Genetics: The Science of Heredity

1. Genetics: The Science of Heredity

2. “I can explain the difference between asexual and sexual reproduction.” I. Reproduction A. Asexual Reproduction 1. Only one parent is needed for reproduction 2. Parent cell divides into two by mitosis and the new cell is an exact copy of the parent cell 3. Examples: yeast, bacteria, protist (ie. paramecium) Paramecium – binary fission Yeast -Budding Bacteria Binary Fission

3. B. Sexual Reproduction 1. Two parents (egg and sperm cell ) join together to form a new individual 2. Sex Cells (gametes) a. Sperm- male sex cell b. Egg- female sex cells Human Egg Cell Egg and Sperm Join Sperm Cell

4. 3. Sex Cells are differentthan other cells: a. Normal human body cells have 46 “double” chromosomes b. Sex cells only have 23 chromosomes (half the usual number) c. Egg and sperm cell have only one chromatid out of each homologous pair d. When sperm and egg cellunite to form a new individual each parent only donates one half of a homologous pair. Ensuring the human offspring will receive a normal number- 46 chromosomes in a body cell 4. Examples: plants, animals, fungi, and some protists

6. Bread Mold Sexual Reproduction (Fungus)

7. “I can describe how genes are inherited, and how traits are the result of gene combinations.”C. Chromosomes and Inheritance 1. Chromosome Theory- genes are carried from parents to offspring on chromosomes 2. Chromosome- the cell structure made of condensed chromatin containing DNA or genetic code

8. 3. Genes are located on chromosomes 4. Genes carry genetic information one from each parent 5. Humans have 46 chromosomes -23 matching pairs 6. Chromosomes control inherited characteristics • Eye color, hair color, skin color, certain diseases 7. Many genes are located on each chromosome Genes located on chromosome http://web.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/index.shtml

9. “I can describe how genes are inherited, and how traits are the result of gene combinations.” II. Details of Genetics • Genes – a set of instructions donated by each parent • Genes are located on the chromosomes 2. Genes are made of DNA 3. Each characteristic of an organism has two sets of instructions one from each parent. (double strand) Ex. Hair color, skin color, ear lobe, flower color, etc.

11. *Draw a picture in the space below showing how genes are passed from parents to offspring.

12. “I can explain DNA and its structures and explain they are located on the chromosomes.”B. What do genes look like?- DNA Connection 1. Discovery of DNA • Watson and Crick (& Franklin) came up with a model for DNA showing how the nucleotides fit together in a pattern • DNA resembles a twisted ladder called a double helix shape Watson and Crick

13. 2. DNA (deoxyribonucleic acid): and proteins make up chromosomes a. DNA must be able to: • Supply instructions for cell processes • Build cell structures • Control the production of proteins • Be copied each time a cell divides – ensuring that each cell has an identical set of genes b. DNA is made of nucleotides

14. DNA Connection (cont.) 3. Nucleotide- the subunits of DNA a. Nucleotide bases consists of 3 materials :sugar, phosphate, base b. DNA molecule is made of four nucleotides bases: • Adenine (A) • Thymine (T) • Guanine (G) • Cytosine ( C) c. Nucleotides are identical except for the bases and have slightly different shapes

16. 4. Rules for Building DNA a. These 4 nucleotide basesform the rungs of the DNA ladder structure (double helix) b. Rungs of the ladder are composed of a pair of nucleotide bases c. Adenine on one side always pairs up with thymine on the other side: the number a A always = T d. Guanine always pairs up with cytosinein same way: the number of G always = C e. The upright part of the ladder is made with alternating sugar and phosphoric acid

17. Rules for Building DNA (cont.) f. One side of DNA molecule is complimentary to the other • Ex. ACCG always binds to the sequence TGGC (allowing the DNA to make a copy and replicate itself) • DNA molecules replicate by splitting down center of ladder- the one side of the ladder can be used as a pattern for a new complimentary side g. Each gene consists of a string of bases: the order of the bases give the cell information about how to make each trait

18. “I can explain the difference between phenotype and genotype.” Details of Genetics (cont.) C. Alleles- forms of a gene for a trait or characteristic • Fertilized egg has two forms (alleles) of the same gene for every characteristic. D. Genotype- inherited combination of alleles (shown with letters) • Ex. Tt, TT, PP, Pp E. Phenotype- organisms appearance (shown with words) -Ex. Tall, Short, Purple, White

19. “I can describe how genes are inherited, and how traits are the result of gene combinations.”III. History of Genetics A. Genetics- The study of heredity or the passing on of traits from parents to offspring i. Geneticist- scientist who studies heredity B. Gregor Mendel- “Father of Genetics” • His studies gave scientists the basic ideas for genetics 2. Mendel studies pea plants: grow quickly, self-pollinate (plants carry both male and female reproductive parts), and come in many varieties 3. Mendel developed a method know as cross-pollination: Anthers of one plant are removed so that the plant can’t self-pollinated; pollen from another plant are used to fertilize the plant without anthers

20. 4. Mendel performed pea-plant crosses to study the seven characteristics below:

21. C. Parental Generation- P-passing of traits (genes) from parents to offspring ( babies ) D. First Generation F1 (offspring from first cross): Cross between two traits of each characteristic- one trait always appeared another vanished ex. Purple flower X White flower = Purple Flower

22. Details of Genetics (cont.) H. Second Generation F2: Mendel allowed the F1 generation plant with dominate trait; to self-pollinate= recessive trait showed up again -some white flower plants came back • ex. Purple flower dominant plants produced 3 purple flowered plants and 1 white flowered plant

24. “I can explain how dominant and recessive genes work.” E. Dominant Trait-Trait that appeared = a stronger trait (shows up in offspring) • Symbol used when writing is an upper case letter ex. T F. Recessive Trait- Trait that vanished or disappeared = weaker traits (masked or covered up in offspring) 1. Symbol used when writing is a lower case letter- ex. t

26. “I can define purebred and hybrid traits giving an example of each.” G. Purebred (true-breeding or homozygous)an organism that has genes (alleles) that are the same for the trait. • Ex. Short plants always produce short offspring tt(purebred short). Tall plants always produce tall offspring TT (purebred tall). SS, EE, ee, PP, pp, CC, cc Genotypes= Purebred

27. L. Hybrid (Heterozygous (different)- an organism that has different genes (alleles) for a trait ( a mixture) • Ex. Hybrid tall plant receives one tall allele T and one short allele t (Tt) *Note-Tt will all be tall plants because it has a dominant gene or allele. “T”covers up or masks the “t”. Tt, Pp, Ee, Cc, Ss Genotypes= Hybrid

28. “I can calculate percentages and probability from a Punnett square.”IV. Probability A. Probability-mathematical chance that an event will occur. - “What are the chances?” 1. Used to predict the results for genetic crosses 2. Shown as a fraction or percentage B. Calculating Probability: Ex. Ten marbles are in a bag, six of the marbles are red. What is the probability of getting a red marble? 6 red marbles/ 10 marbles total= 6/10 or 3/5

29. C. Ratio Results- approx. 3 dominant traits showed up to 1 recessive trait = ratio 3:1

30. “I can calculate percentages and probability from a Punnett square.”“I can complete a Punnett square with a one factor cross to show genetic variation in offspring.”V. Punnett Squares A. Punnett Squares-a special chart used to show all the possible combinations of allele from their parents. 1. Dominant Alleles- symbolized by capital letters (SS, YY, BB) 2. Recessive Allele -symbolized by lowercase letters (ss, yy, bb)

32. B. Practice a Punnett Square 1. Cross purebred (homozygous, true- breeding) tall plant (TT) with a hybrid (heterozygous) tall plant (Tt) TT x Tt T t T T

33. Punnett Squares Results • Probability of purebred (homozygous) tall plant = 2/4 or 50% • Probability of a hybrid (heterozygous) all plant = 2/4 or 50% • Probability of short plant= 0% • Probability of a tall plant = 4/4 or 100% • Genotype = Tt, TT • Phenotype = Tall

34. More Punnett Square Practice 2. Cross a purebred (true breeding, homozygous) white flower (pp), with a hybrid (heterozygous) purple flower (Pp) ____________x___________

35. Punnett Square Results • Probability of getting a hybrid Purple flower = 2/4 or 50% • Probability of getting a homozygous (true-breeding) Purple Flower = 0% • Probability of getting a pure-bred (true-breeding) White Flower= 2/4 or 50% • Genotype= Pp, pp • Phenotype = Purple Flower, White Flower

36. “I can describe how genes are inherited, and how traits are the result of gene combinations.”VI. More News About Traits-Exceptions to Mendel’s Rules A. Co- Dominance- the alleles are neither dominant nor recessive for a trait; both alleles show up in the offspring. • Example: Heterozygous chickens have both black and white feathers. • Note: Co-dominant alleles are written as capital letters with superscripts FB black feather and FWfor white feather

37. Co- Dominance Punnett Square 1. Cross a dominant black-feathered chicken (____) with dominant white-feathered chicken (____) • Probability of getting a heterozygous black and white feathered chicken = 100% • Genotypes = FBFW • Phenotypes = Black and White Feathered FB FB FW FW FWFW X FBFB

38. Co-Dominance Punnett Square 2. Cross a co-dominant heterozygous (hybrid ) black and white feathered chicken (FBFW) with a co-dominant heterozygous (hybrid) black and white feathered chicken (FBFW) ____________x_____________ FB FW FB FW

39. Co-Dominance Punnett SquareResults • Probability of getting heterozygous black and white feathered chicken = 50% • Probability of getting homozygous white feathered chicken = 25 % • Probability of getting a homozygous black feathered chicken = 25 % • Genotypes=FBFB, FBFW, FWFW • Phenotypes= Black feathered, Black and White Feathered, White Feathered

41. B. In-Complete Dominance In-Complete Dominance- 1. Neither allele is fully dominant, offspring have an intermediate phenotype, each allele has its own degree of influence. 2. Show with capital letters and superscript numbers. • Ex. Red snapdragon crossed with a white snapdragon = pink snapdragon Liger

42. In-Complete Dominance Punnett Square 1. Cross a true-breeding R1R1red snapdragon with a true-breeding W1W1white snapdragon • R1R1 X W1W1 W1 W1 R1 R1

43. In-Complete Dominance Punnett Square Results • Probability of pink flowers = 100% • Probability of white flowers = 0% • Probability of red flowers = 0% • Genotype= R1W1 • Phenotype = Pink Flowers + =

44. C. More Exceptions to the Rule 1. Many genes can influence a single trait- called Polygenic Inheritance a. Traits such as eye, hair, and skin color are the results of several genes acting together- difficult to determine if a trait is result of a dominant or recessive trait b. Different combinations of alleles result in slight differences in the amount of pigment present • ex. Different shades of blue eyes, hair color, skin color, etc.

45. “I can infer that changes in genetic material may result in making different proteins, example insertion, deletion and substitution.”VII. How DNA Works Protein Synthesis A. The sequence or order of nucleotides along a gene forms a code that tells the cell what protein to produce

46. How DNA Works (cont.) B.Protein Synthesis-is the process of making protein chains • A three nucleotide basecodes for a specific amino acid(which are the building blocks of proteins) is built to form a protein chain • The order of the basesdetermines the order of the amino acids in a protein • Each gene is a set of instructions for making a protein

47. How DNA Works (cont.) 2. Proteins- acts as chemical messengers • help determine how tall you will grow, whether you have curly or straight hair, your eye color, skin color, nail type a. Human cells contain about 20,000 genes- each genes spells out a sequence of amino acids for specific proteins b. Human body contains about 50,000 different kinds of proteins

48. 3. Making of Proteins (Protein Synthesis) a. During protein synthesis- cell uses information from a gene on a chromosometo make specific proteins • Protein synthesis – takes place on ribosomes in the cytoplasm

49. b. Role of RNA • Messenger RNA (mRNA)-carries the genetic code from DNA inside the nucleus to the ribosomes • Transfer RNA (tRNA)-carries the amino acids and adds them to the growing protein chain

50. “I can explain how transcription and translation works to create a protein.” 4. How Protein Synthesis Works: A. Transcription: • A copy of the section of the DNA strand containing a gene is made and carried outside of the cells nucleus • Messenger RNAmolecules take the genetic information from the nucleus out into the cytoplasm • In cytoplasm a copy of DNA is fed though a “protein assembly line”- this “protein factory” is found in the ribosomes.