1. Unit 5 Cell Division Review

2. Why are cells small? The larger the cell becomes,
The greater demand on its DNA
Becomes less efficient
Carrying things across its cell membrane

3. DNA/chromosomes Spaghetti-like DNA Chromosomes, what are they?
organized packages of DNA, condensed DNA
What is Chromatin?
Spaghetti-like DNA
When do does DNA exist as chromatin?
In interphase

4. Parts of a Homologous Pair of Chromosomes?
Chromosome ?
Centromere ?
Chromatid ?
Homologous Chromosomes

5. Why do cells divide? To Grow Repair replenish
Prokaryotic cell division
Simple or complex?
Simple
Called?
Binary Fission
Two simple steps
DNA duplication
Cell division
Eukaryotic cell division
Complex!!!

6. Eukaryotic Cell Division
Two phases
1. Interphase
Cell growth and DNA replication, cell is doin’ its job
2. Mitosis and cytokinesis
Interphase consists of three phase G1 S G2
Mitosis, by definition is
the division of the nucleus
Consists of four phases
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis, by definition is
the division of the cytoplasm.

7. Prophase What happens? Chromosomes become Centrioles
visible
Centrioles
separate
a structure that helps to move and separate the chromosomes) forms, it is called
Spindle
It comes from the
centrioles
What disappears?
Nuclear envelope

8. Metaphase What happens? Microtubules attach to the
centromeres to move the chromosomes
Chromosomes line up in the
middle of the cell

9. Anaphase What happens? Sister chromatids do what? Chromosomes move to
split in half
Chromosomes move to
opposite poles of the cell

10. Telophase What happens? Chromosomes begin to Uncoil, decondense
and become
less visible
Nuclear envelopes begin to reform around each
cluster of chromosomes
The spindle fibers
Dissolve, get recycled to the cell’s cytoskeleton

11. Cytokinesis Separation of the cytoplasm
During cytokinesis in plant cell
a cell plate forms between the nuclei
During cytokinesis in animals
a cleavage furrow forms pinching the two cells apart

12. Do You Know the Stages of Mitosis?
CYTOKINESIS
TELOPHASE
PROPHASE
ANAPHASE
INTERPHASE
ANAPHASE
METAPHASE

13. Apoptosis, what is it? A process of programmed cell death
Important role in structuring tissues during growth and development
Cell undergoes a series of controlled steps for self-destruction.

14. Meiosis a specialized type of cell division that occurs only in the
reproductive organs,
to create
reproductive cells (sex cells, gametes)

15. Chromosomes in Somatic Cells are Matched in Homologous Pairs
Gametes have a single set of chromosomes
Somatic cell is
a body cell
Contain ? Chromosomes 46
Known as, diploid meaning
2 copies, 2n
There are 23 types of chromosomes which exist as pairs called
homologous chromosomes
Gametes are
sex cells
Examples
Sperm cell and egg cell
Gametes have only 1 copy of each type of chromosome, which is called
Haploid, 1n
When two gamete cells combine, a diploid cell (2n) is created called a
zygote

16. Meiosis reduces the chromosome number from diploid to haploid
Occurs only in
sex cells
Two divisions
Meiosis I and Meiosis II
Creates haploid cells from
diploid cells
Creates genetic diversity through:
Crossing over (Prophase I)

17. Meiosis I Prophase I Grouping of homologous chromosomes
Swapping of genes among
This is called
Crossing over
Metaphase I
Homologous pairs line up
In the middle
Anaphase I
Pairs split
Homologous chromosomes move
to opposite ends of cell
Sister chromatids
stay together (not like mitosis)
Telophase I/Cytokinesis I
How many cells formed? 2

18. Meiosis II Prophase II Metaphase II Chromosomes line up in Anaphase II
In the middle
Anaphase II
Sister chromatids
split
Telophase II/Cytokinesis II
How many cells formed? 4
Are they diploid or haploid?
Haploid
Are they genetically identical or different?
different

19. What does meiosis make? Sex cells/gametes Spermatogenesis Oogenesis
Sperm production
Oogenesis
Egg production

20. Karyotype a photographic inventory of Karyotypes are used to determine
an individual’s chromosomes
Karyotypes are used to determine
gender and to identify chromosomal abnormalities.

21. Chromosome types Chromosomes 1-22 are known as
Autosomes
Chromosomes 23 are known as
Sex chromosomes
Genetically female? XX
Genetically male? XY
Which one determine the gender of offspring?
male

22. Deletion – a piece of a chromosome breaks during division & is lost.
Duplication – a piece of a chromosome is copied and appears twice on a chromosome.

23. Inversion – a piece of a chromosome breaks during division and reattaches in a different place on the SAME chromosome
Translocation – a piece of a chromosome breaks during division and reattaches to a DIFFERENT chromosome

24. Nondisjunction – Error in meiosis in which homologous chromosomes fail to separate.
Ex:

25. Specific syndromes Down syndrome, formally called trisomy 21
Individuals have
three copies of chromosome 21
Klinefelter syndrome, has the sex chromosomes
XXY
Males born are sterile, Low testosterone levels
Turner syndrome, has the sex chromosomes X0
Females lack a second X chromosome.
Short stature, Webbed neck, Sterile