chapter 8

Question 1

what is DNA replication

Answer 1

the process by which a cell copies its DNA to produce 2 identical DNA molecules before it divides so that each new cell has the same genetic info as the original.

Question 2

What is meant by a semiconservative model of DNA replication?

Answer 2

Each new DNA molecule consists of one original (parental) strand and one newly synthesized strand. This ensures genetic continuity and accurate replication.

Question 3

What are the functions of DNA helicase,
DNA polymerase, and DNA ligase

Answer 3

DNA helicase: Unwinds and separates the two DNA strands by breaking the hydrogen bonds between them, creating the replication fork.
DNA polymerase: Synthesizes new DNA strands by adding complementary nucleotides to the template strand in the 5’ to 3’ direction. Also proofreads and corrects errors.
DNA ligase: Joins Okazaki fragments on the lagging strand and seals breaks in the sugar-phosphate backbone to create a continuous DNA strand.

Question 4

What are the functions of binding proteins and primase?

Answer 4

Binding Proteins: Stabilize the single-stranded DNA after helicase unwinds it, preventing the strands from reannealing or being degraded during replication.
Primase: Synthesizes short RNA primers that provide a starting point for DNA polymerase to begin DNA synthesis.

Question 5

What are the
leading and lagging strands?

Answer 5

Leading Strand: The DNA strand synthesized continuously in the 5’ to 3’ direction, following the replication fork as it opens.
Lagging Strand: The DNA strand synthesized discontinuously in short fragments (Okazaki fragments) away from the replication fork, later joined by DNA ligase.

Question 6

What is a replication fork, and what are Okazaki fragments?

Answer 6

Replication Fork: A Y-shaped region where the DNA double helix is unwound by helicase, allowing replication to occur on both strands.
Okazaki Fragments: Short DNA segments synthesized on the lagging strand during replication. These fragments are later joined by DNA ligase to form a continuous strand.

Question 7

In which
direction is DNA replication continuous?

Answer 7

continuous in the 5’ to 3’ direction on the leading strand, following the direction of the replication fork.

Question 8

What are the parent and daughter strands?

Answer 8

Parent Strand: The original DNA strand that serves as a template during DNA replication.
Daughter Strand: The newly synthesized DNA strand that is complementary to the parent strand, created during replication.

Question 9

What is a replication “bubble?”

Answer 9

a region of DNA where the double helix has been unwound and separated by helicase, allowing replication to occur in both directions. It contains two replication forks moving outward from the origin of replication.

Question 10

What is binary fission?

Answer 10

a type of asexual reproduction used by prokaryotic cells (like bacteria) in which a single cell divides into two identical daughter cells.

Question 11

What are the four stages of binary
fission of prokaryotes?

Answer 11

1. duplication
2. elongation
3. pinching/deposition
4. division

Question 12

What are mitosis and meiosis?

Answer 12

Mitosis: A type of cell division in which a single cell divides to produce two genetically identical diploid daughter cells. It is used for growth, repair, and asexual reproduction.

Meiosis: A type of cell division that reduces the chromosome number by half, producing four genetically unique haploid gametes (sex cells). It is essential for sexual reproduction.

Question 13

What are two functions of cell division?

Answer 13

1. Growth and Development
2. Repair and Replacement

Question 14

What are two reasons that
chromosomes condense before cell division?

Answer 14

1. Efficient Separation
2. Protection of DNA

Question 15

What are histones, nucleosomes, and centromeres?

Answer 15

Histones: Proteins around which DNA wraps to form chromatin, helping to compact and organize DNA within the nucleus.
Nucleosomes: The basic units of DNA packaging, consisting of DNA wrapped around a core of eight histone proteins.
Centromeres: The region of a chromosome where sister chromatids are joined, and where spindle fibers attach during cell division.

Question 16

What is the cell cycle?

Answer 16

the series of events that a cell goes through as it grows, prepares for division, and divides into two daughter cells.

Question 17

What is interphase?

Answer 17

the longest phase of the cell cycle, during which the cell grows, performs its normal functions, and prepares for division.

Question 18

What generally occurs during G1, S, G2

Answer 18

G₁ Phase (Gap 1):

Cell grows in size.
Performs normal functions (e.g., protein synthesis, organelle production).
Prepares for DNA replication.
S Phase (Synthesis):

DNA is replicated, resulting in two identical copies of each chromosome (sister chromatids).
G₂ Phase (Gap 2):

Cell grows further.
Produces proteins and organelles needed for cell division.
Checks for DNA replication errors and repairs them.

Question 19

What is the difference between mitosis and cytokinesis?

Answer 19

Mitosis: Division of the cell’s nucleus and its genetic material into two identical nuclei. It occurs in four stages: prophase, metaphase, anaphase, and telophase.
Cytokinesis: Division of the cell’s cytoplasm and organelles, resulting in two separate daughter cells.

Question 20

When does cytokinesis begin?

Answer 20

during telophase, the final stage of mitosis.

Question 21

What general events occur during prophase, prometaphase, metaphase, anaphase, and telophase?

Answer 21

Prophase:

Chromatin condenses into visible chromosomes.
The mitotic spindle begins to form.
The nuclear envelope starts breaking down.
Prometaphase:

The nuclear envelope fully breaks down.
Spindle fibers attach to chromosomes at their kinetochores.
Chromosomes begin moving toward the metaphase plate.
Metaphase:

Chromosomes align at the metaphase plate (center of the cell).
Each sister chromatid is attached to spindle fibers from opposite poles.
Anaphase:

Sister chromatids are separated and pulled toward opposite poles of the cell by spindle fibers.
The cell elongates.
Telophase:

Chromosomes decondense back into chromatin.
The nuclear envelope reforms around each set of chromosomes.
The spindle fibers disassemble, and the cell prepares for cytokinesis.

Question 22

What is the mitotic spindle and when does it form?

Answer 22

a structure made of microtubules and associated proteins that organizes and separates chromosomes during mitosis. It forms during prophase

Question 23

What are kinetochores?

Answer 23

protein structures located at the centromere of each chromosome.

Question 24

What are cleavage, the cleavage furrow, and the cell plate?

Answer 24

Cleavage: The process of dividing the cytoplasm during cytokinesis in animal cells.
Cleavage Furrow: A contractile ring of actin filaments that pinches the cell membrane inward, dividing the cell into two daughter cells.
Cell Plate: A structure formed during cytokinesis in plant cells, where vesicles from the Golgi apparatus fuse at the center of the cell to create a new cell wall, separating the two daughter cells.