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Chapter 4
Cell Reproduction
Section 1: Cell Division and Mitosis
A. Cell division—increases the number of cells and causes many-celled
____________________to grow
B. The Cell Cycle—series of events that takes place from one ____________________ to
the next
1. Cells have periods of formation, growth and development, and death called
________________________________.
2. Interphase—most of the life of any eukaryotic cell, or cell with a nucleus, is
spent in a period of _________________and ________________.
a. During interphase, a cell duplicates its ____________________ and
prepares for cell division.
b. After interphase, the nucleus divides, and then the
______________________separates to form two new cells.
C. Mitosis—process in which the nucleus divides to form two identical
__________________
1. Chromosome—structure in the nucleus that contains ___________________
material
2. Prophase
a. Nucleolus and ______________________________ disintegrate.
b. ________________________ move to opposite ends of the cell.
c. __________________________ begin to stretch across the cell.
3. Metaphase—pairs of ___________________ line up across the center of the cell.
4. Anaphase
a. Each _____________________ divides.
b. Each pair of chromatids __________________ and moves to opposite
ends of the cell.
5. ________________—spindle fibers disappear and a new nucleus forms.
D. Division of the Cytoplasm—for most cells, the _______________ separates after the
nucleus divides.
1. In ___________________ cells, the cell membrane pinches in the middle and the
cytoplasm divides.
2. In ______________________ cells, a cell plate forms.
E. Results of mitosis
1. Each cell in your body, except sex cells, has a nucleus with _____ chromosomes.
2. Allows growth and__________________ worn out or damaged cells
F. __________________________—a new organism is produced from one parent
organism.
1. An organism with no nucleus divides into two identical organisms by
______________.
2. ____________________—a small, exact copy of the adult grows from the body
of the parent.
3. In ________________________, a whole new organism grows from each piece
of the parent.
Discussion Question
Why is cell division important? __________________________________________
_________________________________________________________________
______________________________________________________________
Section 2: Sexual Reproduction and Meiosis
A. ___________________ reproduction—two sex cells, usually an egg and a sperm,
come together.
1. Fertilization—the joining of an __________ and a ____________, generally
from two different organisms of the same species
a. Sperm are formed in the ___________ reproductive organs.
b. Eggs are formed in the ___________________ reproductive organs.
c. A cell that forms from fertilization is a ____________________.
2. Following fertilization, ______________________ begins and a new organism
develops.
3. Human body cells are ________________, because they have 23 pairs of similar
chromosomes.
4. Human sex cells are ________________, because they have 23 single
chromosomes.
B. ___________________—a process that produces haploid sex cells and ensures that
offspring have the same diploid number as its parent
1. In meiosis I, the nucleus divides and produces two new cells with one duplicated
______________________ each.
2. In meiosis II, the nuclei divide and the chromatids separate, producing _______
cells with half the number of chromosomes of the original nucleus.
Discussion Question
Why do you think sex cells must be haploid? _______________________________
_______________________________________________________________
_______________________________________________________________
Section 3: DNA
A. DNA—a ____________________ that contains information that an organism needs to
grow and function
1.Watson and ________________ made an accurate model of DNA in 1953.
2. The structure of DNA is similar to a ______________________________.
a. The sides of the ladder are made up of _________________________.
b. The rungs of the ladder are made up of ________________________.
3. Before a cell divides, its DNA duplicates itself by unwinding and separating its
sides, then each side becomes a pattern on which a ________________- forms.
B. Genes—sections of _________ on a chromosome
1. Contain instructions for making specific _______________
2. RNA carries the ___________ for making proteins from the nucleus to the
ribosomes in the cytoplasm.
a. Messenger RNA carries the code that directs the order in which the
___________________________ bond.
b. Ribosomal RNA makes up ________________, where proteins are built.
c. _______________RNA brings amino acids to the ribosomes to build the
protein.
3. Cells use only the _____________ that direct the making of proteins needed by
that cell.
C. Mutations—any permanent _____________ in the DNA sequence of a cell’s gene or
chromosome
1. Can be caused by outside factors like X rays, _________________, and some
chemicals
2. A change in a gene or chromosome can change the ____________ of an
organism.