12. Meiosis

Introduction to Meiosis

GCSE Biology - Meiosis  #70

Introduction to Meiosis Example 1

Meiosis I & Meiosis II

In Meiosis I, cytokinesis usually occurs after telophase I and produces:a) Four diploid cells.b) Two haploid cells.c) Four haploid cells.d) Two diploid cells.

Phases of Meiosis (simulation)

Sperm and eggs in humans always                   .
a. each have two copies of every gene;
b. each have one copy of every gene;
c. each contain either all recessive alleles or all dominant alleles;
d. are genetically identical to all other sperm or eggs produced by that person;
e. each contain all of the genetic information from their producer

 To make exact copies of the parent cell 

 To make one cell with twice the number of chromosomes as the parent pairs 

 No. Although chromosomes do replicate during meiosis, the function of meiosis is not to make one cell with twice the number of chromosomes as the parent pairs. 

 To make four cells with the same chromosome number as the parent 

 No. Four cells are made, but with a different chromosome number than the parent. 

 No. Meiosis does not produce diploid spores. 

 To make cells with a haploid (half that of the parents) number of chromosomes 

Consider how meiosis differs from mitosis.

What is the function of meiosis?

Stages of Meiosis

Meiosis | Genetics | Biology | FuseSchool

 No. Cytokinesis is division of the cytoplasm; it takes place in both mitosis and meiosis, and is not directly involved in any changes in chromosome number. 

 No. Mitosis results in the production of daughter nuclei that contain the same number of chromosomes as the parental nucleus. 

 No. Interphase is the period between rounds of mitosis; DNA is replicated during interphase, but the chromosome number remains the same. 

 No. This is the phase of mitosis during which chromosomes align along the cell's equator. 

Consider the differences between mitosis and meiosis.

Which of the following results in cells that contain half the parental chromosome number?

The DNA of the haploid cell is replicated.

The RNA of the diploid cell is replicated.

The DNA of the diploid cells is replicated.

The two cells need to be physically separated by cytokinesis.

Which of the following steps must occur before Meiosis I in germ cells?

BioFlix: Meiosis

MAKE CONNECTIONS In Figure 33.7, assume that the two medusae shown at step 4 were produced by one polyp colony. Review Concept 12.1 and Concept 13.3, and then use your understanding of mitosis and meiosis to select which of the following is true. 
(A) Both the medusae and the gametes are genetically identical. 
(B) Neither the medusae nor the gametes are genetically identical. 
(C) The medusae are not genetically identical but the gametes are genetically identical. 
(D) The medusae are genetically identical but the gametes differ genetically.

Animation: Overview of Meiosis

Animation: Meiosis

 exchange of homologous regions of nonsister chromatids 

 No. Independent assortment occurs as a result of the positioning of homologous chromosomes during metaphase I. 

 lining up of tetrads at the metaphase plate 

 division of the cytoplasm to create two cells 

Technically, mitosis and meiosis refer to the distribution of chromosomes to new nuclei in the process of cell division.

Cytokinesis is the __________.

Which synapomorphy (shared, derived trait) distinguishes animals as a monophyletic group, distinct from choanoflagellates?
a. multicellularity
b. coloniality
c. heterotrophy
d. movement

 No. Haploid sex cells contain half as many chromosomes as diploid somatic cells. 

 No. This would result if the cell underwent mitosis. 

Consider the purpose of meiosis in the life cycle of a sexually reproducing organism.

In a diploid cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing __________ chromosomes.

Propose an experiment to test whether Pilobolus shoots its sporangia preferentially toward light. Hypothesize why such a preference might be advantageous.

 No. This would be the result of a diploid cell undergoing mitosis. 

 No. Consider what happens to the number of chromosomal sets when a cell undergoes meiosis. 

 Two haploid cells and two diploid cells 

 No. Four cells are produced, but two of them are not diploid. 

Consider what happens to the chromosomes during the two phases of meiosis.

What is the typical result when a diploid cell has completed meiosis?

No. Diploid cells can undergo mitosis, but there is a better answer.

No. Diploid cells can undergo meiosis, but there is a better answer.

No. Haploid cells can undergo mitosis, but there is a better answer.

 Haploid cells cannot divide by meiosis. 

No. Haploid cells cannot undergo meiosis, but there is a better answer.

 All of the listed responses are correct. 

What are the roles of mitosis and meiosis in different life cycles?

Which of the following statements is most accurate?

In Meiosis II, ________ cells are divided into 4 ___________ daughter cells.a) Diploid; Haploid.b) Haploid; Diploid.c) Haploid; Haploid.d) Diploid; Diploid.

MAKE CONNECTIONS In Figure 33.8, assume that the two medusae shown at step 4 were produced by one polyp colony. Review Concept 12.1 and Concept 13.3, and then use your understanding of mitosis and meiosis to evaluate whether the following sentence is true or false; if false, select the answer that provides the correct reason. Although the two medusae are genetically identical, a sperm produced by one will differ genetically from an egg produced by the other.
a. False (both the medusae and the gametes are genetically identical)
b. False (neither the medusae nor the gametes are genetically identical)
c. False (the medusae are not identical but the gametes are)
d. True

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