Mitosis and Meiosis

What is mitosis?

Nuclear division that produces two genetically identical nuclei.

What are the main functions of mitosis?

Growth, repair of damaged tissues, replacement of cells and asexual reproduction.

What type of cells are produced by mitosis?

Two genetically identical daughter cells, normally with the same chromosome number as the parent cell.

What is a diploid cell?

A cell containing two complete sets of chromosomes, represented by 2n.

How many chromosomes are in a normal human diploid body cell?

46 chromosomes, arranged in 23 pairs.

What happens to DNA before mitosis?

Each chromosome is replicated, producing two identical sister chromatids joined together.

Why must DNA be copied before mitosis?

So that each daughter cell receives a complete set of genetic information.

What happens to chromosomes during mitosis?

They condense, line up at the cell equator, and sister chromatids are separated to opposite poles.

What happens during cytokinesis?

The cytoplasm divides, producing two separate daughter cells.

What is the outcome of mitosis in a typical human body cell?

Two genetically identical diploid daughter cells, each containing 46 chromosomes.

What is meiosis?

A type of nuclear division that produces genetically different haploid cells.

What is the main purpose of meiosis?

To produce haploid gametes for sexual reproduction and contribute to genetic variation.

What are gametes?

Sex cells, such as sperm and egg cells in humans.

What is a haploid cell?

A cell containing one complete set of chromosomes, represented by n.

How many chromosomes are in a normal human haploid cell?

23 chromosomes.

Why must meiosis halve the chromosome number?

So that fertilisation restores the normal diploid chromosome number rather than doubling it in every generation.

What happens to chromosomes before meiosis begins?

DNA is replicated, so each chromosome consists of two sister chromatids.

How many times does the nucleus divide during meiosis?

Twice.

How many daughter cells does meiosis typically produce?

Four haploid products.

What happens during the first division of meiosis?

Homologous chromosomes pair up and separate into different cells, reducing the chromosome number by half.

What happens during the second division of meiosis?

Sister chromatids separate, producing haploid cells.

Why are cells produced by meiosis genetically different?

Crossing over and independent assortment of chromosomes create different combinations of genetic material.

What is crossing over?

The exchange of sections of DNA between non-sister chromatids of homologous chromosomes during meiosis.

What is independent assortment in meiosis?

The random orientation and separation of homologous chromosome pairs, producing different combinations of maternal and paternal chromosomes.

What is the outcome of meiosis in humans?

Four haploid products, each with 23 chromosomes, although in females these normally develop into one functional egg plus polar bodies.

What would happen if gametes were diploid instead of haploid?

Fertilisation would produce a zygote with twice the normal chromosome number, and chromosome numbers would increase in successive generations.

What does 2n mean?

Diploid: two complete sets of chromosomes.

What does n mean?

Haploid: one complete set of chromosomes.

What is the main difference between diploid and haploid cells?

Diploid cells have two complete sets of chromosomes; haploid cells have one complete set.

Which type of cell division produces genetically identical cells?

Mitosis.

Which type of cell division produces genetically different haploid cells?

Meiosis.

How many daughter cells does mitosis usually produce?

Two.

How many haploid products does meiosis typically produce?

Four.

Does mitosis change the chromosome number?

No. Daughter cells normally retain the same chromosome number as the parent cell.

Does meiosis change the chromosome number?

Yes. It halves the chromosome number from diploid to haploid.

Which process is mainly responsible for growth and tissue repair?

Mitosis.

Which process produces gametes for sexual reproduction?

Meiosis.

Why is meiosis important for genetic variation?

It produces cells with different combinations of alleles and chromosomes.

What happens during fertilisation?

A haploid sperm and a haploid egg fuse to form a diploid zygote.

How many chromosomes are present in a typical human zygote?

46 chromosomes, formed from 23 chromosomes from the sperm and 23 from the egg.

What are the main differences between mitosis and meiosis?

Mitosis involves one division and produces two genetically identical diploid cells. Meiosis involves two divisions and produces four genetically different haploid products.