cell division 09
TRANSCRIPT
Mitosis and Meiosis
Cell Division:
Objectives:
To distinguish between chromatin and chromosome
To define homologous chromosomes
To distinguish between diploid and haploid
Chromatin found in the nucleus of a nondividing cell
made of DNA and protein
DNA in chromatin replicatesbefore cell division
Chromatin becomes highlycoiled and condensed
Becomes visible as a chromosome
A Chromosome consists of 2 identical chromatids
Centromere – point at which each pair of chromatids is attached
centromere
Homologous Chromosomes pair of chromosomes that have same size and shape
found in sexually reproducing organisms
human body cells have
23 homologous pairs
Diploid (2N) – cell that contains both chromosomes of a homologous pair
human bodycells 46
Haploid # (N) – cell that has only one chromosome of each homologous pair
egg & sperm
human sex
cells 23
Objectives:
To describe the cell cycle
To define mitosis
To list and describe the stages of mitosis
Cell Cycle – period from beginning of one mitosis to beginning of next
Cell cycle consists of three stages: I. Interphase
II. Mitosis III. Cytokinesis
Interphase
cell growthand
development
DNA replication
Interphase
Plant cell
Animal cell
Mitosis – division of the cell nucleus
number of chromosomes remains the same
occurs in body cells and unicellular organisms
produces identical daughter cells
Mitosis in Human Body Cells
46(2N)
46(2N)
46(2N)
Stages of Mitosis
P M A Trophase
etaphase
elophase
naphase
1) Prophase chromosomes become visible
nuclear membrane disappears
centrioles move to opposite ends of cell and form the spindle
2) Metaphase
chromosomes line up along the equator of the cell
3) Anaphase
chromatids separate and are pulled to opposite ends of the cell
4) Telophase
chromosomes become threadlike forming chromatin
nucleus forms in each cell
Plant cell mitosis Animal cell mitosis
Cytokinesis - division of the cytoplasm
Objectives:
To define meiosis
To list and describe the stages of meiosis
Meiosis – division of the nucleus that reduces the number of chromosomes by half
involved in sexual reproduction
produces sex cells
Overview of Meiosis
46(2N)
23(N)
23(N)
23(N)
23(N)
23(N)
23(N)
Meiosis I (PMAT I)
Meiosis II (PMAT II)
Meiosis IProphase I
• homologous chromosomes pair up during synapsis forming tetrads
• spindle appears
• crossing over may occur
tetrad
tetrad
Crossing Over Between Homologous Chromosomes
Metaphase I
homologous pairs of chromosomes line up along the equator of the cell
Anaphase I
homologous pairs of chromosomes separate
Telophase I
cytoplasm divides forming 2 new daughter cells
Meiosis II
similar to the stages of mitosis chromosomes line up in the center of each cell
chromatids separate
4 cells are produced
Prophase II
Metaphase II
Anaphase II
Telophase II
Products of Meiosis
Objectives:
To define gametes
To define zygote
To define genetic recombination
Gametes sex cells (sperm and egg)
human sperm cells
human egg cell
cell that results fromthe fusion of gametes
forms when sperm
fertilizes the egg
Zygote
process that results in genes being combined in new ways during meiosis
introduces variation between parents and offspring
gives survival advantage to sexually reproducing organisms
Genetic Recombination
Objectives:
To define cancer
To describe the role of gene expression in cancer
To describe the causes of cancer
abnormal, uncontrolled growth of cells that can spread from one part of the body to another
Cancer
Tumor – abnormal proliferation of cells that results from uncontrolled, abnormal cell division
Types of Tumors benign – cells remain within a
mass and do not spread malignant – cells may invade
and destroy healthy tissues elsewhere in the body
spread of cancer cells beyond the original site of growth
cells grow as malignant tumor in epithelium
Metastasis
Types of Genes Implicated in Cancer Development
1. Oncogenes
2. Tumor-Suppressor Genes
3. DNA Repair Genes
proto-oncogene – a gene which
regulates normalcell growth
Oncogene – mutated proto-oncogene that can cause uncontrolled cell growth
and proliferation
inhibits cell division and prevents tumor formation
Tumor-Suppressor Gene
mutations in tumor suppressor genes promote cell division and allow genetically damaged cells to grow out of control
repairs mutations in cellular DNA before a cell enters mitosis
• mutations in repair genes leads to continued transcription of mutated DNA sequences and affects normal cell functioning
DNA Repair Gene
Breast Cancer Cell Line Karyotype
any substance that can induce or promote cancer
Carcinogen