Introduction to Human Genetics Quiz

Course Information

• Course Title: Introduction to Human Genetics
• Course Code: PTH241
• Instructor: Hanan H. Fouad
• Department: Faculty of Physical Therapy
• University: Galala University
• Semester: Fall 2024

Intended Learning Outcomes

• Define genetics and understand its applications.
• Comprehend the central dogma of molecular biology.
• Identify the differences between genes, genome, and chromosomes.
• Describe the number, structure, and classification of human chromosomes.
• Distinguish crucial scientific terms in genetics.
• Explain the phases and checkpoints of the cell cycle.

Genetics

• Definition: The study of genes, genetic variations, and heredity in organisms.
• Applications: Useful method for studying hereditary diseases, cancer, bacteria, viruses, and forensic medicine. Used to produce large quantities of organic molecules (hormones, antibodies, antibiotics, vaccines) and important in personalized medicine.

Important Scientific Terms

• Chromosome: Thread-like structures made of DNA that carry genetic information.
• Gene: Specific length of DNA with a specific sequence of nucleotides. Located at a specific locus on a chromosome and codes for the synthesis of a specific protein.
• Genome: The entire length of the nuclear DNA of an organism.

Alleles

• Definition: Varieties of the same gene with different sequences of nucleotides located at the same locus.
• Types:
  • Dominant alleles: Alleles always expressed in phenotypes.
  • Recessive alleles: Expressed only when dominant alleles are absent (e.g., homozygous aa).
  • Homozygous: Having two identical alleles of a particular gene.
  • Heterozygous: Having two different alleles of a particular gene.

Genotype vs. Phenotype

• Genotype: The genetic constitution (AA, Aa, aa) of an organism, inherited to offspring.
• Phenotype: The observable characteristics (traits) of an organism, resulting from interactions between genes and the environment.

Gene Expression

• Central dogma of molecular biology: DNA → RNA → Protein.
• Describes the flow of genetic information from DNA to RNA to proteins.
• Proteins carry biological and pathological functions in organisms.

Diploid vs. Haploid Cells

• Somatic cells: Diploid cells containing 23 pairs of chromosomes (22 pairs of autosomal and one pair of sex chromosomes).
• Germ cells (gametes): Haploid cells containing 22 autosomal chromosomes and one sex chromosome.

Homologous Chromosomes

• A pair of chromosomes; one paternal and one maternal.
• Have the same length, centromere position, and genes located at the same loci.
• Can be genetically different due to different alleles (e.g., sex chromosomes X and Y).

Types of Chromosomes (1)

• Single chromosomes (s-chromosomes): Made of one DNA molecule.
• Double chromosomes (d-chromosomes/mitotic chromosomes): Formed during DNA replication. Contain two chromatids linked at the centromere.

Types of Chromosomes (2)

• Metacentric: Centromere in the middle.
• Submetacentric: Centromere slightly off-center.
• Acrocentric: Centromere close to one end.
• Telocentric: Centromere at the end.

Types of Chromosomes (3)

• Autosomal chromosomes: Paired chromosomes in somatic cells with the same length, shape, position of the centromere, and genetic information. Carry genes for somatic characteristics.
• Sex chromosomes: Paired chromosomes that differ between males and females. Carry genes for sex characteristics.

Karyotyping

• An individual's complete set of chromosomes.
• A laboratory-produced image of chromosomes isolated from an individual cell, arranged in numerical order.
• Used to look for abnormalities in chromosome number or structure.
• In females, one X chromosome is heterochromatic (Barr body).
• Importance: Regulates the amount of X-linked gene products being transcribed.

Human Chromosome Nomenclature

• Showing the short and long arms, subdivided into regions and bands.

Numbering System of G Bands

• Detailed system for classifying bands on chromosomes (p and q-arms).

Telomeres

• Repetitive DNA sequences (TTAGGG) at the ends of linear chromosomes.
• Form a capped end structure.
• Protect chromosome ends from being ligated together, attacked by exonucleases, and preventing genomic instability, cell death, or cancer.
• Telomeres compensate for incomplete replication of linear chromosome ends.
• Telomeres attach chromosomes to the nuclear envelope (NE lamina) during meiosis.
• Telomeres allow repair systems to distinguish true ends of chromosomes from broken DNA.

Telomerase

• Enzyme that extends the 3' end of DNA.
• Replicates and maintains telomeric length in certain cell types (e.g., germ line cells, stem cells, and cancer cells).

Cell Cycle

• Interphase: Period of cell growth and DNA replication (G1, S, G2).
  • G1: Cell growth and organelle duplication.
  • S: DNA replication, creating identical copies.
  • G2: Preparing for mitosis, protein synthesis.
• Mitosis: The process of cell division.
  • Prophase, Metaphase, Anaphase, Telophase.
• Checkpoints: Ensure DNA and chromosomal structure are intact before proceeding.

Assignments

• Mitosis (Week 1)
• DNA, RNA structure, types (Week 2)
• Replication (Week 3)
• Transcription (Week 4)
• Translation (Week 5)

Test your understanding of human genetics, including key definitions, the structure of chromosomes, and the phases of the cell cycle. This quiz will challenge your knowledge on the applications and importance of genetics in various fields. Prepare to distinguish between crucial scientific terms as you dive into the fascinating world of genes and heredity.