Unit 4 - Concept 3

Meiosis

What is a haploid cell?

A haploid cell is 1 full set of chromosomes.

What is a diploid cell?

A diploid cell is 2 full sets of chromosomes. There’s a set from mom and a set from dad that come together, making the cells we all have. The majority of our types of cells are diploids.

What are examples of haploid cells?

Egg and sperm are examples of this type of cell.

What are examples of diploid cells?

Blood cells, lung cells, muscle cells, heart cells, and more are examples of these cells.

What are other names for haploid cells?

1n cells, gametes are other names for this cell.

What are other names for diploid cells?

2n cells, somatic cells are other names for this cell.

What is the difference between a haploid and diploid cell?

* Haploid cells have only 1 set of chromosomes (23), while diploid cells have 2 sets (46).
* Haploid cells are what are sent for reproduction and combine with other haploid cells to form the diploid cells and an overall new lifeform.

Why is Crossing Over during

Prophase I/Metaphase I so important?

Crossing Over between chromosomes causes some of each chromosome’s DNA to be transferred to each other.

* This causes the chromosomes to become different and nonidentical, and it’s the reason that siblings can be so different genetically.

What is the difference between somatic and sex cells?

Somatic cells are our body cells and have 2 full sets of chromosomes (one from each parent). Sex cells are egg/sperm and have only 1 set of chromosomes.

What is the difference between autosomes and sex chromosomes?

Autosomes are the chromosomes that only carry traits that make you who you are, __**while**__ sex chromosomes carry the traits that make you who you are AND determine your gender.

What is the purpose of meiosis?

This process’s purpose is to create gametes - cells with only 1 set of chromosomes that are only used for reproduction.

What are the results of meiosis?

This process results in 4 unique haploid gametes.

What is the result of mitosis?

This process results in 2 identical diploid somatic cells.

What are the end results of meiosis I?

The end results of this is __**2 haploid daughter cells with duplicated chromosomes**__ that are different from the ones in the original cell.

What are the end results of meiosis II?

The end results of this is 4 genetically unique haploid daughter cells, each with one set of chromosomes.

What happens during the 1st step of Meiosis I (Prophase I)?

During this step:

* The nuclear membrane breaks down
* The centrioles seperate and make spindle fibers
* Homologous chromosomes pair up and become visible
* Crossing over between homologous chromosomes can happen - they line up together and sometimes get tangled together, swapping pieces of DNA and making new combos of DNA.

What happens during the 2nd step of Meiosis I (Metaphase I)?

During this step:

* Homologous chromosomes line up in the **middle** as pairs.

What happens during the 3rd step of Meiosis I (Anaphase I)?

During this step:

* Homologous chromosome pairs seperate, one chromosome (2 sister chromatids) to each side of the cell.
* Sister chromatids stay attached

What happens during the final steps of Meiosis I (Telephase I and Cytokinesis I)?

During these steps:

* Chromosomes gather at poles
* Nuclear membrane MAY fom
* Cytoplasm divides (During Cytokinesis)
* 2 haploid daughter cells with duplicated chromosomes are made.

What happens during the 1st step of Meiosis II (Prophase II)?

During this step:

* Spindle fibers form and attach to the centromeres of the sister chromatids.
* Nuclear membrane breaks down

What happens during the 2nd step of Meiosis II (Metaphase II)?

During this step:

* Sister chromatids line up in the middle of the cell single file

What happens during the 3rd step of Meiosis II (Anaphase II)?

During this step:

* Sister chromatids are pulled apart
* 1 chromatid from each pair travels to each pole

What happens during the last steps of Meiosis II (Telephase II and Cytokinesis II)?

During these steps:

* Nuclear membrane forms around each set of chromosomes
* Spindle fibers dissolve
* Cytoplasm divides
* 4 genetically unique haploid daughter cells, each with 1 chromosome, are made.

What would happen if a mistake was made during Meiosis?

Sex chromosome disorders, mutations in gametes, genetic disorders, and even the deterioration or destruction of gamete cells or the organism can all happen if this were to happen.