Sexual Life Cycles: Meiosis Chapter 13

Learning Target 1 I can explain how offspring acquire genes from parents by inheriting chromosomes. I can distinguish between asexual and sexual reproduction.

Where do your genes come from? Ever wonder where you got your traits from? And where they got their traits from?

What’s a gene? A segment of DNA which codes for a protein Can code for an enzyme, a structural protein or a regulatory protein This determines an organism’s traits More next unit…

Asexual reproduction No gametes produced One parent Prokaryotes – binary fission Single-celled eukaryotes Yeast – budding Amoeba – binary fission Simple multicellular eukaryotes Hydra – budding Complex multicellular eukaryotes - regeneration Sea stars Planaria

Sexual Reproduction Gametes produced by meiosis Two parents Direct contact not required Plants: pollination strategies vary Animals: release of gametes into environment (aquatic)

I can distinguish between the following pairs of terms: Learning Target 2 I can distinguish between the following pairs of terms: Somatic cell and gamete Autosome and sex chromosome Diploid and haploid Zygote and fertilization

Important Vocabulary Diploid Haploid Somatic cell Gamete Diploid Body cell Gamete Reproductive cell (sperm or egg) Diploid Contains 2 sets of homologous chromosomes (2n) Haploid Contains 1 set of homologous chromosomes (n) Diploid Haploid

Important Vocabulary, CONT. Zygote Fertilized egg Fertilization Union of sperm and egg cells in sexual reproduction Autosome Chromosome 1-22 (everyone has) Sex chromosome Chromosome 23 (XX = female, XY= male)

I can explain how haploid and diploid cells differ from each other. Learning Target 3 I can explain how haploid and diploid cells differ from each other. I can state which cells in the human body are diploid and which are haploid.

Haploid Vs. Diploid Somatic cells are diploid Only gametes are haploid – why?

Learning Target 4 I can explain how meiosis generates haploid daughter cells from diploid parent cells. I can list the phases of meiosis I and meiosis II and describe the events characteristic of each phase. I can describe what homologous chromosomes are. I can explain how the spindle fiber separates either homologous chromosomes of sister chromatids. I can recognize the phases of meiosis from diagrams or micrographs. I can explain how genetic recombination occurs.

Meiosis: Production of gametes Alternating processes, alternating stages Chromosome number must be reduced Diploid  Haploid 2n  n Humans 46  23 Meiosis reduces chromosome number Fertilization restores chromosome number Haploid  Diploid n  2n Necessary for sexually reproducing organisms to produce gametes

Steps of Meiosis Meiosis I DNA replication Meiosis II Interphase Prophase I Metaphase I Anaphase I Telophase I Meiosis II Prophase II Metaphase II Anaphase II Telophase II DNA replication 1st division of meiosis separates homologous pairs 2nd division of meiosis separates sister chromatids *just like mitosis*

Homologous chromosomes Paired chromosomes Both chromosomes carry a pair of genes Control same inherited characters Homologous = same information Chromosome 17

Spindle fibers and chromosome movement

I can compare and contrast mitosis, meiosis I and meiosis II. Learning Target 5 I can compare and contrast mitosis, meiosis I and meiosis II.

Mitosis Vs. Meiosis I VS. Meiosis II

Learning Target 6 I can explain how independent assortment, crossing over and random fertilization contribute to genetic variation in sexually reproducing organisms.

Independent assortment Random orientation of homologues at metaphase plate during metaphase I Independent assortment in humans produces 223 (8,388,608) different combinations

Crossing Over During Prophase I Homologous pairs swap pieces of chromosome Sister chromatids intertwine and cross over each other Breakage and re-fusing of DNA Creates completely new combinations of traits in the next generation

Random fertilization Random ovum fertilized by a random sperm Any 2 parents will produce a zygote with over 70 trillion (223 x 223) diploid combinations

Learning Target 7 I can explain why heritable variation is crucial to Darwin’s theory of evolution by natural selection.

Sexual reproduction creates variability Allows us to maintain both genetic similarity and differences Why is this significant to evolution by natural selection?