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  1. 1. Genes Introduction to genetics
  2. 2. What is DNA? <ul><li>DNA stands for D eoxyribo N ucleic A cid </li></ul><ul><li>It is the hereditary material in humans and almost all other organisms. </li></ul><ul><li>Most DNA is located in the cell nucleus. </li></ul><ul><li>“ Blueprint of life” </li></ul><ul><li>The main role of DNA molecules is the long-term storage of information . </li></ul>
  3. 3. DNA Structure <ul><li>DNA is a double-stranded molecule . The shape of the DNA molecule is a double-helix (think of a spiral staircase or like a twisted ladder). The sides of the ladder are composed of alternating sugars (deoxyribose) and phosphates. The rungs of the ladder are composed of nucleotides. </li></ul>
  4. 4. Base pairing rule Nucleotides (also called Bases) Adenine, Thymine, , Guanine, Cytosine or A, T, G, C Nucleotides pair in a specific way - called the Base-Pair Rule Adenine pairs to Thymine Guanine pairs to Cytosine Memory helper - think &quot;A T Granite City&quot; - which is where you live.
  5. 5. <ul><li>The structure of DNA was established by James Watson and Francis Crick. </li></ul>
  6. 6. What is a gene? <ul><li>Gene - a segment of DNA that codes for a protein, which in turn codes for a trait (skin tone, eye color.etc), </li></ul><ul><li>a gene is a stretch of DNA. </li></ul><ul><li>Every person has two copies of each gene, one inherited from each parent. </li></ul>
  7. 7. What is a chromosome? <ul><li>Chromosomes are DNA molecule packaged into thread-like structures in the nucleus </li></ul>
  8. 8. How many chromosomes do people have? <ul><li>In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. </li></ul><ul><li>Diploid a cell that contains “two sets” of chromosome 2N </li></ul><ul><li>Haploid a cell that contains “one set” of chromosome </li></ul>
  9. 9. Sex Determination <ul><li>Sex cell chromosomes determine the sex of an organism </li></ul><ul><li>Sex cells are the sperm and egg–gametes </li></ul><ul><li>Females have two X chromosomes, (XX) </li></ul><ul><li>while males have one X and one Y chromosome (XY) </li></ul><ul><li>Zygote is the union of the sperm and egg (46 chromosomes). </li></ul>
  10. 10. <ul><li>Heredity is the transmission of characteristics from parents to offspring. </li></ul><ul><li>The genes for many traits are passed down in families from parents to children. </li></ul><ul><li>Because you come from two parents, each parent will provide one half of your genes for any trait. That is called an &quot;allele.&quot; So you have two alleles for each gene, one from each parent. </li></ul>
  11. 11. Gregor Mendel
  12. 12. Dominant and recessive <ul><li>Dominant traits are the expressed characteristic. It is always represented with a capital letter </li></ul><ul><li>Recessive traits are the repressed alleles; the ones that are not expressed. It is always represented with a lower case </li></ul>
  13. 13. <ul><li>Homozygous organisms that have two identical alleles </li></ul><ul><li>Heterozygous organism with two different alleles. </li></ul><ul><li>Phenotype is the physical appearance </li></ul><ul><li>Genotype is the genetic make up </li></ul>