BIOL Lab 4: Mitosis, Meiosis & Karyotyping

Question 1

Mitosis

Answer 1

Process where a somatic cell produces two new cells. Continued production of new cells results in further growth of the organism.

Also replaces dead/dying/damaged cells. Example is 2-10 million red blood cells die and are removed from your body every second, and then replaced at the same rate.

Question 2

Somatic Tissues

Answer 2

All tissues that comprise the body of an organism, with the exception of those organs that produce gametes.

Question 3

Tay Sachs Disease PKU

Answer 3

Non-functional genes resulting in being unable to metabolize a certain chemical.

Question 4

Chromosomes

Answer 4

In each cell…

• Humans have 46.
• Corn has 20.
  The fruit fly, Drosophilia, has 8.

Question 5

Diploid Number

Answer 5

2N, the exact number of chromosomes for that species that each somatic cell has. Mitosis ensures this number is retained.

Question 6

Not All Somatic Cells Divide!

Answer 6

Some cells, like nerve and muscle, once specialized during embryological development, lose the ability to divide. These cells can’t be replaced.

Question 7

Meiosis

Answer 7

Type of cell division that occurs in organs/structures (ovaries, testes, anthers) that produce reproductive cells.

Occurs in all organisms that undergo sexual reproduction. Results in production of highly specialized cells called gametes. These cells are referred to as haploid (N), since they only carry half the required number of chromosomes. A necessary reduction to produces viable offspring.

Question 8

Chromatin

Answer 8

Loosely arranged mass of DNA and special proteins called histones.

In preparation for cell division, it is replicated in the nucleus. Then at start of mitosis, it condenses to form individual chromosomes. Each chromosome is made up of two sister chromatids, which are temporarily joined at a region called the centromere or kinetichore.

Question 9

Interphase

Answer 9

A growth and functional phase. Accounts for much on cell’s “life”. (G1, S, G2)

The actual replication of DNA occurs in S (synthesis) phase.

Question 10

Prophase (Animal Mitosis)

Answer 10

In early prophase the chromosomes shorten and condense by coiling. Each chromosome is double-stranded and they become visible as long, tangled threads. In whitefish cells, the centrioles separate and organize formation of the mitotic spindle; a scaffolding of fine microtubules. By mid-prophase, the nuclear membrane has disappeared. The chromosomes have further shortened and thickened; the spindle microtubules are clearly visible, running across the cell from pole to pole.

Question 11

Metaphase (Animal Mitosis)

Answer 11

At metaphase, the double-stranded chromosomes line up along the “equator” of the cell. The centromere of each chromosome attaches to a spindle microtubule.

Question 12

Anaphase (Animal Mitosis)

Answer 12

During anaphase, the centromeres divide and the two sister chromatids of each chromosome move apart and toward opposite poles of the cell. The mechanism of chromosome movement is not completely understood, but the chromosomes appear to be drawn toward the opposite poles by the spindles. Anaphase ends when the two sets of identical, single-stranded chromosomes arrive at opposite poles of the cell.

Question 13

Telophase (Animal Mitosis)

Answer 13

During telophase, the chromosomes uncoil, becoming longer and more diffuse once again. The spindle disappears, the two new nuclear membranes are reassembled.

Question 14

Cytokinesis (Animal Mitosis)

Answer 14

Begins during telophase. This occurs by a cleavage furrow, proceeding from the outside toward the center.

Question 15

Daughter Cells (Animal Mitosis)

Answer 15

The chromosomes are no longer visible, and the new interphase nuclei are enclosed in newly formed nuclear membranes. Each daughter cell is genetically identical to the parent cell, and the cell cycle is complete. The daughter cells enter the G1 phase of the cell cycle.

Question 16

Mitosis in Plant Cells

Answer 16

Unlike animals, plants have a somewhat indeterminate growth pattern, they typically grow new branches and roots from the tips of previous growth. Special regions called meristems are near these tips and are composed of a dense region of actively dividing, but undifferentiated cells.

Question 17

Prophase (Plant Mitosis)

Answer 17

In most higher plants, centrioles are not present but the mitotic spindle forms in much the same way as it does in animal cells.

Question 17

Metaphase (Plant Mitosis)

Answer 17

Same as animal.

Question 18

Anaphase (Plant Mitosis)

Answer 18

Same as animal.

Question 18

Telophase (Plant Mitosis)

Answer 18

Same as animal.

Question 19

Cytokinesis (Plant Mitosis)

Answer 19

In plants, a cell plate forms in the center of the cell and proceeds across the cell toward the outer membrane and cell wall.

Question 19

Daughter Cells (Plant Mitosis)

Answer 19

Same as animal.

Question 20

Prophase I (Meiosis)

Answer 20

A unique feature of Prophase I is the pairing off of homologous chromosomes; this formation is called a tetrad. The lie side by side in an intimate association called synapsis. Synapsis does not occur in Prophase II.

Question 20

Interkinesis

Answer 20

Brief phase after Telophase I/Cytokinesis in Meiosis. Similar to interphase, but without replication of DNA.

Question 21

Karyotypes

Answer 21

Images of 22 homologous chromosome pairs arranged by size and the sex chromosomes. Prepared by culturing cells (lymphocytes or sloghed-off fetal cells from amniotic fluid) and adding colchicine, which arrests the cells in the metaphase stage of mitosis. The cells are then treated and stained, resulting in a random arrangement of the chromosomes. After being photographed and cut out, the chromosomes can be arranged in pairs based on their size, banding pattern, and location of the centromere. Can help to detect genetic disorders.

Question 21

Down Syndrome (Trisomy 21)

Answer 21

Karyotype 47, XY or XX with 3 chromosomes #21. One of the most common causes of mental retardation. It is due to an extra chromosome #21. Individuals of the disorder have characteristics like short stature, broad hands, stubby fingers and toes, a wide, round face and a large, protruding tongue that makes speech difficult. They also have a high incidence of respiratory infections, heart defects and leukemia. The average risk of having a child with trisomy 21 is 1/750 live births. Mothers in their early 20s have a risk of 1/1500; over 35 1/70; over 45 1/25.

Question 22

Klinefelter Syndrome

Answer 22

Karyotype 47, XXY. The condition occurs in 1/1000 live, male births. The characteristics include tall stature, small testicles and sterility. Most men with this syndrome otherwise appear normal.

Question 22

Turner Syndrome

Answer 22

Karyotype 45 XO (monosomy X). This condition occurs when an X-carrying sperm fertilizes an ovum which lacks an X chromosome, or when a sperm lacking an X or Y chromosome fertilizes an X bearing egg. Such females appear normal before puberty, although they are short and have a stocky build. At birth, the distinguishable features are a thick fold skin on either side of the neck. At puberty there is no breast development or menstruation (no ova are produced). The frequency is 1/2500 live, female births.

Question 23

Prophase I (Meiosis)

Answer 23

A unique feature of Prophase I is the pairing off of homologous chromosomes; this formation is called a tetrad. The lie side by side in an intimate association called synapsis. Synapsis does not occur in Prophase II.

Question 24

Interkinesis

Answer 24

Brief phase after Telophase I/Cytokinesis in Meiosis. Similar to interphase, but without replication of DNA.

Question 25

Karyotypes

Answer 25

Images of 22 homologous chromosome pairs arranged by size and the sex chromosomes. Prepared by culturing cells (lymphocytes or sloghed-off fetal cells from amniotic fluid) and adding colchicine, which arrests the cells in the metaphase stage of mitosis. The cells are then treated and stained, resulting in a random arrangement of the chromosomes. After being photographed and cut out, the chromosomes can be arranged in pairs based on their size, banding pattern, and location of the centromere. Can help to detect genetic disorders.

Question 26

Down Syndrome (Trisomy 21)

Answer 26

Karyotype 47, XY or XX with 3 chromosomes #21. One of the most common causes of mental retardation. It is due to an extra chromosome #21. Individuals of the disorder have characteristics like short stature, broad hands, stubby fingers and toes, a wide, round face and a large, protruding tongue that makes speech difficult. They also have a high incidence of respiratory infections, heart defects and leukemia. The average risk of having a child with trisomy 21 is 1/750 live births. Mothers in their early 20s have a risk of 1/1500; over 35 1/70; over 45 1/25.

Question 27

Klinefelter Syndrome

Answer 27

Karyotype 47, XXY. The condition occurs in 1/1000 live, male births. The characteristics include tall stature, small testicles and sterility. Most men with this syndrome otherwise appear normal.

Question 28

Turner Syndrome

Answer 28

Karyotype 45 XO (monosomy X). This condition occurs when an X-carrying sperm fertilizes an ovum which lacks an X chromosome, or when a sperm lacking an X or Y chromosome fertilizes an X bearing egg. Such females appear normal before puberty, although they are short and have a stocky build. At birth, the distinguishable features are a thick fold skin on either side of the neck. At puberty there is no breast development or menstruation (no ova are produced). The frequency is 1/2500 live, female births.

Question 29

Cri-Di-Chat Syndrome

Answer 29

Karyotype 46, XY or XX with a deletion of the short arm of one chromosome #5. This condition occurs when there is a chromosomal break, resulting in a deletion, in either a developing sperm or egg. When this gamete is fertilized, the child will have developmental problems because multiple genes are missing as a result of this deletion, and the absence of each may contribute to the symptoms of the disorder. One of the deleted genes is TERY (telomerase reverse transcriptase), a gene that is vital to cell division because it helps keep the tips of the chromosomes (telomeres) intact. The name of this syndrome is French for “cry of the cat”, referring to the distinctive cry of children with this disorder caused by abnormal larynx development. Symptoms of this disorder include heart, muscle and skeletal defects, and potential behavioral problems or severe mental retardation. Distinctive features such as a small head, a round race, a small chin, widely set eyes, and a small bridge of the nose are common in individuals with Cri-du-chat. This condition affects 1/50000 live births.