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Cell division. Chromosomes Binary Fission Mitosis Cancer. CHROMOSOMES. CHROMOSOMES Are Tightly coiled strands of DNA and chromatin located in the nucleus of each cell control growth and development. CHROMOSOMES. Section 8.2 Summary – pages 201 - 210. - PowerPoint PPT Presentation
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ChromosomesBinary Fission
MitosisCancer
CELL DIVISION
CHROMOSOMES
CHROMOSOMES
Are Tightly coiled strands of DNA and chromatin
- located in the nucleus of each cell- control growth and development
• Become darkly colored when stained.• Are the carriers of the genetic material that is
copied and passed from generation to generation of cells.
• Accurate transmission of chromosomes during cell division is critical.
CHROMOSOMES
CHROMOSOMES
Human Chromosome Number1. 46 total chromosomes2. Diploid cells = contain all 46 (full set) 3. Haploid cells = contain 23 (half set)
CHROMOSOMES
Two types of chromosomes1. Autosomes – 22 pairs2. Sex Chromosomes– 1 pair
B. Sex Chromosomesa. determine male or femaleb. XX = Femalec. XY = Male
CHROMOSOMES
• Chromatin – the relaxed, uncoiled state of the chromosome.
• Chromosome – threadlike structures within the nucleus containing genetic information that is passed from generation to generation.
Terminology
When chromosomes are preparing to divide the DNA replicates itself into two strands called chromatids.
Held together by a centromere
Binary Fission
CELL DIVISION IN
PROKARYOTES
• The process whereby bacteria copy their chromosome and then divide into two different cells.
BINARY FISSION
BINARY FISSION
MITOSIS AND MEIOSIS
CELL DIVISION IN
EUKARYOTES
CELL DIVISIONMitosis
• Occurs in body cells called SOMATIC CELLS• Examples
muscle cells, cheek cells, liver cells, bone cells, red blood cells, etc.
• Makes exact copies (asexual reproduction)
Meiosis• Occurs in sex cells
called GAMETES• Examples
egg cells, sperm cells• Mixes for genetic
variation (sexual reproduction)
Why must cells divide?
Cell division is necessary for:• Growth• Repair• Replacement of dying cells (such as skin
cells or red blood cells)• Reproduction of an organism.
Cell Cycle The process of cell division is called the cell
cycle.
InterphaseThe first part of the cell cycle is called
Interphase
Interphase consists of three stages:-Normal cell activity-DNA (the chromosomes) replication-Final preparation for division
It is the longest phase of the cell cycle.
Cell cycle The next phase of the cell
cycle is mitosis.
The Cell Cycle
MitosisPurpose - to produce an exact copy of a
diploid cell.• After interphase, MITOSIS begins-4
phases(PMAT)–Prophase–Metaphase–Anaphase–Telophase
Cytokinesis in an Animal CellCleavage Furrow
Cytokinesis in an Plant Cell
Cytokinesis Cleavage furrow
Cell plate
Animal cell
Plant cell
Cell division
Which type of cells undergo mitosis?
Cell division
Which type of cells undergo mitosis?
All somatic cells.
Mitosis
Mitosis produces two exact copies of the original cell.
2 Diploid Somatic Cells
When Making New Cells Goes Terribly Wrong
MITOSIS AND CANCER
When is mitosis a BAD thing• When cells reproduce & they are not
needed– these cells take over organs, but don’t do the
right job– they just keep making copies– cancer
• damages organs
Why would cells just make copies?
• If DNA gets damaged, cells stop listening to correct instructions_Mutation: change in genetic makeup and
cause cells to become cancerous • Causes of mutations:
UV radiation chemical exposure radiation exposure heat
cigarette smoke pollution age genetics
Cancer-Causing Mutations• Exposure to environmental agents, virus, or
lifestyle changes may cause a mutation• Certain virus infections can transform the
cell • Human papillomavirus (HPV): Viral
proteins interact with cell proteins, cause cervical cancer
• Mistakes in DNA replication also cause mutations
Cancer• Carcinogens and certain behaviors
increase rate of mutations and cancer risk• Not all tumors are cancerous, benign
tumors, increase in size, but do not metastasize
• Metastasis: Process in which cells are invasive and move to other sites in the body
Cell Cycle Regulation• Normal cells contain check
points to regulate the cell cycle. Stopping at appropriate points.
• Cancerous cells do not respond to check points and continue rapidly through the cell cycle. This results in masses of undefined cells called tumors.
Tumors• Benign tumor
– abnormal cells remain at original site as a lump
– most do not cause serious problems &can be removed by surgery
Tumors• Malignant tumor
– cells leave original site• carried by blood system to other tissues• start more tumors
– damage functions of organs throughout body
Cancer Cells
Treatments for cancers• Treatments kill rapidly dividing cells
– chemotherapy• poisonous drugs that kill rapidly dividing cells
– radiation • high energy beam kills rapidly dividing cells
Cancer Is One Outcome of A Runaway Cell Cycle
Licentious division - prostate cancer cells during division.
Cell Division in Gamete Cells
MEIOSIS
Variation
If the cell cycle produces only exact copies, then how is their variation (variety, differences) among living things? Why is it that you look different from your parents and different from the other students in the room?
ANSWER: Meiosis and Crossing Over in Homologous Chromosomes
Homologous Chromosomes
Are corresponding chromosomes from the opposite-sex parent
Crossing Over• A process occurring during meiosis wherein two
chromosomes pair up and exchange segments of their genetic material.
• Ii important because it results in new combinations of genes that are different from either parent, contributing to genetic variation and diversity.
Crossing Over
Meiosis
Similar to mitosis in some ways but different in other ways.
In meiosis there are two different stages called:
Meiosis I Meiosis II
Meiosis I
Meiosis II
Meiosis
Meiosis produces four cells.4 Haploid Gamete Cells
Meiosis and Egg Cells: OOGENESIS
Meiosis & Sperms Cells: SPERMATOGENESIS
A Comparison
MITOSIS & MEIOSIS
Cell Division
Mitosis Meiosis
Purpose Growth & Repair
Reproduction
Divisions 1 2
Parent Cell Diploid Diploid
Daughter Cells
2 diploids 4 haploids
Cell Type Somatic Gamete