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Cell Division: Binary Fission, Chromosomes, and Mitosis in Prokaryotes & Eukaryotes, Lecture notes of Cell Biology

An in-depth exploration of cell division processes, including binary fission in bacteria, chromosome structure and function, and mitosis in eukaryotic cells. Topics covered include chromosome terms, homologous and haploid chromosomes, the cell cycle, and the differences between prokaryotic and eukaryotic cell division.

Typology: Lecture notes

2021/2022

Uploaded on 09/12/2022

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5/19/14 lev 1cell division.ppt 1
Cell Division
…the formation of new cells
5/19/14 2
1. Bacteria divide in a simple form of
reproduction called Binary Fission.!
A.Bacterium - the single circular
chromosome is duplicated
B.Cell pinches together -2 new cells-exactly
the same genetic info.
Question.. Is this more complicated or less
complicated than a eukaryotic cell?
CHROMOSOME
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5/19/14 lev 1cell division.ppt 1

Cell Division

…the formation of new cells

1. Bacteria divide in a simple form of

reproduction called Binary Fission.!

A. Bacterium - the single circular

chromosome is duplicated

B. Cell pinches together -2 new cells-exactly

the same genetic info.

Question.. Is this more complicated or less

complicated than a eukaryotic cell?

CHROMOSOME

5/19/14 3

Binary fission in bacteria

  • Answers:

• Cancer

• Passage of genetic problems to

offspring

  • FYI: Genetic variation can be a plus or a minus

Q. What types of problems could occur, if the

information stored in cells is copied incorrectly?

5/19/14 7

3. Chromosome terms

a) Sister chromatids -IDENTICAL sides attached at centromere b) Homologous chromosomes- SIMILAR in size, shape, and genetic info, not attached

3. continued

c) Haploid- n one set of chromosomes- 2 common examples: gametes in eukaryotes & chromosome in bacterial cell d) Diploid- 2n two sets of chromosomes Examples: somatic cells and germ cells

5/19/14 9

Homologous Chromosomes

Comparing Haploid and Diploid

5/19/14 13

4. A Karyotype shows each chromosome

aligned with its homologous partner.

A. Humans have 46 chromosomes (2n=46) B. homologous pair - one chromosome from dad and one from mom

5. Sex Chromosomes & Autosomes

A. Each somatic cell has 22 pairs of homologous chromosomes (autosomes) and 1 pair of sex chromosomes. B. Females-XX, Males-XY How many pairs of chromosomes do humans have? What is the diploid chromosome #? What is the haploid chromosome #? How many autosomes do humans have?

5/19/14 15

Autosomes vs Sex Chromosomes

Visual Concept

6. The Cell Cycle describes the life of a

Eukaryotic cell

a) Cell Cycle (4 stages- G 1 S G 2 M)

5/19/14 19

7. G1 (First growth phase) a cell grows rapidly

and carries out normal cell functions.

fyi….G1 is when a cell does the things that it is made to do.

8. During S (Synthesis) phase a cell's DNA is

copied (replication).

(Where does this happen?)

5/19/14 21

9. Before division, each chromosome must be

copied and condensed.

A. This results in two identical sister chromatids Replicated Chromosome

10. G2 (Second growth phase)- preparations

are made for the nucleus to divide.

a) Microtubules (spindle apparatus) built to move chromosomes around. (Centrioles come from centrosome to build it.) b) Organelles are duplicated

5/19/14 25

11. Mitosis - nucleus is divided into two nuclei.

a. Chromosomes made during S are pulled into place by the microtubules built during G2. b. After mitosis each nucleus has the same number of chromosomes containing EXACTLY the same versions of all genes.! c. Somatic cells undergo mitosis

  • Somatic- normal body cells (2n) Another look at Mitosis Interphase is NOT mitosis

5/19/14 27

Another look at Mitosis

12. Cytokinesis -cytoplasm divides!

a. Cell plate

plant

b. Cleavage furrow

animal

5/19/14 31

13. Environmental factors can cause mutations

that promote cancer

a. Drugs and alcohol!

b. UV light from the sun

c. Viruses

d. Smoking

e. overweight

14. Germ cells go through a different form of

division called Meiosis.

A. Germ cells- located in the testes and ovaries. B. Meiosis begins with a diploid cell (2n). C. One replication of chromosomes, followed by 2 divisions results in 4 haploid cells (n). D. This type of division occurs only in the formation of sperm and eggs (gametes). E. Gametes are reproductive cells that are haploid. Fyi…Gametes MUST be haploid or else the number of chromosomes an organism contains would always double.

5/19/14 33

Meiosis- the movie

15. Meiosis I is a reduction division (2n to n)

A. Homologous chromosomes are separated

instead of sister chromatids.

B. 2 cells are formed, each with one copy of

each chromosome type (n).

C. The chromosomes in these n cells, are

still attached to their sister chromatid.

D. It is during Meiosis II that the sister

chromatids are separated.

5/19/14 37

Crossing over - movie

17. Nondisjunction- failure of chromosomes to

separate when they should

5/19/14 39

Results of meiosis

Visual Concept

18. Results

A. Spermatogenesis- formation of sperm

cells

B. Oogenesis- formation of 1 egg and 3

polar bodies

C. Zygote=sperm + egg, this restores the

diploid number