BIOLOGY 1A03 Lecture Notes - Lecture 18: Sister Chromatids, Homologous Chromosome, Synaptonemal Complex

-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.

Question 1 (2 points)

In which phase of cell division is marked by the dissolution of the nuclear membrane, the condensation of chromosomes, and the formation of the mitotic spindle?

Question 1 options:

Question 2 (2 points)

The physical separation of cells during cell division is called:

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Question 3 (2 points)

Meiosis is necessary for sexual reproduction; the gametes formed during this process before fertilization are _______________.

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Question 4 (2 points)

Mitosis is the process by which a ___________ cell separates the chromosomes in its nucleus into two identical sets of nuclei.

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Question 5 (2 points)

Which of the following statements about crossing over is INCORRECT?

Question 5 options:

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 – 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:

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?