remembered. (two kabook)

During the S phase of interphase

In the process of replication, when is DNA copied?

many enzymes and cofactors

The process of DNA replication requires many _________ and __________.

Unwinding

What is the first step of DNA replication?

Breakage of the hydrogen bonds that hold the DNA strands together.

What generally happens in the process of unwinding (DNA replication)?

DNA helicase and single-strand binding proteins

These two works to separate the DNA strands and keep the DNA exposed at many points along the length of the helix during replication.

Separate the strands and keep the DNA exposed at many points along the length of the helix during replication

During the unwinding process (DNA replication) what is the role of DNA helicase and single-strand binding proteins?

DNA Helicase

What enzyme unwinds and separates the two DNA strands by breaking the weak hydrogen bonds?

Separates the two DNA strands by breaking the weak hydrogen bonds

What is the role of the enzyme DNA Helicase?

Single-Strand Binding Proteins

In the process of replication, this attaches and keep the two DNA strands separated and untwisted.

Keep the two DNA strands separated and untwisted.

What is the role of Single-Strand Binding Proteins in the process of DNA unwinding?

Enzyme Topoisomerase

What enzyme attaches to the two forks of the bubble to relieve stress on the DNA molecule as it separates, preventing the super-coiling of DNA?

• Enzyme DNA Helicase unwinds and separates the two DNA strands by breaking the weak hydrogen bonds.

• Single-Strand Binding Proteins attach and keep the two DNA strands separated and untwisted.

• Enzyme Topoisomerase attaches to the two forks of the bubble to relieve stress on the DNA molecule as it separates.

Enumerate the “steps” in the process of DNA Unwinding

• Y shaped structure

• Replication Fork

• What is the shape of the are of DNA at the active region of separation?

• What is this shape referred to?

• Replication bubbles

• Replication Origins

• The replication forks originated from what “structures”?

• It is where (answer from Q1) originated?

Thousands of Origins of Replication

Where is the DNA Replication of Eukaryotic Cells begins?

Daughter Strand

What is the 2nd step of DNA Replication?

Production of complementary strands of DNA

The separated strands of DNA serve as templates for __________?

Chargaff’s rules of base pairing

What rule is followed when the separated strands of DNA serve as templates for production of complementary strands of DNA?

• 3’ end of an existing strand.

• causes NEW strand to be built in a 5’ to 3’ direction

2nd Step: DAUGTHER STAND

• Where are Nucleotides can only be added?

• What is the result of this instance?

Leading strand

What is synthesized as a single strand from the point of origin toward the opening replication fork

synthesized as a single stand

What happens to the Leading Strand from the point of origin toward the opening replication fork?

from the point of origin toward the opening replication fork

Where is the Leading Strand synthesized as a single strand?

RNA primers

Before new DNA strands can form, what must be present in order to start the addition of new nucleotides?

The addition of new nucleotides will STOP

What will happen if RNA primers is not be present during the forming of new DNA strands?

DNA Primase

What enzyme synthesizes the RNA primer?

Synthesizes RNA primer

What is the function of DNA Primase?

DNA polymerase III

What enzyme facilitates the addition of complementary nucleotides to the 3’ end of a newly forming DNA strand?

Facilitates the addition of complementary nucleotides to the 3’ end of a newly forming strand of DNA.

What is the role of the enzyme DNA polymerase III?

3’-hydroxyl end of a base-paired strand

What is required by the enzyme DNA polymerase III in order to add further nucleotides?

Lagging Strand

This is synthesized discontinuously against overall direction of replication

Okazaki Fragments

What do you call the series of short segments on the lagging strand?

Ligase

What enzyme joins the Okazaki fragments to make one strand?

It joins the Okazaki fragments together to make one strand

What is the role/function of the enzyme Ligase?

Semiconservative

What term best describes the process of replication, for the reason being that the net result is creation of two identical DNA molecules, each consisting of a parent DNA strand and a newly synthesized DNA strand?

• 2 identical DNA molecules

• Parent DNA strand and a newly synthesized DNA strand.

• What is the net result of the replication process?

• This “result” consist of what?

Transcription

What is the 1st step in protein synthesis?

linear sequence of nitrogenous bases in triplets.

The genetic information of DNA is stored as a code. What represents this code?

• specific amino acids

• protein molecules

• What are the sequences of triplets nitrogenous bases code for?

• What is formed when the “answer for 1st question” when subsequently linked together?

RNA polymerase

What enzyme controls the Transcription process?

RNA polymerase

This enzyme functions to link ribonucleotides together in a sequence complementary to the DNA template strand

Link ribonucleotides together in a sequence complementary to the DNA template strand

What is the function of RNA polymerase?

temporarily unzips

In the transcription process, what happens to the part of DNA in order for it be used as a template in assembling complementary nucleotides into messenger RNA (mRNA).

messenger RNA (mRNA)

In the process of transcription, part of DNA temporarily unzips and is used as a template to assemble complementary nucleotides into _____________________.

messenger RNA

mRNA abbreviation means?

Promoter Region

This is the regions on DNA that show where RNA Polymerase must bind to begin the transcription of RNA.

TATA box

This is referred to as the promoter on DNA that show where RNA Polymerase must bind to begin the transcription of RNA.

Termination Signal

This is a specific base sequences act as signals to stop.

5’ end of the RNA

Where is the RNA capping happens at which part of RNA?

RNA capping

This usually adds Guanosine triphosphate shortly after RNA polymerase makes the 5’ end of the primary transcript

Guanosine triphosphate

In the process of RNA capping, what is usually added shortly after RNA polymerase makes the 5’ end of the primary transcript?

beginning of transcription

When does RNA occurs?

5’ cap

In the process of RNA capping, what is used as a recognition signal for ribosomes to bind to the mRNA

Recognition signal for ribosomes to bind to the mRNA

The 5’ cap, in the RNA capping process, is used as what?

Polyadenylation

What modifies the 3’ end of the primary transcript by the addition of a string of A’s?

by the addition of a string of A’s.

How does Polyadenylation modifies the 3’ end of the primary transcript?

• transport of mRNA molecules

• stability of the mRNA

POLYADENYLATION: Fill in the blank

• This poly(A) tail helps in the ________________ to the cytoplasm.

• A poly(A) tail of 150 or more adenine nucleotides is added. The tail plays a role in the ________________.

Introns

This is the non-functional segments of DNA that are snipped out of the chain

they non-functional segments of DNA

Why are Introns snipped out of the DNA chain?

Exons

These are the segments of DNA that code for proteins

segments of DNA that code for proteins

What are Exons?

Ligase

What enzyme helps rejoined the Exons segments?

Translation

What do you call the process of decoding the mRNA into a polypeptide chain

polypeptide chain

In the process of translation, the mRNA is decoded into a ____________?

Ribosome

What reads mRNA triplets or one codon at a time and construct the proteins.

Transfer RNA (tRNA)

• It is a single stranded molecule with attachment site at one end for an amino acid

• Its opposite end has three nucleotide bases called anticodon.

amino acid

tRNA is a single stranded molecule with attachment site at one end for an ___________.

• three nucleotide bases

• anticodon

1. Transfer RNA’s (tRNA) opposite end has a ____________

2. These ends is called ___________.

complementary

The 3 bases of an anticodon are _________________ to the 3 bases of a codon

3 bases of a codon

The 3 bases of an anticodon are complementary to the _____________

• Gap 1 (G1)

• Synthesis (S)

• Gap 2 (G2)

What are the three stages of interphase?

Gap 1 (G1)

STAGES OF INTERPHASE:

• Chromosomes exist as single chromatids during this stage.

Gap 1 (G1)

STAGES OF INTERPHASE:

• Cells are metabolically active, and this is when protein synthesis takes place.

Synthesis (s)

STAGES OF INTERPHASE:

• This is when DNA synthesis occurs

Synthesis (S)

STAGES OF INTERPHASE:

• The DNA replicates itself, and the chromosomes then consist of two identical sister chromatids.

Gap 2 (G2)

STAGES OF INTERPHASE:

• During this phase, the cell prepares to undergo cell division.

Gap 2 (G2)

STAGES OF INTERPHASE:

• The completion of this represents the end of interphase.

The completion of G2

What represents the end of interphase?

Prophase

MITOSIS:

• Chromosomes begin to coil, become more condensed, and begin to become visible as discrete structures

Prophase

MITOSIS:

• Nucleoli are visible early, but disappear as the stage progresses

Nucleoli

In the prophase stage, the _______ is early visible but disappear as the stage progresses.

Prometaphase

MITOSIS:

• The nuclear membrane disappears and the spindle fibers begin to appear.

Prometaphase

MITOSIS:

• Chromosomes attach to the spindle fibers at their kinetochores

Kinetochores

During the Prometaphase, Chromosomes attach to the spindle fibers at their ______________.

Metaphase

MITOSIS:

• The mitotic spindle is completed, the centrioles divide and move to opposite poles, and the chromosomes line up on the equatorial plate

Metaphase

MITOSIS:

• It is during this phase that chromosomes are traditionally studied in cytogenetics

Anaphase

MITOSIS:

• Centromeres divide longitudinally and the chromatids separate during this stage.

Anaphase

MITOSIS:

• As this phase progress, sister chromatids migrate to opposite poles

Telophase

MITOSIS:

• The chromosomes uncoil and become indistinguishable again, the nucleoli reform, and the nuclear membrane is reconstructed.

Telophase

MITOSIS:

• Usually followed by cytokinesis or cytoplasmic division

cytokinesis or cytoplasmic division

Telophase is usually followed by _____________.

G1 phase

Interphase:

• Cell growth

S phase

Interphase:

• DNA replication

G2 phase

Interphase:

• Preparation for mitosis

1. Interphase (G1, S, G2)

2. Prophase

3. Metaphase

4. Anaphase

5. Telophase

What are the stages of Mitosis?

Ovaries and Testes

Where is Meiosis only takes place?

Meiosis

A process involving one duplication of the DNA and two cell divisions (I and II) reduces the number of chromosomes from the diploid number to the haploid number.

2n = 46

Diploid number