Presentation on theme: "Click on a lesson name to select. Section 1: Meiosis Section 2: Mendelian Genetics Section 3: Gene Linkage and Polyploidy Chapter 10 Sexual Reproduction."— Presentation transcript:
Click on a lesson name to select. Section 1: Meiosis Section 2: Mendelian Genetics Section 3: Gene Linkage and Polyploidy Chapter 10 Sexual Reproduction and Genetics
Human body cells have 46 chromosomes 10.1 Meiosis Sexual Reproduction and Genetics Each parent contributes 23 chromosomes Chapter 10 Homologous chromosomesone of two paired chromosomes, one from each parent Chromosomes and Chromosome Number
10.1 Meiosis Sexual Reproduction and Genetics Same length Same centromere position Carry genes that control the same inherited traits Chapter 10
Haploid and Diploid Cells Human gametes contain 23 chromosomes. Sexual Reproduction and Genetics A cell with n chromosomes is called a haploid cell. A single set of chromosomes (half the full set of genetic material) A cell that contains 2n chromosomes is called a diploid cell. A cell that has two sets of chromosomes; one set from the father and one from the mother Meiosis An organism produces gametes to maintain the same number of chromosomes from generation to generation. Chapter 10
Meiosis I The sexual life cycle in animals involves meiosis. Sexual Reproduction and Genetics Meiosis produces gametes Meiosis When gametes combine in fertilization, the number of chromosomes is restored. Chapter 10
Stages of Meiosis I Reduces the chromosome number by half through the separation of homologous chromosomes Sexual Reproduction and Genetics Involves two consecutive cell divisions called meiosis I and meiosis II PMAT I and PMAT II 10.1 Meiosis Chapter 10
Meiosis I Sexual Reproduction and Genetics 10.1 Meiosis Interphase Chromosomes replicate. Chromatin condenses. Chapter 10 Interphase
Meiosis I Sexual Reproduction and Genetics 10.1 Meiosis Prophase I Pairing of homologous chromosomes occurs. Each chromosome consists of two chromatids. The nuclear envelope breaks down. Spindles form. Chapter 10 Prophase I
Meiosis I Sexual Reproduction and Genetics 10.1 Meiosis Prophase I Crossing over produces exchange of genetic information. Crossing overchromosomal segments are exchanged between a pair of homologous chromosomes. Chapter 10
Meiosis I Sexual Reproduction and Genetics 10.1 Meiosis Metaphase I Chromosome centromeres attach to spindle fibers. Homologous chromosomes line up at the equator. Chapter 10 Metaphase I
Meiosis I Sexual Reproduction and Genetics 10.1 Meiosis Anaphase I Chapter 10 Anaphase I Homologous chromosomes separate and move to opposite poles of the cell.
Meiosis I Sexual Reproduction and Genetics 10.1 Meiosis Telophase I The spindles break down. Chromosomes uncoil and form two nuclei. The cell divides. Chapter 10 Telophase I
Meiosis II Prophase II Sexual Reproduction and Genetics 10.1 Meiosis Chapter 10 A second set of phases begins as the spindle apparatus forms and the chromosomes condense. Prophase II
Meiosis II Metaphase II Sexual Reproduction and Genetics 10.1 Meiosis Chapter 10 A haploid number of chromosomes line up at the equator. Metaphase II
Meiosis II Sexual Reproduction and Genetics 10.1 Meiosis Anaphase II Chapter 10 Anaphase II The sister chromatids are pulled apart at the centromere by spindle fibers and move toward the opposite poles of the cell.
Sexual Reproduction and Genetics 10.1 Meiosis Meiosis II Chapter 10 Telophase II The chromosomes reach the poles, and the nuclear membrane and nuclei reform. Telophase II
Meiosis II Sexual Reproduction and Genetics Cytokinesis results in four haploid cells, each with n number of chromosomes Meiosis Chapter 10 Cytokinesis
Sexual Reproduction and Genetics 10.1 Meiosis Chapter 10 How to tell which process (mitosis, meiosis I, or meiosis II)? 1)Look at how the chromosomes are lined up? a. PAIRS….must be Meiosis I b. SINGLE FILE…Mitosis or Meiosis II Look at the chromosome number: -# is HAPLOID = must be Meiosis II -# is DIPLOID = must be Mitosis
The Importance of Meiosis Meiosis consists of two sets of divisions Sexual Reproduction and Genetics Produces four haploid daughter cells that are not identical 10.1 Meiosis Results in genetic variation Chapter 10
Sexual Reproduction and Genetics Meiosis Provides Variation Depending on how the chromosomes line up at the equator, four gametes with four different combinations of chromosomes can result. Genetic variation also is produced during crossing over and during fertilization, when gametes randomly combine Meiosis Chapter 10
Sexual Reproduction and Genetics Sexual Reproduction v. Asexual Reproduction Asexual reproduction The organism inherits all of its chromosomes from a single parent. The new individual is genetically identical to its parent. Sexual reproduction Beneficial genes multiply faster over time Meiosis Chapter 10
How Genetics Began 10.2 Mendelian Genetics Sexual Reproduction and Genetics curious of why some pea plants had different physical characteristics (traits). Why they looked different? Gregor Mendel was curious of why some pea plants had different physical characteristics (traits). Why they looked different? He observed that the pea plants' traits were often similar to those of their parents, sometimes they were different. He observed that the pea plants' traits were often similar to those of their parents, sometimes they were different. The passing of traits to the next generation is called inheritance, or heredity. Chapter 10
He used pea plants because they have many traits that exist in only two forms. (tall/short, green seed/yellow seed) and they were self pollinating He decided to cross plants with opposite forms of a trait, for example, tall plants and short plants Mendelian Genetics
The parent generation is also known as the P generation. Sexual Reproduction and Genetics 10.2 Mendelian Genetics Chapter 10
Sexual Reproduction and Genetics The second filial (F 2 ) generation is the offspring from the F 1 cross Mendelian Genetics Chapter 10 The offspring of this P cross are called the first filial (F 1 ) generation.
Mendel studied seven different traits. Sexual Reproduction and Genetics Seed or pea color Flower color Seed pod color Seed shape or texture Seed pod shape Stem length Flower position 10.2 Mendelian Genetics Chapter 10
Some of the traits… Plant Height Tall Short Pod color Seed Shape Pod Shape Seed Color GreenYellow Green Yellow RoundWrinkled SmoothPinched 10.2 Mendelian Genetics
MENDEL CONCLUDED: individual factors must control the inheritance of traits in peas. They exist in pairs and the female parent contributes one factor while the male parent contributes the other Mendelian Genetics
Today we call those factors that control traits genes. They call the different forms of gene alleles. Although his work was not recognized until much later, Mendel is known as the father of genetics for his experiments and papers about his pea plants Mendelian Genetics
Genes in Pairs Sexual Reproduction and Genetics Allele An alternative form of a single gene passed from generation to generation Dominant Recessive 10.2 Mendelian Genetics Chapter 10 Usually we represent these types of traits with letters (TT, Tt, tt)
Dominance Sexual Reproduction and Genetics An organism with two of the same alleles for a particular trait is homozygous. An organism with two different alleles for a particular trait is heterozygous Mendelian Genetics Chapter 10
Genotype and Phenotype Sexual Reproduction and Genetics An organisms allele pairs are called its genotype. (Ex: BB, Bb, bb) The observable characteristic or outward expression of an allele pair is called the phenotype. (Ex: blue eyes, blonde hair, etc.) 10.2 Mendelian Genetics Chapter 10
Sexual Reproduction and Genetics Punnett Squares Predict the possible offspring of a cross between two known genotypes 10.2 Mendelian Genetics Chapter 10
Monohybrid Cross Sexual Reproduction and Genetics A cross that involves hybrids for a single trait is called a monohybrid cross Mendelian Genetics Chapter 10
Monohybrid Cross Punnett square Punnett squares can be used to determine the probability of getting a certain trait Remember that results predicted by probability are more likely to be seen when there is a large number of offspring Sexual Reproduction and Genetics 10.2 Mendelian Genetics Chapter 10
Mendels Law of Segregation 1. Plant traits are handed down through hereditary factors in the sperm and egg. 2. Because offspring obtain hereditary factors from both parents, each plant must contain two factors for every trait. 3. The factors in a pair segregate (separate) during the formation of sex cells, and each sperm or egg receives only one member of the pair. Mendels first law, the Law of Segregation, has three parts. From his experiments, Mendel concluded that:
Mendels Law of Segregation Sexual Reproduction and Genetics Two alleles for each trait separate during meiosis. During fertilization, two alleles for that trait unite. Heterozygous organisms are called hybrids Mendelian Genetics Chapter 10
Sexual Reproduction and Genetics Dihybrid Cross The simultaneous inheritance of two or more traits in the same plant is a dihybrid cross. Dihybrids are heterozygous for both traits Mendelian Genetics Chapter 10
Sexual Reproduction and Genetics Punnett Square Dihybrid Cross Four types of alleles from the male gametes and four types of alleles from the female gametes can be produced. The resulting phenotypic ratio is 9:3:3: Mendelian Genetics Chapter 10
Sexual Reproduction and Genetics Law of Independent Assortment Random distribution of alleles occurs during gamete formation Genes on separate chromosomes sort independently during meiosis. Each allele combination is equally likely to occur Mendelian Genetics Chapter 10
Genetic Recombination & Genetic Disorders
Genetic Recombination The new combination of genes produced by crossing over and independent assortment Combinations of genes can be calculated using the formula 2 n, where n is the number of chromosome pairs. Humans have 23 pairs of chromosomes, so 2 23 = over 8 million; now when fertilization occurs, 2 23 x 2 23 = 70 trillion…no wonder each individual is unique!
Polyploidy is the occurrence of one or more extra sets of all chromosomes in an organism. A triploid organism, for instance, would be designated 3n, which means that it has three complete sets of chromosomes. Polyploidy
Alterations of Chromosome Structure Breakage of a chromosome can lead to four types of changes in chromosome structure –Deletion –Duplication –Inversion –Translocation
A deletion- lose chromosome fragment A duplication- extra segment of chromosome attaches to a sister chromatid.
An inversion chromosome segment in reverse orientation. In translocation, a chromosomal fragment joins a nonhomologous chromosome.
Nondisjunction Results in chromosomal error in which one or more chromosomes have extra or missing copies= ANEUPLOIDY Cell with only 1 copy of a chromosome instead of 2 = MONOSOMY Cell with 3 copies of a chromosome instead of 2 = TRISOMY