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)

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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