cell division 09

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