10.1 cell growth key concept - what problems does growth cause for cells and how does cell division...
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10.1 Cell GrowthKey Concept - What problems does growth cause for
cells and how does cell division solve the problem?
Limits to Cell GrowthLarger cell= more demands the cell’s DNALarger cell = more trouble moving nutrients in across cell membraneLarger cell= more trouble moving wastes out across cell membrane
10.1 Cell Growth
Limits to Cell GrowthLarger cell: more demands cell’s DNA
DNA, “overload”Library metaphor: as the town gets larger, too many people are trying to check out the same books. Better to build another library!
10.1 Cell Growth
Limits to Cell GrowthProblems Exchanging Materials
•Food, Oxygen, and Water need to get in through cell membrane (surface area)•Wastes need to leave the cell through the membrane (surface area)•Amount of nutrients needed and waste produced depends on volume.
10.1 Cell Growth Limits to Cell GrowthProblems Exchanging Materials
Food, Oxygen, and Water get in through cell membrane (surface area)Wastes need to leave the cell through the membrane (surface area)
Amount of nutrients needed and waste produced depends on volume.
Problem: as volume increases, surface area increases But not as quickly as volume increases
10.1 Cell Growth Limits to Cell GrowthProblems Exchanging Materials
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10.1 Cell Growth Limits to Cell GrowthRatio of Surface Area to Volume
Problem: as volume increases, surface area increases But not as quickly as volume increases
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10.2 CellDivision
Prokaryotes: just separate into twoEukaryotes: Two stages
mitosis division of nucleuscytokinesis dividing cytoplasm in two
Chromosomes: Only visible during cell divisionAt other times chromatinAt cell division, chromosomes have been duplicated, and so are seen as two sister chromatids
Chromosomes• Only visible during cell division•At cell division, chromosomes have been duplicated and are seen as two sister chromatids•joined at centromere
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Chromosomes:DNA twisted together with proteinshistonesThen twisted again and
again into chromatids
Cell CycleInterphase: time between divisions
cell growthduplication of genetic
materialMitosis: nucleus and chromosomes divideCytokinesis: cytoplasm divides
Cell Cycle
Cell CycleInterphase: time between divisions
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Cell CycleProphase: Chromatin organizes into chromosomes.Nuclear membrane breaks up
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Cell CycleMetaphase: Chromosomes line up along cell equator
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Cell CycleAnaphase: Chromosomes separate toward opposite poles
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Cell CycleTelophase: Nuclear membrane reformes. Cytokinesis begins.
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Cell Division: Mitosis
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Cell Division: Mitosis
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Work of Gregor MendelGenes and DominanceTrait a specific characteristic (color, height)
that varies from individual to individualMendel crossed plants with different colorsHybrids are offspring of parents with different traitsF1 first generation of that crossMendel expected F1 offspring to be a blend of parent traitsInstead, all the offspring had characteristics of one parent
Work of Gregor MendelGenes and DominanceTrait a specific characteristic (color, height)
that varies from individual to individualMendel crossed plants with different colorsHybrids are offspring of parents with different traitsF1 first generation of that crossMendel expected F1 offspring to be a blend of parent traitsInstead, all the offspring had characteristics of one parent
Genes chemical factors that determine one traitAlleles different forms of that geneDominance some alleles are dominant, some are recessive.
Work of Gregor Mendel
Seed Shape
Flower Position
Seed CoatColor
Seed Color
Pod Color
Plant Height
PodShape
Round
Wrinkled
Round
Yellow
Green
Gray
White
Smooth
Constricted
Green
Yellow
Axial
Terminal
Tall
Short
Yellow Gray Smooth Green Axial Tall
Work of Gregor Mendel
P Generation F1 Generation F2 Generation
Tall Short Tall TallTall Tall Tall Short
Work of Gregor Mendel
P Generation F1 Generation F2 Generation
Tall Short Tall TallTall Tall Tall Short
SegregationWhat happened to the recessive alleles?
Work of Gregor Mendel
P Generation F1 Generation F2 Generation
Tall Short Tall TallTall Tall Tall Short
SegregationWhat happened to the recessive alleles?
Work of Gregor MendelSegregationWhat happened to the recessive alleles?
The F1 CrossHow did the recessive traits disappear and then reappear?SEGREGATION in formation of sex cells or gametes, alleles are separated. Each gamete carries only one copy of each gene.F1 plant produces two types of gametes one with the allele for tallness and one for the allele for shortness.
11.2 Probability and Punnett Squares
•EXPLAIN how geneticicsts use the principles of probability•DESCRIBE how geneticists use Punnett squares
Probaility and Punnett Squares
Genetics and ProbabilityProbability can be used to predict the outcome of genetic crosses
The ratio of probability that an allele will be expressedIs proportional to the number of offspring expressing that allele.
Probaility and Punnett Squares
Punnett Squaresare used to determine the possible gene combinations from a genetic cross
The Punnett square can be used to predict the ratio of offspringPunnett Square vocabulary:•Homozygous has two identical alleles for a given trait (ie tt or TT)•Heterozygous has two different alleles for the trait (ie Tt)•phenotype physical characteristic (Tall Tt or TT)•genotype genetic make up (TT is different than Tt)
Probaility and Punnett Squares
Punnett Square
Probaility and Punnett Squares
Punnett Square
Probaility and Punnett Squares
Punnett Square
Probaility and Punnett Squares
Punnett Square
Probaility and Punnett Squares
Punnett Square
Probaility and Punnett Squares
Punnett Square
Phenotype: tall
Phenotype: tall
Phenotype: tall
Phenotype: short
Probaility and Punnett Squares
Probability and SegregationDid segregation occur?The recessive gene that had been hidden in the F1 generation reappeared in the F2 generation.The ratio was 3 tall plants to 1 short plant
Probaility and Punnett Squares
Probabilities Predict AveragesJust as in a coin flipThe larger the sample, the more likely the result will match the prediction
11.3 Exploring Mendelian Genetics
Independent AssortmentAlleles segregate during gamete formationDo they segregate independently?Does the gene for seed color (Yellow, Y or Green, y) have anything to do with the gene for seed shape (round, R or Wrinkled, r)?
11.3 Exploring Mendelian Genetics
Independent AssortmentTwo Factor Cross: F1
First Mendel crossed an rryy plant with an RRYY plantThat cross produced all RrYy offspringWhat would happen in the next generation (F2)?Would there be any Ry or rY plants?Or would the dominant and recessive alleles stick together?
11.3 Exploring Mendelian Genetics
Independent AssortmentTwo-Factor Cross: F2
RY Ry rY ry
RY RRYY RRRy RrYY RrYy
Ry RRYy RRyy RrYy Rryy
rY RrYY RrYy rrYYrrYy
ry RrYy Rryy rrYy rryy
IndependentAssortmentGenes for differentTraits segregateindependently
11.3 Exploring Mendelian Genetics
Summary of Mendelian Principles• Inheritance determined by genes passed
from parents to offspring• Genes may be dominant or recessive• Adult has two copies of each gene, one
from each parent• Alleles for different genes usually segregate
independently
11.3 Exploring Mendelian GeneticsBeyond Dominant and Recessive
Some alleles are neither dominant nor recessive
Incomplete Dominance Heterozygous offspring show a phenotype somewhere in between the two homozygous phenotypes (pink four o’clocks)
Codominance both alleles contribute to the phenogype of the organism (roan cattle have both red and white hairs)
11.3 Exploring Mendelian GeneticsBeyond Dominant and Recessive
Some alleles are neither dominant nor recessive
Multiple Alleles More than two alleles possible (coat color in rabbits)
PolygenicTraits controlled by more than one gene (human eye color, human skin color)
11.3 Exploring Mendelian GeneticsApplying Mendel’s Principals
Drosophila:Often used in genetic researchFruit fly produce a new generation of hundreds
of offspring every 14 days Human applicationsAlbinism controled by one gene Skin pigment is dominant, Albinism is recessivePigmented parents have an albino child.What is the chance that the next child will be albino?
Focus Week11.4 Meiosis and 11.5 Linkage and Gene Mapping Due Thursday (in class work - not homework)11.4 p 278 q 1 - 511.5 p 280 q 1 - 4HomeworkStudy for final80% of questions will come from study guide and
standardized test prep (end of each chapter)
Skip to Tuesday
Normal human body cells each contain 46 chromosomes. The cell division process that body cells undergo is called mitosis and produces daughter cells that are virtually identical to the parent cell.
1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis?
2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo?
3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?
11.4 MeiosisGOALSContrast the chromosome number of body cells
and gametesSummarize the events of meiosisContrast meiosis and mitosisHOW TO EXPLAIN MENDEL’S OBSERVATIONS
Organisms inheirit a single copy of each gene from each parent
Offspring’s gametes contain only one set of each gene
11.4 MeiosisChromosome Number
Homologous: two genes that belong to the same pair
i.e. Fruit flies have 8 chromosomes, four homologous pairs, 4 chromosomes from each parent
Diploid: containing both sets of homologous chromosomes
2N
11.4 MeiosisChromosome Number
Gametes: contain only a single set of chromosomes (therefore genes)
And so are calledHaploid: containing only one set of
chromosomes N (i.e. N=4)
Homologous: two genes that belong to the same pairi.e. Fruit flies have 8 chromosomes, four homologous pairs, 4 chromosomes from each parentDiploid: containing both sets of homologous chromosomes
2N (i.e. 2N = 8)
11.4 MeiosisPhases of MeiosisMeiosis: reduction division. Chromosome number cut in half by separating homologous chromosomes of diploid cellMeiosis IEach chromosome is replicatedHomologous chromosomes pair up
forming tetrad joined at centromerehomologous chromosomes separate
Meiosis II
11.4 MeiosisPhases of MeiosisMeiosis: reduction division. Chromosome number cut in half by separating homologous chromosomes of diploid cellMeiosis IEach chromosome is replicatedHomologous chromosomes pair up
forming tetrad joined at centromerehomologous chromosomes separate
Meiosis IINo duplication of genetic materialChromosomes (only half of the diploid number) line up and chromatids separate
11.4 MeiosisPhases of Meiosis - Meiosis I
Interphase I
DNA replication, forming duplicate Chromosomes.
11.4 MeiosisPhases of Meiosis - Meiosis I
Interphase I
DNA replication, forming duplicate Chromosomes.
Prophase I
Each chromosome pairs with corresponding homologous chromosome to form a tetrad.
Metaphase I
Spindle fibers attach to the chromosomes.
Anaphase I
The fibers pull the homologous chromosomes toward the opposite ends of the cell.
11.4 MeiosisPhases of Meiosis - Meiosis I
Interphase I
DNA replication, forming duplicate Chromosomes.
Prophase I
Each chromosome pairs with corresponding homologous chromosome to form a tetrad.
Metaphase I
Spindle fibers attach to the chromosomes.
Anaphase I
The fibers pull the homologous chromosomes toward the opposite ends of the cell.
11.4 MeiosisPhases of Meiosis - Meiosis I
Interphase I
DNA replication, forming duplicate Chromosomes.
Prophase I
Each chromosome pairs with corresponding homologous chromosome to form a tetrad.
Metaphase I
Spindle fibers attach to the chromosomes.
Anaphase I
The fibers pull the homologous chromosomes toward the opposite ends of the cell.
11.4 MeiosisPhases of Meiosis - Meiosis II
Prophase II
Meiosis I results in two haploid (N) cells, each with half the number of chromosomes of parent cell
Metaphase II
The chromosomes line up in a similar way to the metaphase in mitosis.
Anaphase II
The sister chromatids separate and move toward opposite ends of the cell.
Telophase II
Meiosis II results in four haploid (N) daughter cells.
11.4 Meiosis
Prophase II
Meiosis I results in two haploid (N) cells, each with half the number of chromosomes of parent cell
Metaphase II
The chromosomes line up in a similar way to the metaphase in mitosis.
Anaphase II
The sister chromatids separate and move toward opposite ends of the cell.
Telophase II
Meiosis II results in four haploid (N) daughter cells.
Phases of Meiosis - Meiosis II
11.4 Meiosis
Prophase II
Meiosis I results in two haploid (N) cells, each with half the number of chromosomes of parent cell
Metaphase II
The chromosomes line up in a similar way to the metaphase in mitosis.
Anaphase II
The sister chromatids separate and move toward opposite ends of the cell.
Telophase II
Meiosis II results in four haploid (N) daughter cells.
Phases of Meiosis - Meiosis II
11.4 Meiosis
Prophase II
Meiosis I results in two haploid (N) cells, each with half the number of chromosomes of parent cell
Metaphase II
The chromosomes line up in a similar way to the metaphase in mitosis.
Anaphase II
The sister chromatids separate and move toward opposite ends of the cell.
Telophase II
Meiosis II results in four haploid (N) daughter cells.
Phases of Meiosis - Meiosis II
11.4 MeiosisCrossing-over
During Meiosis I,
11.4 MeiosisCrossing-over
During Meiosis I, homologous chromosomes may, “cross-over,”
11.4 MeiosisCrossing-over
During Meiosis I, homologous chromosomes may, “cross-over,” and exchange portions of their chromatids.
11.4 MeiosisGamete Formation
•In male animals, meiosis produces four haploid (1N) sperm cells•In female animals one of the haploid egg cell receives most of the cytoplasm the remaining, “polar bodies,” do not participate in reproduction
11.4 MeiosisComparing Mitosis and Meiosis
•Mitosis two genetically identical diploid cells
•Meiosis four genetically different haploid cells
11.5 Gene Linkage and Mapping
Some genes appear to be inherited together, or “linked.”
If two genes are found on the same chromosome, does it mean they are linked forever?
11.5 Gene Linkage and Mapping1. In how many places can crossing over result in genes A and b being on the same chromosome?
2. In how many places can crossing over result in genes A and c being on the same chromosome?
Genes A and e?
3. How does the distance between two genes on a chromosome affect the chances that crossing over will recombine those genes?
11.5 Gene Linkage and Mapping1. Identify the
structures that actually assort independently
2. Explain how gene maps are produced
Independent assortment:Genes are assorted independentlyBut what about genes on the same chromosome
11.5 Gene Linkage and MappingGene Linkage
Mendel worked with 7 characteristicsSix of them happened to be on different chromosomesThe one pair on the same chromosome were so far apart on the chromosome that they appeared to assort independently.
11.5 Gene Linkage and Mapping
11.5 Gene Linkage and MappingGene Linkage
1910 Morgan’s research on fruit fliesStudied 50 traitsMany (red-eyed, short winged) appeared to be, “linked.”Grouped into four linkage groupsFour chromosomesConclusion: It is chromosomes, not individual genes, that assort independently.
11.5 Gene Linkage and MappingGene Maps
Are those linked genes linked forever? No, crossing over may separate linked genes.1911 Sturtevant (student of Morgan) hypothesis:The farther genes are from eachotherThe more likely they will be separated by cross-overProduced gene map using recombination rates