Molecular Structure of DNA and RNA in Genetics

Molecular genetics

Study of DNA structure and function at molecular level.

Genetic material

Substance responsible for inheritance of traits.

Four criteria of genetic material

Information, transmission, replication, variation required.

Information

Contains necessary data to create an organism.

Transmission

Passed from parent to offspring during reproduction.

Replication

Copied to ensure genetic continuity across generations.

Variation

Allows for phenotypic differences within species.

Griffith's experiments

Demonstrated transformation of bacteria using S and R strains.

Streptococcus pneumoniae

Bacteria studied by Griffith, with R and S strains.

Type S bacteria

Smooth strain with protective polysaccharide capsule.

Type R bacteria

Rough strain lacking protective capsule.

Transformation

Process where type R bacteria become type S.

Avery, MacLeod, McCarty

Identified DNA as the transforming substance in 1940s.

Fractionation

Separation of cellular components to identify genetic material.

RNase

Enzyme that degrades RNA in experiments.

Protease

Enzyme that degrades proteins in experiments.

DNase

Enzyme that degrades DNA, confirming its role.

Hershey and Chase experiment

Used bacteriophage T2 to confirm DNA as genetic material.

Bacteriophage T2

Virus composed of DNA and protein infecting bacteria.

Chromosomes

Structures composed of DNA and proteins carrying genetic information.

Heat-killed bacteria

Used in experiments to show transformation without live pathogens.

Polysaccharide capsule

Protective layer around type S bacteria, aiding immune evasion.

Phage coat

Outer layer of virus, remains outside bacterium.

Genetic material

Substance entering bacterial cytoplasm during infection.

Hershey and Chase Experiment

Study determining DNA as genetic material.

Radioactive isotopes

Used to label proteins and DNA in experiments.

32P isotope

Radioactive phosphorus used to label DNA.

35S isotope

Radioactive sulfur used to label proteins.

Non-radioactive cells

Cells not labeled with radioactive isotopes.

Phage infection

Process where phages introduce genetic material into bacteria.

Bacterial cytoplasm

Interior of bacterial cell where DNA enters.

Nucleic acid

Biomolecule type including DNA and RNA.

Nucleotide

Repeating unit of DNA and RNA structures.

Phosphate group

Component of nucleotides, part of DNA and RNA.

Pentose sugar

Sugar component in nucleotides; deoxyribose or ribose.

Nitrogenous base

Component of nucleotides; includes purines and pyrimidines.

Purines

Nitrogenous bases: adenine and guanine.

Pyrimidines

Nitrogenous bases: thymine, cytosine, uracil.

Double helix

Structure formed by two interacting DNA strands.

Chromosomes

Complex structures formed by folded DNA and proteins.

Carbon function

Each carbon in pentose sugar has specific role.

1' carbon

Linked to the nitrogenous base in nucleotides.

2' carbon

Distinguishes between DNA and RNA structures.

3' carbon

Contains a free hydroxyl group in nucleotides.

4' carbon

Considered the least significant in nucleotide structure.

5' carbon

Bonds with the phosphate group in nucleotides.

Nucleotide

Composed of a base, sugar, and phosphate.

Nucleoside

Base bonded to a sugar, without phosphate.

Adenosine

Nucleoside formed from adenine and ribose.

Deoxyadenosine

Nucleoside formed from adenine and deoxyribose.

AMP

Adenosine monophosphate, one phosphate group.

ADP

Adenosine diphosphate, two phosphate groups.

ATP

Adenosine triphosphate, three phosphate groups.

Phosphodiester linkage

Connects nucleotides via phosphate and sugar.

Directionality

DNA strands run from 5' to 3' ends.

Backbone

Formed by sugar and phosphate in DNA.

Base sequence

Defines genetic information in DNA and RNA.

Linus Pauling

Proposed helical structure for proteins using models.

Rosalind Franklin

Used X-ray diffraction to study DNA structure.

Chargaff's Rule

A=T and G=C base pairing in DNA.

Watson and Crick

Developed the double helix model of DNA.

Nobel Prize 1962

Awarded to Watson, Crick, and Wilkins.

Rosalind Franklin's omission

Excluded from Nobel due to her death.

DNA Double Helix

Two twisted strands forming a helical structure.

Base Pairing

Hydrogen bonds between nucleotide bases in DNA.

A-T Pairing

Adenine pairs with Thymine via 2 hydrogen bonds.

G-C Pairing

Guanine pairs with Cytosine via 3 hydrogen bonds.

Antiparallel Strands

One DNA strand runs 5' to 3', other 3' to 5'.

Right-Handed Helix

Helix spirals clockwise when viewed from above.

Major Groove

Wider groove on DNA helix for protein binding.

Minor Groove

Narrower groove on DNA helix for protein binding.

B DNA

Predominant right-handed DNA form in living cells.

Z DNA

Left-handed DNA form with a zigzag structure.

RNA Structure

Typically single-stranded, with ribose sugar.

Transcription

Process of copying RNA from DNA template.

Uracil (U)

Base in RNA replacing Thymine (T) from DNA.

RNA Double Helices

Short regions of RNA can form double-stranded structures.

Complementary Base-Pairing

A pairs with U, C pairs with G in RNA.

RNA Tertiary Structure

3D shape influenced by base-pairing and interactions.

tRNA

Transfer RNA that carries amino acids for translation.

Anticodon Region

Part of tRNA that pairs with mRNA codon.

Base Stacking

Flat sides of bases face each other in DNA.

Complete Twist

10 bases and 3.4 nm per full helical turn.

Biological Role of Z DNA

Potential role in transcription and chromosome compaction.