Test #3 Study

Question 1

How do cells divide in mitosis?

Answer 1

the division of a cell’s nucleus.
Along with cytokinesis (the division of the rest of a cell),
results in a parent cell dividing into two daughter cells
The genetic information within each of these daughter cells is identical.

Question 2

How do cells divide in Meiosis?

Answer 2

a type of cell division specific to reproduction,
halving the number of chromosomes in a cell.

Question 3

humans’ cells contain

Answer 3

46 chromosomes

Question 4

What happens if the cell did not have half of the 46 chromosomes in the sperm and egg?

Answer 4

a fertilized egg will contain 92 chromosomes and be unable to maintain its proper functions

Question 5

Interphase for Mitosis and Interphase I for Meiosis (first)

Answer 5

is the period between cell divisions

chromosomes replicate—each DNA strand unzips into two strands while free-floating bases attach to the unzipped strands
chromosomes are loosely packed
Two pair of centrioles lie just outside the nucleus, next to each other.

A centriole is a cylindrical structure within the cell helps with reproduction.

Question 6

Prophase for Mitosis (second)

Answer 6

chromosomes begin to condense

four arms connected at a point. Each chromosome is, at this time, actually two identical copies. Each copy is called a chromatid.

A spindle begins to form from the centrioles. This spindle is made of fibers. The centrioles begin to separate.

Question 7

Prophase I for Meiosis

Answer 7

same as prophase for Mitosis only difference:
except that in this cell the chromosomes attach to the membrane of the nucleus and then pair up with their corresponding chromosome.

While paired up, enzymes cut sequences of DNA (genes) from the chromosomes. These sequences are exchanged between the chromosomes, which allows for an exchange of genes between the two.

Question 8

Prometaphase in Mitosis

Answer 8

The centrioles are now at opposite ends of the cell.

The spindle fibers from both of the centrioles attach to each one of the chromosomes.

Question 9

Prometaphase I in Meiosis

Answer 9

Same as in mitosis, except that the spindle fibers from each centriole attach to one chromosome of a matching chromosome pair.

In other words, the fibers from one centriole attach to 23 chromosomes, and the fibers from the other centriole attach to the other 23 chromosomes.

Question 10

Metaphase in Mitosis (third)

Answer 10

The chromosomes line up on the metaphase plate, an imaginary line that divides the cell in two.

Also, the fibers begin to tug each chromosome toward opposite ends of the cell.

Question 11

Metaphase in Meiosis

Answer 11

Same as in mitosis, except that the chromosome pairs line up on either side of the metaphase plate.

Question 12

Anaphase in Mitosis (fourth)

Answer 12

The fibers pull the chromatids toward opposite ends of the cell.

Question 13

Anaphase I in Meiosis

Answer 13

The chromosome pairs separate; half of the chromosomes move toward one end of the cell, the other half, to the other end.

The chromosomes’ sister chromatids do not separate as they do in mitosis

Question 14

Telophase in Mitosis (fifth)

Answer 14

The chromatids (now also considered chromosomes) arrive at the opposite ends of the cell, and new nuclear membranes form.

Mitosis, which describes only the division of the nucleus, is now complete.

Question 15

Telophase I in Meiosis

Answer 15

As in mitosis, the chromosomes arrive at opposite ends of the cell, and new nuclear membranes form.

Question 16

End of cytokinesis in mitosis and meiosis

Answer 16

The rest of the cell divides.

Cytokinesis, the division of the cell’s cytoplasm, is now complete.

Question 17

Interphase II Meiosis

Answer 17

Mitosis is finished by this point
The chromosomes do not replicate during this phase, as they do in interphase in mitosis and interphase I in meiosis.

Question 18

Prophase II in meiosis

Answer 18

As in prophase I, the chromosomes condense, spindles form, the centrioles begin to separate, and the nuclear membrane fragments and disperses.

Unlike prophase I, the chromosomes do not attach to the nuclear membrane in order to exchange genetic information.

Question 19

Prometaphase II in meiosis

Answer 19

The spindle fibers attach to the chromosomes. The centrioles are now at opposite ends of the cell.

As in mitosis prometaphase, fibers from both ends of the cells attach to each one of the four chromosomes.

Question 20

Metaphase II in meiosis

Answer 20

The chromosomes align along the metaphase plate.

As in mitosis metaphase, (and unlike meiosis metaphase I), fibers from the centrioles begin to pull on each one of the chromosomes from both directions

Question 21

Anaphase II in meiosis

Answer 21

As in anaphase in mitosis (and unlike anaphase I in meiosis), the fibers pull the chromatids apart and toward opposite ends of the cells.

Question 22

Telophase II in meiosis

Answer 22

The chromatids arrive at the either end of each cell and new nuclear membranes form.

With meiosis in a female, there is only one dividing cell at this point. As in telophase I, the cytoplasm of the cell will be concentrated in one of the two emerging cells. The resulting large cell will become an egg cell. The smaller cell will degenerate

Question 23

End of cytokinesis in meiosis

Answer 23

The rest of the cell continues to divide. Only when two, distinct cells form will cytokinesis, the division of the cell’s cytoplasm, be complete.

There are now four daughter cells. Each cell has one set of chromosomes, or one half the number of the initial cell.

Question 24

Why do cell divide?

Answer 24

to make new cells
A single cell divides to make two cells and these two cells then divide to make four cells, and so on.

We call this process “cell division” and “cell reproduction,” because new cells are formed when old cells divide

Question 25

What is interphase?

Answer 25

is the longest stage in the eukaryote cell cycle prepares cells for cell division the cell acquires nutrients, creates and uses proteins and other molecules, and starts the process of cell division by replicating the DNA

Question 26

Stage of Interphase Gap 1 or G1

Answer 26

After cells have finished dividing their chromosomes, and cytokinesis has divided the cell membrane, the two new cells enter the first stage of interphase, Gap 1 or G1. During this stage, the cell performs its normal functions, and grows in size.

Question 27

Stage of Interphase Synthesis

Answer 27

the cell pauses its normal functioning All resources are dedicated to replicating the DNA. This process starts with the two entwined stands of DNA being “unzipped” by various proteins. Other proteins, known as polymerase enzymes, start creating new strands to pair with each half of the DNA

Question 28

Stage of Interphase Gap 2 or G2

Answer 28

During G2 the cell the cell adds volume to the cytoplasm, and replicates many important organelles In animals, the mitochondria are replicated to provide enough energy for the dividing cell. In plants, both the mitochondria and the chloroplasts must be replicated to provide the daughter cells with organelles capable of producing energy

Question 29

What is Mitosis?

Answer 29

A type of cell division in eukaryotes that creates identical daughter cells. Mitosis is a process of nuclear division in eukaryotic cells that occurs when a parent cell divides to produce two identical daughter cells

Question 30

What is Cytokinesis?

Answer 30

The division of a cell membrane into two cells; the process that completes cell division.

Question 31

What is Meiosis?

Answer 31

Two consecutive cell divisions between which no DNA replication takes place.

Question 32

A cell just finished dividing. It starts gathering nutrients and growing. It stops growing, and does not start DNA replication. What stage is the cell in?

Answer 32

G0 This cell remains in resting phase it will not continue dividing until it receives signals from the body to do so. These signals could come from damage to nearby cell or from growth hormones telling the body to expand. Until then, the cell will remain in G0.

Question 33

A cell has grown a little, and replicated its DNA. What comes next?

Answer 33

Gap2 The cell has just replicated its DNA, which is the interphase stage of synthesis. The next stage is Gap 2, where the cell must prepare for cell division. Without the increased size and organelles produced in Gap 2, the cell would not have enough material to divide and would be much too small after division.

Question 34

Why is there no interphase in bacteria?

Answer 34

Bacteria have no distinct organelles The bacterial cell cycle is divided into 4 phases, A, B, C, and D, which roughly correspond to the various stages of the eukaryotic cell cycle. While A is the process of binary fission in bacteria, B, C, and D are similar to interphase in that the cell functions normally and duplicates its DNA.

Question 35

what type of cells undergo mitosis?

Answer 35

Somatic cells: are the regular cells in the body of multicellular organisms. Some examples of somatic cells are epithelial cells, muscle cells, liver cells, etc Adult stem cells: Some very specialized somatic cells such as cardiac muscle cells, nerve cells, and red blood cells do not undergo mitosis. These types of cells are differentiated from adult stem cells, not from cell division Cells in the embryo: Zygote is the conceptus of fertilization, and it is composed of a single cell with a diploid nucleus. It undergoes three mitotic divisions to form eight-cell stage called the blastocyst. Blastocyst undergoes a large number of mitotic divisions while developing into a young.

Question 36

Organelles in mitosis to make the world spin

Answer 36

the nucleus, mitotic spindle and microtubules.

Question 37

What are microtubules and what is their role in cell division?

Answer 37

hollow tubes roles in cell movement, cell division, and transporting materials within cells. a network of protein filaments that extends throughout the cell, gives the cell shape, and keeps its organelles in place. Microtubules are the largest structures in the cytoskeleton

Question 38

What is the difference between a chromosome, gene, and genome?

Answer 38

genes are building blocks for your body. some give the instructions to make proteins. A protein’s job is to tell your body what types of physical characteristics you should have, like your hair and eye color. Some genes code for RNA, which does other jobs. Chromosomes are structures that look like thread, which live in the nucleus (center) of cells. Chromosomes contain DNA and protein, and they come in different sizes. Proteins called histones allow them to pack up small enough to fit in a nucleus. histones make chromosomes smaller to fit in our body genomes are all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as regulatory sequences

Question 39

Which cells undergo mitosis and which cells undergo meiosis?

Answer 39

mitosis is with somatic cells and ends with two identical cells meiosis is with germ cells that divide for sperm and egg producing cells that only have one copy of each type of chromosomes (haploid)

Question 40

When is DNA in chromatin form?

Answer 40

mainly in interphase when cells prepare to divide, chromatin condenses into chromosomes to get accurate genetic material

Question 41

When is DNA in chromosome form?

Answer 41

during cell division, during mitosis and meiosis in mitosis, Prophase: Chromatin condenses into visible chromosomes, each consisting of two sister chromatids joined at a centromere. Metaphase: Chromosomes align at the cell's equatorial plane (metaphase plate). Anaphase: Sister chromatids are pulled apart to opposite poles of the cell. Telophase: Chromatids reach the poles, and the cell begins to divide. Chromosomes start to de-condense back into chromatin. in meiosis, Meiosis I: Homologous chromosomes pair up and undergo crossing over during prophase I, then align at the metaphase plate, separate during anaphase I, and reach the poles by telophase I. Meiosis II: Similar to mitosis, where sister chromatids align, separate, and reach opposite poles, ending with the formation of four haploid cells.

Question 42

what are centromeres and kinetochores

Answer 42

centromere is a region on a chromosome where sister chromatids are joined together plays crucial role during cell division by ensuring correct segregation of chromatids into daughter cells position can vary, it can be at the center or towards one end or at the very end. Kinetochores are protein complexes that assemble on end of centromere during cell division Serve as attachment for spindle fibers (microtubules) that pull chromatids apart to opposite poles of cell. consist of inner region directly attached to centromere DNA and outer region that interacts with spindle fibers

Question 43

What are centrosomes?

Answer 43

organelles that play role in organizing microtubules and getting cell division started composed two centrioles surrounded by mass of proteins called pericentriolar material serve as main microtubule organizing centers in animal cells

Question 44

What is centrosome's role in cell division

Answer 44

Microtubule Organization: Centrosomes organize the microtubules, which are essential for forming the mitotic spindle. spindle formation: during prophase, centrosomes duplicate, then move opposite ends= bipolar spindle apparatus chromosome segregation: spindle fibers (microtubules) attach to kinetochores to ensure segregation of daughter cells during anaphase

Question 45

How is the cell cycle regulated?

Answer 45

by signals and checkpoints G1 Checkpoint (Restriction Point): Assesses cell size, nutrient availability, and DNA integrity. If conditions are favorable, the cell commits to DNA replication. G2 Checkpoint: Ensures DNA replication is complete and checks for DNA damage. If issues are detected, the cell cycle is halted for repairs. M Checkpoint (Spindle Checkpoint): Occurs during metaphase of mitosis. Ensures all chromosomes are properly attached to the mitotic spindle before proceeding to anaphase.

Question 46

What is the role of positive regulators in the cell cycle? What is the role of negative regulators in the cell cycle?

Answer 46

positive regulators: These proteins promote cell cycle progression. Examples: Cyclins and CDKs. negative regulators: hese proteins inhibit cell cycle progression to prevent uncontrolled cell division. Examples: Tumor suppressor proteins like p53 and Rb.

Question 47

what are cyclins and what do they do

Answer 47

Proteins that regulate the cell cycle by binding to and activating CDKs. Cyclins bind to CDKs, resulting in the activation of the kinase activity of CDKs.

Question 48

What are cyclin-dependent kinases and what do they do?

Answer 48

CDKs are a family of protein kinases that, when activated by binding to cyclins, phosphorylate target proteins to drive cell cycle progression. Function: CDKs add phosphate groups to specific substrates, which can activate or deactivate these proteins, leading to changes in cellular processes that promote the progression through different stages of the cell cycle.

Question 49

relationship between cyclins and CDKs

Answer 49

Cyclins and CDKs form complexes that are essential for the regulation of the cell cycle. Cyclins act as regulatory subunits, while CDKs serve as catalytic subunits. The binding of a cyclin to a CDK activates the kinase activity of the CDK, allowing it to phosphorylate target proteins.

Question 50

Describe how they promote the cell cycle.

Answer 50

G1 Phase: Cyclin D binds to CDK4 and CDK6, forming active complexes that phosphorylate the retinoblastoma (Rb) protein. S Phase: Cyclin E binds to CDK2, forming a complex that further phosphorylates Rb and other targets, driving the cell into the S phase, where DNA replication occurs. G2 Phase: Cyclin A binds to CDK2, forming a complex that is essential for the completion of DNA replication and preparation for mitosis. M Phase: Cyclin B binds to CDK1, forming the maturation-promoting factor (MPF) complex that triggers the entry into mitosis by phosphorylating various substrates involved in chromosome condensation, spindle formation, and other mitotic events.

Question 51

what are proto-oncogenes and oncogenes?

Answer 51

Proto-oncogenes are normal genes that regulate cell growth, division, and differentiation. They encode proteins that stimulate cell proliferation and survival. Function: These genes are essential for normal cellular functions, such as growth factors, growth factor receptors, signal transduction proteins, and transcription factors. Oncogenes are mutated or abnormally activated versions of proto-oncogenes. They can cause uncontrolled cell growth and division, leading to cancer. Function: Oncogenes result from mutations, amplifications, or overexpression of proto-oncogenes, leading to the production of proteins that drive continuous cell proliferation without normal regulatory controls.

Question 52

What are tumor suppressor proteins?

Answer 52

Tumor suppressor proteins are proteins encoded by tumor suppressor genes that inhibit cell proliferation, promote DNA repair, and induce apoptosis (programmed cell death) when necessary. Function: These proteins act as brakes on cell division, ensuring that cells only divide when conditions are favorable and that damaged cells do not continue to proliferate.

Question 53

Describe how mutations in proto-oncogenes and tumor suppressor proteins lead to cancer.

Answer 53

mutations in proto-oncogenes and tumor suppressor proteins disrupt the delicate balance of cell regulation, leading to uncontrolled cell growth and the development of cancer. Understanding these mechanisms is crucial for developing targeted therapies and improving cancer treatment. Point Mutations: A single nucleotide change can result in a hyperactive protein product. Gene Amplification: An increase in the number of copies of a proto-oncogene can lead to overproduction of the protein, driving uncontrolled cell growth. Chromosomal Translocations: Rearrangement of chromosomal segments can create fusion proteins with oncogenic properties Insertions/Deletions: These can lead to frameshift mutations or altered protein products with oncogenic activity.

Question 54

What is the purpose of meiosis?

Answer 54

Meiosis is a special type of cell division that reduces the chromosome number by half, resulting in the production of haploid cells (gametes) from diploid cells. The main purpose of meiosis is to ensure genetic diversity and maintain the correct chromosome number in sexually reproducing organisms. production of gametes: meiosis produces sperm and egg cells with half the number of chromosomes as the parent cell, ensuring fertilization occurs Genetic diversity

Question 55

Which body cells undergo meiosis

Answer 55

Germ Cells: Meiosis occurs in specialized cells called germ cells, which are found in the reproductive organs. In males, germ cells in the testes undergo meiosis to produce sperm cells. In females, germ cells in the ovaries undergo meiosis to produce egg cells (oocytes). The end result of meiosis is four genetically diverse haploid cells, each with half the chromosome number of the original diploid cell. This diversity and reduction in chromosome number are key to the success of sexual reproduction.

Question 56

How is meiosis different from mitosis?

Answer 56

Number of divisions: Mitosis: Involves one division cycle, resulting in two daughter cells. Meiosis: Involves two division cycles (meiosis I and meiosis II), resulting in four daughter cells. purpose: Mitosis: Produces two genetically identical diploid daughter cells from a single diploid parent cell. It's involved in growth, tissue repair, and asexual reproduction. Meiosis: Produces four genetically diverse haploid cells (gametes) from a single diploid parent cell. It's involved in sexual reproduction, generating genetic diversity. chromosomes number: Mitosis: Maintains the diploid chromosome number (2n) in daughter cells, identical to the parent cell. Meiosis: Reduces the chromosome number by half, producing haploid (n) gametes. stages: Mitosis: Prophase: Chromosomes condense, and the nuclear envelope breaks down. Metaphase: Chromosomes align at the metaphase plate. Anaphase: Sister chromatids are pulled apart to opposite poles. Telophase: Chromatids reach the poles, and the nuclear envelope reforms. Cytokinesis: Cytoplasm divides, resulting in two daughter cells. Meiosis: Meiosis I: Prophase I: Homologous chromosomes pair up and undergo crossing over. Metaphase I: Homologous chromosome pairs align at the metaphase plate. Anaphase I: Homologous chromosomes (each with two sister chromatids) are pulled apart. Telophase I and Cytokinesis: Two haploid cells form, each with half the number of chromosomes. Meiosis II: (Similar to mitosis) Prophase II: Chromosomes condense in the two new cells. Metaphase II: Chromosomes align at the metaphase plate. Anaphase II: Sister chromatids are pulled apart to opposite poles. Telophase II and Cytokinesis: Four genetically diverse haploid cells form. genetic variation: Mitosis: Produces genetically identical daughter cells. Meiosis: Introduces genetic variation through crossing over (exchange of genetic material between homologous chromosomes during prophase I) and independent assortment (random orientation of homologous chromosome pairs during metaphase I).

Question 57

What is reduction division?

Answer 57

is another term for the first division in meiosis, also known as meiosis I. It is called reduction division because it reduces the chromosome number by half, resulting in haploid cells from a diploid parent cell. Here's a more detailed look at the process:

Question 58

what is crossing over

Answer 58

process during which homologous chromosomes exchange genetic material. Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosome This process creates new combinations of alleles on each chromosome, increasing genetic variation among offspring.es during meiosis.

Question 59

when does crossing over occur

Answer 59

Prophase I of Meiosis: Crossing over occurs during prophase I of meiosis, when homologous chromosomes pair up to form tetrads. The chromosomes are aligned such that non-sister chromatids are close together. Chiasmata Formation: The points where crossing over occurs are called chiasmata. These are visible under a microscope as cross-shaped structures between homologous chromosomes.

Question 60

steps of crossing over

Answer 60

Synapsis: Homologous chromosomes pair up and align closely with each other. Formation of Chiasmata: Non-sister chromatids break at corresponding points and exchange segments of genetic material. Recombination: The exchanged segments are rejoined, leading to a recombination of genetic material on the chromatids.

Question 61

When does independent assortment happen?

Answer 61

occurs during metaphase I of meiosis It refers to the random orientation of homologous chromosome pairs (tetrads) on the metaphase plate. This process contributes to genetic diversity by allowing different combinations of maternal and paternal chromosomes to be distributed to the gametes.

Question 62

Describe multiple ways that genetic variation is generated during meiosis, including crossing-over and independent assortment.

Answer 62

These mechanisms ensure that each gamete produced during meiosis is genetically unique, contributing to the genetic variation necessary for natural selection and adaptation in sexually reproducing organisms.

Question 63

What is diploid?

Answer 63

refers to a cell or an organism that has two complete sets of chromosomes, one set inherited from each parent. Diploid cells are denoted as 2n. most somatic cells, muscle cells, brain cells and skin cells 46 in humans

Question 64

what is haploid

Answer 64

refers to a cell or an organism that has only one complete set of chromosomes. Haploid cells are denoted as n. humans haploid is 23

Question 65

Be able to identify the number of chromosomes in a given cell.

Answer 65

Diploid (2n) Cells: Contain two complete sets of chromosomes (e.g., 46 in humans). Haploid (n) Cells: Contain one complete set of chromosomes (e.g., 23 in humans). Somatic Cells (Body Cells): Human Diploid Cells: 46 chromosomes (23 pairs) Example: Skin cells, muscle cells, brain cells 2. Gametes (Sex Cells): Human Haploid Cells: 23 chromosomes (no pairs) Example: Sperm cells, egg cells 3. Zygotes: Human Diploid Zygote: 46 chromosomes (23 pairs, formed from the fusion of two haploid gametes) 4. Abnormal Chromosome Numbers: Trisomy 21 (Down Syndrome): 47 chromosomes (extra chromosome 21) Turner Syndrome: 45 chromosomes (missing one X chromosome)