01:119:115 Lecture Notes - Lecture 64: Centriole, Spindle Apparatus, Telophase

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5 Apr 2016

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Meiosis reduces the number of chromosomes sets from diploid to haploid. Like mitosis, meiosis is preceded by the replication of chromosomes. Meiosis takes place in two sets of cell divisions, called meiosis i and meiosis ii. The two cell divisions result in four daughter cells. Each chromosome composed of 2 sister chromatids (exact copies) In the first cell division (meiosis i), homologous chromosomes separate. Meiosis i results in two diploid daughter cells with replicated chromosomes. In the second cell division (meiosis ii), sister chromatids separate. Meiosis ii results in four haploid daughter cells. Division in meiosis i occurs in four phases: Prophase typically occupies more than 90% of the time required for meiosis. In synapsis , homologous chromosomes loosely pair up, aligned gene by gene. In crossing over, nonsister chromatids exchange dna segments. Each pair of chromosomes forms a tetrad, a group of four chromatids. Each tetrad usually has one or more chiasmata, x shaped regions where crossing over occured.

Related Questions

M2A1 Worksheet: Mitosis and Meiosis

A dog is a diploid organisms and has 39 pairs of chromosomes (2n = 78), where n = 39 chromosomes from each parent. Use this example to answer the following question regarding chromosomal number.

INTERPHASE

How many chromosomes are present in the somatic cell?

What do they look like?

What are they âdoingâ in G1 of this phase?

What is happening in the S phase?

What is happening in the G2 phase?

What follows G2 phase in a somatic cell?

What follows G2 phase in a gamete cell?

MITOSIS

Number of chromosomes in the parent cell.

Number of chromatids in the parent cell.

Number of chromosomes in the daughter cell.

Number of chromatids in the daughter cell.

How many daughter cells are produced?

Are the daughter cells haploid or diploid?

How many cell divisions take place?

In what type of cell does this division occur?

Meiosis 1:

Number of chromosomes in the parent cell.

Number of chromatids in the parent cell.

Number of chromosomes in each Meiosis I daughter cell.

Number of chromatids in each Meiosis I daughter cell.

Are the daughter cells haploid or diploid at the end of Meiosis 1?

Meiosis II:

Number of chromosomes in the âparentâ cell (which is a daughter cell from Meiosis I).

Number of chromatids in the âparentâ cell.

Number of chromosomes in each Meiosis II daughter cell.

Number of chromatids in each Meiosis II daughter cell.

Are the daughter cells haploid or diploid at the end of Meiosis II?

Which phase or phases of Meiosis account for the genetic variability among the daughter cells? Howâ¦ what happens in this phase to create the diversity?

Comparing Mitosis and Meiosisâ¦..

How many daughter cells result from Mitosis? Are they diploid or haploid?

How many daughter cells result from Meiosis? Are they diploid or Haploid?

Cell structures and function: Match each organelle to its function:

Organelle Function

Lysosome 1. Lipid synthesis

Rough ER 2. Houses DNA

Nucleus 3. Energy extraction

Smooth ER 4. Dismantles debris

Golgi apparatus 5. detoxification

Mitochondria 6. Protein synthesis

Peroxisome 7. Processes secretions

What is the function of checkpoint proteins in the cell cycle?

How can all of a personâs cells contain exactly the same genetic material, yet specialize as bone cells, nerve cells, muscle cells and connective tissues?

What are the 3 primary germ layers?

Briefly, in one or two sentences, distinguish between

a bacterial cell and a eukaryotic cell

interphase and mitosis

mitosis and apoptosis

an autosome and a sex chromosome

homologous pair of chromosomes and a sister chromatid

centromere and centriole

chromosome and chromatid

monozygotic and dizygotic twins

allele and gene

1). If the diploid chromosome number of an organism is 2N=12, how many chromosomes will be found in this organism's sperm?

a).	6 replicated chromosomes

b).	12 replicated chromosomes

c).	6 unreplicated chromosomes

d).	12 unreplicated chromosomes

2). When do homologous chromosomes segregate into two different daughter cells?

a).	fertilization

d).	meiosis II

3). When do sister chromatids segregate into two different daughter cells? (Choose ALL correct answers)

[]

mitosis

[]	fertilization

[]

meiosis I

[]	meiosis II

4). When does crossing over (the formation of chiasmata) occur?

a).

meiosis I

b).	meiosis II

c).

mitosis

d).	fertilization

graypig334

Title: Meiosis Lab

Part 1: Modeling Meiosis Without Crossing Over (reformat as needed)

Take photos of the following stages of your meiosis bead simulation. Insert and label the following images:

Meiosis 1: Prophase I and Metaphase I

Meiosis 2: Metaphase II and Telophase II

Part 2: Modeling Meiosis With Crossing Over (reformat as needed)

Take photos of the following stages of your meiosis bead simulation. Insert and label the following images:

Meiosis with Crossing Over: Metaphase I and Telophase II

Questions â use the lab Introduction, your textbook and other sources to answer the following.

What is the state of DNA at the end of meiosis I? Are the chromosomes replicated or unreplicated? Diploid or haploid?

Why are chromosomes important?

How are Meiosis I and Meiosis II different?

Name two ways meiosis contribute to genetic recombination or genetic variety.

Why do you use non-sister chromatids to demonstrate crossing over? What would happen if you crossed over sister chromatids?

How many chromosomes were present in your simulation when meiosis I started?

Why is it necessary to reduce the chromosome number in gametes, but not in other cells of an organism?

If humans have 46 chromosomes in each of their body cells, determine how many chromosomes you would expect to find in the following:

Sperm	Egg	Daughter cell after mitosis	Daughter cell after meiosis

Investigate a disease that is caused by a chromosomal mutation due to nondisjunction. When does the mutation occur? What chromosome is affected? What are the consequences?

01:119:115 Lecture Notes - Lecture 64: Centriole, Spindle Apparatus, Telophase

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