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BIO 325_Genetics > Chapter 3_Reproduction And Chromosome Transmission > Flashcards

Chapter 3_Reproduction And Chromosome Transmission Flashcards

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1
Q

Chromosomes

A

Structures within living cells that contain the genetic material.

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2
Q

Where are genes located?

A

They are physically located within chromosomes.

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3
Q

Biochemically speaking, what are chromosomes made of?

A
  • Contains a very long segment of DNA, which is the genetic material
  • Proteins, which are bound to the DNA and provide it with an organized structure.
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4
Q

Chromatin

A

In eukaryotic cells, the complex between DNA and proteins.

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5
Q

Prokaryotes

A
  • Bacteria and archaea

- Their chromosomes are not contained within a membrane-bound nucleus of the cell.

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6
Q

nucleoid

A
  • Region of the cytoplasm in prokaryotes where a single type of circular chromosome is located.
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7
Q

What does the plasma membrane do?

A

Regulates the uptake of nutrients and the excretion of waste products.

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8
Q

Eukaryotes

A
  • Includes some simple species (single celled protists and some fungi) and more complex multicellular species (plants, animals, and other fungi)
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9
Q

Organelles

A
  • Membrane bound compartments with specific functions.

- The cells of eukaryotic species have internal membranes that enclose these highly specialized compartments

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10
Q

Function of ER and golgi body

A

Play a role in protein modification and trafficking.

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11
Q

Nucleus

A

Bounded by two membranes that constitute the nuclear envelope. Most of the genetic material is found within chromosomes that are located in the nucleus.

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12
Q

What else besides the nucleus contains DNA?

A

Mitochondrion, which functions in ATP synthesis, and chloroplast (in plants) which functions in photosynthesis.

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13
Q

Cytogenetics

A

The field of genetics that involves the microscopic examination of chromosomes.

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14
Q

Somatic cell

A

Any cell of the body that is not a gamete or a precursor to a gamete

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15
Q

Gamete

A

(sperm and egg cells or their precursors) are also called germ cells.

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16
Q

At the molecular level, how similar are homologous chromosomes?

A

The sequence of bases of one homolog would usually differ by less than 1% compared to the sequence of the other homolog. HOWEVER, the sequences are not identical, and this 1% is what provides the allelic differences in genes.

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17
Q

Are X and Y chromosomes homologous?

A

No, they are not considered homologous even though they do have short regions of homology.

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18
Q

Locus

A

The physical location of a gene.

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19
Q

Where are the chromosomes in prokaryotes?

A

They are in direct contact with the cytoplasm.

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20
Q

In prokaryotes, how are the two daughter cells separated from each other?

A

By the formation of a septum.

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21
Q

Cell cycle

A

A series of phases that describe the division process of eukaryotic cells.

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22
Q

What are the phases of the cell cycle?

A
  • G1 and G2, gaps between S phase and mitosis.
  • S is for synthesis
  • G1, S, and G2 are collectively known as interphase.
  • Also, cells may remain in G0 phase, which means they are either temporarily not progressing through the cell cycle, or, in the case of terminally differentiated cells, such as most nerve cells in an adult mammal, will never divide again.
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23
Q

Describe G1 phase.

A

A cell may prepare to divide. Depending on cell type and conditions it encounters, a cell in the G1 phase may accumulate molecular changes that cause it to progress through the rest of the cell cycle. This is the restriction point (committed on a pathway that leads to advance to the S phase). S phase is when the chromosomes are replicated.

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24
Q

Kinteochore

A

A group of proteins that are bound to the centromere. These proteins help to hold the sister chromatids together and also play a role in chromosome sorting.

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25
Q

Describe G2 phase.

A

The cell accumulates the materials that are necessary for nuclear and cell division. It then progresses into the M phase of the cell cycle, when mitosis occurs.

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26
Q

What is the purpose of mitosis?

A

To distribute the replicated chromosomes.

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27
Q

Mitotic spindle apparatus

A

Involved in the organization and sorting of chromosomes.

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28
Q

Microtubule organizing centers

A

The spindle apparatus is formed from (MTOCs) which are found in eukaryotic cells from which microtubules grow.

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29
Q

How are microtubules produced?

A

From the rapid polymerization of tubulin proteins.

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30
Q

In animal cells, the mitotic spindle is formed…

A

…from two MTOCs called centrosomes. Each centrosome is located at a spindle pole.

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31
Q

Centriole

A

Found within each centrosome at right angles to each other.

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32
Q

Do plant cells have centrosomes?

A

No, the nuclear envelope functions as a MTOC for spindle formation.

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33
Q

The mitotic spindle of a typical animal cell has three types of microtubules:

A
    1. The aster microtubules emanate outward from the centrosome toward the plasma membrane. They are important for the positioning of the spindle apparatus within the cell and later in the process of cell division.
    1. The polar microtubules project toward the region where the chromosomes will be found during mitosis-the region between the two spindle poles. Polar microtubules that overlap with each other play a role in the separation of the two poles. They help push the poles away from each other.
    1. The kinetochore microtubules have attachments to a kinetochore, which is a complex of proteins that is bound to the centromere of individual chromosomes.
34
Q

The kinetochore proteins form three layers

A
    1. The proteins of the inner plate make direct contact with the centromeric DNA
    1. The outer plate contacts the kinetochore microtubules.
    1. The middle layer connects the two other regions.
35
Q

What is the purpose of the mitotic spindle?

A

Allows cells to organize and separate chromosomes so that each daughter cell receives the same complement of chromosomes.

36
Q

Describe prophase

A

The chromosomes have already replicated. As prophase proceeds, the nuclear membrane begins to dissociate into small vesicles. At the same time, the chromatids condense. The mitotic spindle also begins to form and the nucleolus disappears.

37
Q

Describe prometaphase

A
  • As we go from prophase to prometa, the centrosomes move to opposite ends of the cell and demarcate two spindle poles, one within each of the future daughter cells.
  • Once the nuclear membrane has dissociated into vesicles, the spindle fibers can interact with the sister chromatids.
  • This occurs in prometaphase.
  • Microtubules are rapidly formed. As it grows, if the end of a microtubules happens to make contact with a kinetochore, its end is said to be captured and remains firmly attached to the kinetochore. This is how sister chromatids become attached to kinetochore microtubules.
  • As prometa ends, kinetochore on a pair of sister chromatids is attached to kinetochore microtubules from opposite poles. By the end of prometa, the mitotic spindle is completely formed.
38
Q

Describe metaphase

A
  • Pairs of sister chromatids align themselves along a plane. When this alignment is complete, the cell is in metaphase. At this point, each pair of chromatids is attached to both poles by kinetochore microtubules. . The pairs of sister chromatids have become organized into a single row along the metaphase plate.
39
Q

Describe anaphase

A
  • The connection that is responsible for holding the pairs of chromatids together is broken.
  • Each chromatid, now an individual chromosome, is linked to only one of the two poles.
  • Chromosomes move toward the pole to which they are attached. This involves a shortening of the kinetochore microtubules.
  • The two poles themselves move farther apart due to the elongation of the polar microtubules, which slide in opposite directions due to the actions of motor proteins.
40
Q

Describe telophase

A
  • The chromosomes reach their respective poles and decondense.
  • The nuclear membrane now re forms to produce two separate nuclei.
41
Q

Cytokinesis

A

The two nuclei are segregated into separate daughter cells. Likewise, cytokinesis also segregates cell organelles such as mitochondria and chloroplasts into daughter cells.

42
Q

Myosin and actin

A

A contractile ring, composed of myosin motor proteins and actin filaments, assembles adjacent to the plasma membrane. Myosin hydrolyzes ATP, which shortens the ring and thereby constricts the plasma membrane to form a cleavage furrow that ingresses, or moves inward.

43
Q

When does cytokinesis occur?

A

Begins shortly after anaphase.

44
Q

In plants, how do the daughter cells separate?

A

The formation of a cell plate does this. At the end of anaphase, golgi derived vesicles carrying cell wall materials are transported to the equator of a dividing cell. These vesicles are directed to their location via the phragmoplast, which is composed of parallel aligned microtubues and actin filaments that serve as tracks for vesicle movement. The fusion of these vesicles gives rise to the cell plate, which is a membrane bound compartment. The cell plate begins in the middle of the cell and expands until it attaches to the mother cell wall. Once this attachment has taken place, the cell plate undergoes a process of maturation and eventually separates the mother cell into two daughter cells.

45
Q

The development of multicellularity relies on…

A

…the repeated process of mitosis and cytokinesis.

46
Q

Gametogenesis

A

The process whereby gametes form.

47
Q

Isogamous

A

Gametes are morphologically similar. Not many like this.

48
Q

Heterogamous

A

They produce two morphologically different types of gametes. Male gametes (sperm cells) are relatively small and usually travel far distances to reach the female gamete. The mobility of the male gamete is an important characteristic. The sperm contains a single flagellum that enables them to swim.

49
Q

Overview of Prophase of meiosis I

A
  • Leptotene
  • Zygotene
  • Pachytene
  • Diplotene
  • Diakinesis
50
Q

Leptotene Stage

A

The replicated chromosomes begin to condense and become visible with a light microscope.

51
Q

Zygotene stage

A

Involves a recognition process known as synapsis, in which the homologous chromosomes recognize each other and begin to align themselves.

52
Q

Pachytene stage

A

The homologs have become completely aligned. The associated chromatids are known as bivalents. Each bivalent contains two pairs of sister chromatids, or a total of four chromatids.

53
Q

Synaptonemal complex

A

Formed between homologous chromosomes. Composed of parallel lateral elements, which are bound to the chromosomal DNA, and central element, which promotes the binding of the lateral elements to each other via transverse filaments.

54
Q

Crossing over

A

Prior to the pachytene stage, when synapsis is complete, involves a physical exchange of chromosome pieces.

55
Q

Chiasma

A

The connection that results crossing over.

56
Q

Diplotene stage

A

The synaptonemal complex has largely disappeared. The bivalent pulls apart slightly, and microscopically it becomes easier to see. (bivalent is also called a tetrad).

57
Q

Diakinesis

A

The synaptonemal complex completely disappears.

58
Q

Describe prometaphase of meiosis I

A

The spindle apparatus is complete, and the chromatids are attached via kinetochore microtubules.

59
Q

Descrie metaphase of meiosis I

A
  • Bivalents are organized along the metaphase plate.
  • Random arrangement of homologs is consistent with Mendel’s law of independent assortment. Randomly aligned along metaphase plate.
  • This random alignment allows for vast amount of genetic diversity.
  • Attachment of kinetochore microtubules to the sister chromatids. One pair of sister chromatids is linked to one of the poles, and the homologous pair linked to the opposite pole.
60
Q

Describe anaphase of meiosis I

A

Two pairs of sister chromatids, within a bivalent separate from each other. The connection that holds isster chromatids together does not break. The homologous pair of chromatids moves to the opposite pole.

61
Q

Describe telophase of meiosis I

A
  • Nuclear membrane may re form to produce two separate nuclei. The end result of meiosis I is two cells, each with three pairs of sister chromatids. It is thus a reduction division.
62
Q

Meiosis vs. Mitosis

A
  • Mitosis produces two diploid daughter cells, meiosis produced four haploid daughter cells
  • Daughter cells produced by mitosis are genetically identical; haploid cells produced by meiosis are not genetically identical to each other because they contain only one homologous chromosome from each pair.
63
Q

Spermatogenesis

A
  • The production of sperm, occurs within glands known as the testes.
  • Testes contain spermatogonial cells that divide by mitosis to produce two cells; one of these remains a spermatogonial cell, and the other cell becomes a primary spermatocyte.
  • The spermatocyte progresses through meiosis I and meiosis II to produce four haploid cells, which are known as spermatids. These cells then mature into sperm cells. The structure of a sperm cell includes a long flagellum and a head.
  • Head of sperm contains little more than a haploid nucleus and an organelle at its tip, known as acrosome.
  • Acrosome contains digestive enzymes that are released when a sperm meets an egg cell.
  • These enzymes enable the sperm to penetrate the outer protective layers of the egg and gain entry into the egg cell’s cytosol.
64
Q

Oogenesis

A
  • The production of egg cells, occurs within specialized diploid cells of the ovary known as oogonia
  • Early in the development of the ovary, the oogonia initiate meiosis to produce primary oocytes
  • Primary oocytes enter a dormant phase at prophase of meiosis I, remaining in this stage until the female becomes sexually mature. Beginning at this stage, primary oocytes are periodically activated to progress through the remaining stages of oocyte development.
65
Q

During oocyte maturation, meiosis produces only one cell that is destined to become an egg, as opposed to the four gametes produced from each primary spermatocyte during spermatogenesis. HOW DOES THIS OCCUR?

A
  • The first meiotic division is asymmetrical and produces a secondary oocyte and a much smaller cell, known as a polar body.
  • Most of the cytoplasm is retained by the secondary oocyte and very little by the polar body, allowing the oocyte to become a larger cell with more stored nutrients.
  • Secondary oocyte then begins meiosis II. Secondary oocyte is released form the ovary (ovulation) and travels down the oviduct toward the uterus in mammals.
  • During its journey, if a sperm cell penetrates the secondary oocyte, it is stimulated to complete meiosis II; the secondary oocyte produces a haploid egg and a second polar body. Haploid egg and sperm nuclei then unite to create the diploid nucleus of a new individual.
66
Q

Gametophyte vs. Sporophyte

A
  • Gametophyte is haploid generation
  • Sporophyte is diploid generation
  • Meiosis produces haploid cells called spores, which divide by mitosis to produce the gametophyte.
    • In most plants, the gametophyte is very small, and the sporophyte is what we think of as teh plant.
67
Q

Where does meiosis occur (specifically the male gametophyte) within the sporophyte?

A

The anthers and the ovaries, which produce male and female gametophytes, respectively.

  • In the anther, diploid cells called microsporocytes undergo meiosis to produce four haploid microspores. These separate into individual microspores.
  • Microspores then undergo mitosis, differentiating into a pollen grain, which is the male gametophyte with a thick cell wall. Later, the generative cell undergoes mitosis to produce two haploid sperm cells. In most plant species, this mitosis occurs only if the pollen grain germinates, if it lands on a stigma and forms a pollen tube.
68
Q

How are female gametophytes formed in the sporophyte?

A
  • Produced within ovules found in the plant ovaries. A type of cell known as a megasporocyte undergoes meiosis to produce four haploid megaspores. Three of the four degenerate. The remaining haploid megaspore then undergoes three successive mitotic divisions accompanied by asymmetrical cytokinesis to produce seven individual cells (one egg, two synergids, three antipodals, and one central cell).
  • This 7 celled structure (embryo sac) is the mature female gametophyte. Each is contained within an ovule.
69
Q

For fertilization to occur in plants…

A

…specialized cells within the male and female gametophytes must meet.

  • to begin, pollen grain lands on a stigma; this stimulates the tube cell to sprout a tube that grows through the style and eventually makes contact with an ovule.
  • At the same time, generative cell undergoes mitosis to produce two haploid sperm cells. Sperm cells migrate through the pollen tube and eventually reach the ovule. One of the sperm enters the central cell, which contains the two polar nuclei. This results in a cell taht is triploid (3n). This cell divides mitotically to produce endosperm, which acts as a food storing tissue. The other sperm enters the egg cell.
  • Egga nd sperm fuse to create zygote. THEREFORE, fertilization in flowering plants is actually a double fertilization.
70
Q

X-linked inheritance

A

Confirmed the idea that genes are found on chromosomes. Showed us that not all traits follow simple Mendelian rules. BASICALLY, genes on the X chromosome govern certain traits.

71
Q

Chromosome theory of Inheritance

A

The inheritance patterns of traits can be explained by the transmission patterns of chromosomes during meiosis and fertilization.

72
Q

The five fundamental principles of the chromosome theory of inheritance:

A
  • 1.) Chromosomes contain the genetic material that is transmitted from parent to offspring and from cell to cell.
  • 2.) Chromosomes are replicated and passed along, generation after generation, from parent to offspring. They are also passed from cell to cell during the development of a multicellular organism. Each type of chromosome retains its individuality during cell division and gamete formation.
  • 3.) The nuclei of most eukaryotic cells contain chromosomes that are found in homologous pairs, they are diploid. One member of each pair is inherited from the mother, the other from the father. At meiosis, one of the two members of each pair segregates into one daughter nucleus, and the homolog segregates into the other daughter nucleus. Gametes contain one set of chromosomes, they are haploid.
  • 4.) During the formation of haploid cells, different types of (nonhomologus) chromosomes segregate independently of each other.
  • 5.) Each parent contributes one set of chromosomes to its offspring. The maternal and paternal sets of homologous chromosomes are functionally equivalent; each set carries a full complement of genes.
73
Q

Sex chromsomes

A

Determines sex in many different species.

74
Q

Heterogametic sex

A

Two types of sperm are produced; One that carries only the X and another type that carries the Y.

75
Q

Homogametic sex

A

All eggs carry a single X chromosome.

76
Q

Autosomes

A

Chromosomes that are not sex chromosomes.

77
Q

What causes an offspring to develop into a male or female?

A

The Y chromosome promotes male development.

78
Q

X-0 System in certain insects

A

The male has one sex chromosome (the X) and is designated X0 whereas the female has a pair (two Xs)

79
Q

Z-W System in birds

A

Male is ZZ and the female is ZW. The male is the homogametic sex, and the female is the heterogametic sex.

80
Q

Haplodiploid system in bees

A

The male is produced from unfertilized haploid eggs. Females are produced from fertilized eggs and are therefore diploid.

81
Q

Are chromosomes the only mechanisms in sex development (Gender)?

A

No, temperature can play a role.

BIO 325_Genetics (17 decks)

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