Genetics/Heredity notes

1. Genetics/Heredity notes

2. Heredity • What is Heredity? The passing of traits from parents to offspring (children) 2. Who is Gregor Mendel? Austrian Monk, gardener studied plants as a boy in Father’s orchard known as the “Father of Genetics”

3. More on Genetics 3. What did Mendel do? - 1856 began experimenting with the traits of garden peas (8 years!) - made first recorded study of how single traits pass from one generation to the next 4. How did his experiment work? - He crossed pea plants with different traits - Traits he observed: seed shape, seed color, pod shape, pod color, plant height, flower position, flower color

4. 5. What did Mendel find? - some traits are recessive, some are dominant - recessive traits – Recessive traits showed in the 2nd generation plants - dominant traits – the first generation offspring showed all dominant traits

5. Mendel discovered a couple more important things: 6. An organism with 2 alleles that are the same is called HOMOZYGOUSfor that trait. For example: Tall Pea Plant (TT) Short Pea Plant (tt) 6a. What is homozygous? Alleles for trait are same 7. An organism with 2 alleles that are different is called HETEROZYGOUSfor that trait For example: Tall Pea Plant (Tt) 7a. What is heterozygous? Alleles for traits are different

6. 8. Purebred is the same as homozygous which means the alleles are the same for the trait 9. Hybrid is the same as heterozygous which means the alleles are different for the trait.

7. Genetics 10. Genetics is the study of heredity and the variation of inherited characteristics

8. Genes 11. What is a gene? A section of DNA on a chromosome that determines a particular inherited characteristic. 12. Where are they found? On the DNA found in chromosomes 13. What do they do for an organism? They carry and control “traits”.

9. 14. What is a trait? inherited characteristics of an organism Examples: dimples, hair color 15. Are all genes the same? No. The different forms of a trait that a gene may have are called “alleles” 16. What is an allele? Different forms of a trait For example: the eye-fold gene controls the development of folds in the eyelids. It comes in two Alleles: eye-folds vs. no eye-folds

10. 17. Why are some parents’ traits expressed in their offspring while others are not? Because of probability 18. Traits are either Dominate or Recessive USUALLY, the dominant trait will show! It dominates!!!

11. Genotypes and Phenotypes 19. Genotyperefers to the actual genetic information for a trait For example: BB= genetic code for brown hair 20. Phenotyperefers to the actual physical appearance For example: I can see my mother’s brown hair.

12. DNA 21. What is DNA? What does it do? DNA is a strand of genetic material that hold the codes or instructions for an organism’s growth and function 22. What does DNA stand for? Deoxyribonucleic Acid 23. Where is DNA found? It is stored in the nucleus of a cell. Chromosome in the nucleus are made of strands of DNA

13. 24. What does DNA look like? A DNA strand looks like a twisted ladder or double helix 25. What is DNA made of? The sidesof the DNA ladder are made of sugar and phosphate molecules. The stepsof the ladder are made of nitrogen bases

14. 26. There are the 4 nitrogen bases? a. adenine b. guanine c. cytosine d. thymine 27. Nitrogen bases occur in pairs like pieces to a puzzle: 28. Adenine ALWAYS pairs up with thymine 29. Cytosine ALWAYS pairs up with guanine

15. 30. How does DNA work for the cell? When a cell divides, the chromosomes in the nucleus divide. Chromosomes are made of DNA, so the DNA divides with the chromosomes. 31. Why is DNA important? DNA contains the ‘mastercode’ that instructs all your cells in their daily jobs. It is what makes you who you are. Every cell that has ever been formed in your body or in any other organism contains DNA

16. 32. When did we first know about DNA? Who are the leading scientists in DNA research? 33. 1952- Rosalind Franklin (a WOMAN!) discovered DNA is 2 chains of molecules in a spiral form. She took the first X-Ray pictures of DNA 34. 1953 – James Watson & Frances Crick (of England) made the first model of the DNA “Double Helix”. Eventually won the Nobel Peace Prize. Rosalind Franklin did not. SCANDAL!

17. Chromosomes 35. What are they? - structures in a cell’s nucleus that carries the code for an organism’s inherited characteristics. 36. What are they made of? - compacted strands of DNA 37. Where are they found? - in the nucleus 38. Why are they important? - genes are located on chromosomes - genes are carried from parent to their offspring or children on chromosomes

18. 39. How many chromosomes does a human have? - 46 that form 23 pairs 40. How many chromosomes do other living things have? grasshopper – 24 goldfish – 94 dog – 78 guinea pig – 64 fruit fly - 8

19. 41. What do chromosomes look like? Chromosomes occur in pairs; one from the male and one from the female

20. 42. Which chromosomes tells if a human will be male or female? The 23rd chromosome pair are the “sex chromosomes” In human, the sex chromosomes are called the X-chromosome and the Y-chromosome. A human female has two X chromosomes, while the male has one X Chromosome and one Y Chromosome. In addition to determining the sex of an offspring, the X and Y chromosomes contain other important genes EXAMPLE: Orange color in cats is a sex-linked trait and appears mostly in males

21. Punnett Squares 43. What is a Punnett Square? • A tool used to predict what offspring (children) will look like 44. How does it work? a. letters represent dominant and recessive alleles b. Dominant = Uppercase letters c. Recessive – lowercase letters