Sexual Reproduction and Meiosis Chapter 11-Biology Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Adult somatic (body) cells are diploid. Reduction Division In sexual reproduction, eggs and sperm (gametes) fuse (fertilization) to produce a zygote. Gamete formation involves a mechanism (meiosis) that reduces the number of chromosomes to half that found in other body cells. Adult somatic (body) cells are diploid. Gamete (reproductive) cells are haploid. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Unique Features of Meiosis (What makes it different from Mitosis) Synapsis Homologous pairs of chromosomes pair up on equator Homologous Recombination Genetic exchange (crossing over) occurs between homologous chromosomes. Reduction Division Chromosomes do not replicate between the two nuclear divisions. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Raven - Johnson - Biology: 6th Ed Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

The most important difference between meiosis and mitosis is that meiosis produces _____ cells. Four diploid Four haploid Two haploid Somatic Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Prophase I Chromosomes condense Homologous chromosomes pair up Crossing over may occur while chromosomes are very close together Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Crossing Over-during Prophase I Chiasmata are X-shaped structures Presence of chiasmata indicates crossing over has occured Copyright © McGraw-Hill Companies Permission required for reproduction or display Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Metaphase I Homologues line up on metaphase plate (equator). Orientation of each pair is random (mom’s chromosomes vs. dad’s choromosomes may be to the right or to the left) Tetrads = 1 pair of homologous chromosomes, each with a copied pair of chromatids Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Anaphase I Homologues separate Each pole receives a member of each homologous pair. Due to random orientation, meiosis results in independent assortment. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Telophase I Chromosomes segregated into two clusters. Nuclear membrane re-forms around each cluster of chromosomes. Cells are not identical Cytokinesis occurs to form 2 haploid cells Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

No replication of DNA occurs between Meiosis I and Meiosis II Prophase II - Nuclear envelope breaks down and second meiotic division begins. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Spindle fibers bind to both sides of centromere Meiosis II Metaphase II – Spindle fibers bind to both sides of centromere Chromosomes line up (single file) along equator Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Meiosis II Anaphase II - Spindle fibers contract and sister chromatids move to opposite poles. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Telophase II - Nuclear envelope re-forms. Meiosis II Telophase II - Nuclear envelope re-forms. Final Result – Cytokinesis makes 4 haploid cells. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Which meiosis phase listed below is the most different from mitosis? Prophase II Metaphase I Telophase II Cytokinesis Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Sexual Reproduction - Produces genetic variability. Types of Reproduction Asexual Reproduction - Individual inherits all its chromosomes from a single parent. Sexual Reproduction - Produces genetic variability. Segregation of chromosomes tends to disrupt advantageous combinations. Only some progeny maintain advantages. Parthenogenesis Development of adult from unfertilized egg. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Observed plants in the monastery garden Mendelian Genetics Gregor Mendel (1822-1884) Austrian monk Observed plants in the monastery garden Father of Genetics for determining inheritance patterns in peas Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Tool used to predict the next generation of offspring P1 cross Punnett Squares Tool used to predict the next generation of offspring P1 cross Cross between two parents pure for a trait Produces F1 generation F1 cross Cross between the first generation offspring Produces F2 generation Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

What is the genotype that belongs in square 1? TT Tt tt None of the above 1 Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Genotype is the letter combination of the alleles GG, Gg, or gg Punnett Squares Genotype is the letter combination of the alleles GG, Gg, or gg Phenotype is the manifestation (what trait is produced) Green or yellow Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

What is the phenotype of the yellow peas? Green Yellow GG Gg Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

What is the genotype of the yellow peas? Green Yellow gg Gg Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies