Transcript Meiosis
Chromosomes & Meiosis Meiosis Process of creating sex cells with half the amount of DNA Big Picture Sperm Male sex cell (23) MEIOSIS Sperm = 23 chromosomes Egg Female sex cell (23) Fertilization MITOSIS Zygote = 46 chromosomes Egg = 23 chromosomes Fertilization process where egg and sperm fuse together Zygote First cell created after fertilization (46) Mitosis Process to create identical body cells with the SAME amount of DNA How Do Scientists Make Karyotypes? http://www.youtube.com/watch?v=7ShPzzrCetE Analyzing Karyotypes A picture of a person’s chromosomes is called a karyotype. A person’s body cell has 46 chromosomes in total. However, if we look closely we can see 23 pairs of chromosomes. 23 Analyzing Karyotypes In a karyotype there are 23 pairs of chromosomes. – Pairs 1-22 are called autosomes – Pair 23 is called sex chromosomes Male & female karotypes are different. – Female’s 23rd pair = XX – Male’s 23rd pair = XY – THINK! – Is this karotype showing a male or female? The grey colored bands on the chromosomes represent a person’s genes. 23 Genes on Chromosomes The chromosomes carry the person’s genes. – Both carry the same order of genes. – However, the genes on one chromosomes may be a slightly different version from the genes on the other chromosome. – A person inherits one gene from mom and one gene from dad. – The two genes work together to give a person his/her trait. – THINK? – What is the eye color for each chromosome pair? • Bb = Brown eyes • BB = Brown • bb = blue b B B B b b Activity: Analyzing Karyotypes 1. What is the puppy’s hair length? Short 2. What is the puppy’s hair texture? Silky 3. What is the puppy’s curliness? Curly 4. What is the puppy’s coat pattern? Spotted L t H A 5. For which trait(s) did mom and dad give the SAME versions of genes? curliness, texture l t H a 6. For which trait(s) did mom and dad give DIFFERENT versions? Length, coat pattern Activity: Big Picture Work with your partners to explain each term shown to the right. Use your own words! MEIOSIS Sperm = 23 chromosomes Sperm Male sex cell (23) Egg Female sex cell (23) Fertilization MITOSIS Zygote = 46 chromosomes Egg = 23 chromosomes Meiosis Process of creating sex cells with half the amount of DNA Fertilization process where egg and sperm fuse together Zygote First cell created after fertilization (46) Mitosis Process to create identical body cells with the SAME amount of DNA Meiosis Animation Meiosis – Process used to make sex cells (egg or sperm) – These cells have HALF the amount of DNA Click on image to see the animation! Accidents during Meiosis Accidents during meiosis can cause some individuals to have an extra chromosome or a missing chromosome in his/her sex cell. – An extra chromosome in a pair is called a trisomy. – A missing chromosome in a pair is called a monosomy. – http://learn.genetics.utah.edu/content/begin/traits/predic tdisorder/ Gender: Female Disorder: Trisomy in pair 21 Symptoms: Learning difficulties Unique Facial features Heart Defects Gender: Male Disorder: Trisomy in pair 23 Symptoms: Less prominent male characteristics Gender: Female Disorder: Monosomy in pair 23 Symptoms: Female who can’t make egg cells (sterile)