Bio 221 2

BIO 221

Nouf AlSubhi

King Abdulaziz University

Lecture 2

Introduction

All Cells Have Three Basic Features: Cell Membrane, Genetic Material, Cytoplasm

Types of cells

1-Prokaryotic 2-Eukaryotic

.

Introduction

Transverse section of bacteria and animal cell

Transverse sections of animal and plant cell

Introduction

Nucleus structure:

A Nucleus is made up of 5 parts

1- Nuclear Envelope

2- Nuclear Pores

3- Nuclear sap

4-Chromatin / Chromosomes

5- Nucleolus

Central dogma of genetics

DNA Transcription RNA Translation Protein

A- Chromosome Morphology:

1- Two arms separated by

centromere

2- Two sister chromatids

contains tightly coiled DNA

Chromosomes

Chromosomes

Identify the numbered part on chromosome?

B- Chromosome Number:

1-Diploid chromosome number: is the number of chromosome in somatic cell (2N) in human = 23pairs

2-Haploid chromosome number: is the number of chromosome in gametes (from eggs, sperm ) cell (1N) in human = 23single

Chromosomes

Eukaryotic Cell Cycle

• The eukaryotic cell cycle consists of two basic stages: Interphase and mitosis.

Interphase:is the phase of the cell cycle

in which the cell spends the

majority of its time

Preparing for cell division

Interphase =20 h

Mitosis =1 h

• Mitosis for proliferation of somatic cell.

• Mitosis results in:

division in the nucleus to produce two nuclei has the same type and numbers of chromosomes .

• Mitosis is divided into four stages: prophase, metaphase, anaphase, and telophase.

Cell division: Mitosis

Nuclear envelope disappears

Chromosome along the equator of the cell

formation of cell plate

formation of two Nucleoli as same number and type of

chromosome

Nucleoli and

Cytokinesis and cleavage

• Cytokinesis follows mitosis, and it is the last stage of the cell cycle.

• Cytokinesis divides the entire cell into two new cells.

• Cytokinesis plant cell

• Cleavage + Cytokinesis animal cell

Steps of root tip squash method

1-Growing onions and wait it for root growth and then treated it by 2ml Carnoy fixative or alchohol 70% for 24 h.

2- Using scissors , cut 2 roots tips about 1cm long and transfer them into a test tube

3- Fill the tube about 2-3ml with 1NHCL and cover the tube by gauze then tie it with rubber

4- Place the tube in 60 °C water bath and incubate for 5 min.

5- Remove the tube from water bath


6- remove the HCL from the test tube and rinse the roots in the water about 3 times

7- cover the root with the aceto carmine stain and incubate the root in the stain for 12 min.

8- Transfer a root to the slide

9- using a razor blade cut off most of the unstained part of the root and discard it

10-Cover the root tip by a cover slip then press down formally with one fingerfor flattening the sample


11- put one more drop of stain and leave it for 1min then rinse it and cover the root tip by a cover slip

12-Examine under the microscope at low power and high power

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Mitosis in Onion Root Tips





Technology

Bio 221 2