Characteristics of living things REMEMBER THE… Characteristics of living things Living things are made up of cells Unicellular – one celled organisms Multicellular – many celled organisms

Characteristics of living things Living things grow and develop

Characteristics of living things Sexual reproduction Two parents, offspring are not identical to parents Living things reproduce to make offspring of the same species Asexual reproduction One parent, offspring are identical to parent

Body cells vs. gametes Body Cells: (hair, skin, blood) Diploid (2N) Produced through mitosis Gametes: (sperm, egg) Haploid (N) Produced through meiosis Diploid (2N) - have 2 sets of chromosomes Haploid (N) - have 1 set of chromosomes

How many chromosomes are in a…? Sperm Cell? 23 chromosomes haploid (N) Egg Cell? White Blood Cell? 46 chromosomes diploid (2N)

Homologous Chromosomes Chromosomes that code for the same thing One comes from the mom and one from the dad. Paternal Maternal eye color locus B = brown eyes b = blue eyes

Meiosis During Meiosis the Chromosome # is cut in half by separation of homologous chromosomes in diploid cells 4 haploid (N) sex cells (gametes) are produced Genetically different from each other & the original cell

Meiosis Cytokinesis 1 Cytokinesis 2

Differences between Mitosis & Meiosis MITOSIS produces 2 identical diploid (2N) body cells MEIOSIS produces 4 different haploid (N) gametes

Crossing Over Before separating during meiosis, homologous chromosomes exchange genetic information Creates genetic variation library.thinkquest.org/ 19037/genome3.html

Segregation When gametes are made during meiosis the alleles separate during a process called segregation. Creates Genetic Variation.

Independent Assortment Chromosomes separate without influincing eachother’s inheritance. (Blue eyes doesn’t always pair up with Freckles.) Creates Genetic Variation B b sperm haploid (n) meiosis II Bb diploid (2n) meiosis I Ff F f This means all gametes will be different!

Sibling Variation Independent Assortment insures that every sperm and egg that you make will be a little bit different which means you won’t look exactly like your siblings.

biology.clc.uc.edu/ courses/bio104/meiomito.htm http://www.cellsalive.com/meiosis.htm