Exam 3 Review Notes

Chapter 11

  • DNA Basics

    • Function: Stores genetic material.
    • Encoding Information: Information encoded in the sequence of nucleotides.
    • Packaging: DNA is packaged into chromosomes stored in the nucleus.

  • Levels of Nucleotide Organization:

    • Nucleotide
    • Single strand
    • Double Helix
    • Chromosome
    • Genome

  • DNA Nucleotides: Composed of a phosphate group, deoxyribose sugar, and a nitrogenous base.

  • Nitrogenous Bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T).

  • RNA Base: RNA contains Uracil (U) instead of Thymine (T).

  • Strands Orientation: Strands run anti-parallel in the double-stranded helix.

  • Complementary Base Pairing Example:

    • Given 30% C, the % of A = 20% (A pairs with T, and C pairs with G).
    • For strand 5’-AGT CGC TTC GAT ATT-3’, complementary strand = 3’-TCA GCG AAG CTA TAA-5’ (leading strand, since it runs 5’-3’ continuously).

  • Replication:

    • Semi-Conservative: Each new helix has one parental strand and one daughter strand.
    • Lagging strand produced as Okazaki fragments.

Chapter 12

  • Flow of Genetic Material:

    • DNA → RNA → Polypeptide.

  • Transcription: Copying DNA nucleotides to RNA nucleotides.

  • Translation: Sequence of mRNA converted into amino acids.

  • mRNA Sequence from DNA:

    • Coding strand (5’-ACG TAG GCA CCT ATC-3’): Corresponding mRNA = 5’-ACG UAG GCA CCU AUC-3’.
    • Non-coding template strand (3’-CGA ATG AGC GTA CCT-5’): Corresponding mRNA = 5’-GCU UAC UCG CAU GGA-3’.

  • Transcription Stages:

    • Initiation: RNA polymerase binds to promoter.
    • Elongation: RNA polymerase synthesizes complementary RNA strand.
    • Termination: Transcription ends, polymerase dissociates.

  • Codon: Sequence of 3 nucleotides coding for a specific amino acid.

  • tRNA Function: Brings amino acids to the ribosome.

  • Splicing: Introns removed, exons joined by the spliceosome.

Chapter 15

  • Protein Function: Determined by structure/shape.

  • Structure/Shape Determination: Defined by amino acid sequence.

  • Gene Mutations: Alter DNA sequence of a gene.

  • Types of Mutations:

    • Point Mutation: Substitution of a single base pair.
    • Silent Mutation: Codon codes for the same amino acid (does not change protein structure/function).
    • Missense Mutation: Codon codes for a different amino acid (can change protein structure/function).
    • Nonsense Mutation: Encodes a STOP codon, resulting in shorter proteins.

  • Cancer Development:

    • Stages: Initiation (mutation), followed by promotion (proliferation of mutated cells).
    • p53 Gene: Tumor suppressor gene involved in regulating cell division.
    • Thymine Dimer: Caused by UV exposure, can impair p53 gene function, leading to skin cancer.

  • Proto-oncogenes vs Tumor Suppressor Genes:

    • Proto-oncogenes: Normal genes that promote cell division when mutated become oncogenes.
    • Tumor suppressor genes: Prevent cell division; loss of function leads to cancer.
    • Apoptosis: Programmed cell death.

Chapter 16

  • Chromosome Sets:

    • Diploid: 2 sets of chromosomes.
    • Haploid: 1 set of chromosomes.
    • Polyploid: 3 or more sets of chromosomes.

  • Human Chromosome Sets:

    • One set = 23 chromosomes.
    • Autosomal Chromosomes: 22 pairs (not sex-related).
    • Sex Chromosomes: 1 pair (determines gender; XX or XY).

  • Cell Cycle Stages:

    • G1 phase
    • S phase (DNA replication occurs here)
    • G2 phase
    • M phase (mitosis or meiosis)

  • Mitosis: Diploid parent cell divides into 2 genetically identical diploid daughter cells.

  • Meiosis: Process divides a diploid cell to produce 4 haploid gametes (2 rounds: Meiosis I and II).

    • Bivalents form during Prophase I (crossing over).

Chapter 17

  • Gene Variations: Different forms of genes are called alleles.

  • Trait Forms: Dominant and recessive traits.

  • Genotype vs Phenotype:

    • Genotype: Genetic makeup.
    • Phenotype: Observable characteristics.

  • Pedigree Analysis:

    • Autosomal recessive disorder: Not all generations affected, affected offspring from unaffected parents.
    • X-linked Recessive Traits: More frequent in males.

  • Dominance Relationships:

    • Incomplete Dominance: Heterozygote exhibits intermediate phenotype.
    • Codominance: Both dominant alleles expressed.

  • Environmental Influence: Affects phenotypic expression.

  • Polygenic Traits: Traits like height influenced by multiple genes.

  • Mendelian Genetics Example:

    • In cows: Black fur (B) dominant, brown fur (b) recessive. Heterozygous cross results in 25% (¼) chance of brown calf.
    • Red-green colorblindness: X-linked recessive disorder. Genotypes: Adam (XAXa), Eve (XAXA). Boy's probability of being colorblind = 50% (½).