Genetics Review for Chapters 12-14

Part 1 - Chapters 12-14 Test Review

• Pay close attention to the text in blue.
• Red, green, and black text are supporting material.

Genotype and Phenotype

• Genotype: genetic makeup (genes represented by letters, e.g., PP, Pp, pp)
• Phenotype: observable traits (e.g., purple or white flowers)

Parental Generation (P)

• When a purple flower (PP) is crossed with a white flower (pp), each parent contributes one allele to the offspring.
• PP x pp = Pp (resulting in purple flowers)

Homozygous and Heterozygous

• Homozygous: organisms with two identical alleles (e.g., PP or pp)
• Heterozygous: organisms with two different alleles (e.g., Pp)
• The term "same" refers to homozygotes, while "hybrid" refers to heterozygotes

Punnett Square

• Used to predict the outcome of a cross.
• One parent's genotype is placed across top and the other on side.
• Example: RR (round) x rr (wrinkled) peas will produce all round offspring (Rr)

Probability and Heredity

• Not all organisms with the same characteristics have the same alleles.
• GG and Gg result in green pods.
• Organisms with identical alleles (homozygous): GG or gg.
• Organisms with different alleles (heterozygous): Gg

Mendel's Experiments

• Studied inheritance in garden peas.
• Crossed true-breeding plants.
• Controlled variables by studying one or two traits at a time.
• Dominant alleles are expressed over recessive alleles.

Principle of Dominance

• Organisms with both dominant and recessive alleles for a trait will exhibit the dominant characteristic.

Punnett Squares (Example)

• Parent Genotype (Pp): 25% white and 75% purple offspring.
• Both parents are heterozygous for the color trait.

Genes and Alleles

• Genes: factors passed from parents to offspring.
• Alleles: different forms of a gene.
• Mendel crossed true-breeding plants with different traits (P generation).

Independent Assortment

• Genes for different traits can be segregated independently during gamete (sex cell) formation.
• Mendel's results were close to a 9:3:3:1 ratio.

Chromosome Number

• Homologous chromosomes: matching pairs of chromosomes (one from each parent).
• Diploid (2n): Cells with two sets of homologous chromosomes.
• Haploid (n): Cells with one set of chromosomes.

Meiosis

• Process that reduces the number of chromosomes per cell in half through separation of homologous chromosomes in a diploid cell.
• Involves two distinct divisions (Meiosis I & Meiosis II).
• Produces four haploid cells.

Comparing Meiosis & Mitosis

• Mitosis: single division resulting in two identical diploid daughter cells.
• Meiosis: two divisions resulting in four different haploid daughter cells.

Prophase 1 of Meiosis

• Homologous pairs join: chromosomes crossover (sections switch places): increases variation in gametes.

DNA Structure

• Made of nucleotides, including phosphate, deoxyribose sugar, and a nitrogenous base.
• Nitrogenous bases: A, T, G, C.

The Double Helix Model

• Hydrogen bonds between nitrogenous bases (A-T and G-C).

Copying the Code (Replication)

• During DNA replication, two new complementary strands are synthesized using the original strand's base-pairing rules.
• Example: original strand: TACGTTGCCT, new strand: ATGCAACGGA.

Replication Process (Details)

• Enzymes unzip the DNA molecule by breaking hydrogen bonds between base pairs.
• Helicase is the "unzipping enzyme".
• Replication starts at a single point and proceeds in two directions.
• Each strand serves as a template to build a complementary strand.

Chargaff's Rule

• The percentages of adenine (A) and thymine (T) are equal, as are guanine (G) and cytosine (C) in DNA samples.

The Genetic Code

• Codons (three-base sequences) code for amino acids.
• Use a genetic code chart to translate codons into amino acids.

Mutations

• Errors during genetic processes can cause mutations.
• Mutagens: chemical or physical agents in the environment.
• Examples: certain pesticides, alkaloids, tobacco smoke, UV light, x-rays.
• Most mutations are neutral or have little or no effect.

Effects of Mutations

• Some mutations are harmful by dramatically changing protein structure or activity.
• Some mutations are helpful, creating beneficial variations.

Designing Controlled Experiments

• Variables: changeable factors in the experiment.
• Independent variable: is changed by the researcher.
• Dependent variable: observed variable that's influenced by the independent variable.
• Control groups: serve as a baseline to compare the experimental groups.

Bacterial Transformation Experiment

• Demonstrates that bacteria can change their genetic traits through the process of transformation as part of genetics study and experimentation.