Class notes Biology

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Class notes Biology

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2024/2025

Institution Freshman / 9th Grade

Course Biology

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In biology, the study of DNA, cells, mitosis, and meiosis is fundamental to understanding the building blocks of life. DNA, or deoxyribonucleic acid, is a molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known organisms. It is composed of two strands that coil around each other to form a double helix structure. DNA contains the genetic information that is passed from one generation to the next, and it plays a crucial role in determining an organism's traits. Cells are the basic structural and functional units of all living organisms. They can be classified into two main types: prokaryotic cells, which lack a nucleus and membrane-bound organelles, and eukaryotic cells, which have a distinct nucleus and membrane-bound organelles. Cells carry out various functions such as metabolism, growth, and reproduction, and they are capable of responding to stimuli from the environment. Mitosis is a process of cell division that results in two daughter cells with the same number of chromosomes as the parent cell. It is essential for growth, development, and tissue repair in multicellular organisms. During mitosis, the genetic material is duplicated and then segregated into two identical sets, ensuring that each daughter cell receives a complete set of chromosomes. Meiosis, on the other hand, is a type of cell division that occurs in sexually reproducing organisms. It involves two successive divisions that result in the production of four daughter cells, each with half the number of chromosomes as the parent cell. Meiosis is essential for the formation of gametes (sperm and egg cells) and contributes to genetic diversity through the process of genetic recombination. Understanding the intricacies of DNA, cells, mitosis, and meiosis is crucial for comprehending the mechanisms underlying life processes and inheritance. It provides insights into the diversity of life forms and the underlying principles that govern biological systems.

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‭Science‬‭Exam‬‭review‬
‭DNA‬
-‭ ‬‭Carbon,‬‭Nitrogen,‬‭Phosphorus,‬‭Oxygen,‬‭and‬‭Hydrogen‬
‭-A‬‭double‬‭helix‬‭formed‬‭from‬‭two‬‭complementary‬‭strands‬‭of‬‭nucleotides‬‭held‬‭together‬‭by‬‭hydrogen‬‭bonds‬
‭between‬‭g-c‬‭and‬‭A-t‬‭base‬‭pairs.‬‭Duplication‬‭of‬‭genetic‬‭information‬‭occurs‬‭by‬‭using‬‭one‬‭DNA‬‭strand‬‭as‬‭a‬
‭template‬‭for‬‭forming‬‭a‬‭complementary‬‭strand.‬
‭-Deoxyribonucleic‬‭acid=‬‭DNA‬
‭-Adenine‬‭(A),‬‭Thymine‬‭(T),‬‭Guanine‬‭(G),‬‭and‬‭Cytosine‬‭©‬
‭-Nucleotide‬‭parts=‬‭A‬‭sugar,‬‭and‬‭nitrogenous‬‭base,‬‭And‬‭a‬‭phosphate‬‭group‬
‭Phosphate‬‭group:‬‭The‬‭phosphate‬‭group‬‭is‬‭a‬‭molecule‬‭that‬‭consists‬‭of‬‭one‬‭phosphorus‬‭atom‬‭bonded‬‭to‬‭four‬
‭oxygen‬‭atoms.‬‭It‬‭plays‬‭a‬‭crucial‬‭role‬‭in‬‭various‬‭biological‬‭processes,‬‭particularly‬‭in‬‭the‬‭structure‬‭and‬
‭function‬‭of‬‭nucleic‬‭acids‬‭(DNA‬‭and‬‭RNA)‬‭and‬‭in‬‭cellular‬‭energy‬‭transfer‬‭through‬‭molecules‬‭like‬‭ATP‬
‭(adenosine‬‭triphosphate).‬
‭-DNA‬‭contains‬‭the‬‭instructions‬‭needed‬‭for‬‭an‬‭organism‬‭to‬‭develop,‬‭survive,‬ ‭and‬‭reproduce‬
‭-They‬‭have‬‭DNA‬‭as‬‭their‬‭genetic‬‭material=‬‭plants,‬‭animals,‬‭bacteria,‬‭and‬‭fungi‬
‭-The‬‭DNA‬‭in‬‭prokaryotes‬‭is‬‭contained‬‭in‬‭a‬‭central‬‭area‬‭of‬‭the‬‭cell‬‭called‬‭the‬‭nucleoid,‬‭which‬‭is‬‭not‬
‭surrounded‬‭by‬‭a‬‭nuclear‬‭membrane.‬
‭-‬‭for‬‭the‬‭eukaryote‬‭cells,‬‭it‬‭is‬‭the‬‭nucleus‬
‭-The‬‭four‬‭bases‬‭that‬‭make‬‭up‬‭the‬‭rungs‬‭of‬‭the‬‭DNA‬‭ladder‬‭are‬‭Adenine‬‭(A),‬‭Thymine‬‭(T),‬‭Guanine‬‭(G),‬‭and‬
‭Cytosine‬‭(C).‬
‭It‬‭is‬‭important‬‭that‬‭weak‬‭hydrogen‬‭bonds‬‭hold‬‭the‬‭strands‬‭together‬‭in‬‭the‬‭DNA‬‭double‬‭helix‬‭because‬‭these‬
‭weak‬‭bonds‬‭allow‬‭the‬‭DNA‬‭to‬‭unzip‬‭and‬‭replicate‬‭easily‬‭during‬‭processes‬‭such‬‭as‬‭DNA‬‭replication‬‭and‬
‭protein‬‭synthesis.‬‭If‬‭the‬‭bonds‬‭were‬‭too‬‭strong,‬‭it‬‭would‬‭be‬‭difficult‬‭for‬‭the‬‭DNA‬‭to‬‭separate‬‭and‬‭carry‬
‭out‬‭these‬‭essential‬‭biological‬‭processes.‬
‭-Three‬‭scientists‬‭who‬‭significantly‬‭contributed‬‭to‬‭the‬‭discovery‬‭of‬‭the‬‭structure‬‭of‬‭DNA‬‭are‬‭James‬
‭Watson,‬‭Francis‬‭Crick,‬‭and‬‭Rosalind‬‭Franklin.‬
‭-‬‭James‬‭Watson‬‭and‬‭Francis‬‭Crick‬‭are‬‭credited‬‭with‬‭discovering‬‭the‬‭double‬‭helix‬‭structure‬‭of‬‭DNA‬‭in‬
‭1953.‬‭Their‬ ‭model‬‭revealed‬‭that‬‭DNA‬‭is‬‭made‬‭up‬‭of‬‭two‬‭strands‬‭that‬‭twist‬‭around‬‭each‬‭other‬‭in‬‭a‬‭spiral,‬
‭forming‬‭a‬‭double‬‭helix.‬

, -‭ ‬‭Rosalind‬‭Franklin,‬‭a‬‭biophysicist,‬‭made‬‭critical‬‭contributions‬‭to‬‭the‬‭understanding‬‭of‬‭DNA's‬
‭structure‬‭through‬ ‭her‬‭X-ray‬‭diffraction‬‭images‬‭of‬‭DNA,‬‭which‬‭provided‬‭key‬‭insights‬‭into‬‭the‬‭helical‬
‭structure‬‭of‬‭DNA‬‭strands.‬
‭-DNA:‬‭Deoxyribonucleic‬‭acid,‬‭a‬‭molecule‬‭that‬‭carries‬‭the‬‭genetic‬‭instructions‬‭used‬‭in‬‭the‬‭growth,‬
‭development,‬‭functioning,‬‭and‬‭reproduction‬‭of‬‭all‬‭known‬‭living‬‭organisms‬‭and‬‭many‬‭viruses.‬

D‭ ouble‬‭helix:‬‭The‬‭structure‬‭formed‬‭by‬‭double-stranded‬‭molecules‬‭of‬‭nucleic‬‭acids‬‭such‬‭as‬‭DNA.‬‭It‬‭consists‬
‭of‬‭two‬‭helical‬‭polynucleotide‬‭strands‬‭coiling‬‭around‬‭a‬‭common‬‭axis.‬

N‭ ucleotide:‬‭The‬‭basic‬‭building‬‭block‬‭of‬‭nucleic‬‭acids‬‭such‬‭as‬‭DNA.‬‭It‬‭consists‬‭of‬‭a‬‭phosphate‬‭group,‬‭a‬
‭five-carbon‬‭sugar‬‭(deoxyribose‬‭in‬‭DNA),‬‭and‬‭a‬‭nitrogenous‬‭base.‬

P‭ hosphate:‬‭A‬‭molecule‬‭that‬‭consists‬‭of‬‭one‬‭phosphorus‬‭atom‬‭bonded‬‭to‬‭four‬‭oxygen‬‭atoms.‬‭It‬‭plays‬‭a‬
‭crucial‬‭role‬‭in‬‭various‬‭biological‬‭processes,‬‭particularly‬‭in‬‭the‬‭structure‬‭and‬‭function‬‭of‬‭nucleic‬‭acids‬
‭and‬‭in‬‭cellular‬‭energy‬‭transfer.‬

‭5-carbon‬‭sugar:‬‭The‬‭sugar‬‭component‬‭of‬‭a‬‭nucleotide,‬‭which‬‭in‬‭the‬‭case‬‭of‬‭DNA‬‭is‬‭deoxyribose.‬

N‭ itrogenous‬‭base:‬‭A‬‭nitrogen-containing‬‭molecule‬‭that‬‭has‬‭the‬‭same‬‭chemical‬‭properties‬‭as‬‭a‬‭base.‬‭In‬
‭DNA,‬‭the‬‭nitrogenous‬‭bases‬‭are‬‭adenine,‬‭thymine,‬‭guanine,‬‭and‬‭cytosine.‬

G‭ enetic‬‭material:‬‭The‬‭material‬‭of‬‭which‬‭the‬‭genes‬‭are‬‭composed.‬‭In‬‭living‬‭organisms,‬‭genetic‬‭material‬
‭is‬‭usually‬‭DNA,‬‭but‬‭in‬‭some‬‭viruses‬‭it‬‭is‬‭RNA.‬

C‭ hromatin:‬‭The‬‭material‬‭of‬‭which‬‭the‬‭chromosomes‬‭of‬‭organisms‬‭are‬‭composed.‬‭It‬‭consists‬‭of‬‭DNA‬‭and‬
‭associated‬‭proteins.‬

P‭ rokaryote:‬‭A‬‭type‬‭of‬‭cell‬‭that‬‭does‬‭not‬‭have‬‭a‬‭nucleus‬‭or‬‭other‬‭membrane-bound‬‭organelles.‬‭DNA‬‭in‬
‭prokaryotic‬‭cells‬‭is‬‭contained‬‭in‬‭a‬‭central‬‭area‬‭of‬‭the‬‭cell‬‭called‬‭the‬‭nucleoid.‬

E‭ ukaryote:‬‭A‬‭type‬‭of‬‭cell‬‭that‬‭has‬‭a‬‭nucleus‬‭and‬‭other‬‭membrane-bound‬‭organelles.‬‭In‬‭eukaryotic‬‭cells,‬
‭DNA‬‭is‬‭located‬‭within‬‭the‬‭nucleus.‬

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School year: 1
Uploaded on: September 23, 2024
Number of pages: 5
Written in: 2024/2025
Type: Class notes
Professor(s): Dr. allen
Contains: Biology

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