ANSWER KEY

KEYSTONE REVIEW PACKET ANCHOR 5: CELL GROWTH AND REPRODUCTION

LEARNING OBJECTIVES: Describe the there stages of the cell cycle: Interphase, Nuclear Division, and Cytokinesis

o Describe the events that occur during the cell cycle: interphase, nuclear division (ie. Mitosis or meiosis), cytokinesis

o Compare the processes and outcomes of mitotic and meiotic nuclear divisions Explain how genetic information is inherited

o Describe how the process of DNA replication results in the transmission and/or conservation of genetic information

o Explain the functional relationships between DNA, genes, alleles, and chromosomes and their roles in inheritance

Vocabulary:

Concepts To Know:

Main Idea #1: The Cell Cycle The Cell cycle – period of time from the

beginning of one cell division to the beginning of the next

o During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells, each of which then begins the cell cycle again (only in mitosis)

o Consists of 3 phases :1) INTERPHASE (longest)

G1 – intense growth and activity S phase – copying of

chromosomes (DNA replication) G2 – intense growth and activity

2) NUCLEAR DIVISION – (mitosis or meiosis– the division of the cell nucleus

3) CYTOKINESIS – cytoplasmic division

MITOSIS

Anaphase Crossing over Interphase NondisjunctionAllele Cytokinesis Gene recombination ProphaseCell cycle DNA replication Interphase Semiconservative replicationCentromere Gamete MeiosisChromosomes Gene MetaphaseChromatids Homologous Mitosis

Biologists divide the events of mitosis into 4 phases: prophase, metaphase, anaphase, and telophase1. Prophase – 1st and longest phase of mitosis (50-60% of total time)

o chromosomes become visible as pairs of identical sister chromatids, joined at the centromereo centrioles separate and take up positions on opposite sides of the nucleus

chromosomes attach to spindle at the centromere plants do not have centrioles

organize spindle from areas called centrosomeso nucleolus disappearso nuclear envelope breaks down

2. Metaphase – 2nd phase of mitosiso chromosomes line up along center of the cello microtubules connect the centromere of each chromosome to the poles of the spindle

3. Anaphase – 3rd phase of mitosiso centromeres that join the sister chromatids splito chromatids separate and become individual daughter chromosomeso chromatids get pulled apart, to the poles of the spindle

4. Telophase – 4th phase of mitosiso chromosomes become loose and begin to disperseo nuclear envelope reformso spindle breaks aparto a nucleolus reappearso cytokinesis begins during telophase

CYTOKINESIS – division of the cytoplasm in animals, cell membrane pinches in at the middle in plants, cell plate forms midway through the cell, eventually growing to become new wall

1. Match the correct term to the events being described:

___B__ Stage of Interphase where DNA is copied A. G1 Phase

___H__ Stage of Mitosis where sister chromatids are pulled apart B. S Phase

___E__ When cytoplasm divides and daughter cells are made C. G2 Phase

___A__ Stage of Interphase when cell grows in size D. Mitosis or Meiosis

___G__ Stage of Mitosis when chromosomes are lined up at equator of cell E. Cytokinesis

___C__ Stage of Interphase when cell prepares for mitosis F. Prophase

___D__ Nuclear division G. Metaphase

___F__ Stage of Mitosis where sister chromatids condense and become visible H. Anaphase

2. Use the following word bank to label the diagram below: (#’S NEXT TO TERMS REFER TO BOX #’S)

(3) spindle fibers (1) centrioles (2) chromatin (4 & 9) interphase (2X)

(5) prophase (6) metaphase (7) anaphase (8) telophase

MEIOSIS Meiosis is a process of reduction division in which the number of chromosomes per cell is cut in half and

homologous chromosomes in a diploid cell are separatedo Involves two distinct stages: meiosis I and meiosis IIo One diploid (full # of chromosomes) cell becomes 4 haploid (half # of chromosomes) cells

Homologous chromosomes – pairs of chromosomes (one from mom and one from dad) with genes for same traits on them

o Body Cells have both sets of chromosomes = DIPLOID (2n) 2 complete sets of chromosomes (so have 2 complete sets of genes)

o Gametes (egg and sperm) have only one set of chromosomes = HAPLOID (n) contain only one set of genes

Meiosis I – prior to meiosis I, each chromosome is replicated o Chromosomes line-up similar to mitosis, except the homologous

chromosomes form a tetrad (4 chromatids) Occurs during prophase I Crossing over may occur – results in the exchange of alleles

between homologous chromosomes and produces new combinations of alleles

o Homologous chromosomes separate and two new cells are formed Meiosis II – cells from meiosis I enter meiosis II

o Cell does not undergo chromosome replication before Meiosis IIo Anaphase II – chromatids separate instead of homologous pairs

o Each resulting sex cell (gamete) has one copy of each gene

3.Label

the stages of Meiosis Below. Indicate where you see crossing over occur.

PROPHASE IANAPHASE IIANAPHASE I

CROSSING OVER

Main Concept #2: Compare the processes of mitotic and meiotic nuclear division

4. In the table provided, place a check in the column that is true for the description in the left column. (note: you may have checks in both columns if the statement relates to both Mitosis and Meiosis)

Description / Event Mitosis Meiosis

Nuclear membrane breaks down X X

Creates Gametes (egg & sperm) X

Daughter cells are identical to parent X

Body cells result X

Is used for growth and repair X

Final chromosome # is the same as the parent cell X

Diploid (2n) cells result at end X

Homologous chromosomes join, forming Tetrads X

DNA is replicated before it begins X X

TELOPHASE IMETAPHASE II

TELOPHASE II

METAPHASE I

PROPHASE II

Haploid (n) Cells Result X

Crossing over happens X

Errors in Mitosis and Meiosis

Cancer – Uncontrolled cell division; cells continue to divide, creating a tumor. Results from a mutation(s) in genes that control the cell cycle.

Nondisjunction - failure of homologous chromosomes to separate during meiosis. If nondisjunction occurs, abnormal numbers of chromosomes may find their way into gametes, and a chromosome disorder may result (e.g. Down Syndrome, 3 chromosomes at 21st pair)

Main Concept #3: Describe how the process of DNA replication results in the transmission and/or conservation of genetic information.

Structure of DNA: DNA is a double helix (two strands that coil around each other) and resembles a twisted ladder. Each chain is a polymer made of nucleotides (monomer unit of nucleic acids). One nucleotide contains three parts:

Deoxyribose sugar Phophate Group Nitrogen-containing Base (Adenine, Guanine, Cytosine, or Thymine)

The sides of the ladder are alternating deoxyribose sugar molecules and phosphate groups. A nitrogen-containing base is connected to each sugar molecule.

5. On the diagram below, label each deoxyribose sugar with a “D”, each phosphate group with

a “P”, and indicate the correct missing bases.

P

PP

P

PP

D

D

D

D

T

GC

6. Using the diagram to the right, explain the relationship between the bases of DNA (nucleotides), genes, and chromosomes.

CHROMOSOMES ARE A COLLECTION OF DIFFERENT GENES, WHICH ARE SEQUENCES OF DNA NUCLEOTIDES

DNA Replication – copying of DNA o Ensures that each resulting cell will have a

complete set of DNA moleculeso During DNA replication, the DNA molecule

separates into two strands, then produces two new complementary strands following the rules of base pairing. Adenine (A) pairs with Thymine (T) and Cytosine (C) pairs with Guanine (G)

o Each strand of the double helix of DNA serves as a template against which the new strand is made called semiconservative replication

PP

D

D

D

DA

7. On the diagram to the right, color the original parent DNA strands red, and the new DNA strands blue.

8. Looking at the diagram you colored above, explain what the statement “DNA replication is semi-conservative” means.

DURING DNA REPLICATION, EACH SIDE OF THE PARENT DNA MOLECULE IS USED AS A TEPMPLATE TO BUILD A NEW COMPLIMENTARY STRAND. THEREFORE, THE DAUGHTER DNA MOLECULES CONSIST OF ONE STRAND (SEMI) FROM THE ORIGINAL PARENT MOLECULE (CONSERVATIVE) AND ONE NEWLY BUILT STRAND.

9. Why is DNA replication a vital step in the cell cycle (S Phase)? What would happen if this phase did not occur?

IF NO DNA REPLICATION OCCURRED DURING THE CELL CYCLE, THE ORIGINAL CHROMOSOMES OF THE PARENT CELL WOULD NOT BE COPIED. WHEN CELL DIVISION OCCURRED, THERE WOULD NOT BE ENOUGH CHROMOSOMES FOR THE TWO DAUGHTER CELLS.

10. Using base-pairing rules, list the correct nucleotides that would be complimentary to the sequence listed below:

Side #1: A T C G T C A G T A C G C A T T A C G A C G

Side #2: T A G C A G T C A T G C G T A A T G C A G C

Practice Questions:

1. Which statement best describes the phase of the cell cycle shown?A. The cell is in prophase of mitosis because the number of chromosomes has doubled.B. The cell is in prophase I of meiosis because the number of chromosomes has doubled.C. The cell is in telophase of mitosis because the cell is separating and contains two copies of each

chromosome.D. The cell is in telophase of meiosis because the cell is separating and contains two copies of each chromosome.

2. Mitosis and meiosis are processes by which animal and plant cells divide. Which statement best describes a difference between mitosis and meiosis?

A. Meiosis is a multi-step process.B. Mitosis occurs only in eukaryotic cells.C. Meiosis is used in the repair of an organism.D. Mitosis produces genetically identical daughter cells. (MEIOSIS PRODUCES GENETICALLY DIFFERENT CELLS)

3. Which of the following statements is true?A. Mitosis results in the formation of two haploid gametes which can then combine to form a diploid daughter

cell.B. During the process of meiosis, haploid cells are formed. After fertilization, the diploid number of

chromosomes is restored.C. The process of meiosis forms daughter cells which are genetically identical to their parent cells.D. The daughter cells formed during mitosis are genetically similar to, though not identical to, their parent cell.

4. Which of the following best describes the way that genes, chromosomes, and DNA are related?A. Chromosomes contain several genes, which are made up of sequences of DNA.B. Genes contain several chromosomes, which are made up of sequences of DNA.C. Genes contain several sequences of DNA, which are made up of chromosomes.D. Sequences of DNA contain several genes, which are made up of chromosomes.

5. If a cat has 38 chromosomes in each of its body cells, how many chromosomes will be in each daughter cell after mitosis?

A. 19 C. 11B. 76 D. 38

6. A cell in the process of cell division contains the normal chromosome number. Each chromosome consists of two identical sister chromatids. During which stages and processes can such a cell exist?

A. telophase of mitosis, but no stage of meiosisB. metaphase of mitosis, but no stage of meiosisC. anaphase I of meiosis and anaphase of mitosisD. prophase I of meiosis and prophase of mitosis

7. Sometimes an error called non-disjunction occurs during meiosis. What is the result of this error?

A. Cytokinesis fails to happenB. Daughter cells do not get createdC. Daughter cells with an incorrect number of chromosomes are formedD. Meiosis stops early