Sexual Reproduction
What is Mitosis? What is the purpose of Mitosis? Growth Repair Asexual reproduction What is the ultimate result of Mitosis? http://www.youtube.com/watch?v=1fyfdfdrymq
Somatic cells Component of body tissue. Example: muscle, bone, skin, nerve, heart and brain. 46 chromosomes or 23 pairs Mitosis Gametes Sex cells; involved in sexual reproduction. Example: sperm cell and egg cell. 23 chromosomes Meiosis Sperm + egg (fertilized egg) = zygote
We need to produce cells with ½ the amount of chromosomes (23). We do that through Meiosis!
Most cells in the body are produced by. Only gametes are produced by. At fertilization, 23 chromosomes are donated by each parent. (total = 46 or 23 pairs). Fertilization results in diploid zygote. Diploid cell; 2n = 46. (n = 23 in humans) Gametes (sperm/ova): Contain 22 autosomes and 1 sex chromosome. Are haploid (haploid number n = 23 in humans).
Ploidy refers to the numberofsets of homologous chromosomes in cells haploid one copy of each chromosome designated as n (gametes) diploid two copies (= pair) of each chromosome designated as 2n (somatic cells) Diploid organisms receive one of each type of chromosome from female parent (maternal chromosomes) and one of each type of chromosome from male parent (paternal chromosomes) Homologous Chromosomes - Two chromosomes composing a pair that both carry genes controlling the same inherited characteristics.
2n Clone Same genetic information in parent cell and daughter cell. Give me another one just like the other one! 1n Daughter cells different from parent cell and from each other. Daughter cells have ½ the number of chromosomes as somatic cell. Shuffling the genes (Mix it up!)
Tetrad: Four sister chromatids or a pair of homologous chromosomes.
Meiosis: A process of cell division that produces gametes. Stages of Meiosis I: Diploid Haploid 1.Prophase I Chromosomes become visible Nuclear membrane disappears Crossing-over occurs
Crossing Over Homologous chromosomes associate Sister chromatids of homologous chromosomes overlap. Sister chromatids exchange genetic material Increases genetic diversity
2. Metaphase I Homologous pairs of chromosomes line up in tetrads at the equator. Independent Assortment- The way a pair of chromosomes line up in metaphase I does not affect how the other pairs line up.
3. Anaphase I Each homologue (replicated chromosome) moves to an opposite side of the cell. Chromatids do not separate at the centromeres!
4. Telophase I Chromosomes gather at the poles as the cytoplasm begins to divide Nuclear membrane reforms Chromosomes uncoil into chromatin 5. Cytokinesis Cytoplasm divides to produce 2 haploid cells. **No replication of DNA between Meiosis I and Meiosis II!
Meiosis: A process of cell division that produces gametes. Stages of Meiosis II: Haploid Haploid 1.Prophase II Chromatin Chromosomes Nuclear membrane disappearing Centrioles begin to form spindle fibers
2. Metaphase II Chromosomes line up at the equator in single-file! Centrioles move to poles Spindle fibers attach to centromeres
3. Anaphase II Centromeres split Sister chromatids (chromosomes) are pulled to opposite poles
4. Telophase II Chromosomes chromatin Nuclear membrane reforms Spindle fibers disappear Cytoplasm begins to divide (pinch) 5. Cytokinesis Cytoplasm divides producing 4 haploid cells.
Sexual Reproduction = Variety! -Three sources 1) Independent Assortment during meiosis 2 n = in our lab 2 2 = 4 in humans 2 23 = 8 million! is this enough Variety?
Dad has 8 million different sperm Mom has 8 million different eggs 8 million x 8 million = 64 trillion!!! babies Is this enough?
Crossing over squares the number of outcomes 64 trillion squared = 27 zeros!! Whyisgeneticdiversitya goodthing?
What are fraternal twins? Two fertilized eggs What are identical twins? A single zygote that splits in two or three or... C:\Documents and Settings\b714968\Desktop\mitosis meiosis\fertilization.mov
Eukaryotic DNA is organized in. have specific places on chromosomes. - carry genes. unit of heredity made of DNA.