1. DNA and genes

2. DNA is a double helix discovered by Watson and Crick in 1953 they won a Nobel prize for their work

3. The structure of DNA uncoiled diagramdiagram space- filling model

4. Chromosome – condensed DNA Chromatin– extended DNA

5. Chromosome – condensed DNA Chromatin– extended DNA

7. The structure of DNA P P P P P P G C TA S S S S S S

8. DNA is made of the same repeating subunits called…… Nucleotides. The basic chemical makeup of DNA: Phosphate 5 carbon sugar deoxyribose Nitrogenous Base Forms the “ backbone ” and always the same Variables: A, T, G, C

9. The base pairs Cytosine C Guanine G Hydrogen bond Thymine T Adenine A

10. Chargaff’s Rule Adenine must pair with Thymine Guanine must pair with Cytosine because they always pair together, their amounts in a DNA molecule are the same G C TA

11. Question: If there is 30% Adenine in a strand of DNA, how much Cytosine is present?

12. Answer: there would be 20% Cytosine: Adenine (30%) = Thymine (30%) Guanine (20%) = Cytosine (20%) (50%) = (50%)

13. Genes DNA is not a sequence of random information, it is broken up into areas with different functions sections of DNA with particular functions are called genes

14. start of human chromosome 1 These are all genes!

15. Alleles different versions of the same gene are called alleles e.g. the gene for eye pigment in fruit flies (Drosophila) has a red allele, a white allele, and a brown allele chromosomes are always paired, so it is possible to have two different alleles for any given gene

16. eye colour alleles in Drosophila

17. Genes and alleles You will need: 1 pencil crayon or pen (preferably purple)

18. Ishihara Colour Blindness Test

19. everyone sees 12

20. normal = 8 red-green = 3 total = nothing

21. normal = 74 red-green = 21 total = nothing

22. normal = 6 red-green = nothing total = nothing

23. Gregor Mendel: father of genetics discovered heredity – the passing on of characteristics from parent to offspring bred pea plants until they were true-breeding, the offspring always resembled the parents

24. Mendel’s experiment he took one plant of each type, such as purple and white flowers, and bred them together:  all the offspring were purple took two of these offspring and bred them to make a second generation:  3 purple offspring / 1 white offspring

25. cross-fertilise Parental generation First generation (F1) true-breeding purple flowers true-breeding white flowers all offspring purple

26. First generation (F1) self-fertilise Second generation (F2) all offspring purple 3/4 purple1/4 white

27. Mendel’s Conclusions 1. parents pass on ‘elements’ to their offspring; these ‘elements’ remain unchanged during life 2. offspring receive one ‘element’ from each parent; therefore offspring have a pair 3. each parent can pass on a different version of the ‘element’ Mendel’s ‘elements’ are now called GENES.

28. Number of genes Carsonella ruddii (bacterium) 180 Streptococcus pneumoniae (bacterium)2,300 Escherichia coli (bacterium)4,400 Saccharomyces cerevisiae (yeast)5,800 Drosophila melanogaster (fruit fly)13,700 Caenorhabditis elegans (nematode) 19,000 Strongylocentrotus purpuratus (urchin) 23,300 Homo sapiens (human)27,000 Mus musculus (mouse)29,000 Oryza sativa (rice)50,000

29. Dominant vs. recessive dominant = when one allele overwrites the expression of another allele recessive = when one allele is masked by the expression of another allele the dominant allele is given a capital letter (P), the recessive allele a lower case letter (p)

30. Dominant and recessive traits in peas

31. Human dominant/recessive traits: Cleft in chinNo cleft dominant, cleft recessive HairlineWidow peak dominant, straight hairline recessive Eyebrow sizeBroad dominant, slender recessive Eyebrow shapeSeparated dominant, joined recessive Eyelash lengthLong dominant, short recessive DimplesDimples dominant, no dimples recessive EarlobesFree lobe dominant, attached recessive FrecklesFreckles dominant, no freckles recessive Tongue rollingRoller dominant, nonroller recessive Tongue foldingInability dominant, ability recessive Finger mid-digital hair Hair dominant, no hair recessive Bent little fingerBent dominant, straight recessive Interlaced fingersLeft thumb over right dominant, right over left recessive Hair on back of handHair dominant, no hair recessive

32. Heterozygous vs. homozygous Heterozygous = having two different alleles for a particular gene (e.g. Pp) Homozygous = having two of the same allele for a particular gene (e.g. PP or pp)

33. Genotype vs. phenotype genotype = the genetic characteristics of an organism eg. PP or Pp phenotype = the visible physical features of an organism e.g. white flower Phenotype Genotype PP or Pp purple flower white flower pp

34. The Punnett Square In three steps, it’s an easy way to determine the probability of offspring: Step 1: Make a 2 X 2 Square grid Step 2: Put the alleles of each parent on the outside of the square Step 3: Combine alleles to make potential offspring in the middle of the square

35. Sample Punnett problem The gene for free ear-lobes is dominant (E), and the gene for attached earlobes is recessive (e). If a heterozygous male mates with a homozygous recessive female, what is the probability that their child will have attached earlobes?

36. Solution: 50% chance heterozygous (Ee – free lobes) 50% homozygous recessive (ee – attached lobes) Male FemaleEe eEeee eEeee

37. Fruit fly genetics lab

38. Drosophila chromosomes

39. Fruit fly genetics lab the common fruit fly, Drosophila melanogaster is a staple of genetics research it reproduces quickly and is easy to keep in the laboratory we know more about the genetics of this organism than any other (even humans)

40. wildtype (normal) Drosophila ♀ (female) ♂ (male)

41. Vestigial wing mutant Wing phenotype varies from almost absent (left) to shriveled (right)

42. Today’s procedure in brief: 1. carefully pour out your bottle of flies 2. sort them by sex and by wing phenotype (normal or vestigial) into four categories 3. count and record the number of flies in each category 4. share and record the fly counts from the other groups

43. How to tell males from females: sex combs ♀ (female) ♂ (male) small, dark abdomen large, striped abdomen no sex combs