Chapter 9 & 10

Question 1

What is a chromosome?

Answer 1

DNA molecules are packaged into chromosomes. Each eukaryotic chromosome consists of one very long, linear DNA molecule associated with many proteins.

Question 2

What is a chromatid?

Answer 2

A chromatic is one of the original two joined copies of the original chromosome. Each chromatid contains identical DNA molecules.

Question 3

What is a chromatin?

Answer 3

The complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.

Question 4

What are differences in mitosis between prokaryotes and eukaryotes?

Answer 4

eukaryotes – including humans – almost all cell division includes mitosis. Certain specialized cells called germ cells can also divide replicated DNA through meiosis, which results in specialized cells containing only one copy of each chromosome. Most cells have two copies of each.

Prokaryotes, such as bacteria, do not have a nuclear membrane surrounding their cellular DNA, so cell division is happens differently than in eukaryotes. Even though the cell does not undergo mitosis, the end result is the same. The single chromosome is replicated, and the two copies split into two halves of a dividing cell. In these organisms, the process is called binary fission.

Question 5

Role of centrosomes?

Answer 5

A centrosomes is a structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division. A centrosome has two centrioles.
In animal cells, the spindle arises from the centrosomes and includes spindle micro tubules and asters. Basically, the centrosomes nucleated microtubules can interact with the chromosomes to build the mitosis spindle.

Question 6

Cytokinesis in plant vs. animal. What is responsible for making the cell plate?

Answer 6

In animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches the cell in two. A cleavage furrow is a small groove in the cell surface near the old metaphase plate. Cytokinesis in plant cells, which have cell walls, is markedly different. There is no cleavage furrow. Instead, during telophase, vesicles derived from the Golgi apparatus move along microtubules to the middle of the cell, where they coalesce, producing a cell plate. Cell wall materials carried in the vesicles collect in the cell plate as it grows. The cell plate en,argues until its surrounding membrane fuses with the plasma membrane along the perimeter of the cell. Two daughter cells result, each with its own plasma membrane. Meanwhile, a new cell wall arising from the contents of the cell plate has formed between the daughter cells.

Question 7

What is the Go phase and what type of cells would you find in this phase?

Answer 7

A nondividing state occupied by cells that have left the cell cycle, sometimes reversibly. Most cells of the human body are actually in the G0 phase. As mentioned earlier, mature nerve cells muscle cells never divide. Other cells, such as liver cells, can be “called back” from the G0 phase to the cell cycle by external cues,much as growth factors released during injury.

Question 8

What happens in each part of interphase?

Answer 8

Interphase is divided into three parts, G1 phase, S phase, and G2 phase. In G1, the first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins. In S phase, the synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated. In G2, the second gap, or growth phase, of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs.

Question 9

Compare density dependent inhibition to substrate

Answer 9

Density dependent inhibition is the process in which crowded cells stop dividing. Anchorage dependent inhibition is the process in which normal cells must be attached to a substrate to divide.

Question 10

Review cancer cell growth

Answer 10

Cancer occurs when a single cell acquires the ability to reproduce aggressively and to invade other tissues. Cancer: 1) mistake in cell cycle 2) cancerous cells form tumors (masses of tissue)
3) tumors deprive normal cells of nutrients 4) malignant tumors (invasive) may spread across in a process called metastasis.

Question 11

Compare and contrast asexual reproduction to sexual reproduction.

Answer 11

In asexual reproduction, a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes. An individual that reproduces asexually gives rise to a clone, a group of genetically identical individuals. Mutations come from things that reproduce asexually. In sexual reproduction, two parents give rise to offspring that have unique combinations of genes inherited from the two parents.

Question 12

What is a karyotype?

Answer 12

A karyotype is a display of the chromosome pairs of a cell arranged by size and shape.

Question 13

Asexual reproduction vs sexual reproduction part 2.

Answer 13

In asexual reproduction, a single parent produces genetically identical offspring by mitosis. Sexual reproduction combines genes from two parents, leading to genetically diverse offspring.

Question 14

If the chromosome number of a species is 2n = 20 how many homologous pairs are there? A gamete from this species has how many chromosomes? During the S phase of the cell cycle how many chromosomes will there be?

Answer 14

A) 10 I think?
B) don’t know
C) don’t know

Question 15

What type of sex chromosomes do females have? Males?

Answer 15

Female: XX
Male: XY
The latter determines whether the person is a female or male

Question 16

Compare cells at the beginning of meiosis to those at the end of meiosis

Answer 16

Cells at the beginning of meiosis have two sets of chromosomes so they are diploid. At the end of meiosis, the cells have only one set of chromosomes and are haploid and it introduces genetic variability among the gametes. This is the whole point of meiosis (to produce haploid gametes)

Question 17

Give the details of prophase 1

Answer 17

Each homologous pair undergoes synapsis and crossing over between non sister chromatids with the subsequent appearance of chiasmata.
Synapsis: The pairing and physical connection of duplicated homologous chromosomes during prophase I of meiosis.
Chiasmata: The X-shaped, microscopically visible region where crossing over has occurred earlier in prophase I between homologous nonsister chromatids. Chiasmata become visible after synapsis ends, with the two homologs remaining associated due to sister chromatid cohesion.

Question 18

Give the details of metaphase 1

Answer 18

Chromosomes line up as homologous pairs on the metaphase plate

Question 19

Give the details of anaphase 1

Answer 19

Homologs separate from each other; sister chromatids remain joined at the centromere

Question 20

Be able to name a phase of mitosis or meiosis by looking at a picture

Answer 20

Okay

Question 21

Compare and contrast mitosis to meiosis

Answer 21

In mitosis, there are 4 main steps while in meiosis there are 5 main steps. Synapsis of homologous chromosomes does not occur in mitosis. Basically, meiosis reduces the number of chromosome sets from two to one, whereas mitosis conserves the number. Meiosis produces cells that differ genetically from their parent cell and from each other, whereas mitosis produces daughter cells that are genetically identical to their parent cell and to each other.

Question 22

What are three events that are unique to meiosis during meiosis 1?

Answer 22

Synapsis and crossing over, homologous pairs at the metaphase plate, and separation of homologs

Question 23

Summarize how genetic variation may occur

Answer 23

1) Crossing over: during prophase 1, the exchange of genetic material between no sister chromatids
2) Independent assortment of chromosomes: in metaphase 1 when homologous chromosomes line up on plate they could face either pole
3) Random fertilization: each gamete is different and each combination of sperm and egg is unique

Question 24

Explain how independent assortment, crossing over, and random fertilization contribute to genetic variation in sexually reproducing organisms.

Answer 24

Independent assortment, crossing over, and random fertilization contribute to genetic variation in sexually reproducing organisms in that in independent assortment, because each pair of homologous chromosomes is positioned independently of the other pairs at metaphase 1, the first meiotic division results in each pair sorting its maternal and paternal homologs into daughter cells independently of every other pair, crossing over produces chromosomes with new combinations of maternal and paternal alleles, and in random fertilization, the fusion of a male gamete with a female gamete during fertilization will produce a zygote with any of about 70 trillion diploid combinations which adds to the genetic variation arising from meiosis.

Question 25

Cell division

Answer 25

The reproduction of cells.

Question 26

Cell cycle

Answer 26

The life of a cell from the time it is first formed from a dividing parent cell until its own division into two daughter cells.

Question 27

Parts of interphase

Answer 27

G1 phase, S phase, & G2 phase

Question 28

Cell plate

Answer 28

A membrane-bounded, flattened sac located at the midline of a dividing plant cell, inside which the new cell wall forms during cytokinesis.

Question 29

Cyclins

Answer 29

A key regulatory protein

Question 30

Diploid number

Answer 30

Anyone cell with two chromosome sets is called a diploid cell and has a diploid number of chromosomes, abbreviated 2n. For humans, the diploid number is 46, (2n = 46), the number of chromosomes in our somatic cells.

Question 31

Chiasmata

Answer 31

The X-shaped, microscopically visible region where crossing over has occurred earlier in prophase I between homologous nonsister chromatids. Chiasmata become visible after synapsis ends, with the two homologs remaining associated due to sister chromatid cohesion. (Site of crossing over)

Question 32

Genome

Answer 32

The genetic material (DNA) of a cell

Question 33

Phases of mitosis

Answer 33

Prophase
Prometaphase
Metaphase
Anaphase
Telophase

Question 34

What is the prophase

Answer 34

The first stage of mitosis, in which the chromatin condenses into discrete chromosomes visible with a light microscope, the mitotic spindle begins to form, and the nucleolus disappears but the nucleus remains intact.

Question 35

Prometaphase

Answer 35

The second stage of mitosis, in which the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the chromosomes.

Question 36

Metaphase

Answer 36

The third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate.

Question 37

Anaphase

Answer 37

The fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell.

Question 38

Telophase

Answer 38

The fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun.

Question 39

Mitosis spindle

Answer 39

An assemblage of microtubules and associated proteins that is involved in the movement of chromosomes during mitosis.

Question 40

Parts of chromosome

Answer 40

Look at notes

Question 41

Gametes

Answer 41

Reproductive cells

Question 42

Somatic cells

Answer 42

All cells except reproductive cells

Question 43

Binary fission

Answer 43

A method of asexual reproduction by “division in half.” In prokaryotes, binary fission does not involve mitosis, but in single-celled eukaryotes that undergo binary fission, mitosis is part of the process.

Question 44

Cleavage furrow

Answer 44

The first sign of cleavage in an animal cell; a shallow groove around the cell in the cell surface near the old metaphase plate.

Question 45

Cell cycle control system

Answer 45

A cyclically operating set of molecules in the eukaryotic cell that both triggers and coordinates key events in the cell cycle.

Question 46

What is a checkpoint? Name them

Answer 46

A control point in the cell cycle where stop and go-ahead signals can regulate the cycle. Major checkpoints: G1 phase (make sure cell is up to the correct size), G2 phase (DNA must be replicated and replicated accurately), M phase (DNA at each end of the cell, split evenly)
2) Kinases: enzymes that control the cycle, they are only active when connected to cyclin proteins (cyclin dependent kinases (Cdk))

Question 47

Gene

Answer 47

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).

Question 48

Synapsis

Answer 48

The pairing and physical connection of duplicated homologous chromosomes during prophase I of meiosis.

Question 49

Haploid number

Answer 49

For humans, the haploid number is 23 (n = 23). The set of 23 consist of the 22 autosomal plus a single sex chromosome.

Question 50

Homologous chromosomes (homologs)

Answer 50

A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism’s father, the other from the mother. Also called homologs, or a homologous pair.

Question 51

Phases of meiosis

Answer 51

Meiosis 1: prophase, metaphase 1, anaphase 1, telophase 1 and cytokinesis
Meiosis 2: prophase 2, metaphase 2, anaphase 2, telophase 2 and cytokinesis

Question 52

Meiosis 1

Answer 52

The first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Question 53

Meiosis 2

Answer 53

The second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Question 54

Homologous chromosomes (homologs)

Answer 54

A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism’s father, the other from the mother. Also called homologs, or a homologous pair.

Question 55

Phases of meiosis

Answer 55

Meiosis 1: prophase, metaphase 1, anaphase 1, telophase 1 and cytokinesis
Meiosis 2: prophase 2, metaphase 2, anaphase 2, telophase 2 and cytokinesis

Question 56

Meiosis 1

Answer 56

The first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Question 57

Meiosis 2

Answer 57

The second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Question 58

Centrioles

Answer 58

A structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a 9 + 0 pattern. A centrosome has a pair of centrioles. A pair of centrioles is located at the center of the chromosome, but they are not essential for cell division.