DNA & Proteins: Chromosomes and Cells

DNA & Proteins: Chromosomes and DNA

• DNA stores and transmits genetic information, functioning similarly in all organisms.
• DNA is a helical, double-stranded molecule.
• In eukaryotes, DNA is bound to proteins (histones) within linear chromosomes located in the nucleus.
• In prokaryotes, DNA is unbound and circular, found in the cytosol, and also within mitochondria and chloroplasts of eukaryotes.
• DNA replication allows genetic information to be inherited.
• Base-pairing rules and the method of DNA replication are universal.
• DNA's structure includes nucleotide composition, pairing, and weak bonds allowing replication.
• Complementary base pairing (A-T and C-G) is crucial.
• Semi-conservative DNA replication is a fundamental biological process.

Types of Cells

• Cells are broadly categorized into prokaryotes and eukaryotes.
• Prokaryotic cells are typically smaller (1-10 µm) and lack a nucleus and membrane-bound organelles.
• Prokaryotic DNA is circular and located in the nucleoid region.
• Eukaryotic cells are typically larger (10-100 µm), possess a nucleus and membrane-bound organelles.
• Eukaryotic DNA is linear and located within the nucleus.

Prokaryotes

• Prokaryotes, like bacteria, are approximately 1µm in size.
• Their genetic material is a single circular piece of coiled DNA.
• Prokaryotes do not have a true nucleus (lack a membrane around the DNA).
• DNA is located in a region called the nucleoid.
• Prokaryotes have ribosomes.
• Prokaryotes do not contain membrane-bound organelles.

Eukaryotes

• Eukaryotic genetic material (DNA) is linear (chromosomes).
• Eukaryotic cells have a true (membrane-bound) nucleus.
• The region between the nucleus and the cell membrane is called the cytoplasm.
• Eukaryotic cytoplasm contains membrane-bound organelles with specialized functions.
• Eukaryotes typically range in size from 10 to 100µm.

Eukaryotes vs Prokaryotes

• Prokaryotic cells are small (1-10 µm), while eukaryotic cells are large (10-100 µm).
• Prokaryotic cells lack a nucleus, while eukaryotic cells have a nucleus.
• Prokaryotic cells have a low level of internal organization, while eukaryotic cells have a high level of internal organization.
• Prokaryotic organelles are not bound by membranes, while eukaryotic organelles are membrane-bound.
• Prokaryotes typically have one circular chromosome, while eukaryotes have multiple linear chromosomes.
• Prokaryotes often lack extra-chromosomal DNA; eukaryotes, on the other hand, may have it in the form of plasmids or DNA in chloroplasts and mitochondria.
• Most prokaryotic cells have peptidoglycan in their walls. Walls of eukaryotic cells may be made of polysaccharides (e.g cellulose, chitin).

A Little Bit of Chemistry

• Matter is composed of atoms.
• Atoms of different elements bond to form molecules, requiring energy.
• Macromolecules (large numbers of atoms) are held together by numerous bonds and contain substantial energy.
• Living organisms are largely composed of carbon, hydrogen, oxygen, and other elements like nitrogen, phosphorus, and sulfur (CHONPS).

Organic Molecules

• Macromolecules are all organic molecules containing carbon, hydrogen, and oxygen.
• Four major types of organic compounds in cells and organisms include proteins, lipids, carbohydrates/polysaccharides, nucleic acids.
• Each macromolecule type is synthesized from monomers (proteins from amino acids, carbohydrates from monosaccharides, and so forth.)

Nucleic Acids

• DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are two types of nucleic acids.
• DNA stores and transmits genetic information needed to direct cell processes.
• DNA's structure was discovered by Watson and Crick.

Universal DNA

• DNA is universal across all species on Earth.
• Every species has a unique arrangement of DNA nucleotides, leading to variation.
• The number of chromosomes varies from species to species, as does the base sequence of genes and the length of DNA molecules.

DNA Structure

• DNA is a long chain molecule (polymer) composed of repeating sub-units called nucleotides.
• A nucleotide consists of a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base.
• There are five nitrogenous bases (Adenine, Cytosine, Guanine, Thymine, Uracil).
• DNA comprises two strands with complementary base pairs (A-T, C-G).
• These strands are held together by hydrogen bonds and form a double helix structure.

Complementary Bases

• DNA has four bases (A, T, G, and C), with A and G being purines and C and T being pyrimidines.
• Adenine always binds to thymine, and guanine always binds to cytosine (complementary base pairing).
• Identical amounts of A and T, and G and C in species' DNA is evidence of this.
• Complementary bases are held together by weak hydrogen bonds, making the strands easily separated.

DNA & Chromosomes

• DNA molecules are very long.
• In eukaryotes, DNA is "wrapped up" with proteins called histones, forming structures called chromatin.
• DNA is supercoiled using enzymes to compact it into chromosomes.
• The tightly packaged structure of DNA within chromosomes is essential for its efficient organization and function.

Chromosomes and Number in Humans

• Humans have 46 individual chromosomes arranged in 23 pairs.
• One pair (sex chromosomes: XX or XY) determine gender.
• The other 22 pairs (autosomes) influence various characteristics.
• Errors in DNA replication sometimes result in disorders (e.g. Klinefelter's Syndrome, Down Syndrome).

Genetic Diseases in Humans

• Errors in DNA can lead to genetic diseases.
• Extra or missing chromosomes, or errors within genes, can cause significant health problems.
• Common genetic diseases include Klinefelter’s, Down Syndrome, Hemochromatosis, Cystic Fibrosis, Huntington disease, Deafness, Sickle cell disease, Neurofibromatosis, Marfan syndrome, Tay Sachs disease, Fragile X.

Genes

• Genes are segments of DNA on chromosomes that contain instructions for making a protein or RNA.
• Each gene has a specific location (locus) on a chromosome.
• Examples include the genes for keratin (hair, nails, skin), colour vision, and cystic fibrosis (chr 7).

Chromosomes: Summary

• Chromosomes are the structural units of genetic information.
• Chromatin is the thread-like structure composed of DNA wrapped around proteins (histones), present when the cell isn't dividing.
• Chromatids are duplicate copies of chromosomes, visible during cell division (mitosis and meiosis).
• Each pair of chromosomes has equivalent genes, although specific codes differ between species.

C Words

• Cancer is uncontrolled cell division where cells reproduce rapidly.
• Centrioles are microtubules that form a spindle, essential for cell division.
• Centromere binds sister chromatids and is a key element involved in cell division.
• Centrosomes include two centrioles.
• Chromatids are duplicate copies of chromosomes.
• Chromatin is DNA and protein strands.
• Chromosomes are DNA strands carrying genetic information.
• Cytokinesis is the splitting of the cytoplasm.

Telomeres

• Telomeres are repeating DNA sequences at the ends of chromosomes.
• They protect the chromosome ends from damage and prevent them from fusing together.
• Telomeres do not code for genes. They are repetitive sequences.

Websites and Videos

• (Various websites and videos are listed here). Note these are links to outside websites and resources, not part of the generated summary.

Explore the fundamental concepts of DNA and proteins, focusing on their structure, replication, and the differences between prokaryotic and eukaryotic cells. This quiz delves into the intricate mechanisms of genetic information storage and transmission. Understand the universal nature of DNA replication and its implications in biology.