Exam 3 Study Guide: Macromolecules, Meiosis, Mendelian Genetics, and Chromosomal Inheritance

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Chapter 3: The Structure and Function of Large Biological Molecules

Section 3.2: Polymers and Monomers

Biological macromolecules are large molecules composed of smaller subunits called monomers. These monomers are linked together to form polymers through specific chemical reactions.

Polymer: A long molecule consisting of many similar or identical building blocks (monomers) linked by covalent bonds.
Monomer: The repeating subunit that serves as the building block of a polymer.
Dehydration synthesis: A reaction in which two monomers are covalently bonded to each other with the removal of a water molecule.
Hydrolysis: A reaction that breaks the bond between monomers by adding a water molecule.
Enzyme: A macromolecule that acts as a catalyst to speed up chemical reactions, including those that build or break down polymers.

Section 3.5: Proteins and Their Structure

Proteins are polymers of amino acids and perform a vast array of functions in cells, including catalysis, structure, and signaling.

Polypeptide: A polymer of amino acids joined by peptide bonds.
Amino acid: The monomer of proteins, containing an amino group, a carboxyl group, and a unique side chain (R group).
Protein: One or more polypeptides folded and coiled into a specific three-dimensional structure.
Peptide bond: The covalent bond formed between amino acids during protein synthesis.
Catalyst: A substance that increases the rate of a chemical reaction without being consumed.
Protein structure: Proteins have four levels of structure: primary (sequence of amino acids), secondary (alpha helices and beta sheets), tertiary (3D folding), and quaternary (association of multiple polypeptides).
Denaturation: The loss of a protein's native structure due to environmental factors, causing loss of function.

Section 3.6: Nucleic Acids

Nucleic acids store and transmit hereditary information. DNA and RNA are the two main types.

Nucleic acids: Polymers made of nucleotide monomers.
Polynucleotide: A polymer consisting of many nucleotide monomers in a chain.
Ribose: The five-carbon sugar in RNA nucleotides.
Deoxyribose: The five-carbon sugar in DNA nucleotides.
Double helix: The structure of DNA, consisting of two polynucleotide strands wound around each other.

Section 3.3: Carbohydrates

Carbohydrates serve as fuel and building material for cells. They include sugars and their polymers.

Carbohydrate: A molecule consisting of carbon, hydrogen, and oxygen, usually with a 1:2:1 ratio.
Monosaccharide: The simplest carbohydrate, or simple sugar (e.g., glucose).
Disaccharide: A double sugar, consisting of two monosaccharides joined by a glycosidic linkage.
Glycosidic linkage: A covalent bond formed between two monosaccharides by a dehydration reaction.
Polysaccharide: A polymer of many monosaccharides, such as starch, glycogen, and cellulose.
Starch: A storage polysaccharide in plants.
Glycogen: A storage polysaccharide in animals.
Cellulose: A structural polysaccharide in plant cell walls.

Section 3.4: Lipids

Lipids are hydrophobic molecules that include fats, phospholipids, and steroids. They are important for energy storage, membrane structure, and signaling.

Lipid: A diverse group of hydrophobic molecules, not true polymers.
Fat: A lipid composed of glycerol and fatty acids; used for energy storage.
Fatty acid: A long hydrocarbon chain with a carboxyl group at one end.
Saturated fatty acid: A fatty acid with no double bonds between carbon atoms; solid at room temperature.
Unsaturated fatty acid: A fatty acid with one or more double bonds; liquid at room temperature.
Phospholipid: A lipid with a phosphate group, major component of cell membranes.
Steroid: A lipid with a carbon skeleton consisting of four fused rings.
Cholesterol: An important steroid, component of animal cell membranes.

Chapter 10: Meiosis and Sexual Life Cycles

Section 10.1: Genes and Chromosomes

Genetic information is organized into genes, which are located on chromosomes. Organisms reproduce either asexually or sexually.

Gene: A unit of hereditary information on a chromosome.
Gamete: A reproductive cell (sperm or egg) with half the number of chromosomes.
Somatic cell: Any cell in a multicellular organism except a gamete.
Locus: The specific location of a gene on a chromosome.
Asexual reproduction: Offspring arise from a single parent and are genetically identical to the parent.
Clone: A genetically identical individual produced by asexual reproduction.
Sexual reproduction: Two parents give rise to offspring with unique combinations of genes.

Section 10.2: Chromosome Sets

Karyotype: The ordered display of an individual's chromosomes.
Homologous chromosome: Chromosomes that have the same genes at the same loci but possibly different alleles.
Sex chromosome: Chromosomes that determine the sex of an individual (X and Y in humans).
Autosome: Any chromosome that is not a sex chromosome.
Diploid (2n): A cell with two sets of chromosomes.
Haploid (n): A cell with one set of chromosomes.
Fertilization: The fusion of gametes to form a diploid zygote.
Meiosis: A type of cell division that reduces the chromosome number by half, producing four haploid cells.

Section 10.3: The Process of Meiosis

Meiosis I: Homologous chromosomes separate, reducing chromosome number by half.
Meiosis II: Sister chromatids separate, similar to mitosis.
Chromosomes: Structures that carry genetic information.
Sister chromatid: Two identical copies of a chromosome connected by a centromere.
Crossing over: Exchange of genetic material between homologous chromosomes during meiosis I, increasing genetic diversity.

Section 10.4: Genetic Variation

Independent assortment: Random orientation of homologous chromosomes during meiosis I, leading to genetic variation.
Recombinant chromosome: Chromosome created from crossing over, containing DNA from both parents.
Random fertilization: Any sperm can fertilize any egg, further increasing genetic variation.

Chapter 11: Mendel and the Gene Idea

Section 11.1: Mendelian Genetics

Mendel's experiments with pea plants established the basic principles of heredity, including the concepts of dominant and recessive alleles, segregation, and independent assortment.

Character: A heritable feature that varies among individuals (e.g., flower color).
Trait: A variant of a character (e.g., purple or white flowers).
True-breeding: Organisms that produce offspring of the same variety when self-pollinated.
P generation: Parental generation in a genetic cross.
F1 generation: First filial generation, offspring of the P generation.
F2 generation: Second filial generation, offspring of the F1 generation.
Law of segregation: Two alleles for a gene separate during gamete formation.
Allele: Alternative versions of a gene.
Dominant allele: An allele that determines the phenotype in a heterozygote.
Recessive allele: An allele that is masked in the presence of a dominant allele.
Punnett Square: A diagram used to predict the outcome of a genetic cross.
Homozygous / homozygote: An individual with two identical alleles for a gene.
Heterozygous / heterozygote: An individual with two different alleles for a gene.
Phenotype: Observable traits of an organism.
Genotype: Genetic makeup of an organism.
Test cross: Breeding an individual with a dominant phenotype with a homozygous recessive to determine genotype.
Monohybrid / Monohybrid cross: A cross between individuals heterozygous for one gene.
Dihybrid / Dihybrid cross: A cross between individuals heterozygous for two genes.
Law of Independent Assortment: Each pair of alleles segregates independently during gamete formation.

Section 11.3: Extensions of Mendelian Genetics (optional)

Complete dominance: Phenotype of heterozygote is identical to dominant homozygote.
Incomplete dominance: Heterozygote phenotype is intermediate between the two homozygotes.
Codominance: Both alleles are fully expressed in the heterozygote.
Epistasis: One gene affects the expression of another gene.
Polygenic inheritance: Multiple genes independently affect a single trait.

Section 11.4: Human Genetics

Pedigree: A diagram showing the inheritance of a trait over several generations.
Carrier: An individual who is heterozygous for a recessive disorder allele.
Multifactorial disorder: A disorder influenced by both genetic and environmental factors.

Chapter 12: The Chromosomal Basis of Inheritance

Overview (Fig 12.2): Chromosome Theory of Inheritance

The chromosome theory of inheritance states that genes are located on chromosomes, which segregate and independently assort during meiosis.

Chromosome theory of inheritance: Genes are carried on chromosomes.
Homologous chromosome: Chromosomes with the same genes but possibly different alleles.
Sister chromatid: Identical copies of a chromosome connected by a centromere.
Gamete: Reproductive cell with half the chromosome number.

Section 12.2: Sex-Linked Genes

Sex-linked gene: A gene located on a sex chromosome (usually the X chromosome).
X-linked gene: A gene located specifically on the X chromosome.

Section 12.4: Chromosomal Alterations

Nondisjunction: Failure of homologous chromosomes or sister chromatids to separate properly during meiosis.
Aneuploidy: Abnormal number of chromosomes.
Monosomic: A cell with only one copy of a particular chromosome.
Trisomic: A cell with three copies of a particular chromosome.
Polyploidy: More than two complete sets of chromosomes.
Deletion: Loss of a chromosome segment.
Duplication: Repetition of a chromosome segment.
Inversion: Reversal of a chromosome segment.
Translocation: Movement of a chromosome segment to a nonhomologous chromosome.

Short Answer Practice

1. Dehydration Reaction and Maltose Formation

When two glucose molecules (C6H12O6) are joined by a dehydration reaction to form maltose, the formula is not simply double that of glucose. This is because a water molecule (H2O) is lost during the reaction.

Equation:
Explanation: The loss of H2O accounts for the difference in the molecular formula.

2. Gene Expression and Inheritance of Traits

Traits such as hair color are inherited because genes (DNA sequences) are passed from parents to offspring. These genes are expressed through transcription and translation, resulting in proteins that determine physical traits.

Gene expression: The process by which information from a gene is used to synthesize a functional gene product (usually a protein).
Inheritance: Offspring inherit one allele from each parent, which combine to determine the phenotype.

3. Genetic Cross: AA x Aa

For a gene with dominant allele A and recessive allele a, the cross AA x Aa produces the following offspring:

Genotypes: 50% AA (homozygous dominant), 50% Aa (heterozygous), 0% aa (homozygous recessive).
Phenotypes: All show the dominant trait.

4. X-Linked Inheritance in Drosophila (Fruit Flies)

When a red-eyed (wild-type) female Drosophila (XRXR) is crossed with a white-eyed (mutant) male (XrY), the Punnett square below shows the possible offspring:

Punnett square for X-linked cross between red-eyed female and white-eyed male Drosophila

Predicted offspring: All females (XRXr) will have red eyes (carriers), all males (XRY) will have red eyes.
Why more males are white-eyed: Males have only one X chromosome, so a single recessive allele (Xr) results in the white-eyed phenotype. Females need two copies of the recessive allele to show the trait.

Additional info:

Figures referenced (e.g., 3.7, 10.3, 11.1, 12.2) are likely from a standard biology textbook and illustrate key concepts such as macromolecule structure, meiosis stages, Mendelian crosses, and chromosomal inheritance.
Practice with Punnett squares, pedigrees, and meiosis diagrams is essential for mastering these topics.