BIO152H5 Lecture Notes - Lecture 5: Sister Chromatids, G1 Phase, G2 Phase

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16 Aug 2020

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Most cell division results in daughter cells with identical genetic information (dna) as the parent cell, and as each other. The exception is meiosis, a special type of division that produces sperm and egg cells. Chromosomes consist of chromatin, a complex of dna and protein that condenses during cell division. In preparation for cell division, dna is replicated and chromosomes condense. Each duplicated chromosome consists of two sister chromatids (joined copies of the original chromosome), and are held together by cohesin proteins. In humans, somatic cells (non-reproductive cells) have two sets of chromosomes (2 23 = 46 total) Gametes (reproductive cells: sperm and eggs) have half as many chromosomes as somatic cells. During cell division, sister chromatids separate and move into two nuclei. Once they have been separated, the sister chromatids are called chromosomes. Mitosis: the division of the genetic material in the nucleus. Gametes produced by a variation of cell division called meiosis.

Related Questions

Carefully read the following statements about cell division (1) After meiosis, the number of chromosomes in the newly formed cell is the same as that in the parent cell. Whereas, in mitosis, the chromosome number in daughter cell is reduced to half. (2) Cytokinesis is a highly regulated event in which cellular organelles are evenly distributed forming two daughter cells. (3) In Meiosis, DNA replication occurs only once whereas the cells divide twice and it is the mechanism that produces genetic variation in daughter cells. (4) In diplotene, chiasmata are formed between homologous chromosomes followed by crossing over and segregation of sister chromatids. (5)The kinetochore is a DNA protein complex which serves as the attachment point for spindle fibers. Which of the above statement or combination of statements is correct?

-Complete the following sentences: metaphase of mitosis, prophase II of meiosis, crossing over, anaphase I of meiosis, variable, random fertilization, identical, random orientation, metaphase I of meiosis, prophase I of meiosis, metaphase II of meiosis, reduction division

Two processes that occur during meiosis produce genetically ____________ cells.

In a process called ____________ , paired homologous chromosomes align randomly at the cell equator. This occurs during this stage of cell division: ____________ .

In a process called ____________ , genetic material is exchanged between homologous chromosomes. This occurs during this stage of cell division: ____________ .

-Complete the following paragraph to describe nondisjunction and the resulting effects on chromosome number.

words: euploidy, primary nondisjunction, nomal, nondisjunction, secondary nondisjunction, homologous chromosomes, abnormal, trisomy, monosomy, sister chromatids, aneuploid

1.During meiosis I, ____________ separate and move towards opposite ends of the poles.

2.During meiosis II, ____________ separate and move towards opposite ends of the poles.

3.During meiosis I, if both members of a homologous pair go into the same daughter cell, ____________ is said to occur and no normal gametes are produced.

4.During meiosis II, if the sister chromatids fail to separate and both daughter chromosomes go into the same gamete, ____________ is said to occur. Half the gametes are aneuploid while the other half are euploid.

5.If an egg that contains 24 chromosomes instead of 23 chromosomes is fertilized by a normal sperm, ____________ is said to have occurred.

6.If an egg that contains 22 chromosomes instead of 23 chromosomes is fertilized by a normal sperm, ____________ is said to have occurred.

Match the term with its correct definition or explanation.

Chromatin

Homologous Chromosomes

Sister chromatids

Diploid

Interphase

S Phase

Synapsis

Crossing Over

Cell Plate

Cleavage Furrow

A. The exchange of genetic material between homologous chromosomes during meiosis I.

B. The pairing or tight association of homologous chromosomes in meiosis I. Results in the formation of a tetrad.

C. Non-identical copies of the same chromosome. Present in all diploid cells, even before replication. These chromosomes are the same length and contain genes for the same characteristics, but may have different alleles for each gene. D.

The period of the cell cycle that includes G1, S phase, and G2. E. A structure that develops during cytokinesis in plants.

F. Condensed chromosomes.

G. An invagination that develops during cytokinesis in animal cells.

H. When an organism has two copies of every chromosome (2n).

I. Two identical copies of a chromosome. These are only present after DNA replication.

J. The phase of the cell cycle when DNA is replicated.

BIO152H5 Lecture Notes - Lecture 5: Sister Chromatids, G1 Phase, G2 Phase

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