chapt04_Genetics and Cell function

The Unity of Form and Function

  • Overview of the chapter highlighting key anatomical and physiological concepts.

DNA Molecular Structure

  • DNA (Deoxyribonucleic Acid): A polymer made of nucleotides.

  • Nucleotide Components:

    • Sugar

    • Phosphate group

    • Nitrogenous base (Adenine, Guanine, Cytosine, Thymine, Uracil)

  • Types of Nitrogenous Bases:

    • Purines: Adenine (A), Guanine (G)

    • Pyrimidines: Cytosine (C), Thymine (T), Uracil (U)

DNA Structure

  • Molecular Shape: Double helix configuration.

  • Base Pairing:

    • A pairs with T

    • C pairs with G

  • Law of Complementary Base Pairing: One strand's base sequence dictates the other's.

Discovery of the Double Helix

  • Components of DNA known by 1900.

  • X-ray diffraction in 1953 revealed DNA's geometry.

  • Nobel Prize (1962) awarded to Watson, Crick, and Wilkins, with Rosalind Franklin's contributions recognized.

DNA Function

  • Gene: DNA segment coding for specific proteins.

  • Genome: Total set of genes in 23 pairs of chromosomes (~30,000 genes; ~2% coding DNA).

  • Chromosomal Structure: 46 chromosomes consisting of two sets of 23.

Chromatin and Chromosomes

  • Chromatin: DNA complexed with proteins (histones) in non-dividing cells.

  • Nucleosomes: Structural units of chromatin.

  • Dynamic changes reflecting gene activity.

RNA: Structure and Function

  • RNA: Smaller than DNA (single-stranded).

  • Sugar: Ribose instead of deoxyribose; Uracil replaces thymine.

  • Types of RNA:

    • mRNA, rRNA, tRNA

  • Functions to interpret DNA code for protein synthesis.

Comparison of DNA and RNA

  • Sugar: Deoxyribose in DNA; Ribose in RNA.

  • Bases: DNA (A, T, C, G); RNA (A, U, C, G).

  • Structure: DNA (double helix); RNA (single strand).

Genetic Code

  • Code System: Four nucleotides encoding amino acid sequences.

  • Base Triplet: Three nucleotides corresponding to one amino acid (Codon in mRNA).

  • Ribosomes and tRNA play crucial roles in protein synthesis.

Summary of Protein Synthesis

  • Transcription: DNA to mRNA in the nucleus.

  • Translation: mRNA to protein primarily in cytoplasm.

Transcription Process

  • RNA Polymerase: Enzyme that synthesizes mRNA from DNA.

  • Terminator: Sequence that stops transcription.

  • Pre-mRNA Processing: Includes splicing of introns and exons.

Amino Acids and Translation

  • tRNA: Transfers amino acids to ribosomes.

  • Steps of translation involving mRNA and ribosomal functions.

Review of Peptide Formation

  • Sequence of DNA, mRNA codons, tRNA anticodons, and resultant peptide chains.

Protein Packaging and Secretion

  • Mechanisms involving rough ER and Golgi complex in processing proteins.

Gene Regulation Example: Casein Production

  • Role of prolactin in initiating gene transcription for breast milk components.

Genes and Hormonal Control

  • Hormonal pathways and their effects on enzyme production and gene control detected at the cellular level.

Synthesizing Compounds Other Than Proteins

  • Role of cells in synthesizing other compounds under enzymatic reactions, indirectly controlled by genes.

DNA Replication

  • Mechanisms including the roles of DNA helicase and DNA polymerase in replicating DNA.

  • Semiconservative Replication: Each new DNA helix contains one old strand and one new strand.

Errors and Mutations in DNA

  • Mutation Causes: Replication errors and environmental factors (radiation, chemicals).

  • Some mutations are benign while others may have serious consequences.

Cell Cycle Phases

  • Phases of the Cell Cycle:

    • Interphase (G1, S, G2)

    • M phase (division)

    • G0 phase (quiescent state)

Chromosomes in Cell Division

  • Overview of chromosomal behavior as cells prepare to divide.

Timing of Cell Division

  • Conditions that stimulate or inhibit cell division:

    • Nutrient availability

    • Growth factor presence

    • Environmental cues

Heredity and Chromosome Structure

  • Heredity: Genetic transmission from parents to offspring.

  • Chromosomal structure: homologous pairs, diploid vs haploid.

Karyotypes and Genetic Organization

  • Karyotype: Visual representation of chromosomes.

  • Locus and Alleles: Gene location and variation in forms.

Dominant and Recessive Alleles in Genetics

  • Genotype and Phenotype: Definitions and examples of dominant and recessive traits.

Genetics: Punnett Squares and Inheritance Patterns

  • Visual representation of genetic crosses and probability of traits.

Multiple Alleles and Codominance

  • Genetic traits influenced by multiple alleles and examples of codominance.

Polygenic Inheritance

  • Traits influenced by multiple genes and the resulting phenotypic variability.

Pleiotropy and Genetic Effects

  • One gene could affect multiple traits, via examples like sickle-cell disease.

Sex Linkage in Genetics

  • Traits linked to sex chromosomes and their inheritance patterns.

Environmental Effects on Traits

  • Penetrance and the interaction of environmental factors on phenotype expression.

Common Myths in Genetics

  • Dominance of alleles in populations, including misconceptions about allele frequency.

Cancer and Tumor Growth

  • Differentiation between benign vs malignant tumors and their growth patterns.

Causes of Cancer

  • Overview of carcinogens and types of cancers based on tissue origin.