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 3.3: Carbohydrates

Carbohydrates are sugars and their polymers, serving as fuel and building material for cells.

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

Section 3.4: Lipids

Lipids are a diverse group of hydrophobic molecules, including fats, phospholipids, and steroids.

Lipid: A class of large biological molecules that do not form polymers and are hydrophobic.
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: Has no double bonds between carbon atoms; solid at room temperature.
Unsaturated fatty acid: Has one or more double bonds; liquid at room temperature.
Phospholipid: A lipid with two fatty acids and a phosphate group; forms cell membranes.
Steroid: A lipid with a carbon skeleton consisting of four fused rings (e.g., cholesterol).
Cholesterol: An important steroid in animal cell membranes and a precursor for other steroids.

Section 3.5: Proteins

Proteins are polymers of amino acids and perform a vast array of functions in cells.

Polypeptide: A polymer of amino acids linked by peptide bonds.
Amino acid: The monomer of proteins, containing an amino group, carboxyl group, and side chain (R group).
Protein: A biologically functional molecule made up of one or more polypeptides folded into a specific shape.
Peptide bond: The covalent bond between amino acids in a polypeptide.
Catalyst: A substance that increases the rate of a chemical reaction without being consumed.
Protein structure: Proteins have four levels of structure: primary, secondary, tertiary, and quaternary.
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.

Nucleic acid: Polymers made of nucleotide monomers (DNA and RNA).
Polynucleotide: A polymer consisting of many nucleotide monomers.
Ribose: The sugar in RNA nucleotides.
Deoxyribose: The sugar in DNA nucleotides.
Double helix: The structure of DNA, consisting of two polynucleotide strands wound around each other.

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 of a somatic cell.
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 organism 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 number and visual appearance of chromosomes in a cell.
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 organism (e.g., 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: The exchange of genetic material between homologous chromosomes during meiosis I, increasing genetic diversity.

Section 10.4: Genetic Variation

Independent assortment: The random distribution of homologous chromosomes during meiosis I.
Recombinant chromosome: A chromosome created from crossing over, containing genes from both parents.
Random fertilization: The random combination of gametes increases 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.

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: Expressed in the phenotype even if only one copy is present.
Recessive allele: Expressed only when two copies are present.
Punnett Square: A diagram used to predict the outcome of a genetic cross.
Homozygous / homozygote: Having two identical alleles for a gene.
Heterozygous / heterozygote: Having 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 individual 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

Complete dominance: One allele completely masks the other in the phenotype.
Incomplete dominance: The phenotype is intermediate between the two parental varieties.
Codominance: Both alleles are fully expressed in the phenotype.
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 family tree that shows the inheritance of a trait over generations.
Carrier: An individual who is heterozygous for a recessive disorder allele but does not show symptoms.
Multifactorial disorder: A disorder influenced by multiple genes and environmental factors.

Chapter 12: The Chromosomal Basis of Inheritance

Overview (Fig 12.2): Chromosome Theory of Inheritance

Chromosome theory of inheritance: Genes are located on chromosomes, and the behavior of chromosomes during meiosis accounts for inheritance patterns.
Homologous chromosome: Chromosomes with the same genes but possibly different alleles.
Sister chromatid: Identical copies of a chromosome connected by a centromere.
Gamete: A reproductive cell with half the chromosome number of a somatic cell.

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: Alterations of Chromosome Number or Structure

Nondisjunction: The failure of homologous chromosomes or sister chromatids to separate properly during meiosis.
Aneuploidy: An abnormal number of chromosomes in a cell.
Monosomic: A cell missing one chromosome (2n-1).
Trisomic: A cell with an extra chromosome (2n+1).
Polyploidy: A condition in which an organism has 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 within a chromosome.
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 are inherited from parents through the transmission of genes. Each gene encodes information for a specific protein, which determines a trait. Offspring inherit one allele from each parent, and the combination of alleles determines the phenotype (observable trait).

3. Genetic Cross: AA x Aa

For a cross between AA (homozygous dominant) and Aa (heterozygous):

Possible offspring genotypes: AA, Aa
Proportions: 50% AA (homozygous dominant), 0% aa (homozygous recessive), 50% Aa (heterozygous)

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

When a red-eyed (wild-type) female (XRXR) is crossed with a white-eyed (mutant) male (XrY):

All female offspring will be XRXr (red-eyed, carriers).
All male offspring will be XRY (red-eyed).
It is more probable for males to be white-eyed because they have only one X chromosome; if they inherit the Xr allele, they express the trait, while females need two copies of Xr to show white eyes.

Punnett square for X-linked inheritance in Drosophila: red-eyed female x white-eyed male

Additional info:

Figures referenced (e.g., 3.7, 10.3, 11.1, 12.2) correspond to textbook diagrams illustrating molecular structures, meiosis stages, Punnett squares, and chromosomal behavior. Review these in your textbook for visual reinforcement.
Practice with Punnett squares, pedigree analysis, and meiosis diagrams is essential for mastering these concepts.