chapter 4. section 1 allows us to grow. replaces worn out cells. one-celled organisms reproduce...
TRANSCRIPT
LIFE’S STRUCTURE AND FUNCTION
Chapter 4
CELL DIVISION AND MITOSIS
Chapter 4Section 1
Cell Division- Multicellular
Allows us to grow.
Replaces worn out cells.
One-celled organisms reproduce this way.
Cell Cycle
Organisms formation
Growth and Development
Death
Length of Cell Cycle
The time it takes to complete the cell cycle differs depending on whether you are referring to a plant, animals or humans.
Interphase is the longest part of the cell cycle.
Interphase
Hereditary material is copied
Preparation for cell division
Nerve and Muscle cells no longer divide, they are always in interphase
http://www.youtube.com/watch?v=s4PaOz7eWS8&feature=related
Why is hereditary material copied prior to dividing?
Each of the two new cells will get a complete copy of hereditary materialto carry out life functions
Mitosis
Process in which the nucleus divides to form two identical nuclei.
Each new nucleus is identical to the original nucleus.
Steps of Mitosis
Prophase
Metaphase
Anaphase
Telophase
Chromosomes
It is a structure in the nucleus that contains hereditary material.
During interphase the chromosomes duplicate.
Chromatids
These are duplicated chromosome coils that are tightly coiled into two thickened identical strands.
Centrioles
Found at opposite ends of the cell.
Between the centrioles, spindle fibers form that stretch across the cell.
Plant cell also form spindle fibers, but do not have centrioles.
Centromere
Chromatids are held together at a region called a centromere.
Prophase
Pairs of Chromatids are fully visible.
Nucleus and Nucleolus membrane disintegrates.
Metaphase
The pairs of chromatids line up across the center of the cell.
Centromere of each pair usually becomes attached to two spindle fibers-one from each side of the cell.
Anaphase
Each centromere divides, spindle fibers shorten
Each pair of chromatids separates, the chromatids begin to move to opposite sides of the cell
Separated chromatids are now called chromosomes.
Telophase
Spindle fibers start to disappear.
Chromosomes start to uncoil.
New nucleus forms.
http://www.stolaf.edu/people/giannini/flashanimat/celldivision/crome3.swf
Plant verses Animal Cells
Animal cells- cell membrane pinches in the middle, and the cytoplasm divides.
Plant cells- the appearance of a cell plate indicated that the cytoplasm is being divided.
Results of Mitosis
Division of the Nucleus
Produces two new nuclei that are identical.
Every cell in our bodies, except sex cells, has a nucleus with 46 chromosomes.
Every cell in our body has the same identical 46 chromosomes.
Every cell has the same hereditary material.
We grow and develop through the process of cell division.
Replaces worn out cells.
Replaces damaged cells.
Asexual Reproduction
A new organism is produced from one organism.
Hereditary material is identical to that of the parent organism.
Examples of Asexual Reproduction
Fission
Budding
Regeneration
Asexual reproduction in eukarytic cells happens through cell division.
An example is a sweet potato growing in a jar of water.
Mitosis is the division of the nucleus.
Bacteria do not have a nucleus.
Bacteria reproduces asexually by fission.
Budding and Regeneration
Budding is made possible by cell division.
Regeneration is the process that uses cell division to regrow body parts.
A whole new organism can grow from each piece.
Question
Compare the DNA in one of your brain cells to the DNA in one of your heart cells.
Meiosis Square Dance
https://www.youtube.com/watch?v=XROMXTrklmQ
Answer
The DNA is identical.
Sexual Reproduction
Egg and Sperm come together.
Formed in reproductive organs.
Sperms found in male reproductive organs.
Eggs found in the female reproductive organs.
Fertilization- the joining of an egg and sperm.
Zygote- it is the cell that forms when the egg and sperm join.
Come from two different organisms of the same species.
Types of Cells
Body cells- Far outnumber sex cells Typical cell has 46 chromosomes 23 pairs of chromosomes
Cells that have pairs of similar chromosomes are said to be diploid.
Sex cells do not have pairs of chromosomes.
Have half the number of chromosomes
Egg and sperm have 23 single chromosomes.
Meiosis
Produces haploid sex cells.
Most animals would not survive with a double set of chromosomes.
2 haploid cell combine which produces one diploid zygote.
During meiosis, two divisions of the nucleus occurs.
Called meiosis I and meiosis II.
Meiosis I
Before meiosis begins, each chromosome is duplicated
Steps are Prophase I, Metaphase I, Anaphase I and Telophase I
Prophase I
Each duplicated chromosome comes near its duplicated mate.
Difference In mitosis, they do not come near each
other.
Metaphase I
The pairs of duplicated chromosomes line up in the center of the cell.
The centromere of each chromotid pair becomes attached to one spindle fiber.
DifferenceIn mitosis, the centromere splits and each become attached to a spindle fiber.
Anaphase I
The two pairs of chromatids of each similar pair move to opposite ends of the cell.
Difference
The chromatids do not separate in anaphase one as they do during mitosis
Telophase I
The cytoplasm divides, and two new cells form.
Each new cell has one duplicated chromosome from each similar pair.
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Prophase II
Two cells now begin meiosis II
The duplicated chromosomes and spindle fibers reappear in each new cell.
Metaphase II
The duplicated chromosomes move to the center of the cell.
Difference from Metaphase I Each centromere now attaches to two
spindle fibers instead of one.
Anaphase II
The centromere divides.
Chromatids separate and move to opposite ends of the cell.
Each chromatid is now a separate chromosome.
Question
Compare what happens to chromosomes during Anaphase I and Anaphase II ?
Answer
Anaphase I: duplicated chromosome pairs separate and move to opposite ends of the cell.
Anaphase II: chromatids separate and move to opposite ends of the cell.
Telophase II
Spindle fibers disappear.
Nuclear membrane forms around each new nucleus at each end of the cell.
When meiosis is finished, the cytoplasm divides.
http://www.stolaf.edu/people/giannini/flashanimat/celldivision/meiosis.swf
Summary of Meiosis
Two cells form
Meiosis II, both of these cells form two cells.
The two divisions of the nucleus results in four cells.
Produces four cells with 23 unpaired chromosomes.
Mistakes in Meiosis
Can produce sex cells with the wrong number of chromosomes.
Organisms with the wrong number of chromosomes may not grow normally.
Question
How many chromosomes are in a sex cell?
Answer
Sex cells, the egg and sperm, contain 23 single chromosomes.
Question
Compare and contrast the steps of meiosis I and meiosis II.
Answer
Prophase I and Prophase II:In prophase I, the duplicated
chromosomes approach each other.
In prophase II, the duplicated chromosomes and spindle fibers reappear.
Metaphase I and Metaphase II: In Metaphase I, pairs of duplicated
chromosomes line up in the center of the cell and attach to one spindle fiber.
In Metaphase II, each centromere now attaches to two spindle fibers after the duplicated chromosomes move to the center of the cell.
Anaphase I and Anaphase II:In anaphase I, the two pairs of
chromatids of each similar pair move away to opposite ends of the cell.
In anaphase II, the centomere divides and the chromatids separate and move to opposite ends of the cell.
Telophase I and Telophase II:In telophase I, the cytoplasm divides, and two new cells form.
In telophase II, the cytoplasm of the two cells divides and four new cells form.
What is DNA??
Deoxyribonucleic acid
Genetic code is stored in hereditary material.
Hereditary material of all your body cells is the same.
Rosalind Franklin discovered that DNA is two chains of molecules in a spiral form.
Watson and Crick Each side of the ladder is made up of
sugar-phosphate molecules. Each molecule consists of the sugar
deoxyribose and a phosphate group.
The rungs of the ladder are made up of nitrogen bases:
Adenine, Guanine, Cytosine, Thymine
Cytosine = Guanine Adenine = Thymine
http://www.youtube.com/watch?v=qy8dk5iS1f0
Structure of DNA
Bases will only bond with the correct partner.
http://science.howstuffworks.com/cell6.htm
Copying DNA
The amount of DNA in the nucleus is doubled.
The two sides of the DNA unwind and separate.
Each side then becomes a pattern for a new side to form.
Copying DNA
The amount of DNA in the nucleus is doubled.
The two sides of the DNA unwind and separate.
Each side then becomes a pattern for a new side to form.
Copying DNA
The amount of DNA in the nucleus is doubled.
The two sides of the DNA unwind and separate.
Each side then becomes a pattern for a new side to form.
DNA in our cells store the instructions for making proteins.
The proteins made determine your characteristics such as hair color, your height, and how things taste.
Nucleus Chromosomes
DNA wrapped aroundproteins
Genes are composed of
DNA
Each chromosome contains 100’s or 1000’s of genes.
Proteins are made of chains of amino acids.
Genes determine the order of the amino acids.
Different order makes a different protein.
Where are proteins made?
Proteins are manufactured on the ribosomes.
Ribosomes are located in the cytoplasm.
RNA
Genes are in the nucleus.
Proteins are made in the cytoplasm.
Codes for making protein carried from the nucleus to the cytoplasm viaRNA.
How is RNA made?
RNA is made in the nucleus on a DNA pattern
RNA is also a twisted ladder
RNA has the base uracil instead of thymine
Types of RNA
Messenger RNA
Ribosomal RNA
Transfer RNA
DNA in the nucleus is used to make the mRNA.
mRNA carries the code from the nucleus to the cytoplasm.
mRNA cytoplasm Ribosomes attach to mRNA
tRNA in cytoplasm bring
Amino acids toRibosomes
Three nitrogen bases on the mRNAtemporarily match with three Nitrogen bases on the tRNA
The amino acids which are attached to the tRNA molecules form bonds. This is the beginning of a protein.
The code carried on the mRNA directs the order in which the amino acids bond.
The ribosome moves along the mRNA.
New tRNA molecules with amino acids match up and add amino acids to the protein molecule.
http://www.youtube.com/watch?v=NJxobgkPEAo
Protein Synthesis
http://www.wisc-online.com/objects/index_tj.asp?objid=AP1302
http://www.youtube.com/watch?v=NJxobgkPEAo
Manufacturing of Protein
Controlling Genes
Each cell in a multicellular organism uses only some of the thousands of genes that it has to make proteins.
Cells must be able to control genes by turning some off and some on.
Question
Why is it necessary for cells to regulate gene function?
Answer
Different cells in our bodies have different functions. Therefore, depending on the cells function, different proteins are necessary to carry on a specific function.
The genes you inherit dictate what proteins are made in different cells.
Mutations
Mistakes when DNA is copied
Proteins made from the instructions may not be made correctly
Any permanent change in the DNA sequence
Mitosis and Meiosis
http://www.youtube.com/watch?v=35ncSrJOwME&feature=related