When Plans Change

1. When Plans Change Topic 5

2. Review from last year • You learned parts of the cell • The control center is called… • This control center contains…. Now we get to look at that in much more detail! Look familiar??

3. Journey Into Human DNA • http://www.pbs.org/wgbh/nova/body/journey-into-human-dna.html

4. DNAhttp://www.youtube.com/watch?v=ckZEds5taX4http://www.youtube.com/watch?v=FUA6_Ucw3i4DNAhttp://www.youtube.com/watch?v=ckZEds5taX4http://www.youtube.com/watch?v=FUA6_Ucw3i4 • Stands for deoxyribonucleicacid • It is the inherited material responsible for variation • Found in all living things • Found in the nucleus of each cell • Needs to reproduce itself • Must move from parent to offspring • Controls all the structures and functions of the cells.

5. DNA Guanine and Cytosine will always fit together Adenine and Thymine will always fit together DNA includes nucleotides, each made of a phosphate, sugar and nitrogen base.

6. More animations and Interactive sites • http://www.youtube.com/watch?annotation_id=annotation_815353&feature=iv&src_vid=hnSPGlpZx_Q&v=zwibgNGe4aY • http://learn.genetics.utah.edu/content/begin/tour/

7. Genetic Code • The arrangement of these four bases form the entire genetic code • The backbone of the ladder is always the same • The structure is similar to a ladder that has been twisted into a spiral – it is known as a double helix • James Watson and Francis Crick were the scientists who discovered the structure of DNA

8. Chromosomes • Are packages of DNA • Each human cell nucleus has 46 chromosomes (dogs have 78, cats have 38) • Chromosomes are organized into pairs, humans have 23 pairs. • http://www.youtube.com/watch?v=bVk0twJYL6Y&feature=related

9. Genes • Are a segment of DNA which contains coded instructions • Are located on chromosomes • Each chromosome has many gene locations • Come in pairs • Both genes in a pair carry the DNA for the same trait (eye colour, leg length) • http://www.youtube.com/watch?v=ubq4eu_TDFc&feature=related • http://www.youtube.com/watch?v=5MQdXjRPHmQ

10. Alleles • Are possible forms of a gene • Organisms have two alleles for each trait. • The arrangement of those alleles will determine what trait will be expressed (shown). • The gene for seed shape in pea plants exists in two forms, one form or allele for round seed shape (R) and the other for wrinkled seed shape (r). • Example: A dog hair can be curly or straight, short or long, coarse or fine, etc.

11. Bill Nye Genes

12. Check and Reflect • Define the term DNA in your own words and explain its function. • What four chemicals make up the genetic code? Describe how these chemicals are arranged in a DNA molecule. • What is a chromosome? Describe its function. • What is an allele? Describe its function. • Explain why chromosomes are considered to be the “source of diversity.” • Which of the following contains DNA? • Chromosome • Nucleus of a cell • Gene • If a chromosome was compared to a book, what would the words of the book be compared to? Explain your answer.

13. Normal Cell Replacement • The human body is incredibly complex and is made up of many different kinds of body cells – aka somatic cells. • There are 60 trillion – 100 trillion somatic cells in your body. • Some last a lifetime, some last a few days. • Chart on page 50 in your textbook.

14. Changing our Genetic Information • Changes to the DNA are called mutations • Causes (mutagens) • X-rays • Ultraviolet rays • Cosmic rays • Chemicals • Results • Cause changes in the structure of the DNA. The individual bases could be mixed up.

15. Mutations • Mutations in individual cells can cause cancer. One mutated cell divides and creates a tumor. That tumor could continue to spread. • If a mutation happens in a sex cell, the changes could be passed on from parent to child. • Mutations are not always negative, they are sometimes beneficial, and often harmless.

16. Cell Division and Asexual Reproductionhttp://www.stolaf.edu/people/giannini/flashanimat/celldivision/crome3.swf • Mitosis occurs in the body cells (for growth and repair) • Recall that when organisms divide through binary fission, the two new organisms created are identical. • In order for them to be identical, they have to have the same DNA. • In order for this to happen, the parent must double its DNA before it divides. • In multicellular organisms, that production of two new cells with the same number of chromosomes is called MITOSIS • http://www.bcscience.com/bc9/pgs/v_animate_001_mitosis.html

17. Cell Division and Sexual Reproduction in Plants and Animals • Recall that in sexual reproduction, two gametes join together to form a zygote • Human body cells have 46 chromosomes, half come from the mother’s gamete (23 chromosomes) and the other half from the father’s gamete (23 chromosomes) • MEIOSIS is the type of cell division that produces gametes (sex cells) with only half the DNA of a normal cell • Meiosis involves two divisions. http://www.stolaf.edu/people/giannini/flashanimat/celldivision/meiosis.swf

18. Chromosomes from parents Chromosomes Duplicate http://www.johnkyrk.com/meiosis.html Chromosomes swap some DNA

19. Try This

20. Answers

21. Complete the Online Mitosis/Meiosis Animation Activity

22. Review Questions • In way what is DNA a code? • Explain why the body cells of organisms that reproduce sexually have even numbers of chromosomes. • What is the main value of variation? • What form of reproduction favours variation? Explain why by referring to DNA. • Is variation always an advantage? Explain.

23. Inheritance • Traits • Characteristic of an organism • Purebred • Refers to a plant/animal that has ancestors with the same form of a trait • Hybrid • Organism produced by crossing two individuals purebred for two different traits • Dominant Trait • Cancels out any other trait. Ex. Black cat • Recessive Trait • Is cancelled out unless no dominant trait is present. Ex. White cat • Incomplete dominance • Both traits are shown, neither is dominant or recessive

24. Offspring Unlike Either Parent • Explain why some traits like hair colour, eye colour, and skin colour cannot always be explained by just looking at the parent. • There are many gene locations and several possible alleles involved

25. Environmental Factors • Can genes be influenced by the environment? Give an example. • Yes, workers who work with really strong chemicals can end up with mutated cells if proper precautions aren’t taken. • Yes, alcohol in a pregnant woman’s bloodstream interferes with brain development and facial features of the baby (even though DNA is normal)

26. Review Questions • How could two black cats produce a kitten that has white fur? Use a diagram to explain your answer. • If you wanted to be certain that a trait would appear in the offspring of the plants or animals that you were breeding, what would you have to find out about the parents? Explain your answer. • Suppose a new flower in your garden displays intermediate colour. For example, you begin to see orange flowers although you originally planted only red and yellow flowers. What pattern of inheritance would you be observing in this situation? Explain your answer.