Asexual Reproduction
Asexual ReproductionSingle parent – complete copy of DNA
Offspring is identical to parentProkaryotes
Advantages:
Disadvantages:
Types of Asexual ReproductionBinary fission –
Fragmentation –
Budding –
Parthenogenesis -
Sexual Reproduction
Sexual ReproductionEukaryotesTwo parents give genetic material to produce
offspring that are genetically different from parents
Gamete – Zygote – Germ cell – Somatic cell –
Advantages /disadvantages of sexual reproduction
Chromosome NumberEach chromosomes contains thousands of
genes that control development and function of organisms.
Humans have _____ (diploid)Mom gives ____ and Dad gives ____ (haploid)Chromosome reduction is MEIOSIS!
Meiosis means reduction division – halves the number of chromosomes
Diploid – 2n (human 2n=46)Haploid - n (human n=23)
Homologous ChromosomesHomologous chromosomes – similar in size,
shape, and genes. A diploid cell contains pairs of chromosomes made up of two homologous chromosomes. One set comes from mom, and one set comes from dad.
Autosomes and Sex ChromosomesAutosomes – DO NOT determine sex of
individualSex Chromosomes – DETERMINE sex of
individualMALE – XY (Mom donates the X, father
donates the Y)FEMALE – XX (Mom donates the X, Father
donates the other X)
Sex ChromosomesSex Chromosomes
XX chromosome - femaleXY chromosome - male9
Karyotype (Human)Karyotype (Human) AAn organized organized
picture picture of the chromosomes of a human arranged arranged in pairs by size in pairs by size from largest to smallest.
PPairs 1-221-22 called AUTOSOMESAUTOSOMES
LLast pair are SEX SEX CHROMOSOMESCHROMOSOMES
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Male - XYMale - XY
Human Chromosomes
12Female - XXFemale - XX
Gamete Production
Interphase IInterphase I Similar to mitosismitosis interphase. CHROMOSOMESCHROMOSOMES (DNA)(DNA) replicate in the
S phaseS phase Each duplicated chromosomechromosome consist
of twotwo identicalidentical SISTER SISTER CHROMATIDS CHROMATIDS attached at their CENTROMERESCENTROMERES.
CENTRIOLECENTRIOLE pairs also replicate.
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Interphase IInterphase I
Nucleus and nucleolus visiblevisible.
Nucleus
nucleolus
cell membrane
chromatin
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MeiosisMeiosisSimilar in many ways to mitosisSimilar in many ways to mitosisSeveral differences howeverSeveral differences however
Involves 2 cell divisionsInvolves 2 cell divisionsResults in 4 cells with 1/2 the normal genetic information.Results in 4 cells with 1/2 the normal genetic information.
Vocabulary:Vocabulary:Diploid (2N)Diploid (2N) - Normal amount of genetic material - Normal amount of genetic materialHaploid (N)Haploid (N) - 1/2 the genetic material. - 1/2 the genetic material.
Meiosis results in the formation of haploid cells.Meiosis results in the formation of haploid cells.In Humans, these are the In Humans, these are the OvaOva (egg) and (egg) and spermsperm..Ova are produced in the Ova are produced in the ovariesovaries in females in females
Process is called Process is called oogenesisoogenesisSperm are produced in the Sperm are produced in the testestestes of males. of males.
Process is called Process is called spermatogenesisspermatogenesisMeiosis occurs in 2 phases: Meiosis occurs in 2 phases: Meiosis 1Meiosis 1 & & Meiosis 2Meiosis 2
Meiosis I (four phases)Meiosis I (four phases)
Cell division Cell division that reduces the chromosome number chromosome number by one-half.one-half.
Four phasesFour phases:
a.a. Prophase IProphase I
b.b. Metaphase IMetaphase I
c.c. Anaphase IAnaphase I
d.d. Telophase ITelophase I
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Prophase IProphase I
Prophase IProphase I LongestLongest and and most complex most complex phase (90%).phase (90%).
ChromosomesChromosomes condense. SynapsisSynapsis occurs - Homologous chromosomesHomologous chromosomes come togetherto form a tetradtetrad.
TetradTetrad is two chromosomestwo chromosomesor four chromatids four chromatids (sister and non-sister chromatids).
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Non-Sister Chromatids-Non-Sister Chromatids-HOMOLOGSHOMOLOGS
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•Homologs contain DNA that codes for the same genes , but different versions of those genes
•Genes occur at the
same loci
Meiosis I.Meiosis I.Prior to division, amount of DNA doublesPrior to division, amount of DNA doubles
Overview of MeiosisOverview of Meiosis
Prophase 1Prophase 1
During prophase 1 During prophase 1 homologous homologous chromosomes line-chromosomes line-up along the up along the metaphase platemetaphase plate
Areas of Areas of homologous homologous chromosomes chromosomes connect at areas connect at areas called called chiasmatachiasmata
Crossing OverCrossing OverSegments of Segments of
homologous homologous chromosomes break chromosomes break and reform at similar and reform at similar locations.locations.
Results in new Results in new genetic combinations genetic combinations of offspring.of offspring.
This is the main This is the main advantage of sexual advantage of sexual reproductionreproduction
Non-Sister Chromatids-Non-Sister Chromatids-HOMOLOGSHOMOLOGS
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•Homologs contain DNA that codes for the same genes , but different versions of those genes
•Genes occur at the
same loci
Genetic Recombination Genetic Recombination
nonsister chromatids
chiasmata: site of crossing over
variation
Tetrad
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Metaphase IMetaphase IShortest phaseTetrads align on the equator.Independent assortment occurs –
chromosomes separate randomly causing GENETIC RECOMBINATION
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Metaphase IMetaphase I
Homologs line up at equator or
metaphase plate
OR
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Question:Question:
In terms of In terms of Independent Independent AssortmentAssortment -how many -how many different combinations of different combinations of sperm could a sperm could a humanhuman malemale produce? produce?
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AnswerAnswer
Formula: 2Formula: 2nn
Human chromosomes:Human chromosomes: 2n = 2n = 4646
n = 23n = 23 222323 = ~8 million combinations = ~8 million combinations
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Anaphase 1Anaphase 1 During anaphase 1, each homologous chromosome is pulled to opposite During anaphase 1, each homologous chromosome is pulled to opposite
sides of the cell. Unlike mitosis, sides of the cell. Unlike mitosis, THE CENTROMERES DO NOT THE CENTROMERES DO NOT BREAKBREAK..
Nuclei may or may not reform following division.Nuclei may or may not reform following division. Cytokenesis may or may not occur.Cytokenesis may or may not occur.
Telophase ITelophase I
Each pole now has haploidhaploid (1n) set of chromosomeschromosomes.
CytokinesisCytokinesis occurs and two haploid daughter cells are formed.
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Telophase ITelophase I
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cytokinesis
Meiosis IIMeiosis II
DNA DNA does notdoes not double doubleChromosomes randomly line-up along metaphase plate Chromosomes randomly line-up along metaphase plate
like regular mitosis.like regular mitosis.During anaphase 2, During anaphase 2, CENTROMERES BREAKCENTROMERES BREAK and and
each chromosome is pulled to opposite sides of the cell.each chromosome is pulled to opposite sides of the cell.Nuclei reform and cytokenesis usually occurs (although it Nuclei reform and cytokenesis usually occurs (although it
is often unequal).is often unequal).
Telophase ITelophase I
Each pole now has haploidhaploid (1n) set of chromosomeschromosomes.
CytokinesisCytokinesis occurs and two haploid daughter cells are formed.
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Telophase ITelophase I
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cytokinesis
Meiosis IIMeiosis II
No Interphase II No Interphase II or very shortor very short ****No DNA ReplicationNo DNA Replication Remember: Meiosis II is similar Remember: Meiosis II is similar
to mitosisto mitosis
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Prophase IIProphase II Same as Same as ProphaseProphase in in mitosismitosis
Nucleus & nucleolus disappearNucleus & nucleolus disappear Chromosomes condenseChromosomes condense Spindle formsSpindle forms
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Metaphase IIMetaphase II
Same as Metaphase in mitosis
Chromosomes (not homologs) line up at equator38
Anaphase IIAnaphase II
Same as AnaphaseAnaphase in mitosismitosis **SISTER CHROMATIDS **SISTER CHROMATIDS separateseparate
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Telophase IITelophase II Same as Same as TelophaseTelophase in mitosis. in mitosis. Nuclei and Nucleoli Nuclei and Nucleoli reform, reform,
spindle disappearsspindle disappears CYTOKINESISCYTOKINESIS occurs. occurs. Remember: Remember: FOUR HAPLOID FOUR HAPLOID
DAUGHTER cells DAUGHTER cells are produced.are produced.
Called Called GAMETESGAMETES (eggs and sperm) (eggs and sperm)
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1n Sperm cell
fertilizes 1n egg to form 2n zygote
Telophase IITelophase II
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VariationVariation Also known as Also known as GENETIC GENETIC
RECOMBINATIONRECOMBINATION Important to population as the raw Important to population as the raw
material for material for NATURAL SELECTION.NATURAL SELECTION. All organisms are All organisms are NOTNOT alike alike StrongestStrongest “ “most fit” most fit” survive to survive to
reproduce & pass on traitsreproduce & pass on traits
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Question:Question: What are the What are the 33 sources of sources of genetic recombination genetic recombination or or variation? variation?
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Answer:Answer:
1.1. CROSSING OVER CROSSING OVER (prophase (prophase I)I)
2.2. INDEPENDENT INDEPENDENT ASSORTMENT ASSORTMENT (metaphase (metaphase I)I)
3.3. RANDOM FERTILIZATIONRANDOM FERTILIZATION
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Question:Question:
A cell containing 20 20 chromosomeschromosomes (diploid)(diploid) at the beginning of meiosis would, at its completion, produce cells containing how many chromosomeschromosomes?
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Answer:Answer:
1010 chromosomes (haploid chromosomes (haploid or 1n)or 1n)
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Haploid
Diploid
Meiosis and Gamete formationOogenesis
Ovum and 3 polar bodiesUn-equal distribution of the cytoplasm
Spermatogenesis4 sperm
MeiosisMeiosis Sex cells divide to produce
GAMETESGAMETES (sperm or egg)(sperm or egg). Gametes have HALFHALF the # of chromosomes.
Occurs only in GONADSGONADS (testes (testes or ovaries).or ovaries).
Male: Male: SPERMATOGENESIS -SPERMATOGENESIS -spermsperm
Female: Female: OOGENESIS - OOGENESIS - egg or egg or
ovaova 50
SpermatogenesisSpermatogenesis
2n=46
humansex cell
diploid (2n)
n=23
n=23
Meiosis I
n=23
n=23
n=23
n=23
sperm
haploid (n)
Meiosis II 51
OogenesisOogenesis
2n=46
humansex cell
diploid (2n)
n=23
n=23
Meiosis I
n=23
eggHaploid (1n)
Meiosis II52
Polar Bodies (die)
Spermatogenesis & Oogenesis
Egg/Ova4 sperm
University of Arizona Biology Pagehttp://www.biology.arizona.edu/cell_bio/tutori
als/meiosis/main.html
Cell’s Alivehttp://www.cellsalive.com/meiosis.htm
55Female - XXFemale - XX
FertilizationFertilization The fusion of a spermsperm and eggegg to form a zygotezygote.
A zygote is a FERTILIZED FERTILIZED EGGEGG
n=23egg
sperm n=23
2n=46zygote
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Question:Question:
A cell containing 40 40 chromatidschromatids at the beginning of meiosis would, at its completion, produce cells containing how many chromosomeschromosomes?
(Tricky! Think!)
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Answer:Answer:
10 chromosomes10 chromosomes
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Multicellular Life CyclesLIFE CYCLE – events in the growth and
development of an organism until it reaches sexual maturity.
Most animals have a DIPLOID LIFE CYCLEDuring meiosis, germ cells undergo meiosis to produce haploid gametes.
Fertilization – joining of 2 haploid cells to form a zygote which then undergoes mitosis to grow and develop into a new organism.
Haploid Life Cycle
Alternation of Generations
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