Chapters 12-14 Genetics Review PDF

Part 1 - Chapters 12-14 Test Review. PAY CLOSE ATTENTION TO THE TEXT IN BLUE. Red, Green and Black are supporting material GENOTYPE - genetic make-up, PP pp genes or letters, the organism has (PP, Pp, pp) PHENOTYPE - what it looks like (purple or white)...

Part 1 - Chapters 12-14 Test Review. PAY CLOSE ATTENTION TO THE TEXT IN BLUE. Red, Green and Black are supporting material GENOTYPE - genetic make-up, PP pp genes or letters, the organism has (PP, Pp, pp) PHENOTYPE - what it looks like (purple or white) Pp When the purple flower was crossed with the white flower, each parent contributes ONE allele to the offspring. PP x pp = Pp These plants are called HOMOZYGOUS (same) The hybrid offspring are called HETEROZYGOUS Setting up a Punnett Square Round is dominant to wrinkled 1. Place one parent genotype across the top. 2. Place the other on the side. 3. Fill in the punnett Square. Example: Show the cross between a round (RR) plant and a wrinkled (rr) plant. RR x rr r r 5. Identify the phenotypes and their proportion: R R ___ out of 4 are round ___ out of 4 are wrinkled.  Probability & Heredity Using segregation to predict outcomes (continued): ○ Not all organisms with the same characteristics have the same alleles, as shown in the F2 generation. GG and Gg resulted in green pods. Organisms that have two identical alleles for a gene are called homozygous (GG or gg). Organisms that have two different alleles for the same gene are heterozygous (Gg). If a trait which is not evident in the parents appears in their offspring, the parental genotypes are most likely heterozygous  Mendel’s Experiments Mendel’s studied the inheritance of certain traits in garden peas. He crossed true-breeding pea plants. He analyzed his data mathematically. He controlled variables by studying one or two traits at a time. Dominant & Recessive Alleles ○ Some alleles are dominant and others are recessive; An organism with both a dominant allele and a recessive allele for a particular trait will exhibit the dominant characteristic--- this is the Principle of Dominance Punnett squares are used to predict 25% white and 75% the outcome of a cross purple if both parents carry the Dominant and Parent Genotype ( Pp ) Recessive gene. Note: Both parents are P p heterozygous for the color trait P PP Pp p Pp pp Phenotype Genes - factors that are passed from parents to offspring Alleles - different forms of a gene P Generation Mendel’s Experiments Crossed true breeding plants with different traits (P generation) Offspring are the F1 (first filial) generation All F1 are purple. What happened to the white color?  Independent The Two-Factor Cross: F Assortment 2 ○ Mendel’s results were very close to a 9:3:3:1 ratio. ○ Principle of Independent Assortment: genes for different traits can segregated independently during the formation of gametes.  Chromosome Number Homologous: in sets of chromosomes, each of the chromosomes from the male parent has a corresponding chromosome from the female parent. ○ A cell with two sets of homologous chromosomes is said to be diploid, meaning “double”. The diploid number of chromosomes is represented by 2n. ○ A cell with a single set of chromosomes and single set of genes is said to be haploid, meaning “single”. The haploid number of chromosomes is represented by n. ○ Example: Each cell of the fruit fly, Drosophila, has 8 chromosomes: 4 from the male parent and 4 from the female parent. The diploid number for Drosophila is 8, or 2N=8, where N (Haploid) represents the single set of chromosomes found in a sperm or egg cell.  Meiosis Meiosis: process in which the number or chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell. ○ Meiosis is a process that reduces chromosomes to the haploid number, provides genetic variation, and ensures the correct distribution of chromosomes into the gametes ○ Involves two distinct divisions: Meiosis I & Meiosis II. By the end of meiosis, a single diploid cell that has produced four haploid cells.  Comparing Meiosis & Mitosis Number of cell divisions ○ Mitosis: single cell division resulting in 2 genetically identical diploid daughter cells. Homologous chromosomes line up at the center of the cell (Only once). ○ Meiosis: requires 2 rounds of cell division and produces 4 genetically different haploid daughter cells with half the number of chromosomes of the original body cell. Sister chromatids separate and move to opposite poles.  PROPHASE 1 of MEIOSIS - homologous pairs join - CROSSING -OVER (sections of chromosomes switch places) - Increases variation in gametes formed - homologous chromosomes may exchange segments in a crossing-over event. The Structure of DNA - made of nucleotides - 3 parts: phosphate, deoxyribose sugar, N-base Phosphate Base Sugar N-Bases = the steps or rungs of the DNA ladder A,T,G,C The Double Helix Model Hydrogen Bonds ○ Hydrogen bonds (weak chemical bond) form between the Nitrogenous base pairs. Adenine bonds with Thymine (remember: apple in the tree) Guanine bonds with Cytosine (remember: car in the garage)  Copying the Code The Replication Process ○ Replication: During S phase of the cell cycle, two strands of each DNA molecule separate and two new complementary strands are then synthesized following the rules of base pairing. If the base on the original strand is adenine, then thymine is added to the newly forming strand. Guanine is always paired with cytosine. Example: Original strand: TACGTTGCCT New strand: ATGCAACGGA (complimentary)  Copying the Code The Replication Process ○ Replication Result: two DNA molecules identical to each other and to the original molecule. Step 1 - Enzymes “unzip” a molecule of DNA by breaking the hydrogen bonds between base pairs and unwinding the two strands of the molecule. Helicase is the “unzipping enzyme. Step 2 - Replication starts from a single point and proceeds in two directions until the entire chromosome is copied. Each strand then serves as a template for the attachment of complementary bases. Step 3 - Regulatory proteins bind to the starting point on the chromosome. Step 4 - The two new chromosomes are separated when the cell divides to form two new cells.  Solving the Structure of DNA Chargaff’s Rule ○ Biochemist Edwin Chargaff discovered that the percentages of the bases Adenine [A] and thymine [T] are approximately equal in any sample of DNA. This is also true for the bases guanine [G] and cytosine [C]. ○ [A]=[T] and [G]=[C] became known as “Chargaff’s Rule”. Scientists found that DNA from all organisms obeyed this rule. Example If T = 30%, what are the percentages of the other 3 bases?  KNOW HOW TO READ THIS CHART Many amino acids may be encoded by more than one codon Start Codon (AUG) - initiates translation Stop Codon - ends translation IN ALL ORGANISMS THE GENETIC CODE IS PASSED FROM ONE GENERATION TO THE NEXT THEREFORE GIVEN THE NAME “THE UNIVERSAL GENETIC CODE CHART” SINCE WE ALL SHARE THE SAME DNA  Effects of Many mutations are produced by errors in genetic processes. Mutations ○ Example: some point mutations are caused by errors during DNA replication Mutagens: chemical or physical agents on the environment ○ Chemical mutagens include certain pesticides, a few natural alkaloids, tobacco smoke, and environmental pollutants. ○ Physical mutagens include some forms of electromagnetic radiation, such as ultraviolet light and x-rays. When cells cannot repair the damage, the DNA base sequence changes permanently. Some mutagens weaken the DNA strand and cause breaks that produce mutations.  Effects of Mutations Harmful & helpful mutagens ○ Some mutations have little or no effect, some produce beneficial variations, and some negatively disrupt gene function. Most are neutral, having little or no effect. The percentage of mutations that actually effect the outcome of the protein being produced is relatively low, around 10% ○ Mutations are the source of genetic variability in a species. ○ Harmful effects: the most harmful mutations are those that dramatically change protein structure or gene activity--- can result in genetic disorders  SCIENTIFIC Scientific methodology METHODOLOGY ○ Designing controlled experiments: Controlling variables Variables: changeable factors Independent variable: variable that is changed throughout the experiment Dependent variable: variable that is observed and that changes in response to the independent variable Experiments are usually divided into control and experimental groups Control group: exposed to the same conditions as the experimental group, except for changes in the independent variable UNDERSTAND THIS EXPERIMENT / DIAGRAM IN PPT CHAPTER 13.1