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10.1 Cell Growth Key Concept - What problems does growth cause for cells and how does cell division solve the problem? Limits to Cell Growth Larger cell=

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Presentation on theme: "10.1 Cell Growth Key Concept - What problems does growth cause for cells and how does cell division solve the problem? Limits to Cell Growth Larger cell="— Presentation transcript:

1 10.1 Cell Growth Key Concept - What problems does growth cause for cells and how does cell division solve the problem? Limits to Cell Growth Larger cell= more demands the cell’s DNA Larger cell = more trouble moving nutrients in across cell membrane Larger cell= more trouble moving wastes out across cell membrane

2 10.1 Cell Growth Limits to Cell Growth Larger 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!

3 10.1 Cell Growth Limits to Cell Growth Problems 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.

4 10.1 Cell Growth Limits to Cell Growth Problems 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

5 10.1 Cell Growth Limits to Cell Growth Problems Exchanging Materials

6 10.1 Cell Growth Limits to Cell Growth Ratio of Surface Area to Volume Problem: as volume increases, surface area increases But not as quickly as volume increases

7 10.2 CellDivision Prokaryotes: just separate into two Eukaryotes: Two stages mitosis division of nucleus cytokinesis dividing cytoplasm in two Chromosomes: Only visible during cell division At other times chromatin At cell division, chromosomes have been duplicated, and so are seen as two sister chromatids

8 Chromosomes Only visible during cell division At cell division, chromosomes have been duplicated and are seen as two sister chromatids joined at centromere

9 Chromosomes: DNA twisted together with proteins histones Then twisted again and again into chromatids

10 Cell Cycle Interphase: time between divisions cell growth duplication of genetic material Mitosis: nucleus and chromosomes divide Cytokinesis: cytoplasm divides

11 Cell Cycle

12 Interphase: time between divisions

13 Cell Cycle Prophase: Chromatin organizes into chromosomes. Nuclear membrane breaks up

14 Cell Cycle Metaphase: Chromosomes line up along cell equator

15 Cell Cycle Anaphase: Chromosomes separate toward opposite poles

16 Cell Cycle Telophase: Nuclear membrane reformes. Cytokinesis begins.

17 Cell Division: Mitosis

18

19 Work of Gregor Mendel Genes and Dominance Trait a specific characteristic (color, height) that varies from individual to individual Mendel crossed plants with different colors Hybrids are offspring of parents with different traits F 1 first generation of that cross Mendel expected F 1 offspring to be a blend of parent traits Instead, all the offspring had characteristics of one parent

20 Work of Gregor Mendel Genes and Dominance Trait a specific characteristic (color, height) that varies from individual to individual Mendel crossed plants with different colors Hybrids are offspring of parents with different traits F 1 first generation of that cross Mendel expected F 1 offspring to be a blend of parent traits Instead, all the offspring had characteristics of one parent Genes chemical factors that determine one trait Alleles different forms of that gene Dominance some alleles are dominant, some are recessive.

21 Work of Gregor Mendel Seed Shape Flower Position Seed Coat Color Seed Color Pod Color Plant Height Pod Shape Round Wrinkled Round Yellow Green Gray White Smooth Constricted Green Yellow Axial Terminal Tall Short YellowGraySmoothGreenAxialTall

22 Work of Gregor Mendel P Generation F 1 Generation F 2 Generation TallShort Tall Short

23 Work of Gregor Mendel P Generation F 1 Generation F 2 Generation TallShortTall Short Segregation What happened to the recessive alleles?

24 Work of Gregor Mendel P Generation F 1 Generation F 2 Generation TallShortTall Short Segregation What happened to the recessive alleles?

25 Work of Gregor Mendel Segregation What happened to the recessive alleles? The F 1 Cross How 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.

26 11.2 Probability and Punnett Squares EXPLAIN how geneticicsts use the principles of probability DESCRIBE how geneticists use Punnett squares

27 Probaility and Punnett Squares Genetics and Probability Probability can be used to predict the outcome of genetic crosses The ratio of probability that an allele will be expressed Is proportional to the number of offspring expressing that allele.

28 Probaility and Punnett Squares Punnett Squares are used to determine the possible gene combinations from a genetic cross The Punnett square can be used to predict the ratio of offspring Punnett 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)

29 Probaility and Punnett Squares Punnett Square

30 Probaility and Punnett Squares Punnett Square

31 Probaility and Punnett Squares Punnett Square

32 Probaility and Punnett Squares Punnett Square

33 Probaility and Punnett Squares Punnett Square

34 Probaility and Punnett Squares Punnett Square Phenotype: tall Phenotype: short

35 Probaility and Punnett Squares Probability and Segregation Did segregation occur? The recessive gene that had been hidden in the F 1 generation reappeared in the F 2 generation. The ratio was 3 tall plants to 1 short plant

36 Probaility and Punnett Squares Probabilities Predict Averages Just as in a coin flip The larger the sample, the more likely the result will match the prediction

37 11.3 Exploring Mendelian Genetics Independent Assortment Alleles segregate during gamete formation Do 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)?

38 11.3 Exploring Mendelian Genetics Independent Assortment Two Factor Cross: F 1 First Mendel crossed an rryy plant with an RRYY plant That cross produced all RrYy offspring What would happen in the next generation (F 2 )? Would there be any Ry or rY plants? Or would the dominant and recessive alleles stick together?

39 11.3 Exploring Mendelian Genetics Independent Assortment Two-Factor Cross: F 2 RYRyrYry RYRRYYRRRyRrYYRrYy RyRRYyRRyyRrYyRryy rYRrYYRrYyrrYY rrYy ryRrYyRryyrrYyrryy Independent Assortment Genes for different Traits segregate independently

40 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

41 11.3 Exploring Mendelian Genetics Beyond 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)

42 11.3 Exploring Mendelian Genetics Beyond 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)

43 11.3 Exploring Mendelian Genetics Applying Mendel’s Principals Drosophila: Often used in genetic research Fruit fly produce a new generation of hundreds of offspring every 14 days Human applications Albinism controled by one gene Skin pigment is dominant, Albinism is recessive Pigmented parents have an albino child. What is the chance that the next child will be albino?

44 Focus Week 11.4 Meiosis and 11.5 Linkage and Gene Mapping Due Thursday (in class work - not homework) 11.4 p 278 q p 280 q Homework Study for final 80% of questions will come from study guide and standardized test prep (end of each chapter) Skip to Tuesday

45 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?

46 11.4 Meiosis GOALS Contrast the chromosome number of body cells and gametes Summarize the events of meiosis Contrast meiosis and mitosis HOW 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

47 11.4 Meiosis Chromosome 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

48 11.4 Meiosis Chromosome Number Gametes: contain only a single set of chromosomes (therefore genes) And so are called Haploid: containing only one set of chromosomes N (i.e. N=4) 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 (i.e. 2N = 8)

49 11.4 Meiosis Phases of Meiosis Meiosis: reduction division. Chromosome number cut in half by separating homologous chromosomes of diploid cell Meiosis I Each chromosome is replicated Homologous chromosomes pair up forming tetrad joined at centromere homologous chromosomes separate Meiosis II

50 11.4 Meiosis Phases of Meiosis Meiosis: reduction division. Chromosome number cut in half by separating homologous chromosomes of diploid cell Meiosis I Each chromosome is replicated Homologous chromosomes pair up forming tetrad joined at centromere homologous chromosomes separate Meiosis II No duplication of genetic material Chromosomes (only half of the diploid number) line up and chromatids separate

51 11.4 Meiosis Phases of Meiosis - Meiosis I Interphase I DNA replication, forming duplicate Chromosome s.

52 11.4 Meiosis Phases of Meiosis - Meiosis I Interphase I DNA replication, forming duplicate Chromosome s. 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.

53 11.4 Meiosis Phases of Meiosis - Meiosis I Interphase I DNA replication, forming duplicate Chromosome s. 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.

54 11.4 Meiosis Phases of Meiosis - Meiosis I Interphase I DNA replication, forming duplicate Chromosome s. 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.

55 11.4 Meiosis Phases 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.

56 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

57 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

58 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

59 11.4 Meiosis Crossing-over During Meiosis I,

60 11.4 Meiosis Crossing-over During Meiosis I, homologous chromosomes may, “cross-over,”

61 11.4 Meiosis Crossing-over During Meiosis I, homologous chromosomes may, “cross-over,” and exchange portions of their chromatids.

62 11.4 Meiosis Gamete 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

63 11.4 Meiosis Comparing Mitosis and Meiosis Mitosis two genetically identical diploid cells Meiosis four genetically different haploid cells

64 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?

65 11.5 Gene Linkage and Mapping 1. 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?

66 11.5 Gene Linkage and Mapping 1.Identify the structures that actually assort independently 2.Explain how gene maps are produced Independent assortment: Genes are assorted independently But what about genes on the same chromosome

67 11.5 Gene Linkage and Mapping Gene Linkage Mendel worked with 7 characteristics Six of them happened to be on different chromosomes The one pair on the same chromosome were so far apart on the chromosome that they appeared to assort independently.

68 11.5 Gene Linkage and Mapping

69 Gene Linkage 1910 Morgan’s research on fruit flies Studied 50 traits Many (red-eyed, short winged) appeared to be, “linked.” Grouped into four linkage groups Four chromosomes Conclusion: It is chromosomes, not individual genes, that assort independently.

70 11.5 Gene Linkage and Mapping Gene Maps Are those linked genes linked forever? No, crossing over may separate linked genes Sturtevant (student of Morgan) hypothesis: The farther genes are from eachother The more likely they will be separated by cross-over Produced gene map using recombination rates

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