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, typically with a hydrogen:oxygen atom ratio of 2:1.
Monosaccharide: The simplest carbohydrate, also known as simple sugars (e.g., glucose).
Disaccharide: Consists of two monosaccharides joined by a glycosidic linkage (e.g., maltose).
Glycosidic linkage: A covalent bond formed between two monosaccharides by a dehydration reaction.
Polysaccharide: Polymers of many monosaccharides, serving storage (starch, glycogen) or structural (cellulose) roles.
Starch: A storage polysaccharide in plants, composed of glucose monomers.
Glycogen: A storage polysaccharide in animals, also composed of glucose.
Cellulose: A structural polysaccharide in plant cell walls, composed of β-glucose monomers.

Section 3.4: Lipids

Lipids are hydrophobic molecules, including fats, phospholipids, and steroids, that serve as energy storage, membrane structure, and signaling molecules.

Lipid: A diverse group of hydrophobic molecules, not true polymers.
Fat: Constructed from glycerol and fatty acids; used for energy storage.
Fatty acid: A long hydrocarbon chain with a carboxyl group at one end.
Saturated fatty acid: No double bonds between carbon atoms; solid at room temperature.
Unsaturated fatty acid: One or more double bonds; liquid at room temperature.
Phospholipid: Two fatty acids and a phosphate group attached to glycerol; major component of cell membranes.
Steroid: Lipids with a carbon skeleton consisting of four fused rings (e.g., cholesterol).
Cholesterol: An important steroid in animal cell membranes and precursor for other steroids.

Section 3.5: Proteins

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

Polypeptide: A polymer of amino acids linked by peptide bonds.
Amino acid: The monomer of proteins, containing an amino group, carboxyl group, hydrogen atom, and R group.
Protein: One or more polypeptides folded into a specific three-dimensional structure.
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: Four levels: primary (sequence), secondary (α-helix, β-sheet), tertiary (3D folding), quaternary (multiple polypeptides).
Denaturation: Loss of protein structure (and function) due to environmental changes (e.g., heat, pH).

Section 3.6: Nucleic Acids

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

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

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 chromosome number of somatic cells.
Somatic cell: Any cell in the body except gametes; diploid.
Locus: The specific location of a gene on a chromosome.
Asexual reproduction: Offspring arise from a single parent; genetically identical (clones).
Clone: A genetically identical individual produced by asexual reproduction.
Sexual reproduction: Offspring arise from the fusion of gametes; genetically diverse.

Section 10.2: Chromosome Sets

Karyotype: The ordered display of an organism’s chromosomes.
Homologous chromosome: Chromosome pairs with the same genes but possibly different alleles.
Sex chromosome: Chromosomes that determine sex (X and Y in humans).
Autosome: Non-sex chromosomes.
Diploid (2n): Two sets of chromosomes.
Haploid (n): One set of chromosomes.
Fertilization: Fusion of gametes to form a diploid zygote.
Meiosis: Cell division that reduces chromosome number by half, producing haploid gametes.

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 carrying 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 pairs during meiosis I, leading to genetic variation.
Recombinant chromosome: Chromosomes with new combinations of alleles due to crossing over.
Random fertilization: Any sperm can fertilize any egg, further increasing genetic diversity.

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 segregation and independent assortment.

Character: A heritable feature (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 F1 individuals.
Law of segregation: Two alleles for a gene separate during gamete formation.
Allele: Alternative versions of a gene.
Dominant allele: Expressed in the phenotype if present.
Recessive allele: Masked in the phenotype unless homozygous.
Punnett Square: Diagram to predict the genetic outcome of a cross.
Homozygous / homozygote: Two identical alleles for a gene.
Heterozygous / heterozygote: Two different alleles for a gene.
Phenotype: Observable traits.
Genotype: Genetic makeup.
Test cross: Cross with a homozygous recessive to determine genotype.
Monohybrid / Monohybrid cross: Cross involving one gene.
Dihybrid / Dihybrid cross: Cross involving two genes.
Law of Independent Assortment: Genes on different chromosomes assort independently during gamete formation.

Section 11.3: Extensions of Mendelian Genetics

Complete dominance: Phenotype of heterozygote is the same as homozygous dominant.
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 influence a single trait.

Section 11.4: Human Genetics

Pedigree: Diagram showing inheritance patterns in families.
Carrier: Heterozygote for a recessive disorder allele.
Multifactorial disorder: Disorders influenced by genetic and environmental factors.

Chapter 12: Chromosomal Basis of Inheritance

Overview and Section 12.2: Chromosome Theory and Sex-Linked Genes

Chromosome theory of inheritance: Genes are located on chromosomes, which segregate and assort independently.
Homologous chromosome: Chromosome pairs with the same genes.
Sister chromatid: Identical copies of a chromosome.
Gamete: Reproductive cell.
Sex-linked gene: Gene located on a sex chromosome (usually X).
X-linked gene: Gene located on the X chromosome.

Section 12.4: Chromosomal Alterations

Nondisjunction: Failure of chromosomes to separate properly during meiosis.
Aneuploidy: Abnormal number of chromosomes.
Monosomic: Missing one chromosome (2n-1).
Trisomic: Extra chromosome (2n+1).
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. Formation of Maltose from Glucose

When two glucose molecules join via a dehydration reaction, a water molecule is lost. The formula for glucose is C6H12O6. The formula for maltose is C12H22O11 because one H2O is removed during bond formation.

Equation:
Explanation: The loss of one water molecule (H2O) accounts for the difference in the formula.

2. Inheritance of Parental Traits

Traits are inherited through the transmission of genes from parents to offspring. During fertilization, offspring receive one allele from each parent for each gene, and the combination of these alleles determines the phenotype (observable trait), such as hair color.

3. Offspring Genotype Proportions from AA x Aa Cross

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

4. Red-Eyed Female x White-Eyed Male Drosophila Cross

Genotypes: Female (XRXR), Male (XrY)
Punnett Square:

Punnett square for red-eyed female x white-eyed male Drosophila cross

Predicted offspring: All females (XRXr) are red-eyed; all males (XRY) are red-eyed.
Why more males are white-eyed: The gene is X-linked; 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 be white-eyed.