BIO EXAM 3 PPTX2 Lecture 23

Flashcards

  • DNA molecule

    • Definition: A DNA molecule is a long chain of nucleotides that contains the genetic information of an organism. It is composed of deoxyribonucleic acid, which carries instructions for development, functioning, growth, and reproduction.

  • Allele

    • Definition: An allele is a variant form of a gene that can occupy the same locus on a chromosome. Alleles are responsible for the variations in traits among individuals.

  • Gene

    • Definition: A gene is a segment of DNA that contains the necessary information to produce a functional product, usually a protein. Genes are the basic units of heredity.

  • Chromosome

    • Definition: A chromosome is a DNA molecule that has been packaged into a compact structure. In eukaryotes, chromosomes are linear and contain DNA along with associated proteins.

  • Nucleus

    • Definition: The nucleus is a membrane-bound organelle found in eukaryotic cells that contains most of the cell's genetic material in the form of DNA organized into chromosomes.

  • Gene locus

    • Definition: The gene locus is the specific physical location of a gene on a chromosome. It is the address of a gene in the genomic map.

  • Genome

    • Definition: The genome is the complete set of genetic material present in an organism, including all of its genes and non-coding sequences.

  • Dermal papilla cells

    • Definition: Dermal papilla cells are specialized cells located in the skin that play a critical role in hair growth and the overall health of hair follicles.

  • Muscle cells

    • Definition: Muscle cells, also known as myocytes, are specialized cells that make up muscle tissue and are responsible for contraction and movement.

Lecture Objectives for Chapter 13

  • Explain why/how DNA is replicated

    • DNA replication is the process by which a cell duplicates its DNA before cell division, ensuring that each daughter cell receives an identical copy of the DNA.

  • List and describe the function of enzymes used in DNA replication

    • Key enzymes in DNA replication include:

    • DNA helicase: unwinds the double-stranded DNA.

    • DNA polymerase: adds nucleotides to the growing DNA strand.

    • DNA ligase: connects Okazaki fragments on the lagging strand.

  • Explain each step of DNA replication and which enzymes are used in each step

    • Initiation: starts at the origin of replication, initiated by helicase.

    • Elongation: DNA polymerase synthesizes the new strands.

    • Termination: completion of the newly synthesized strands occurs with ligase sealing gaps.

  • State the role of the template DNA and the 3' hydroxyl group

    • The template DNA provides the sequence for the new strand to be synthesized, and the 3' hydroxyl group is essential for DNA polymerase to add new nucleotides.

  • Describe the relationship between PCR and DNA replication

    • Polymerase Chain Reaction (PCR) mimics the natural DNA replication process but amplifies specific DNA sequences through repeated cycles of denaturation, annealing, and elongation.

Carbon Numbering

  • Carbon numbering in nucleotides:

    • 1': Nitrogenous base

    • 2': Type of sugar (ribose in RNA, deoxyribose in DNA)

    • 3': Hydroxyl group

    • 5': Phosphate group

  • Types of sugars:

    • Ribose: Sugar in RNA, has hydroxyl group on 2' carbon.

    • Deoxyribose: Sugar in DNA, lacks the oxygen on the 2' carbon.

Chromosomes in Eukaryotes and Prokaryotes

  • Definition of chromosome:

    • In prokaryotes: A single, circular DNA molecule.

    • In eukaryotes: A structure composed of DNA and proteins (histones) that carries genetic information.

  • Structure of chromosomes:

    • Arm: The long and short segments of the chromosome.

    • Sister chromatids: Duplicated chromosomes joined at the centromere.

    • Centromere: The region where sister chromatids are held together.

    • Telomere: The protective end caps of eukaryotic chromosomes.

DNA Packaging in Eukaryotes

  • Levels of DNA packing:

    • DNA double helix

    • Nucleosome: Core of eight histone molecules wrapped by DNA.

    • Chromatin: A complex of DNA and histone proteins.

    • Scaffold-associated chromatin: Higher-order chromatin structure.

    • Condensed heterochromatin: Tightly packed DNA during cell division.

    • Compacted chromosome: Highest level of DNA packaging before cell division.

  • Packing ratios:

    • The degrees to which DNA is packed:

    • 8000:1 in fully condensed chromosomes.

    • Variations include 10:1, 50:1, 250:1, and 5000:1 at different stages.

Anti-parallel Nature of DNA Strands

  • Anti-parallel orientation:

    • DNA strands run in opposite directions.

    • One strand runs from 5' to 3' while the complementary strand runs from 3' to 5'.

  • Implications of anti-parallel structure:

    • Important for replication and enzyme activity, as DNA polymerase can only add nucleotides to the 3' end of a growing strand.

Structural Features of DNA

  • Key features of DNA:

    • Double helix: The overall structure of DNA with uniform diameter resultant from base pairing.

    • Antiparallel: Strands run in opposite directions, affecting function and interactions.

    • Right-handed helicity: The twist direction of the helix.

    • Major and minor grooves:

    • Exposed nitrogenous bases allow proteins to interact with the DNA.

    • Complementary base pairing: Specific pairing between adenine and thymine (A-T), and cytosine and guanine (C-G) stabilizes the double helix.

Nitrogenous Bases and Hydrogen Bonding

  • Complementary base pairing

    • Adenine (A) pairs with Thymine (T) with two hydrogen bonds (A ::: T).

    • Guanine (G) pairs with Cytosine (C) with three hydrogen bonds (G ::: C).

  • Chargaff's Rule: The amount of adenine equals thymine, and the amount of guanine equals cytosine.

DNA Functions in Cells

  • Primary roles of DNA:

    • Store genetic information: Holds instructions for all cellular functions.

    • Mutability: DNA can undergo mutations, which can lead to disease or evolution.

    • Precise replication: Ensures genetic information is accurately copied for cell division.

    • Phenotype expression: Encodes the information necessary for the synthesis of proteins.

    • Binding sites: Enzymes and regulatory proteins can bind to DNA for various functions.

  • Site of DNA:

    • In eukaryotic cells: Located within the nucleus and nucleolus.

    • In prokaryotic cells: Localized within the nucleoid region.

  • Genome: The complete collection of an organism's genetic information, including all genes and non-coding sequences.