Std.7 Meiosis ReviewDescribe the steps to meiosis I and meiosis 2. What types of cells are produced?

Provide examples and identify the location of gametes. How does fertilization restore chromosome number (hint: n →2n)

Word List: Fill in the blanks to make each statement correct. Some words may be used more than onceDiploid crossing-over egg fertilization four (4) gametes haploid homologous sperm tetrad unique zygote

Meiosis produces what type of cells: ___________________ Examples: _______________ cells & __________ cells

Meiosis results in ______ (#) __________________(n) cells that are genetically ______________________

During prophase I of meiosis _____________________ (pairs) chromosomes come together to form a ____________

and exchange segments of genes. This process is called _________________________ and results in unique gametes

During _______________________ 2 ________________ gametes come together to form a _____________ zygote.

Question AnalysisThe diagram below shows a cellular process that occurs in organisms. This process is known as: __________________

Cells produced are (circle one): haploid diploid

Write True/False for each statement about meiosis. Correct false statements.

______ Cells divide only once during meiosis.

______ Meiosis does not occur in reproductive cells.

______ The cells produced at the end of meiosis are genetically identical to the parent cell.

______ The cell produced at the end of meiosis contain half the number of chromosomes as the parent cell.

Write True/False for each statement about meiosis. Correct false statements.

______ It is carried out in all tissues that require cell replacement.

______ It occurs only in the reproductive structures of organisms

______ It happens in all tissues except the brain and spinal cord.

______ It is the first stage of mitosis

Explain why diploid chromosome number is even (see table)

Write an equation for what happens to chromosome # during fertilization:

______ (haploid) + _______ (haploid) = ________ (_________________)

This process is called

_________________________ &

_______________ are exchanged

during meiosis making gametes genetically unique.

Label: gametes &homologous chromosomes

Sperm cell

Egg cellzygote

Std.7 Meiosis Study GuideI. Meiosis *Results in formation of gametes → sex cells (sperm/ eggs)

Results in 4 , genetically unique gametes Two cell divisions (cytokinesis/ cytokinesis II) Gametes - are haploid (n) in chromosome #

o Single set of chromosomes (no pairs) Location = Gonads – testicles and ovaries

o gametes → sperm cells and eggs cells

II. Phases of Meiosis*Meiosis I

Prophase I – chromosomes condenseo Homologous chromosomes line up & form

tetrado Crossing over – homologous

chromosomes exchange pieces of genetic information Crossing over results in genetically unique

gametes

Metaphase I – homologous chromosomes align at center of cell

Anaphase I – homologous chromosomes separate

Telophase I – Nuclear membrane forms followed by cytokinesis Io Following telophase I and cytokinesis I,

chromosome number is reduced to haploid* Meiosis I results in 2 haploid (n) daughter cells

*Meiosis II

Prophase II – chromosomes condense

Metaphase II – chromosomes align in center of cell

Anaphase II – sister chromatids separate & move to opposite ends of the cell

Telophase II & cytokinesis II– Nuclear membrane reforms resulting in 4 haploid cellso After telophase II and cytokinesis II each

haploid cell has a single copy of each gene

End Result of Meiosis: o 4 haploid, genetically unique gametes

Sperm cells (4 sperm) Egg Cells (1 egg + 3 polar bodies)

III. Fertilization

* fertilization restores chromosome number from haploid to diploid (n → 2n)

Haploid gametes come together → form diploid zygote

Meiosis I

Meiosis II

Zygote = fertilized egg → diploid (n + n = 2n) DNA (chromosomes) come from each parent