ESSENTIAL QUESTION

SEXUAL REPRODUCTION!

…IT’S NOT JUST FOR HUMANS!!

…IT’S NOT JUST FOR HUMANS!!

…IT’S NOT JUST FOR HUMANS!!

ASEXUAL REPRODUCTION EXAMPLES: BACTERIA – BINARY FISSION YEAST – BUDDING  

ASEXUAL REPRODUCTION NUMBER OF PARENTS: ONE OFFSPRING: IDENTICAL WHERE DOES THE DNA COME FROM? All from one parent! ADVANTAGES? DISADVANTAGES?  

SEXUAL REPRODUCTION – What do you predict? EXAMPLE: HUMAN NUMBER OF PARENTS: TWO OFFSPRING: DIFFERENT WHERE DOES THE DNA COME FROM? Half from mom; half from dad! ADVANTAGES? DISADVANTAGES?  

SEXUAL REPRODUCTION – Can you write a definition? ASEXUAL REPRODUCTION: production of genetically identical offspring from one parent SEXUAL REPRODUCTION: production of genetically different offspring from two parents  

2. What cells are involved in sexual reproduction? The sperm and the egg are called gametes, and only have half as much DNA as other cells in our bodies. We say these cells are haploid, and use the symbol 1N when talking about these cells GAMETES = HAPLOID = 1N  

2. What cells are involved in sexual reproduction? These cells are made by a process called meiosis. During this process, DNA from different chromosomes gets mixed up in a process called crossing over. This creates new combinations of genes!  

3. What about the other cells in our body? The rest of our body cells are called somatic cells. These cells have double the DNA, so we say they are diploid, and use the symbol 2n when talking about these cells. SOMATIC (BODY) CELL = DIPLOID = 2N  

SEXUAL REPRODUCTION – Check for understanding Which human cells are haploid? What are these cells called? What symbol do we use for these cells? Which human cells are diploid?  

What are the steps of sexual reproduction? Meiosis Sperm Egg Fertilization Zygote

SEXUAL REPRODUCTION – Check for understanding What do we call the process where a sperm and an egg join? What is a zygote? Are sperm and egg haploid or diploid before fertilization? Is the zygote haploid or diploid? If a sperm cell of a tick has 6 chromosomes, how many chromosomes will be present in the fertilized zygote?  

SUMMARY 1N _____ 2N Haploid Gamete Sperm Egg Unfertilized

Steps For Calculating Chromosome Number 1. HAMMER out the question 2. Use your 1N and 2N columns to figure out what you have and what you are trying to find 3. Use the following rules to calculate chromosome number: 1N 2N MULTIPLY BY 2   2N 1N DIVIDE BY 2  

TEACHER EXAMPLE #1 A human skin cell has 46 chromosomes. How many chromosomes will be in a human egg cell?    

TEACHER EXAMPLE #2 An egg cell of a cockroach has 5 chromosomes. How many chromosomes will be in the fertilized zygote?    

YOUR TURN: A squirrel tail cell has 50 chromosomes. How many chromosomes are present in the squirrel’s unfertilized egg cell?    

TIME TO PRACTICE!!!