Biology: Cell Division

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Questions and Answers

What is the primary function of meiosis in germ line cells?

To repair DNA damage

To produce gametes (correct)

To increase genetic variation

To produce somatic cells

What is the result of non-disjunction during anaphase 1 and/or anaphase 2 of meiosis?

Production of gametes with a proper chromosome number

Production of gametes with an improper chromosome number (correct)

Production of gametes with a diploid set of chromosomes

Production of gametes with a haploid set of chromosomes

During meiosis, what is the result of DNA replication in a stem cell?

92 chromosomes, each with two chromatids

46 chromosomes, each with one chromatid

92 chromosomes, each with one chromatid

46 chromosomes, each with two chromatids (correct)

What is the outcome of Meiosis I?

Two cells, each with 23 chromosomes Signup and view all the answers

What occurs during the S phase of the cell cycle?

DNA replication occurs, resulting in duplicated chromosomes. Signup and view all the answers

What is the term for a condition where some of the cells in an organism are aneuploid?

Mosaicism Signup and view all the answers

During which stage of Mitosis do the chromosomes line up along the equator of the cell?

Metaphase Signup and view all the answers

What is the term for a condition where an organism has three copies of a particular chromosome?

Trisomy Signup and view all the answers

What is the term for the exchange of genetic material between homologous chromosomes during meiosis?

Crossing over Signup and view all the answers

What is the karyotype of an individual with Turner's syndrome?

45, X Signup and view all the answers

In a karyotype, what is the term for the two chromosomes in a pair?

Homologous chromosomes Signup and view all the answers

What is the primary function of the spindle fibers during Mitosis?

To attach to the kinetochore and separate sister chromatids Signup and view all the answers

What is the result of polyspermy during fertilization?

Triploidy Signup and view all the answers

During which stage of Mitosis do the cohesin proteins binding the sister chromatids together break down?

Anaphase Signup and view all the answers

What is the primary function of cohesin proteins in cell division?

To bind to DNA and keep strands/sister chromatids together Signup and view all the answers

What is the primary mechanism by which meiosis increases genetic variation?

Independent assortment Signup and view all the answers

What is the result of Cytokinesis?

The formation of two daughter cells Signup and view all the answers

What is the number of chromosomes in a human gamete?

23 Signup and view all the answers

What is the result of meiosis in terms of the number of chromosomes in the daughter cells?

Four unidentical haploid daughter cells Signup and view all the answers

What is the characteristic of an individual with Trisomy 13?

Cleft lip and polydactyly Signup and view all the answers

During which phase of the cell cycle does the cell perform maintenance and other functions?

G0 phase Signup and view all the answers

What is the result of non-disjunction during meiosis I?

Production of gametes with an improper chromosome number Signup and view all the answers

What is the process by which somatic cells divide to produce two identical daughter cells?

Mitosis Signup and view all the answers

During which phase of the cell cycle do the organelles duplicate and proteins synthesize?

G1 Signup and view all the answers

What is the primary function of the nuclear envelope during Mitosis?

To break down and reform during Mitosis Signup and view all the answers

What is the term for the entire complex of DNA and proteins that condenses during cell division?

Chromatin Signup and view all the answers

What is the term for the gain of a whole haploid set of chromosomes?

Polyploidy Signup and view all the answers

What is the purpose of the centromere in a chromosome?

To link the sister chromatids together Signup and view all the answers

What occurs during the Prometaphase stage of Mitosis?

The nuclear envelope breaks down and spindle fibers attach to the kinetochore Signup and view all the answers

What is the percentage of the cell cycle spent in the Mitotic Phase?

10% Signup and view all the answers

How many sets of chromosomes do somatic cells in humans have?

2 sets of 46 chromosomes Signup and view all the answers

What is the result of mitosis in terms of the genetic information in the daughter cells?

Two diploid daughter cells with identical genetic information Signup and view all the answers

What is the result of Independent Assortment of chromosomes during meiosis?

Each pair of chromosomes undergoes independent assortment independently of the other pairs. Signup and view all the answers

What is the total number of possible diploid combinations resulting from Random Fertilisation in humans?

More than 70 trillion. Signup and view all the answers

What is the stage of meiosis where the sister chromatids are split, resulting in four daughter cells?

Meiosis II. Signup and view all the answers

What is the result of Crossing Over during meiosis?

Recombinant chromosomes are formed, combining DNA from two parents. Signup and view all the answers

What is the key difference between Mitosis and Meiosis?

Meiosis has the same preparatory steps as somatic cells, but they stop at S phase and don’t go through the G2 phase. Signup and view all the answers

What is the term for a condition characterized by the presence of an abnormal number of chromosomes?

Aneuploidy. Signup and view all the answers

How many possible combinations of chromosomes are possible due to Independent Assortment in humans?

More than 2^23. Signup and view all the answers

What is the purpose of Meiosis?

To produce gametes with genetic variation. Signup and view all the answers

Study Notes

What is a Karyotype

A karyotype is an ordered display of the pairs of chromosomes from a cell.
The two chromosomes in a pair are called homologous chromosomes, which are the same shape and size, carry genes, but are alleles of each other.

Cell Division: Meiosis

Meiosis occurs in germ line cells to produce gametes.
Meiosis I divides the homologous chromosome pairs, creating two cells, each with 23 chromosomes (comprising 46 chromatids).
Meiosis II splits the sister chromatids, resulting in four daughter cells, each with 23 individual chromosomes.

Meiosis Stages

Prophase: chromatin condenses into condensed chromosomes, spindle fibers emerge from centrosomes, nuclear envelope breaks down, and nucleolus disappears.
Prometaphase: nuclear envelope dissolves and spindle fibers attach to the kinetochore.
Metaphase: chromosomes line up along the equator of the cell, each sister chromatid is attached to a spindle fiber originating from opposite poles.
Anaphase: cohesin proteins binding the sister chromatids together break down, sister chromatids are split and are pulled to opposite poles of the cell.
Telophase: nuclear envelope reforms, cytoplasm begins to cleave, and chromosomes arrive at opposite poles and decondense.
Cytokinesis: splitting of the cytoplasm which results in the formation of two daughter cells.

Genetic Variations within Gametes

Three ways of genetic variations within gametes: crossing over, independent assortment, and random fertilization.
Independent Assortment of Chromosomes: homologous pairs of chromosomes orient randomly at metaphase I of meiosis, resulting in 2^n possible combinations.
Crossing Over: produces recombinant chromosomes, combining DNA inherited from each parent, contributing to genetic variation.
Random Fertilisation: any sperm can fuse with any ovum, producing a zygote with any of about 70 trillion diploid combinations.

Compare Mitosis and Meiosis

Mitosis: two diploid daughter cells with identical genetic information.
Meiosis: division that can produce sperm and egg cells (4 unidentical haploid daughter cells).

Aneuploidy and Chromatin

Aneuploidy: a condition characterized by the presence of an abnormal number of chromosomes.
Chromatin: the entire complex of DNA and proteins, which condenses during cell division.

Cohesin Proteins and Chromosome Structure

Cohesin proteins: proteins that bind to DNA to keep strands/sister chromatids together.
Chromosome structure: p arm (short arm), q arm (long arm), and centromere (specialized DNA sequence which links the sister chromatids).

Cell Cycle

The cell cycle consists of 90% Interphase and 10% Mitotic Phase.
Interphase: G0 (resting phase), G1 (cell growth), S (DNA replication), and G2 (cell preparation).

Meiotic Non-Disjunction and Mosaicism

Meiotic Non-Disjunction: failure of homologous chromosomes to segregate properly during anaphase 1 and/or sister chromatids in anaphase 2, resulting in the production of gametes with an improper chromosome number.
Mosaicism: some of the cells are aneuploid.

Polyploidy and Trisomy

Polyploidy: gain of a whole haploid set of chromosomes.
Trisomy: gain of an extra chromosome, resulting in conditions such as Down syndrome, Edward's syndrome, and Patau syndrome.

Turner's Syndrome and Klinefelter's Syndrome

Turner's syndrome: a condition where only one X chromosome is inherited, resulting in a sterile female, short in stature, and heart and kidney defects.
Klinefelter's syndrome: a condition where an individual has an extra X chromosome, resulting in a male with abnormal physical and reproductive characteristics.

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Description

Learn about karyotypes, homologous chromosomes, and alleles in cell division. Understand the concept of ordered display of chromosome pairs in a cell.

Biology: Cell Division - Karyotype

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