Topic 8

Question 1

Binary fission

Answer 1

Bacteria have a single, circular DNA molecule, and replicate via binary fission

The chromosome is replicated, and the two products are partitioned to each end of the cell prior to the actual division of cell

Bacteria cell division replication and division as a concerted process, while in Eukaryotic cell division DNA replication occurs early in division, and chromosomes separate occur much later

Question 2

Mitosis

Answer 2

is the phase of the cell cycle in which the spindle apparatus assembles, binding to the chromosomes, and moves the sister chromatids apart, and is essential for separation of the two daughter genomes. It is subdivide into five stages: prophase, prometaphase, metaphase, anaphase, and telophase.

Question 3

Meiosis

Answer 3

is a special form of division, that occurs in the formation of gametes, that results in the production of cells with half the normal number of chromosomes

Question 4

Stages of Meiosis

Answer 4

Meiosis I: This stage is divided into five sub-stages:

Prophase I: The chromatin condenses into discrete chromosomes, and homologous chromosomes pair up and exchange genetic information through a process called crossing-over

Metaphase I: The homologous chromosome pairs align at the metaphase plate, and the spindle fibers attach to the kinetochores of each chromosome

Anaphase I: The homologous chromosomes separate and move towards opposite poles of the cell

Telophase I: The chromosomes reach the opposite poles of the cell, and the cell undergoes cytokinesis, resulting in two haploid daughter cells

Interkinesis: This is an optional stage that occurs between meiosis I and meiosis II. During this stage, the cell undergoes a period of rest, and the chromosomes may partially decondense

Meiosis II: This stage is divided into four sub-stages:

Prophase II: The chromosomes condense again, and the spindle fibers begin to form

Metaphase II: The chromosomes align at the metaphase plate, and the spindle fibers attach to the kinetochores of each chromosome

Anaphase II: The sister chromatids separate and move towards opposite poles of the cell

Telophase II: The chromosomes reach the opposite poles of the cell, and the cell undergoes cytokinesis, resulting in four haploid daughter cells

Question 5

Cell Cycle

Answer 5

is divided into five phases, based on the key events of genome duplication and segregation

Question 6

Prophase

Answer 6

It is a part of M phase

Chromatin condenses, forming visible chromosomes

Duplicate chromosomes (sister chromatids) are held together by a centromere

Centrosomes – start making microtubules, mitotic spindle, asters

Golgi and ER are dispersed, and Nuclear envelop breaks down.

Question 7

Prometaphase

Answer 7

Is typically said to be a part of prophase

Chromosomes attach to microtubules at the kinetochores

Each chromosome is oriented such that the kinetochores of sister chromatids are attached to microtubules from opposite poles

Chromosomes move to equator of the cell

Question 8

Metaphase

Answer 8

Is part of M phase

Centromeres of chromosomes are precisely aligned at cell’s equator

The imaginary plane midway between poles is called metaphase plate

Chromosomes are attached to opposite poles and are under tension.

Question 9

Anaphase

Answer 9

is part of M phase

Shortest of all phases

Centromeres of chromosomes splits simultaneously each sister chromatid now becomes a separate chromosome

Chromosomes are pulled toward their respective poles by motor proteins of kinetochores

One Chromosome of each original pair goes to opposite poles

Question 10

Telophase

Answer 10

Is part of M phase

Begins when chromosome movement stops.

Each set of chromosomes (at opposite ends of cell) uncoils to form chromatin

New nuclear membranes form around each chromatin mass

Nucleoli reappear

Spindle disappears

Question 11

G1 phase (gap phase 1)

Answer 11

Part of Interphase

is the primary growth phase of the cell, the term gap phase refers to its filling the gap between cytokinesis and DNA synthesis. For most cells this is the longest phase.

Question 12

G2 phase (gap phase 2)

Answer 12

Is part of interphase

is the second growth phase, and preparation for separation of the newly replicated genome. This phase fills the gap between DNA synthesis and the beginning of mitosis. During this phase microtubules begin to reorganize to form a spindle.

Question 13

S phase

Answer 13

Is part of interphase

is the phase in which the cell synthesizes a replica of the genome

Before a cell can divide the genome must be replicated first in S phase.

Question 14

M Phase

Answer 14

Mitosis – is the phase of the cell cycle in which the spindle apparatus assembles, binding to the chromosomes, and moves the sister chromatids apart, and is essential for separation of the two daughter genomes. It is subdivide into five stages: prophase, prometaphase, metaphase, anaphase, and telophase.

Question 15

Interphase

Answer 15

is the portion of the cell cycle between cell division (G1, S, and G2)

Question 16

Cytokinesis

Answer 16

is the phase of the cell cycle when the cytoplasm divides, creating two daughter cells. In plant cells, a plate forms between dividing cells forming a cell wall

Begins during late anaphase and continues through mitosis

Ring of actin microfilaments contracts to form cleavage furrow

Two daughter cells are pinched apart

Question 17

G0 phase

Answer 17

no further division occurs

is a “resting phase” in which the cell is paused in G1 phase, and remain in this phase for days to years before resuming cell division.

Question 18

Understand the difference between binary fission and Mitosis

Answer 18

binary fission and mitosis are two different processes of cell division that occur in different types of cells. Binary fission is a type of asexual reproduction that occurs in prokaryotes, while mitosis is a process of cell division that occurs in eukaryotes

binary fission does not involve spindle fibers, and the DNA is not packaged into chromosomes

Question 19

Mitosis results in what type of daughter cells?

Answer 19

2 genetically identical diploid daughter cells

Question 20

Meiosis results in what type of daughter cells?

Answer 20

4 unique haploid daughter cells

Question 21

Define: Karyotype, Diploid, Haploid, Chromosome, and Chromatin, and list the number of Chromosomes found in different organisms.

Answer 21

Karyotype – is the array of chromosomes/normal set an individual organism possess.

Diploid (2n) – is the total number of chromosomes in a cell (2 sets of chromosomes)

Haploid (n) – is one complete set of chromosomes necessary chromosomes for that organism

Chromosome - made up of DNA and proteins and carry our genetic information in the nucleus.

Chromatin - a complex of DNA that condenses to form chromosomes

there is a chart on slide 7 showing the # of chromosomes in different organisms

Question 22

chromatid

Answer 22

One half of a replicated chromosome

Chromosomes are copied in preparation for cell division, and the two identical copies are called sister chromatids

Question 23

somatic cells

Answer 23

diploid cells that are not sperm or egg cells, meaning they have two sets of chromosomes and can be affected by DNA mutations but not passed on to offspring

Question 24

gametes

Answer 24

haploid sex cells, specifically sperm and egg

The subsequent fusion of two of these cells ensures a consistent chromosome number from one generation to the next

Question 25

cleavage furrow

Answer 25

A cleavage furrow is an indentation of the cell’s surface that begins the process of cell division.

It occurs when the cell is preparing to split into two daughter cells by pinching its cell membrane and cytoplasm down the middle.

Question 26

crossing over

Answer 26

Genetic recombination also called crossing over, and random orientation of chromosomes on the metaphase plate, increase genetic diversity in the gametes, thus resulting in increase rate of genetic diversity.

Question 27

homologous chromosomes

Answer 27

Homologous chromosomes are pairs of chromosomes that come from each parent. Containthe alleles of the same genetype in the same locations . Homologous chromosomes carry the same genes, one from each parental source, and are responsible for genetic variation in offspring. Each homologous pair consists of one paternal and one maternal chromosome

Question 28

Cyclin-dependent kinases

Answer 28

class of enzymes that are responsible for the phosphorylation of other key enzymes in the cell cycle, and Cdks will become activated when forming a complex with Cyclin – called MPF (Mitosis-promoting factor)

are proteins that are activated or deactivated by cyclins producing Cyclin-Cdk complex, that initiates enzymatic cascades needed for cell division.

are destroyed after mitotic cell division, and process begins again, by MPF activity during M phase

Question 29

Maturation-promoting factor (MPF)

Answer 29

Maturation-promoting factor (MPF) is a complex cellular protein that stimulates cell division in eukaryotic cells. It is also called mitosis-promoting factor or M-Phase-promoting factor 1. MPF is a protein complex that includes the protein cyclin, which accumulates during interphase and triggers mitosis or meiosis

cdk and cyclin complex

Question 30

Cancer

Answer 30

the malignant growth due to uncontrolled cell division

Missense mutations that multiply over time, leading to cell cycle disruption and the formation of tumors.

Daughter cells with too many or too few chromosomes, a feature known as aneuploidy.

Errors at any point in the process of mitosis can introduce errors into cells’ genetic programming that lead to cancer or other diseases.

Question 31

proto-oncogenes

Answer 31

A proto-oncogene is a healthy gene found in the cell that is responsible for making a protein involved in cell growth, division, and other processes. Most of the time, these genes do their jobs without problems. However, if an error (mutation) occurs in a proto-oncogene, the gene can become turned on when it isn’t supposed to be. If this happens, the proto-oncogene can turn into a malfunctioning gene called an oncogene. Cells will start to grow out of control, which leads to cancer

Question 32

tumor suppressor genes

Answer 32

Tumor suppressor genes are normal genes that slow down cell division or tell cells to die at the right time. They are among the most common genes protecting the body from cancer. When tumor suppressor genes don’t work properly, cells can grow out of control, which can lead to cancer