Molecular Genetics

9th grade biology

Smooth (S) strain

A virulent strain of Streptococcus pneumoniae characterized by its smooth appearance due to a polysaccharide capsule, which protects it from the host's immune response.

Rough (R) strain

Bacterial strain that lacks a protective capsule, leading to a rough appearance and reduced virulence compared to the smooth strain.

pathogenic

A type of bacteria capable of causing disease, characterized by the presence of a smooth polysaccharide capsule that aids in evading the host's immune response.

transformation

The process by which a bacterium takes up foreign DNA from its environment and incorporates it into its own genome, potentially changing its genotype and phenotype.

bacteriophage

A virus that infects and replicates within bacteria, often used in molecular genetics and biotechnology.

x-ray

A type of radiation that can penetrate biological tissues, often used in imaging and therapeutic applications in medical settings.

crystallography

A scientific method using X-ray diffraction to determine the atomic and molecular structure of crystallized substances.

What was Griffith’s expiriment

he injected mice with a mix of heat killed S strain and live R strain bacteria. He found out that the harmless strain transformed into a lethal strain, killing the mice.

What were Griffith’s findings

his experiment showed that bacteria can transfer genetic information through a process called transformation.

What was Avery’s experiment

He found that removing DNA from heat villed virulent bacterua stopped them from transforming non virulent bacteria, proving DNA holds hereditary information.

What were Avery’s findings

He identifies that DNA, not protein, is the transforming principle responsible for transforming genetic information.

What was Hershey and Chase’s experiment

the used bacteriophage viruses labeled with radioactive tracers, they demonstrated that only the phosphorus labeled DNA entered the bacteria to produce new viruses.

What were Hershey and Chase’s findings

they proved that DNA is the genetic material.

What was Chargaff’s expirement.

he used chromatography and UV spectrophotometry to analyze the base composition of DNA across various species.

What were Chargaffs findings.

Chargaff's findings demonstrated that in DNA, the amount of adenine equals thymine and the amount of guanine equals cytosine. This rule provided key insights into the base-pairing mechanism in the structure of DNA.

What was Franklin and Wlkins’ experiment

they used X-ray cystalography to determine the physical structure of DNA.

What were Franklin and Wilkin’s finding

They revealed that DNA is a double helix with phosphate groups on the outside anf specific structural spacing.

What was Watson and Crick’s experiment.

they used existing x ray diffraction data. they built physical, cardboard cutout models of DNA, they determined the structure of DNA is a double helic, providing the key to how genetic info is stored and replicated.

What were Watson and Crick’s findings

they found that DNA consists of two antiparallel sugar-phosphate backbones connected by base pairs, twisting into a double helix.

What us complementary base pairing

the matching of nitrogen bases in DNA and RNA.

What is the nucleoid Region

a non-membrane found region in prokaryotic cells containing mos of the genetic material.

Where is DNA locted in Prokaryotic cells

the nucleoid region.

Where is DNA located in Eukaryotic cells

the nucleus

What is the monomer that makes up nucleic acids.

the nucleotide

What is replication

the biological process of producing two identical replicas of DNA from one original DNA molecule, occurring in all living organisms.

what is DNA helicase

an essential enzyme that acts as a "molecular motor," utilizing energy from ATP hydrolysis to break hydrogen bonds between complementary base pairs in double-stranded DNA.

what is the replication fork

a Y-shaped structure formed during DNA replication where the double-stranded DNA helix is unwound into two single strands.

what is semi-conservative replication.

the mechanism of DNA replication where the two strands of the original double helix separate, and each acts as a template for a new complementary strand.

what is a parent strand vs. a daughter strand.

The parent (or template) strand is the original DNA strand used as a blueprint during replication, while the daughter (or new) strand is the newly synthesized complementary strand.

Where does DNA replication occur

the nucelus

what is the goal of DNA replication

to create an identical copy of a cell's DNA before cell division, ensuring that each new daughter cell receives a complete and accurate set of genetic instructions.

what phase does DNA replication occur

s phase

Where is helicase found

at the replication fork during replication.

what steps are involved in DNA replication

to create an identical copy of a cell's DNA before cell division, ensuring that each new daughter cell receives a complete and accurate set of genetic instructions.

what are the enzymes in DNA and what are the functions

helicase (unwinds the helix), DNA polymerase (synthesizes new DNA), primase (initiates synthesis with RNA primers), ligase (joins fragments), and topoisomerase (relieves torsional strain)

how does the spell checl function work in DNA replication

DNA spell-checking (proofreading) occurs during replication when DNA polymerase detects a mismatched base, stops, and reverses its direction. It uses exonuclease activity to remove the wrong nucleotide and replaces it with the correct one, improving accuracy 100- to 1000-fold. Mismatch repair (MMR) enzymes later correct any errors missed during this process.

what is RNA

RNA (Ribonucleic Acid) is a crucial, usually single-stranded nucleic acid found in all living cells that acts as a versatile molecular messenger and worker. Its primary role is to interpret DNA genetic information to create proteins via translation.

what is mRNA

Transcribed from DNA, mRNA acts as a template for protein synthesis, carrying the genetic code from the nucleus to the ribosome.

what is rRNA

Associates with proteins to form ribosomes, acting as the structural and functional site where proteins are assembled.

what is tRNA

• Smallest type (75-95 nucleotides) that decodes mRNA by delivering specific amino acids to the ribosome during protein translation.

what is a gene

the basic physical and functional unit of heredity, composed of specific DNA or RNA sequences located on chromosomes.

what is a protein

large, complex biomolecules essential to all living organisms, composed of one or more long chains of amino acids

what is a ribosome

essential molecular machines found within all living cells that act as protein factories, translating genetic instructions from messenger RNA (mRNA) into functional proteins.

what is the promoter region

A promoter region is a specific DNA sequence located upstream () of a gene's coding sequence that initiates gene transcription. It acts as a binding site for RNA polymerase and regulatory transcription factors, acting as a molecular switch to ensure genes are expressed in the correct cells, at the right time, and in appropriate amounts.

what is transcription

ranscription is the first step of protein synthesis, where a specific segment of DNA (a gene) is copied into a complementary messenger RNA (mRNA) molecule by the enzyme RNA polymerase.

what is translation

Translation is the process where ribosomes in a cell's cytoplasm create proteins by decoding messenger RNA (mRNA) sequences into a chain of amino acids. It is the second step of protein synthesis (following transcription), converting genetic information from a nucleotide code into a functional protein code.

what is a anticodon

An anticodon is a three-nucleotide sequence located on a transfer RNA (tRNA) molecule that is complementary to a specific codon in messenger RNA (mRNA).

what is an amino acid

organic compounds that serve as the fundamental building blocks of proteins, essential for life.

what is a peptide bond

a covalent chemical bond linking two amino acids together, formed via a condensation reaction between the carboxyl group of one amino acid and the amino group of another, releasing a water molecule. These amide-type bonds are rigid, planar, and form the backbone of proteins.

what is a polypeptide

a long, unbranched chain of amino acids linked together by peptide bonds, typically containing 50 or more amino acids.

what is the central dogma of biology

DNA → RNA → Protein

what is a point mutation

a genetic alteration where a single nucleotide base pair in the DNA or RNA sequence is substituted, added, or deleted. These "single-letter" changes, often occurring due to DNA replication errors or environmental factors like UV light, can result in silent, dysfunctional, or altered proteins.

what is substitution

a type of genetic mutation where a single nucleotide base (A, T, C, or G) in a DNA sequence is replaced by a different base. Often called a point mutation, this change can alter the resulting protein's amino acid sequence. While many substitutions are neutral, some can cause functional changes in proteins, leading to diseases like sickle cell anemia.

what is insertion

a type of genetic mutation where one or more nucleotide base pairs are added into a DNA sequence. This addition can change the reading frame of the genetic code, leading to the production of nonfunctional or different proteins. Insertions can range from a single base to large segments of a chromosome

what is deletion

a genetic error where one or more nucleotides (DNA bases) are removed from a DNA sequence. These mutations can range from the loss of a single base pair to large segments of a chromosome, often leading to nonfunctional proteins

what is a frameshift mutation

a genetic mutation caused by the insertion or deletion of nucleotides (DNA bases) in a number not divisible by three. Because DNA is read in three-letter codons, this shifts the "reading frame," resulting in a completely different, often dysfunctional, protein sequence. These mutations frequently lead to premature stop codons or significant changes in amino acid sequences.

what is the reading frame

a method of dividing a nucleotide sequence (DNA or RNA) into consecutive, non-overlapping triplets called codons, which are translated into amino acids during protein synthesis. Because genetic code is read in three-base sets, there are three possible reading frames for each strand, determined by the starting nucleotide.

what are three types of point mutations

• Silent Mutation:

  A substitution that changes a codon, but due to the redundancy of the genetic code, it still codes for the same amino acid, resulting in no change in the protein.

• Missense Mutation: A substitution that changes a codon to code for a different amino acid, which may alter or diminish the function of the resulting protein.

• Nonsense Mutation: A substitution that converts a codon that codes for an amino acid into a premature stop codon, causing the protein to be shortened and usually nonfunctional.

what point mutations result in frameshift mutations

insertions (the additions of letters to the dna squence) and deletion (the removal of letters from the dna sequence)

which point mutation never results in a frame shift mutation

substution

what are 3 causes of mutations.

spontaneous errors during replication, natural chemical instability of DNA, or externam factors like UV radiation and chemicals.