Download Cell reproduction chpt 10

Cell reproduction
 Cell Division and Mitosis
 Cell cycle
 Mitosis and cell divisions
 Asexual reproduction
 Sexual Reproduction and Meiosis
 Sexual reproduction
 Meiosis and Sex Cells
 DNA
 What is DNA
 Genes
 Mutations
Cell Division and Mitosis
 Why is cell division important
 In multi celled organisms an increase
in the numbers of cells is how they
grow
 In single celled organisms cell
division is the only way cells
reproduce
Cell cycle
 Length of Cycle
 Vary in time depending on cell
 Can be a matter of seconds or days to
divide
 Cycle of a cell is the time between the
start of cell division and the beginning of
cell division of the next generation
Interphase cycle
 Eukaryote cells spend most of their life in period of
growth and development during interphase
 During interphase the cell copies its genetic
information and prepares for cell division
 Some cells spend all of their lifetime in interphase
(muscles, nerve cells) and never divide
 At the end of interphase, all genetic information has
been duplicated
Mitosis and Cell Division
 Process in which the nucleus divides to form two
identical nuclei is mitosis
 Steps of Mitosis
 Chromosomes are structures in nucleus that contains
hereditary material (these are duplicated in
interphase)
 Chromosomes become thickened after duplication
and are called chromatids
Prophase
 Nuclear membrane begin to
disintegrated
 Centrioles move to opposite ends of
cell
 Attached to centrioles are threadlike
spindle fibers stretched across cells
 Plant cells do not have centrioles but
do have spindle fibers
Metaphase
 Pairs of chromatids line up in middle
of cell
 Centromeres hold the identical
chromosomes and are attached by
spindle fibers when lined up in center
 Spindle fibers attached to centrioles
to opposite end of cell
Anaphase
 Chromatids separate at centromeres and move to
opposite ends
 The separated chromatids become the identical
chromosomes of new cells
Telophase
 Nuclear membrane begins to form and two new cells
begin to close
 In animal cells, the cell pinches off to form two new
cells
 Plant cells form a cell plate that develops into cell wall
that separates into two new cells
 This ends mitosis and the cell goes into interphase
until it begins the cell cycle over again
Mitosis steps
 http://www.cellsalive.com/mitosis.htm
 http://microscopy.fsu.edu/micro/gallery/mitosis/mito
sis.html
Results of Mitosis and Cell
Division
 Three things to remember about mitosis
 1. results in division of nucleus
 2. produces two new nucleus identical to the original
and to each other
 3. original cell doesn’t exists after division
 Cells of organisms have a specific number of
chromosomes in their nucleus (humans have 46
chromosomes) fruit fly has 8
Asexual Reproduction
 New organisms are produced from one individual
 New organisms are identical to parent organisms
 Cellular Asexual Reproduction
 Eukaryotic cells reproduce by mitosis and cell division
 Sweet potato produces runners with same hereditary as
parent plant
 Bacteria (prokaryotic cell) doesn’t have nucleus so it
reproduces by fission
 Cell copies its genetic material and then divides into
two identical organism
Asexual Reproduction
 Budding and Regeneration
 When an organisms grows from the side of an
organisms and drops off as a new organism it is called
budding (Figure 8)
 Hydra is an example of budding
 Uses mitosis and cell division as source of new
individual
 Regeneration is process that uses mitosis and cell
division to regrow body parts
 Starfish, planarian are example
Regeneration
 rre
Budding
Sexual Reproduction
section 2
 The reproduction of a new organism due to union of
two sex cells is sexual reproduction
 Egg and sperm cells are sex cells
 Sperm is formed from male reproductive organs
 Egg is produced from female reproductive organs
 When the egg and sperm unite it is called
fertilization
 Cell that is produced from fertilization is called zygote
 After fertilization the zygote mitosis and cell division
begins
Diploid cells
 Human body contains two types of cells
 Body cells and sex cells
 Human cells are composed mostly of body cells
(muscle, nerve, blood, bones, tissues and organ
cells)
 Sex cells are only egg or sperm cells
 Body cells have pairs of similar chromosomes and
are called diploid cells
 Human body cells have 46 chromosomes in 23
pairs of similar size, shape, and DNA
Haploid cells
 Sex cells do not have pairs of chromosomes and are
called Haploid cells
 Contain half the number of chromosomes
 Human haploid sex cells have 23 chromosomes
 When the sperm (23 chromosomes) unite with egg (23
chromosomes) it then re-establishes the correct
number of chromosomes in new individual
 In order to cut the number of chromosomes in half
Meiosis takes place to reduce the number of
chromosomes
Meiosis and Sex Cells
 Meiosis is the process that produces
haploid cells with half the number of
chromosomes
 Two divisions occurs during meiosis
 Meiosis I and Meiosis II
 Steps have similar names to mitosis and are numbered
for the division
Meiosis I
 First step begins with duplication of chromosomes
(like mitosis)
 Prophase I : similar to mitosis
 Metaphase I: lines up in middle
 Anaphase I: doubled chromosomes move toward
each end
 Telophase I: two cells form identical to original
 Meiosis I is similar to mitosis
 Figure 11
Meiosis II
 The two cells produced in Meiosis I begin Meiosis II
 Prophase II : chromitids (paired chromosomes)
appear
 Metaphase II: chromatids line up in middle with
spindle fibers attached to centroiles
 Anaphase II: spindle fibers pull the chromatid pairs
apart toward the centroiles
 Telophase II : Four cells are produced, each with half
the number of chromosomes
 Human sex cells contain 23 chromoso
 Figure 11
http://www.youtube.com/watch?v=D1_-mQS_FZ0
http://www.cellsalive.com/meiosis.htm
Mistakes in Meiosis
 Sex cells are produced many times in
reproductive organs
 Mistakes are more commonly made in
plants
 Too many or too few chromosomes might be
produced
 Often in animals the zygote will die
 New individual does not grow normally if it
survives the incorrect number of chromosomes
DNA
Deoxyribonucleic Acid
Carries the code that is stored in its
hereditary material
When cells divides, the DNA code
is copied and passed on to new
cells
DNA Structure and Model
 Looks like a spiral staircase with handrails on each
side
 Handrails are composed of sugar(deoxyribose )
and-phosphate molecules
 Rungs of the staircase composed of nitrogen bases
 Four nitrogen bases compose DNA
 Adenine(A), guanine(G), cytosine(C), thyamine (T)
 Paired in specific combinations


A-T, C-G, T-A, G-C
The interlocking ends of each bases only fits these
combinations
Copying DNA
 The two handrails and a nitrogen base separate and
pick up nitrogen bases on each handrail and base
 Results in producing two strands of identical DNA
 http://www.stolaf.edu/people/giannini/flashanimat/
molgenetics/dna-rna2.swf
 http://www.stolaf.edu/people/giannini/flashanimat/
molgenetics/dna-rna2.swf
Genes
 Characteristics that you have are based on the types of
proteins that are produced (hair and eye color, skin
color, height, weight etc)
 Proteins build cells or work as enzyme
 Instructions for making a specific protein are found in
a gene
 Genes are a specific section of DNA on a
chromosome
 Proteins are made up of amino acids and genes
determine the order of amino acids in protein
Making Proteins
 Genes are found in nucleus but protein is made on
ribosomes in cytoplasm
 Codes are carried from nucleus to ribosomes by RNA
(ribonucleic acid)
RNA
 RNA is made in the nucleus on a DNA pattern that is
different from DNA
 RNA is like the ladder cut in half with 1 handrail
(ribose sugar ) and only 1 nitrogen base and instead of
thymine, RNA has uracil (U)
 The pairs match up C-G, G-C, A-U, U-A
 Three kinds of RNA are
 Messenger RNA (mRNA)
 Transfer RNA (tRNA)
 Ribosomal RNA (rRNA)
RNA
 Protein production begins when mRNA enters with
the code, to the cytoplasm
 mRNA attach to the ribosomes which are made of
rRNA
 Amino acids, in groups of 3, are brought to ribosomes
by tRNA molecules, where they are matched in correct
combination for protein production
Controlling Genes
 Production of protein is based on directions of genes
 Genes turn on and off for the production of different
type of cells
 Cells must control the genes by turning some genes off
and others on
 If incorrect proteins are produced, the organism can’t
function
Mutations
 If DNA isn’t copied correctly, proteins made would not
be correct and a mistake takes place called mutations
 Mutations are permanent changes in the DNA
sequence of gene or chromosome
 X-rays, sunlight and some chemicals can cause
mutations
 Mutations if occur in body cells, may or may not be life
threatening
 Mutations in sex cells often are harmful, but if the
mutation is beneficial to organism, and makes
organism more advantageous in its environment, it
may be able to pass that on to offspring