Mitosis VS Miosis

HOW MANY CHROMOSOMES ARE FOUND IN EACH HUMAN BODY CELL? Warm-UP HOW MANY CHROMOSOMES ARE FOUND IN EACH HUMAN BODY CELL?

Section 10.2 Summary – pages 263-273 In the body cells of animals and most plants, chromosomes occur in pairs. In each pair, you inherited one from your mom, the other from your dad. From Mom From Dad Section 10.2 Summary – pages 263-273

Section 10.2 Summary – pages 263-273 Homologous Chromosomes The two chromosomes of a pair are called homologous chromosomes. Each pair of homologous chromosomes has genes for the same traits. Section 10.2 Summary – pages 263-273

Section 10.2 Summary – pages 263-273 Diploid Cells A cell with two of each kind of chromosome is called a diploid cell or somatic (body) cells. All of your body cells are diploid (2n). Section 10.2 Summary – pages 263-273

Section 10.2 Summary – pages 263-273 Each person can only pass on ONE of their homologous chromosomes to their young. HUMANS = 46 CHROMOSOMES IN THEIR BODY CELLS Each parent passes 23 to their young. Sperm(23)+Egg(23)=46 chromosomes Section 10.2 Summary – pages 263-273

Section 10.2 Summary – pages 263-273 Haploid Cells A cell containing only one of each kind of chromosome is called a haploid cell (n). Sex cells (gametes) are haploid cells. Section 10.2 Summary – pages 263-273

Section 10.2 Summary – pages 263-273 Sexual Reproduction Zygote Section 10.2 Summary – pages 263-273

● Body cells are made by the division process MITOSIS. Since they have different amounts of chromosomes, they are made in different ways ● Body cells are made by the division process MITOSIS. ● Sex cells are made by the division process MEIOSIS.

The cell cycle (or entire life cycle of the cell) consists of: Before a cell can divide by either method, it must first prepare for cell division. The cell cycle (or entire life cycle of the cell) consists of: INTERPHASE: The longest/busiest stage in a cell’s life 1. Chromosomes (DNA) replicates 2. Cell grows bigger NUCLEAR DIVISION: Mitosis or Meiosis CYTOKINESIS: When the cytoplasm divides and the cell completely separates.

Mitosis: cell division that makes BODY CELLS. 46 It starts with a DIPLOID cell Chromosomes Replicate 92 46 46 It ends with TWO IDENTICAL DIPLOID cells

The cell division process that occurs in haploid cells is called meiosis. Meiosis I Meiosis II

Meiosis: cell division that makes SEX CELLS. 46 It starts with a DIPLOID cell Chromosomes Replicate 92 46 46 23 23 23 23 It ends with FOUR HAPLOID cells (NOT identical)

Takes place during Prophase I Crossing-Over During Meiosis: Homologous chromosomes actually break and exchange traits- in a process known as crossing over. Takes place during Prophase I

Crossing over can occur at any location on a chromosome, and it can occur at several locations at the same time. This causes the traits found in each gamete varied. This is why siblings of the same parents can look so different from each other.

Section 10.2 Summary – pages 263-273 Nondisjunction The failure of homologous chromosomes to separate properly during meiosis is called nondisjunction. This would occur when homologous chromosomes are suppose to separate from each other. Section 10.2 Summary – pages 263-273

Section 10.2 Summary – pages 263-273 Meiosis When a sperm fertilizes an egg, the resulting zygote once again has the diploid number of chromosomes. VIDEO Zygote = a fertilized egg Section 10.2 Summary – pages 263-273

Get your comp book 1. Put in your Meiosis Notes 2 Get your comp book 1. Put in your Meiosis Notes 2. Prepare a page for “Crossing Over/ Genetic Variation” In this activity, you will model Crossing over that occurs during Prophase I of Meiosis and discover how this small event causes genetic variation in siblings.

Take your strip of paper This will end up being one homologous pair of chromosomes. The six bands will represent different genes What are genes?

# The bands 1-6 starting at the top Write the # of the band on both sides

Color the bands as follows: 1. Blue 2. Red 3. Purple 4. Green 5. Brown 6. Yellow Label the Type of Gene at the bottom of each band… 1. Dimples 2. Hair Texture 3. Tongue Curl 4. Hitch Hiker Thumb 5. Cleft Chin 6. Anxiety

Cut your strip in half long-ways These two strips represent Homologous chromosome pair #1

For example: In the “Hair Texture” band you could write 6. For each chromosome, assign a characteristic that was passed down for each gene. For example: In the “Hair Texture” band you could write Straight, Curly, or Wavy Give only 1 characteristic per gene

Homologous Chromosome Pair #1 Pretend this homologous pair is in either a Spermatocyte or Oocyte… and it is time for Meiosis

Homologous Chromosomes break and exchange genes (Crossing Over) During Meiosis Prophase I Homologous Chromosomes break and exchange genes (Crossing Over) 7. Cut away two genes on both chromosomes and exchange them

Tape up your newly crossed-over chromosomes. This ‘mixes it up’ So your chromosomes should still have the same genes in the same order 1-6, BUT have a different mix of characteristics than before.

9. Find someone in class and trade ONE of your homologous chromosomes. During Anaphase your chromosomes are parted from each other and are put in different sex cells. When one of these sex cells unites with another then the new baby will have a complete set of homologous chromosomes. 9. Find someone in class and trade ONE of your homologous chromosomes.

Pretend you and your classmate have created siblings (two children from the same parents) Tape/glue your sibling’s homologous pair #1 in your comp book. -One chromosome should be yours -The other chromosome should be from the other parent. Answer the questions on the next slide about crossing over and genetic variation.

Answer these questions in your comp. book: How does Crossing Over create genetic variation? Specifically how were the genes/characteristics different in the siblings even though they came from the same parents? Why is Crossing over important in Meiosis? Are there any traits that your sibling could possibly pass down to the next generation that the other sibling could not? EXPLAIN.