REPRODUCTION All cells come from cells.All cells come from cells. Essential for the continuation of...
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Transcript of REPRODUCTION All cells come from cells.All cells come from cells. Essential for the continuation of...
REPRODUCTION
• All cells come from cells.All cells come from cells.
• Essential for the continuation of a species
Why do cells divide?Cells need to remain small. A greater surface area to
volume ratio is needed to maintain homeostasis
• for reproduction
– one celled organisms (clones)
• for growth & development– from fertilized egg to multi-celled
organism
• for repair– replace cells that die from
normal wear & tear or from injury
Asexual Reproduction
Types of Reproduction
Parents Variation Mate Selection
ASEXUAL
One parent
Results in clones (genetically identical)
Very little or no variation in offspring
No mate selection needed
SEXUAL
Two parents –
egg and sperm sex cells (gametes)
Great variation Great variation (diversity) (diversity) due to crossing over (exchanging genetic info)
Varying degrees of mate selection
METHODS OF ASEXUAL REPRODUCTIONMETHODS OF ASEXUAL REPRODUCTION
1. BINARY FISSION– DNA copies itself and then
cell divides in half– results in 2 identical, equally
sized offspring (cells) – EX: bacteria, amobea
http://www.brainpop.com/science/cellularlifeandgenetics/asexualreproduction/
AMOBEA
2. BUDDING•NUCLEUS DIVIDES EQUALLY, CYTOPLASM DOES NOT•RESULTS IN different sized “BUDS” offspring
• EX: YEAST, HYDRAYEAST, HYDRA
Hydra
3. SPORULATION 3. SPORULATION “SPORE SPORE FORMATIONFORMATION”•single specialized cells made by mitosis that grow (germinategerminate) into a new organism under proper conditions (WATERWATER AND FOOD)!•EX: OCCURS IN MOLD MOLD AND OTHER FUNGI FUNGI
Spores
4. REGENERATION4. REGENERATION:: is the ability to replace body parts.•Example – Starfish, worms, hydras
• To what extent can regeneration occur in humans? Why?
Humans can regenerate certain organs like the skin but not old body parts
5. VEGETATIVE PROPAGATION can be produced asexually from the roots,
stems and leaves of an existing plant. a) Natural:
– Bulbs – tulips, onions and lilies
– Runners– Grass and strawberries
– Tuber -potato
b) Artificial:– Cuttings – segments separated from the
plant and placed in soil to grow a new plant
– Grafting – attaching a branch or stem of one plant on to another
Vegetative Propagation
PROS CONS• Plants are
identical –good if productive & strong
• Faster than planting a seed
• Producing Producing Seedless Seedless fruitfruit
• Can be wiped out by disease or a disaster (flooding or a drought)
• Can be more Can be more susceptible to susceptible to insecticidesinsecticides
Cell Reproduction: Vocabulary
1. DNA: instructions for making proteins
2. Genes: a segment of DNA that tells the ribosome to make ONE specific protein
3. Chromosome: a tightly packed piece of DNA containing over a 1000 different genes
4. Chromatin: chromosomes all stretched out; thread-like DNAthread-like DNA
5. Homologous chromosomes: a pair of chromosomes carrying the same genes (one from each parent)
6. Centromere: the point where the chromosomes
join together
nucleus
Sister Chromatids
CentromereChromatid
Mitosis - HOW “NORMAL” CELLS DIVIDEA. What is Mitosis?
• The process of distributing exact copies of genetic information.
Malfunction of Cell Reproduction: Uncontrolled mitosis:•Production of numerous, nonfunctional cells •Force out functional cells by stealing their nutrients•Very dangerous when cancer cells enter the endocrine
or circulatory systems.•Results: Cancers and Tumor Growth
Thyroid Cancer
http://www.brainpop.com/science/cellularlifeandgenetics/mitosis/ (2:09)
http://www.iteachbio.com/Life%20Science/LifeFunctionsandTheCell/Mitosis.mov
B. What is Mitosis used for?1. Growth & development
• from fertilized egg to multi-celled organism
2. Repair of the body• Replace cells that die from normal
wear & tar or from injury3. Asexual reproduction • Mitosis (nuclear division)
C. How does Mitosis happen? 1. Genetic material within the nucleus makes an exact
copy of itself.2. It is then packaged and separated into two new nuclei.3. Each daughter cell gains exactly one copy of the
genetic material.
Mitosis
InterphaseProphaseMetaphaseAnaphaseTelophaseCytokinesis
Mito
sis
The Cell Cycle
• Interphase• Prophase• Metaphase• Anaphase• Telophase• Cytokinesis
STAGES/PHASES OF THE CELL CYCLE
MITOSIS
Pneumonic Pneumonic DeviceDevice
II PPrayray MMore ore AAtt TThe he CChurchhurch Cell cycle video http://www.youtube.com/watch?v=3k
pR5RSJ7SA&feature=related
18
http://www.cellsalive.com/mitosis.htm
IPMATC
Mitosis: Animal v. PlantMitosis: Animal v. Plant
Overview of mitosis
Copy DNA
Line Up Separate Divide
http://www.sumanasinc.com/webcontent/animations/content/mitosis.html
KEYS TO MITOSISKEYS TO MITOSIS Original cell has complete set of chromosomesOriginal cell has complete set of chromosomes
This is known as This is known as DIPLOID DIPLOID or 2Nor 2N One division results in One division results in 2 DAUGHTER CELLS
No genetic material exchangedNo genetic material exchanged Cells are Cells are GENETICALLY IDENTICALGENETICALLY IDENTICAL DaughterDaughter Cells are also DIPLOID or 2NCells are also DIPLOID or 2N
Ex. Original cell has 46 chromosomes, daughter cells will Ex. Original cell has 46 chromosomes, daughter cells will have 46 chromosomeshave 46 chromosomes
IN SINGLE CELLED ORGANISMS:IN SINGLE CELLED ORGANISMS: Method of reproduction Method of reproduction (ASEXUAL)(ASEXUAL)
ProtistsProtists, some Algae, and , some Algae, and MoldsMolds IN MULTI-CELLED ORGANISMS:IN MULTI-CELLED ORGANISMS:
Mitosis used for Mitosis used for GROWTH and REPLACEMENTGROWTH and REPLACEMENT of of BODYBODY (somatic)(somatic) CELLSCELLS (skin, liver, heart etc…) (skin, liver, heart etc…)
Turn in article reviews on Stem Cells and Telomeres
Never Say Die Scientific American Frontiers - Season 10 The Clock of Life- http://chedd-angier.com/frontiers/season10.html (start at 15:11minutes) (9 minutes)
Your turn: Complete the 2 article reviews on TELOMERES
WHAT ARE STEM CELLS” https://www.youtube.com/watch?v=jF2iXpoG5j8
Your turn: Complete the article review on Stem Cells
Complete Pearson activity on mitosisHW: complete RB worksheet BQuiz Monday on Mitosis
SEXUAL REPRODUCTION
Meiosis – A Source of DistinctionMeiosis – A Source of Distinction
Why do you share some but not all characters of each parent?
At one level, the answers lie in meiosis.
What is meiosis? It is a special type of cell division that makes egg and sperm
How? Chromosomes replicate Each cell divides twice
This provides each cell with half the number of chromosomes
Why? Meiosis is necessary to halve the number of chromosomes
going into the sex cells Why halve the chromosomes in gametes?
At fertilization the male and female sex cells will provide ½ of the chromosomes each – so the offspring has genes from both parents
This makes for a lot of genetic diversity. Genetic diversity is important for the evolution of
populations and species.
Let’s review some vocabulary first:
1. Homologous chromosomes (homologs):
A PAIR of chromosomes carrying the SAME GENES (ONE from each parent)
HOMOLOGOUS = same information
Humans have 23 PAIRS
2. Sister CHROMATIDS: 2 “identical” strands of
DNA that make up each member of a homologous pair
Draw and label this diagram in the box of your notes
23
2346
egg
sperm
46meiosis
Haploid (n)Diploid (2n)
3. DIPLOID (2N): having 2 of each chromosome type
ex. mitosis always STARTS and RESULTS in a diploid number (46)
ex. meiosis always STARTS with diploid number (46)
4. HAPLOID (N): A cell (always a gamete) that contains ½ the number of
CHROMOSOMES Meiosis results in cells with ½ NUMBER OF CHROMOSOMES
(23)!
5. Fertilization - THE JOINING OF SEX CELLS½ genetic (egg) + ½ genetic (sperm) = 1 genetically whole organism
(n=23) (n=23) = (2n=46)
egg + Sperm zygote.
=
n=23egg sperm
n=23
2n=46zygote
6. Zygote6. Zygote
is a FERTILIZED
egg
MitosisMitosis
FertilizationFertilization
ZygoteZygoteEmbryoEmbryo
Draw and label this diagram in the box of your notes
•A method of organizing A method of organizing the the chromosomeschromosomes of a of a cell in relation to cell in relation to number, size, and type.number, size, and type.
•There are two categories There are two categories of chromosomes:of chromosomes:
•Sex chromosomesSex chromosomes
•X, YX, Y
•AutosomesAutosomes – 1, 2, 3, – 1, 2, 3,….. (numbers 1-22 in ….. (numbers 1-22 in humanshumans))
7.7. KARYOTYPE KARYOTYPE - -
XX chromosome - femaleXY chromosome - male
8. CROSSING-OVER:•Process when homologous Process when homologous chromosomes “cross” each chromosomes “cross” each other andother and EXCHANGE EXCHANGE genesgenes
•SOURCE OF VARIATION-SOURCE OF VARIATION-givesgives NEW COMBINATIONS NEW COMBINATIONS of mom of mom and dad’s genes in one and dad’s genes in one chromosomechromosome
Images of Chromosomes crossing over
How does this explain:family resemblance & differences!
Why are the kids so similar to the parents but not exact?
Martin & Charlie Sheen, Emilio Estevez
Michael & KirkDouglas
Baldwin brothers
MEIOSIS: Cell Division to MEIOSIS: Cell Division to form Gametesform Gametes
Meiosis Animation
Meiosis: Meiosis: SEXSEX!!!!!!!!!! A form of CELL DIVISIONCELL DIVISION by which sex cells called
GAMETESGAMETES (egg and sperm), (egg and sperm), are produced. Takes place in reproductive structures called GONADS
(ovaries and testes) Diploid Diploid (2n) (2n) haploid haploid (n)(n) EACH CELL DIVIDES TWICE EACH CELL DIVIDES TWICE - - (meiosis I meiosis I and meiosis IImeiosis II)
Each sex cell has halfhalf the number of CHROMOSOMESCHROMOSOMES ALLOWS FOR GENETIC VARIATION OF OFFSPRING gametes of offspring do not have same genes as gametes from parents
offspring
from Dad
from Mom new gametes made by offspring
variation
We’remixing things
up here!
PRIOR TO MEIOSIS MEIOSIS I
Sister chromatids
Tetrad (4 chromatids from homologous chromosomes)
1. Chromosomesreplicate inparent cell.
2. Synapsis (joining) of homologous (sister) chromosomes. Crossing over of non-sister chromatids – brings about Variation
3. Tetrads migrate to middle of cell. Independent Independent assortment assortment (random line (random line up)- more up)- more variation!variation!
4. Homologsseparate.
MEIOSIS I: HOMOLOGOUS CHROMOSOMES SEPARATE
MEIOSIS II
5. Cell divides into 2 haploid (N) daughter cells.
6. Chromosomes begin moving to
middle of cell.
7. Chromosomes line up at middle of cell.
8. Sister chromatids separate.
9. Cell division results in four haploid daughter cells. Leads to random fertilization.
MEIOSIS II: SISTER CHROMATIDS SEPARATE
Learning Target: I can illustrate meiosis from a diagram and explain the possible outcomes and the source of variation amongst the cells..
Individually observe Figure 11-15 in textbook and read pages 276-277.
As a group complete the condensed meiosis diagram on the mitosis –meiosis summary sheet. Use colored pencils to represent the homologous chromosomes. Discuss the best way to illustrate the process. When you agree fill in sheet. Label where homologous chromosomes separate and where sister chromatids separate. Use page 278 for help as well.
When finished answer the questions on the back as a group. I expect all to be participating!!
9. Gametogenesis9. Gametogenesis
Making gametes (sex cells- Making gametes (sex cells- EGGEGG and and SPERMSPERM)) Spermatogenesis:
Formation of 4 FUNCTIONAL sperm
Oogenesis:Formation of egg cells (1 functional CELL and 3 polar bodies)
Basic diagram of Meiosis- OvaBasic diagram of Meiosis- Ova
Female Human Female Human Pre-GametePre-Gamete
4646chromosomechromosome
ss
4646differentdifferent
chromosomechromosomess
4646differentdifferent
chromosomechromosomess
Replication Replication and Crossing-and Crossing-
OverOver
2323
1 functional
ovum and 3 polar bodies
First cell First cell divisiondivision
Oogenesis:• Formation of egg cells (ova)• Results in 1 functional gamete and 3 polar bodies
Basic diagram of Meiosis- SpermBasic diagram of Meiosis- Sperm
Male Human Male Human Pre-GametePre-Gamete
4646chromosomechromosome
ss
4646differentdifferent
chromosomechromosomess
4646differentdifferent
chromosomechromosomess
Replication Replication and Crossing-and Crossing-
OverOver
2323 2323 2323 2323
44 functional functional spermsperm
After 2After 2ndnd cell cell divisiondivision
First cell First cell divisiondivision
Spermatogenesis:•Formation of sperm cells•Results in 4 functional gametes
ADVANTAGES OF SEXUAL REPRODUCTION
1. Sexual reproduction increases individual VARIATION within a SPECIES
Asexual Reproduction (Mitosis):
Results in offspring = to parents
Sexual Reproduction (Meiosis):
Results in offspring that are not = to parents
2. GENETIC DIVERSITY may produce some organisms that are ADAPTABLE to non favorable conditions:
Susceptibility to PATHOGENS
ENVIRONMENTAL changes
VariationVariation
Important to population as the raw material Important to population as the raw material for for natural selectionnatural selection..
Genetic diversity is important for the Genetic diversity is important for the evolution of populations and speciesevolution of populations and species
Question:Question:
What are the three sexual sources ofWhat are the three sexual sources of
genetic variation? genetic variation?
Write this down
Answer:Answer:
1. crossing over (prophase I)1. crossing over (prophase I)
2. independent assortment (metaphase I)2. independent assortment (metaphase I)
3. random fertilization3. random fertilization
Remember: variation is good!
Write this down
HYPOTHETICAL EXAMPLE OF INDEPENDENT ASSORTMENT
Eye color
Gene thatcontributes to browneyes
Gene thatcontributes to blueeyes
Maternalchromosome
Paternalchromosome
Hair color
Gene thatcontributes to black hair
Gene thatcontributes to red hair
Maternalchromosome
Paternalchromosome
During meiosis I, tetrads can line up two different waysbefore the homologs separate.
OR
Brown eyesBlack hair
Blue eyesRed hair
Blue eyesBlack hair
Brown eyesRed hair
HYPOTHETICAL EXAMPLE OF INDEPENDENT ASSORTMENT
MEIOSIS & GENETIC VARIATION
Random Fertilization: Each human can produce an
nearly 8.4 million different kinds of gametes
Crossing over not taken into account!!!
Sex yields: 8.4 mill x 8.4 mill = 70.6 x 10 12
genetically distinct offspring can be produced
DISADVANTAGES OF SEXUAL REPRODUCTION
1. Sex SLOWS RATE of Reproduction!
Sexual reproduction should decline in frequency relative to asexual reproduction
Sexual Reproduction: Only FEMALES
produce offspring, therefore fewer are produced
Asexual Reproduction:
All individuals can produce offspring
2. Errors In Inheritance:
Genetic disorders occur for various reasons:NONDISJUNCTION:
Failure of a pair of chromosomes to separate during gamete formation
ABNORMAL numbers of one or more chromosomes is usually, but not always, fatal
Includes Genetic Disorders Like: DOWN’S SYNDROME (chromosome #21)
Comparing Mitosis & Meiosis – 1 min
AnimationAnimation
KEYS TO MEIOSISKEYS TO MEIOSIS
Original cell has complete set of chromosomes Original cell has complete set of chromosomes (Diploid or 2N)(Diploid or 2N)
2 divisions2 divisions result in result in 4 DAUGHTER CELLS (gametes: 1 ova 4 DAUGHTER CELLS (gametes: 1 ova or 4 sperm)or 4 sperm) Genetic material is exchanged during Genetic material is exchanged during CROSSING OVERCROSSING OVER
CHROMOSOMES CHROMOSOMES “criss-cross” “criss-cross” EXCHANGING GENESEXCHANGING GENES Daughter cells (gametes) are genetically differentDaughter cells (gametes) are genetically different Daughter cells (gametes) are now Daughter cells (gametes) are now HAPLOID HAPLOID or N ( ½ the or N ( ½ the
original # )original # ) Ex.Ex. If original cell has 46 chromosomes, gametes that If original cell has 46 chromosomes, gametes that
result from meiosis will have 23 chromosomesresult from meiosis will have 23 chromosomes OCCURS OCCURS ONLYONLY IN IN MULTICELLUARMULTICELLUAR, SEXUALLY , SEXUALLY
REPRODUCING ORGANISMSREPRODUCING ORGANISMS
I II – like mitosis BUT twice
Crossing over occurs
• Crossing over (during prophase I) brings about VARIATION!!!!!Crossing over (during prophase I) brings about VARIATION!!!!!
Parent cell
DNA Synthesis
Mitosis & Cytokinesis
Parent cell and daughter cells contain thesame complement of chromosomes.
A REVIEW OF MITOSIS
Two daughter cells
Note: Mitosis Is Part Of The Cell Cycle!!
COMPARISON OF MITOSIS AND MEIOSIS
Characteristic
Mitosis Meiosis (SEX)
Function GROWTH, DEVELOPMENT, REPLACEMENT, REPAIR
Make GAMETES (egg and sperm)
Occurs in BODY (Somatic) cells Immature REPRODUCTIVE cells
Results in 2 daughter cells (clones of each other)
4 daughter cells (all different)
Chromosome #
Daughter cells are DIPLOID
(2n) = 46 chromosomes
Daughter cells are HAPLOID (1n) = 23 chromosomes
Reproduction Type
ASEXUAL – 1 parent SEXUAL – 2 parents
Stages
Drawing
1 cell division (IPMAT) 2 cell divisions (PMAT x 2)
464646
46 2323
232346
46