Genetics

1. Genetics

2. What is Genetics? • Branch of Biology that studies heredity • Gene: Part of DNA that holds genetic material • DNA- “genetic code” • Two factors that influence genetics • Heredity: passing of traits from parent to offspring • Environment: all of the outside influences that act upon an organism

3. Genetics Words to Know • Dominant: The trait that is expressed (what you see). • Is always an upper case letter • Ex: T=tall t=short • Tt= Tall organism • Recessive: The trait that is not expressed. • Is always a lower case letter • Ex: T=tall t=short • tt= Short organism

4. Homozygous: Having a pair of identical genes for a trait (pure bred). • Homo= same • Example: TT or tt • Heterozygous: Having two different genes for a trait (hybrid) • Hetero= different • Example: Tt • Allele: Each copy of a gene • Phenotype: Physical appearance • Remember Ph= Physical! • Genotype: Genetic make up • Remember Gene= Genetic!

5. Mendelian Genetics

6. Gregor Mendel • Father of genetics • He was a monk • Studied pea plants • Interested in why some plants were different colors and why their seeds differed

7. Reasons for Mendel’s success: • He picked a organism that was easy to grow (peas) • short time for new generations • he was able to control pollination • He studied one trait at a time • 7 traits in all • Recorded data very carefully • He analyzed his data with mathematical reasoning

8. Mendel named offspring: • P generation: Parent generation • F1 generation: First filial generation (off spring of the P generation) • F2 generation: Second filial generation (off spring of the F1 generation) P generation-parents F1 generation F2 generation

9. Mendel's Laws of Heredity • Developed two laws that all genetics is based upon. • Law of Segregation: When a gamete is formed, each pair of alleles separate • Each gamete gets a separate allele • Law of Independent Assortment: When a gamete is formed, pairs of alleles separate independent of one another • One gamete may get a recessive allele while the other gets a dominant allele

11. Predicting Heredity Outcomes • Probability: The likelihood a specific event will occur Number of one type of possible outcome Total number of all possible outcomes Example: You have 4 red marbles and 6 blue marbles in a bag. What is the probability of pulling a blue marble from the bag? 6/10

12. Punnett Squares • A diagram that helps predict the probable outcome of a genetic cross • Named for inventor Reginald Punnett • Uses Mendel’s laws and probability

13. Monohybrid Cross T T • A genetic cross that involves one pair of traits REMEMBER • T= Dominant • t= Recessive • TT= Homozygous • Tt= Heterozygous • Phenotype (physical) 4:0 • Geneotype (genetic) 2:2 or 1:1 TT TT T Tt Tt t

14. Punnett Squares T T • Parental : TT x Tt • F1 Generation: TT, TT, Tt, Tt • F2 Generation: Cross the results of the f1 generation Ex: TT x Tt TT TT T Tt Tt t

15. Punnett Squares • Monohybrid Example In guinea pigs, black coat is dominant to white coat. Cross a heterozygous black coated pig with a homozygous white pig Step One: Identify what genotypes you are working with B=black b=white

16. Step Three Complete the Punnett Square using the genotypes from step two Step Two Set up your cross Bb x bb Step Four Determine ratios -Phenotype: 2:2 or 1:1 -Geneotype: 2:2 or 1:1 B b bb Bb b bb b Bb

17. Punnett Square example two: In pea plants, wrinkled peas are dominant to smooth peas. Cross a heterozygous wrinkled pea with a homozygous smooth pea • W=wrinkled w=smooth 2. Ww x ww W w w Ww ww 3.P: 1:1 G: 1:1 Ww w ww

18. Step Three Complete the Punnett Square using the genotypes from step two Step Two Set up your cross Bb x bb Step Four Determine ratios -Phenotype: 2:2 or 1:1 -Geneotype: 2:2 or 1:1 B b bb Bb b bb b Bb

19. Dihybrid Punnett Square • Dihybrid Cross: A genetic cross that involves two pairs of traits • Example: • Looking at the offspring of a white cat with a long coat and a black cat with a short coat

20. Dihybrid Cross Example: • In snapdragons, red petal color is dominant over white petal color and tall plants are dominant over short plants. Cross a purebred red tall plant with a white short plant. Step One: Identify what phenotypes you are working with: R=red r=white T=tall t=short

21. Punnett Square example two: In pea plants, wrinkled peas are dominant to smooth peas. Cross a heterozygous wrinkled pea with a homozygous smooth pea • W=wrinkled w=smooth 2. Ww x ww W w w Ww ww 3.P: 1:1 G: 1:1 Ww w ww

22. Step Two: • Set up your cross • RRTT x rrtt • Step Three: • Determine your F1 generation RT Only do this step when the P generation is homozygous dominant x homozygous recessive! RRRTT x rrtt rt RrTt

23. Step Four Cross your f1 generation to determine what phenotypes to use in the Punnett square RrTt x RrTt FOIL First Outer Inner Last RT Rt rT rt RT Rt rT rt

24. RT Rt rT rt Step Five Complete the Punnett square using the F1 phenotypes from step four RRTT RRTt RrTT RrTt RT RRTt RRtt RrTt Rrtt Rt RrTT RrTt rrTT rrTt rT rt RrTt Rrtt rrTt rrtt

25. Step Six: • Determine pheonotypical and geonotypical ratios • P- 9:3:3:1 • G-1:2:2:4:1:2:1:2:1 These each add up to 16- total number of squares in box! Example Two: In flies, double wings are dominant over single wings and green body color is dominant over black body color. Cross a purebred double winged green fly with a single winged black fly

26. D=double d=single • G=green g=black 2. DDGG x ddgg DG Do this step since homozygous dominant x homozygous recessive! 3. dg DdGg 4. DdGg x DdGg DG Dg dG dg DG Dg dG dg

27. DG Dg dG dg DdGg DDGG DDGg DdGG DG DDgg Ddgg DDGg DdGg Dg DdGG DdGg ddGG ddGg dG dg DdGg Ddgg ddGg ddgg

28. Incomplete Dominance: A trait that is intermediate between two parents • Ex. A red snapdragon and a white snapdragon produce a pink snapdragon • Codominance: Two dominant alleles are expressed at the same time • Ex: Roan coat in horses

29. REPRODUCTION Sexual Reproduction Asexual Reproduction Does not require a partner Genetically identical to parent Short reproduction time Good if stable environment not needing change • Gametes through meiosis • Genetic variability • Takes more time – growth and development • Good if changing environment

30. Meiosis (review) • Increases genetic variability through genetic recombination (re-assortment of chromosomes) • Crossing over – 2 chromosomes overlap and exchange genetic material • Independent assortment (remember)

31. Genetics and Humans

32. DNA Technology • Biotechnology: Commercial application of biological principles • Recombinant DNA Technology: DNA of an organism is cut into pieces to create specific proteins. • Is used in agriculture to improve crops • Genetically altered crops can cause allergic reactions • GMO (genetically modified organism) • GEO (genetically engineered organism)

33. Biotechnology in Medicine: • Used to make vaccines (Hepatitis B) • Interferon: Used to fight cancer • Gene Therapy: Bad gene is replaced with a good gene • Used to fight diseases such as cystic fibrosis and sickle cell anemia.

34. Stem Cell Research: • Stem cells can be ANY type of cell, they are not specialized • Alzheimer's, Dementia, Parkinson’s • Is VERY controversial • Three sources of stem cells in humans: • Adult bone marrow • Umbilical cord blood • Embryos

35. Cloning: • Making two genetically EXACT organisms • Dolly the sheep was cloned in 1997 Other organisms such as a cat, mule and pig have been cloned since • Very controversial due to possible human cloning • May help with disease (cloning healthy tissue)

36. DNA Fingerprinting: • All DNA (except identical twins) is different • Scientists look at a small piece of DNA to determine a match • Process that pulls “markers” out is called gel electrophoresis • Used in paternity testing and forensic science

37. Human Genome Project: • Genome: An organism’s complete set of DNA • Humans have aprox. 3 BILLION base pairs • 1990 scientists began mapping the genome to find out which base pairs make up specific chromosomes • Completed in 2003

38. Sex Linked Traits • Determined by a gene on the x chromosome • Colorblindness

39. Sex Influenced and Sex Limited Traits Sex Influenced • Traits that are dominant in one sex but recessive in the other • Baldness in males Sex Limited • Traits that only appear in the presence of estrogen or testosterone • Beards in men • Male or female body shape

40. Twins • Fraternal Twins: • Most common type • Two eggs are fertilized by two sperm • Genetically different • Identical Twins: • Are always the same sex • One fertilized egg splits into two • Genetically identical

41. Genetic Mutations • Mutation: A change in the genetic code • Point Mutation: One nitrogen base in the sequence is altered • Insertion Mutation: An extra nitrogen base is added to sequence • Deletion Mutation: One nitrogen base is deleted from the sequence • Substitution Mutation: Base pairings are incorrect (ex: T&G pair or A&C pair)

42. What Can Cause Mutations? • DNA Replication Errors: • DNA polymerase misses an error when proofreading new DNA strand • Mutagens: • Agents in the environment that can cause a mutation • Example: UV rays and chemicals

43. Disorders Caused By Genetic Mutations • Sickle Cell Anemia: • Mainly occurs in the African American race • Recessive gene • Attacks red blood cells • Crescent shaped cells rupture easily and get lodged in circulatory system • People with malaria are naturally resistant

44. Hemophilia • Blood does not clot • Is called the “Royal Disease” • Recessive gene • Sex-linked trait

45. Tay-Sachs Disease • Attacks Nervous System • Recessive trait • Occurs mainly in Orthodox Jewish population • Appears around 6 months of age, death usually occurs by 4 years old

46. Phenylketonuria (PKU) • Causes mental retardation if left untreated • Recessive gene • Caused by a defective enzyme (can not change phenylalanine into tyrosine) • Tested for at birth

47. Cystic Fibrosis • Thick mucus covers lungs, liver and pancreas • Recessive gene • May cause secondary infections • Occurs mostly in white race

48. Huntington’s Disease • Causes insanity • Is usually fatal • Dominant gene • Deterioration of brain tissue in middle age (begins 35-40 years old)

49. Nondisjunction • Chromosomes do not separate during meiosis • Down’s Syndrome • Extra 21st Chromosome • Autosomal nondisjunction • Called Trisomy 21 • Trisomy: Diploid individual has an extra chromosome

50. Turner’s Syndrome • In sex chromosomes • XO (no second sex chromosome) • Abnormally short female • No sex organs-sterile • Webbed neck