Chapter 5- Heredity


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Chapter 5- Heredity

  1. 1. Heredity Chapter 5
  2. 2. Heredity and Genetics section 5-1 H.W. pg 132 ques. 1-5 <ul><li>Heredity is the passing down of traits from parent to offspring. </li></ul><ul><li>You inherit traits or body features from your parents, and them from their parents, etc… </li></ul><ul><li>All of the traits that you express and carry are inside your DNA on what we call alleles. </li></ul><ul><li>An allele is basically one half, of one piece of DNA that is responsible for gene. </li></ul>
  3. 3. Heredity and Genetics <ul><li>Sex cells contain one half of all of the alleles in your DNA (or half of your DNA). </li></ul><ul><li>So when a sperm and egg fertilize each other, their alleles combine to produce genes. (now full DNA,46 Chromosomes) </li></ul><ul><li>And the study of how traits are inherited through the interactions of alleles is what we call genetics. </li></ul>
  4. 4. Mendel <ul><li>An Austrian monk named Gregor Mendel is known as the father of genetics. </li></ul><ul><li>Through science and mathematics, he studied how traits get passed on from generations to generation, using pea plants. </li></ul><ul><li>He used pea plants because they grew quickly and they had different colored pea flowers. This made it easy to see where the traits were passed on to. </li></ul>
  5. 5. Mendel <ul><li>He looked at characteristics like the color of the peas, color of the pea pod, shape of the pea pod, height of the pea plant, and color of the flowers. </li></ul><ul><li>The way he studied the plants is by cross mating two pea plants that expressed totally different traits. </li></ul><ul><li>He found that the offspring from these 2 different plants produced an offspring which always looked like on of the parent plants. </li></ul><ul><li>He called these offspring plants Hybrids, because they received different alleles for a trait from each parent. </li></ul>
  6. 6. Mendel <ul><li>He found that it was easy to breed pea plants that had pure traits. That means that an organism that always produces the same traits generation after generation, and is called a pure breed. </li></ul><ul><li>An example is that tall plants will always produce tall offspring. </li></ul><ul><li>To see how genetics worked in nature he took pollen from short plants and fertilized a tall plant seed, just like a bee might carry pollen randomly from one plant to another. </li></ul><ul><li>When you mate two pure breeds of different traits (short and tall for example) it is called cross breeding. </li></ul>
  7. 7. Mendel <ul><li>The result of this cross breeding, was that all the offspring were tall. Whatever it was that made the short plants short appeared to be gone. </li></ul><ul><li>He than referred to the tall trait as a dominant trait because it overcame the short trait or covered it up. </li></ul><ul><li>He referred to the short trait as recessive because it seemed to disappear. </li></ul><ul><li>However, he found that these recessive traits didn’t disappear because as he kept cross breeding his pea plants he found that they reappeared. </li></ul><ul><li>So, the recessive traits did not disappear, they were just not expressed because a dominant trait was present. </li></ul>
  8. 8. Alleles and Punnett Squares <ul><li>Almost every cell in your body has two alleles for every trait. One from mommy and one from daddy. </li></ul><ul><li>These alleles are on your chromosomes inside the nucleus of your cells. </li></ul><ul><li>An organism that has two alleles that are the same for one trait is said to be called homozygous. TT </li></ul><ul><li>An organism that has two different alleles for a single trait is called heterozygous. Tt </li></ul><ul><li>We use these terms to express an organisms phenotype, or a trait that can physically can be seen without knowing what alleles it has. </li></ul><ul><li>Ex: I have black hair, so my phenotype for hair color is black. </li></ul>
  9. 9. Alleles and Punnett Squares <ul><li>We also use these terms to express what is called, an organisms genotype. This is genetic make up of the alleles an organism has. </li></ul><ul><li>Ex: I might have black hair, but I might not have 2 alleles for black hair, but b/c one allele is black, and black is dominant over any other color allele, I have black hair. Bb </li></ul><ul><li>We can not assume what an organisms genotype is just by looking at its phenotype. </li></ul>
  10. 10. Alleles and Punnett Squares <ul><li>To test the probability of what traits will get passed down from the cross breeding of parent genotypes, to offspring, we use Punnett squares. </li></ul><ul><li>In a Punnett square we use 2 letter abbreviations for traits. </li></ul><ul><li>Capital letters stand for dominant traits and lower case letters represent recessive traits. </li></ul>
  11. 11. Punnett Square
  12. 12. Alleles and Punnett Squares <ul><li>Even though Mendel didn’t know about DNA and Chromosomes he did teach us 3 principles of heredity. </li></ul><ul><li>1) Traits are controlled by alleles on chromosomes. </li></ul><ul><li>2) An allele can be dominant or recessive. </li></ul><ul><li>3) When a pair of chromosomes separate during meiosis, the different alleles for a trait move into separate sex cells. </li></ul>
  13. 13. Genetics Since Mendel section 5-2 H.W. pg 140 ques. 1-4 <ul><li>Since we have found what is called incomplete dominance. This is when the offspring of 2 homozygous parents produce an intermediate or middle offspring. </li></ul><ul><li>Ex: A pure white flower and a pure red flower could give a pink flower. </li></ul><ul><li>This occurs with hair color of horses and other animals and feather color of birds. </li></ul>
  14. 14. Multiple alleles <ul><li>We also learned that many traits are controlled by more than just two traits. </li></ul><ul><li>A trait that is controlled by more than two alleles is said to be controlled by multiple alleles. </li></ul><ul><li>An example is blood type. There are 3 alleles for blood type: A B O </li></ul><ul><li>A could be AA or AO </li></ul><ul><li>B could be BB or BO </li></ul><ul><li>AB is only AB </li></ul><ul><li>O is only OO </li></ul>
  15. 15. Polygenic Inheritance <ul><li>Some traits are produced because many genes combine to form it. When a group of genes act together to produce a trait its called polygenic inheritance. </li></ul><ul><li>An example is skin color. It is estimated that 3-6 genes control what skin color an offspring will have. </li></ul><ul><li>Eye color is also a polygenic trait, among others. </li></ul>
  16. 16. Mutations <ul><li>Sometimes during cell division DNA is not copied correctly. And these incorrect copies of DNA are called mutations and can be harmful or advantages to an organism. (diseases or a 4 leaf clover) </li></ul><ul><li>There can also be chromosome disorders. These disorders occur when an organism contains to few or to many chromosomes. </li></ul><ul><li>When this happens the fetus or embryo usually dies before birth. </li></ul><ul><li>If it does live it could result in mental or physical disorders like down syndrome (3 chromosome 21’s) </li></ul>
  17. 17. Recessive Genetic disorders <ul><li>A lot human genetic disorders, like cystic fibrosis, are caused by mutated recessive genes. </li></ul><ul><li>To get this disease one would have to inherit 2 recessive alleles. aa </li></ul><ul><li>This could mean that the parents of this offspring could have only been carriers of the disease and had no shown symptoms of it. </li></ul>
  18. 18. Sex Determination <ul><li>The sex of an organism is determined by special sex chromosomes. </li></ul><ul><li>The female sex chromosome is the X chromosome and the male is the Y chromosome. </li></ul><ul><li>In order for a female to be produced it needs to inherit 2 X chromosomes: XX </li></ul><ul><li>If a Y is inherited the result is a male: XY </li></ul><ul><li>YY is not possible </li></ul>
  19. 19. Sex linked disorders <ul><li>Some genetic disorder occur because of mutations of genes on sex chromosomes or sex linked genes. </li></ul><ul><li>These disorders can only be expressed in certain sexes. </li></ul><ul><li>Ex: Color blindness is only expressed on the X chromosome. So men only need one allele for colorblindness to become color blind where women will need two. </li></ul>
  20. 20. Pedigree Chart <ul><li>We use a pedigree chart to find out how a trait was passed on from generation to generation. </li></ul>
  21. 21. Genetic Engineering <ul><li>Genetic engineering is used to correct genetic disorder. We want to fix a piece of DNA that is damaged or missing something. </li></ul><ul><li>We do it in a couple of ways: one way is with recombinant DNA. We do this with diabetics a lot. </li></ul><ul><li>Here we place DNA for insulin inside of a bacteria’s DNA. </li></ul><ul><li>This will cause the bacteria to produce insulin that can be used for people with diabetes. </li></ul>
  22. 22. Genetic Engineering H.W. pg 149 & 150 ques 1-18 <ul><li>Another way is called gene therapy. Here we try to fix a bad gene inside of a cell. </li></ul><ul><li>We take a good gene and place it into a virus genome. Then we infect a person that doesn’t have the good gene with this virus and hopefully it corrects the problem. </li></ul>
  23. 23. Test on Chapter 5 in one Week!!!!!