Introduction to Genetics: Meiosis Ch. 11 Adams Pearson Prentice Hall Biology

11.1 The Work of Mendel Heredity: basically just the passing on of genetic traits from parents to offspring. Gregor Mendel: demonstrated that inheritance followed particular patterns Every organism inherits a single copy of every gene from each of its “parents.” Offspring acquire genes from parents by inheriting chromosomes Pearson Prentice Hall Biology

11.1 The Work of Mendel Genes and Dominance Inheritance is possible because: Sperm and ova carrying each parent’s genes are combined in the nucleus of the fertilized egg True Breeding: (sometimes also called a purebred), is an organism that always passes down certain physically expressed traits (purebred German Shepard) Hybrids: also known as cross breed, is the result of mixing, through sexual reproduction, two animals or plants of different breeds, varieties, species (German shepherd basset hound) True Breed Hybrid http://www.nextdogbreed.com/bhao/images/132.jpeg http://media.gettyimages.com/photos/german-shepherd-picture-id128603647?s=170667a Pearson Prentice Hall Biology

11.1 The Work of Mendel Genes and Dominance Simplifying Genetics: So we've all got chromosomes, which are the form that our DNA takes in order to get passed on from parent to child. Human cells have 23 pairs of chromosomes Gene: a section of DNA in a specific location on a chromosome that contains information that determines a trait. (hair color) Allele: specific gene, version of a gene (brown hair color) Pearson Prentice Hall Biology

11.1 The Work of Mendel Genes and Dominance Simplifying Genetics: So we've all got chromosomes, which are the form that our DNA takes in Physical trait: a reflection of a bunch of different genes working together Pearson Prentice Hall Biology

11.1 The Work of Mendel Genes and Dominance Simplifying Genetics: Polygenic trait: are those traits that are controlled by more than one gene (hair color, eye color, height…) Pleiotropic. : is single gene can influence how multiple traits are going to be expressed Gamete is the male or female reproductive cell that contains half the genetic material of the organism. Pearson Prentice Hall Biology

11.1 The Work of Mendel Mendel’s Two Conclusions: 1st Conclusion: Biological inheritance is determined by factor that are passed down from one generation to the next Factors are now called genes Each trait he studied was controlled by one gene in two forms producing different contrasting forms These different forms called alleles Pearson Prentice Hall Biology

11.1 The Work of Mendel 2nd Conclusion: Mendel’s Two Conclusions: Principle Of Dominance Some alleles are dominant and some are recessive Dominant traits will always show in offspring Recessive only show when the dominant trait is not present Pearson Prentice Hall Biology

11.1 The Work of Mendel http://www.slideshare.net/guest9476bb/ib-biology-genetics-3807192

11.1 Segregation Pearson Prentice Hall Biology http://www.slideshare.net/guest9476bb/ib-biology-genetics-3807192 Pearson Prentice Hall Biology

11.1 Segregation Genotypes: 25% = TT 50% = Tt 25% = tt What happens to the recessive alleles? ~25% the recessive genes reappeared in Mendel’s experiments T-> dominant (TT; Tt) dominant trait will show (75%) T-> recessive (tt) only recessive trait will show (25%) Genotypes: 25% = TT 50% = Tt 25% = tt Pearson Prentice Hall Biology

11.2 Probability and Punnett Squares Mendel used the laws of probability to help predict results in plant succession Probability: how likely something is going to happen Relate to Genetics: Alleles segregation is random but the laws of probability can be used to predict outcomes Pearson Prentice Hall Biology

11.2 Punnett Squares Drawings used to help predict genetic outcomes Below: Brown eyes are dominant (B); blue eyes are recessive (b). Both “parents” heterozygous for eye color Meaning that they carry the allele for both brown and blue eyes This cross shows that 75% of the time offspring will have brown eyes but 25% they will have blue Phenotype: Brown eyes or blue eyes (phenotype is the physical characteristics) Genotype: 50% heterozygous 25% homozygous dominant 25% homozygous recessive http://study.com/cimages/multimages/16/Punnett_hetero_x_hetero.svg.png Pearson Prentice Hall Biology

11.2 Punnett Squares Drawings used to help predict genetic outcomes Here we have one homologous recessive and one heterozygous W w 50% homozygous 50% heterozygous 50% dominant 50% recessive Ww ww w Ww ww w Pearson Prentice Hall Biology

Drawings used to help predict genetic outcomes Below: Red flowers dominant(F); pink flowers recessive(f). Both “parents” homozygous for petal color Meaning that they carry the allele for either red or white only This cross shows that 100% of the time offspring will have red petals but will be carriers for both Genotype: the genotype for this cross is Rr. The genetic make up (it’s the letters) The phenotype is red petals http://dvbiology.org/biologyweb/pun2.gif Pearson Prentice Hall Biology

11.2 Punnett Squares Probability and segregation 25% of the time recessive genes that were segregated will reappear Probability and predict averages Higher your population of study the closer your averages are Pearson Prentice Hall Biology

Mendel’s Conclusions Pearson Prentice Hall Biology http://www.slideshare.net/guest9476bb/ib-biology-genetics-3807192 Pearson Prentice Hall Biology

11.3 Exploring Mendelian Genetics Independent Assortment Alleles can separate independently during the formation of gametes Any one pair can combine with any other pair independently during construction This gives different traits equal opportunities to be expressed in offspring Pearson Prentice Hall Biology

11.3 Independent Assortment http://www.slideshare.net/guest9476bb/ib-biology-genetics-3807192 Pearson Prentice Hall Biology

11.3 Independent Assortment HOMOZYGOUS HOMOZYGOUS TWO-FACTOR CROSS http://68.media.tumblr.com/18ac04cb50bf98a2362a93e8b02c685e/tumblr_inline_n92ctxcO5a1qg4nwx.png Pearson Prentice Hall Biology

11.3 Summary Mendel Biological inheritance is determined by individual genes In organisms that reproduce sexually, genes are passed from parent to offspring In cases of two or more forms of the gene for a single trait exist, some genes will exhibit over others Dominance and recessive In most sexually reproducing organisms each offspring has two copies of a trait, one from each parent These traits can be segregated and reformed in new gametes Alleles for different genes will mostly segregate independently of one another Pearson Prentice Hall Biology

11.3 Beyond Dominant and Recessive Mendel's Principles have two major exceptions Not all genes show simple patterns of dominant or recessive Many traits are controlled by one or more gene Majority of genes have more than one allele Pearson Prentice Hall Biology

11.3 Incomplete Dominance Incomplete Dominance: intermediate inheritance where one allele for a specific trait is not entirely expressed over its paired allele. Results: in a third phenotype in which the expressed physical trait is a combination of the phenotypes of both alleles. http://www.biologia.arizona.edu/mendel/sets/mono/graphics/10TF1.gif Pearson Prentice Hall Biology

11.3 Codominance Codominance: Both alleles contribute to the phenotype. This results in offspring with a phenotype that is neither dominant nor recessive. http://cdn.shopify.com/s/files/1/0267/4223/products/codominance-panda-t-shirt-teeturtle_800x.jpg?v=1480438537 Pearson Prentice Hall Biology

11.3 Multiple Alleles Multiple Alleles Genes that have more than two alleles More than two possible alleles can exist https://ka-perseus-images.s3.amazonaws.com/d6049ca09dfc688504e47172cc9e692b04f3ca00.png Pearson Prentice Hall Biology

11.3 Polygenetic Other examples: Fingerprints Eye color height http://www.slideshare.net/guest9476bb/ib-biology-genetics-3807192 Pearson Prentice Hall Biology

11.3 Polygenetic Pearson Prentice Hall Biology https://www.ontrack-media.net/biology/bm2l5rimage3.jpg Pearson Prentice Hall Biology

11.4 Meiosis Key terms: Homologous Chromosome pairs: similar relation ½ of chromosomes come from mom/other ½ from dad Each of the chromosomes from dad have a corresponding pair from mom Diploid: meaning two sets of chromosomes (one inherited from each parent) Not identical Haploid: meaning one set Pearson Prentice Hall Biology

11.4 Meiosis Chromosome Number The gametes (sex cells) haploid Meiosis: Not exact copies of parent Somatic cells (body cells) are diploid Mitosis: Clones of parents Pearson Prentice Hall Biology

Human Life Cycle Sex chromosomes: determine gender (XX; XY) Each human somatic cell (body cell) has 46 chromosomes or 23 matching pairs (diploid) Sex chromosomes: determine gender (XX; XY) Autosomes: non-sex chromosomes (somatic) Pearson Prentice Hall Biology

Review Chromosome: location of genetic information in the form of genes Chromatid: Each strand of a chromosome that divides longwise during cell division.  Centromere: What connects the chromatids https://dr282zn36sxxg.cloudfront.net/datastreams/f-d%3A0cfa6ca6bdccc9a09f3ffe60c5e3d777529c14771d85ab4cc4f712b1%2BIMAGE_THUMB_POSTCARD_TINY%2BIMAGE_THUMB_POSTCARD_TINY.1 Pearson Prentice Hall Biology

Phases of Meiosis Phases of Meiosis Mixture of chromosomes from both parental chromosomes Meiosis involves two divisions, meiosis I and meiosis II. By the end of meiosis II, the diploid cell that entered meiosis has become 4 haploid cells. Pearson Prentice Hall Biology

Phases of Meiosis I Major differences in Prophase I (meiosis) and Prophase (mitosis) Crossover During meiosis, the number of chromosomes per cell is cut in half through the separation of the homologous chromosomes. The result of meiosis is 4 haploid cells that are genetically different from one another and from the original cell. http://pumatrendbio.weebly.com/uploads/6/0/9/7/60977291/398998105.png Pearson Prentice Hall Biology

Interphase I Cells undergo a round of DNA replication, forming duplicate chromosomes. Each chromosome pairs with its corresponding homologous chromosome to form a tetrad Tetrad is formed: structure of 4 chromatid Like Mitosis: cells undergo a round of DNA replication, forming duplicate chromosomes. Interphase I - Cells undergo a round of DNA replication, forming duplicate chromosomes. http://www.phschool.com/science/biology_place/labbench/lab3/images/interpha.gif Pearson Prentice Hall Biology Pearson Prentice Hall Biology

Prophase I: Different from Mitosis Pairs of homologous chromosomes now will intertwine Crossover occurs Chromosomes swap genetic info http://pumatrendbio.weebly.com/uploads/6/0/9/7/60977291/398998105.png Pearson Prentice Hall Biology

Cross Over When homologous chromosomes form tetrads in meiosis I, they exchange portions of their chromatids in a process called crossing over. Crossing-over produces new combinations of alleles. Crossing-over occurs during meiosis. Homologous chromosomes form a tetrad. Chromatids cross over one another. The crossed sections of the chromatids are exchanged. http://biologycellcycles.weebly.com/uploads/4/2/5/7/42572589/8819453_orig.jpg Pearson Prentice Hall Biology

Metaphase I: Like Mitosis Spindle fibers attach to the chromosomes. Chromosomes line up in the middle (just like mitosis) Pearson Prentice Hall Biology

Anaphase I: Like Mitosis The fibers pull the homologous chromosomes toward opposite ends of the cell. Pearson Prentice Hall Biology

Telophase I Nuclear membrane reforms, Nucleoli form within Chromosomes unwind into chromatin Crease forms Pearson Prentice Hall Biology

End of Round 1 We now have two haploid cells with 23 chromosomes each with unique combinations But we want to have 4 cells so we go for Round 2. Which is the same process but with different goal Instead of duplicating chromosomes we want to pull them apart into separate single strand chromosomes Unlike meiosis I, neither cell goes through chromosome replication. Each of the cell’s chromosomes has 2 chromatids. Pearson Prentice Hall Biology

Meiosis II During meiosis, the number of chromosomes per cell is cut in half through the separation of the homologous chromosomes. The result of meiosis is 4 haploid cells that are genetically different from one another and from the original cell.

Prophase II Prophase II is where the nuclear membrane will again break down and the spindle fibers are formed.  The chromosomes condense again after a interphase but this time there is NO DNA replication http://www.utm.utoronto.ca/~w3bio380/picts/supp/supp2/Meiosis_ProphaseII.jpg Pearson Prentice Hall Biology Pearson Prentice Hall Biology

Metaphase II The chromosomes line up in the center of cell. http://images.slideplayer.com/15/4802798/slides/slide_9.jpg Pearson Prentice Hall Biology

Anaphase II The sister chromatids separate and move toward opposite ends of the cell. http://images.slideplayer.com/15/4802798/slides/slide_10.jpg Pearson Prentice Hall Biology

Telophase II Meiosis II results in four haploid (N) daughter cells. Cytokinesis when they finally separate MEIOSIS II Telophase II and Cytokinesis - Meiosis II results in four haploid (N) daughter cells. http://keltonlesliealvarado.weebly.com/uploads/9/6/2/6/9626115/1652037.png Pearson Prentice Hall Biology

Comparing Mitosis and Meiosis Mitosis results in the production of two genetically identical diploid cells. Meiosis produces four genetically different haploid cells. Copyright Pearson Prentice Hall

Comparing Mitosis and Meiosis Cells produced by mitosis have the same number of chromosomes and alleles as the original cell. Mitosis allows an organism to grow and replace cells. Some organisms reproduce asexually by mitosis. NO change in number of chromosomes in daughter parent as parent cell. Copyright Pearson Prentice Hall

Comparing Mitosis and Meiosis Cells produced by meiosis have half the number of chromosomes as the parent cell. These cells are genetically different from the diploid cell and from each other. Meiosis is how sexually-reproducing organisms produce gametes. Number of chromosomes are reduced to half of the number of the parent Copyright Pearson Prentice Hall

Meiosis Mitosis Similar but not exact Exact copy Gametes Somatic cells Creates 4 cells Two rounds of division Interphase I Prophase I Metaphase I Anaphase I Telophase/Cytokinesis I Interphase II Prophase II Metaphase II Anaphase II Telophase/Cytokinesis II Mitosis Exact copy Somatic cells Creates two cells One round of cell division Interphase Prophase Metaphase Anaphase Telophase/Cytokinesis