1. Contains the sugar ribose instead of deoxyribose. 2. Single-stranded instead of double stranded. 3. Contains uracil in place of thymine.

Transcription

1 Protein Synthesis & Mutations

2 RNA 1. Contains the sugar ribose instead of deoxyribose. 2. Single-stranded instead of double stranded. 3. Contains uracil in place of thymine.

3 RNA Contains: 1. Adenine 2. Cytosine 3. Guanine 4. Uracil (not Thymine)

4 Three Main Types of RNA 1. Messenger RNA (mrna) - Carries copies of instructions, for the assembly of amino acids into proteins, from DNA to the ribosome (serve as messenger ) * Made in the nucleus

5 Three Main Types of RNA 2.Ribosomal RNA (rrna) Makes up the major part of ribosomes, which is where proteins are made. Made in the nucleolus Ribosomal RNA

6 Three Main Types of RNA 3. Transfer RNA (trna) Transfers (carries) amino acids to ribosomes as specified by codons in the mrna

7 Proteins Proteins are made up of a chain of amino acids. Proteins are enzymes, which catalyze and regulate chemical reactions.

8 2 Steps to Make a Protein 1. Transcription DNA RNA 2. Translation RNA Protein (Chain of amino acids)

9 Step 1: Transcription Transcription - Process in which part of the nucleotide sequence of DNA is copied into a complementary sequence in RNA. RNA polymerase separates the DNA strands. One strand of DNA is used as a template from which nucleotides are assembled into a strand of RNA. Occurs in the nucleus.

10 Transcription: DNA RNA

11 After Transcription The mrna leaves the nucleus and travels to the ribosomes in the cytoplasm.

12 Codons Codon - Three-nucleotide sequence on messenger RNA that codes for a single amino acid.

13 The Genetic Code The language of mrna instructions is called the genetic code. The genetic code is read three letters at a time, so that each word of the coded message is three bases long.

14 mrna, Codons 1. How the code is read: a. Every 3 bases on mrna is called a codon. b. Every codon codes for an amino acid (building block of protein) c. Amino acids are abbreviated most times by using the first 3 letters of the amino acid s name. Met = methonine Leu = leucine

15 Start and Stop Codons Start Codons: Found at the beginning of a protein; Only one - AUG (methionine) Stop Codons: Found at the end of a protein; three exist, which make the production of the protein stop: UAA, UAG,UGA

16 Reading the Codon Chart Examples: AUG = Methionine CAU = Histidine UAG = Stop First Position Third Position Try these: GCU: UAC: CUG: UUA: Answers: Alanine Tyrosine Leucine Leucine This chart only works for mrna codons!

17 Step 2: Translation Translation - Decoding of a mrna message into a protein (amino acid chain) Takes place on the ribosomes Each trna contains: 1. An amino acid 2. Three unpaired bases.

18 Anticodon Each trna molecule has three unpaired bases called the anticodon, which are complementary to one mrna codon.

19 Steps of Translation 1. Begins when an mrna molecule in the cytoplasm attaches to a ribosome. 2. As each codon of the mrna molecule moves through the ribosome, the proper amino acid is brought into the ribosome by trna. 3. The ribosome forms a peptide bond between the first and second amino acids. 4. The polypeptide chain continues to grow until the ribosome reaches a stop codon on the mrna molecule and a protein has been made.

20 Translation mrna Nucleus Phenylalanine t RNA Lysine Jan 2006 Methionine Anticodon Ribosome mrna Start codon Go to Section:

21 Translation The Polypeptide Assembly Line Growing polypeptide chain Ribosome trna Jan 2006 Lysine trna mrna mrna Ribosome Translation direction Completing the Polypeptide Go to Section:

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25 Mutations Mutation - Change in a DNA sequence that affects genetic information; error or mistake in copying DNA.

26 Types of Mutations Chromosomal Mutations - Involve changes in the number or structure of chromosomes. Ex. Downs Syndrome Gene Mutations - Mutations that produce changes in a single gene.

27 Types of Gene Mutations 1. Point Mutations - affect a single nucleotide, or point in the DNA sequence, usually by substituting one nucleotide for another. Original: AUGUAC Met Tyr Mutated: AUGUAG Met Stop (causes the amino acid chain to stop protein production early)

28 Types of Gene Mutations Frameshift Mutations - Mutation that shifts the reading frame of the genetic message by inserting or deleting a nucleotide. Insertions A base is inserted into the DNA sequence. Deletions - A base is removed from the DNA sequence. Original: The fat cat ate the wee rat. Frame Shift: The fat caa tet hew eer at. (Frame shift mutations affect all subsequent amino acids!)

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30 Meiosis & Genetics (Chromosomes & Punnett Squares)

31 Chromosomes & Genes Chromosome - Very long, continuous single piece of DNA, contains many genes Gene - Sequence of DNA that codes for a protein and thus determines a trait

32 Homologous Chromosomes Homologous Chromosomes - Term used to refer to chromosomes that each have a corresponding chromosome from the opposite-sex parent. Both chromosomes have all the same genes in the same location, but different versions of those genes.

33 Haploid vs. Diploid Haploid - Term used to refer to a cell that contains only a single set of chromosomes and therefore only a single set of genes; one set ; represented by N. Diploid - Term used to refer to a cell that contains both sets of homologous chromosomes; two sets ; represented by 2N.

34 Gamete vs. Zygote Gamete - A mature sexual reproductive cell that has a haploid numbers that unites with another cell to form a new organism. Example: Sperm or egg cell Zygote - The cell formed by the union of two gametes.

35 Sexual Reproduction - Process by which two cells from different parents unite to produce the first cell of a new organism. Haploid sperm (gamete) 1n Haploid egg (gamete) + 1n = Diploid zygote 2n

36 Meiosis Meiosis - Process by which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell; Haploid (N) gamete cells are produced from diploid (2N) cells. Begin with Diploid (2N) Cells Produce Haploid (N) Cells

37 Four gametes are made during cell division by meiosis. The gamete cells have half the number of chromosomes as the original cell.

38 Meiosis Meiosis usually involves two distinct divisions: 1. Meiosis 1 2. Meiosis 2

39 Meiosis 1 Prior to meiosis I, each chromosome is replicated. The cells then begin to divide in a way that looks similar to mitosis. One big difference: Each chromosome pairs with its corresponding homologous chromosome to form a structure called a tetrad and exchange portions of their chromatids in a process called crossing-over.

40 Crossing Over Produces new combinations of alleles. Meiosis 1 is similar to mitosis except: The two cells produced by meiosis I have sets of chromosomes and alleles that are different from each other and from the diploid cell that entered meiosis I.

41 Meiosis 2 Two cells produced by meiosis I now enter a second meiotic division. Unlike the first division, neither cell goes through a round of chromosome replication before entering meiosis II. Those four daughter cells now contain the haploid number (N) just 2 chromosomes each.

42 Nondisjunction The most common error in meiosis occurs when homologous chromosomes fail to separate. This is known as nondisjunction. Results in abnormal numbers of chromosomes in gametes. Example - Down syndrome, which results when an individual has three copies of chromosome 21.

43 Mitosis vs. Meiosis Mitosis Allows an organism's body to grow and replace cells. Used in asexual reproduction to produce a new organism. New (daughter) cell is identical to the parent cell and to each other. Produces two diploid (2N) daughter cells. Meiosis Used in sexual reproduction to produce gametes. New (daughter) cells are genetically different from the parent cells and from one another. Produces four haploid (N) cells. Is responsible for the genetic variation among species.

44 Inheritance & Cell Type You can only inherit a trait from gametes, not other somatic (body) cells! Mutations within somatic (body) cells do not affect future offspring genes. Whereas, mutations within gametes do alter offspring genes. For example, if your mother has skin cancer, you will not inherit this mutation because the mutation is on her somatic (body) cells and these are not inherited.

45 Dominant vs. Recessive Dominant - Masks the other trait; the trait that shows if present Represented by a capital letter Recessive An organism with a recessive allele for a particular trait will only exhibit that trait when the dominant allele is not present; Will only show if both alleles are present Represented by a lower case letter R r

46 Dominant & Recessive Practice T straight hair t - curly hair TT - Represent offspring with straight hair Tt - Represent offspring with straight hair tt - Represents offspring with curly hair

47 Homozygous vs. Heterozygous Homozygous Term used to refer to an organism that has two identical alleles for a particular trait (TT or tt) Sometimes called purebred RR rr Heterozygous - Term used to refer to an organism that has two different alleles for the same trait (Tt) Sometimes called hybrid Rr

48 Genotype vs. Phenotype Genotype The genetic makeup of an organism; The gene (or allele) combination an organism has. Example: Tt, ss, GG, Ww Phenotype The physical characteristics of an organism; The way an organism looks Example: Curly hair, straight hair, blue eyes, tall, green

49 Punnett Squares Punnett Square Diagram showing the gene combinations that might result from a genetic cross Used to calculate the probability of inheriting a particular trait Probability The chance that a given event will occur

50 Punnett Square Parent Parent Offspring

51 How to Complete a Punnett Square

52 Y-Yellow y-white Genotype: 1:2:1 (YY:Yy:yy) 25%, 50%, 25% Phenotype: 3 Yellow, 75% 1 White, 25%

53 You Try It Now! Give the genotype and phenotype for the following cross: TT x tt (T = Tall and t = Short)

54 TT x tt Step One: Set Up Punnett Square (put one parent on the top and the other along the side) t T T t

55 TT x tt Step Two: Complete the Punnett Square t t T Tt Tt T Tt Tt

56 TT x tt Step Three: Write the genotype and phenotype t t T Tt Tt T Tt Tt Genotype: 4 Tt or 100% Phenotype: 100% Tall Remember: Each box is 25%

57 You Try It Now! Give the genotype and phenotype for the following cross: Tt x tt

58 Tt x tt Step One: Set Up Punnett Square (put one parent on the top and the other along the side) t T t t

59 Tt x tt Step Two: Complete the Punnett Square t t T Tt Tt t tt tt

60 Tt x tt Step Three: Write the genotype and phenotype t T Tt t tt Genotype: Tt - 2 (50%) tt - 2 (50%) t Tt tt Remember: Each box is 25% Phenotype: 50% Tall 50% Short

61 Four Types of Chromosomal Mutations 1. Deletion A chromosome segment is deleted or removed. 2. Duplication A chromosome segment is duplicated or repeated

62 Four Types of Chromosomal Mutations 3. Inversion A segment of a chromosome breaks off, turns around, and reattaches in the reverse order; reverses a segment within a chromosome 4. Translocation A segment of a chromosome is moved to another chromosome.