Lecture Notes for Test 4: DNA Function, Replication, Gene Expression and Biotechnology

These flashcards cover key concepts related to DNA function, replication processes, gene expression, and biotechnology.

DNA

Deoxyribonucleic Acid, the molecule that carries genetic information.

Nucleotide

The monomer of DNA, consisting of a phosphate, deoxyribose sugar, and a nitrogenous base.

Semiconservative Replication

The process of DNA replication where each daughter molecule contains one original and one new strand.

Leading Strand

The DNA strand that is replicated continuously in the 5’ to 3’ direction.

Lagging Strand

The DNA strand that is replicated discontinuously, forming Okazaki fragments.

Codon

A sequence of three bases in mRNA that codes for a specific amino acid.

Operon Model

A mechanism for regulating gene expression in prokaryotes, involving regulatory genes, promoters, and operators.

Euchromatin

Less condensed form of chromatin that allows for transcription to occur.

Heterochromatin

Tightly packed form of chromatin that is usually transcriptionally inactive.

Transgenic Organisms

Organisms that contain DNA from different species, often created for genetic modification.

Helicase

An enzyme that unwinds the DNA double helix during replication.

DNA Polymerase

An enzyme that synthesizes new DNA strands by adding nucleotides to a growing chain during replication.

Primase

An enzyme that synthesizes short RNA primers necessary for DNA polymerase to start synthesis on the lagging strand.

Ligase

An enzyme that connects Okazaki fragments on the lagging strand by forming phosphodiester bonds between them.

Topoisomerase

An enzyme that prevents supercoiling of DNA by cutting and rejoining DNA strands during replication.

Prokaryotic DNA Replication

The process of DNA replication in prokaryotes occurs in the cytoplasm, typically starting from a single origin of replication and proceeding bidirectionally.

Eukaryotic DNA Replication

Eukaryotic DNA replication occurs in the nucleus and involves multiple origins of replication on each chromosome to speed up the process.

Origin of Replication

A specific sequence in the DNA where replication begins; prokaryotes have a single origin, whereas eukaryotes have multiple origins per chromosome.

Replication Fork

Y-shaped region where the DNA is being unwound and replicated; present in both prokaryotic and eukaryotic replication processes.

Okazaki Fragments

Short segments of DNA synthesized discontinuously on the lagging strand during replication; necessary in both prokaryotic and eukaryotic DNA replication.

Telomerase

An enzyme that extends the telomeres at the ends of eukaryotic chromosomes, preventing loss of genetic information during replication.

DNA Replication Licensing

In eukaryotes, a mechanism regulating when DNA replication can begin at each origin, ensuring that each origin is only activated once per cell cycle.

James Watson and Francis Crick

Together, they proposed the double helix structure of DNA in 1953, based on X-ray diffraction images taken by Rosalind Franklin.

Rosalind Franklin

Her X-ray crystallography work provided critical evidence for the helical structure of DNA, which helped Watson and Crick in their model.

Erwin Chargaff

Known for Chargaff's rules, which state that the amount of adenine equals thymine and the amount of guanine equals cytosine in DNA, these observations were crucial for understanding base pairing.

Gregor Mendel

Often called the father of genetics, his work on pea plants in the 1860s laid the groundwork for understanding heredity, which is fundamental to modern genetics and DNA research.

Fred Griffith

In 1928, conducted the transforming principle experiment, which demonstrated that genetic material could be transferred between bacteria, hinting at the existence of DNA.

Avery, MacLeod, and McCarty

In 1944, they identified DNA as the substance responsible for transformation in bacteria, effectively confirming DNA's role as genetic material.

Hershey and Chase

In 1952, their experiments with bacteriophages provided evidence that DNA, not protein, is the genetic material, conclusively proving DNA's role in heredity.

Kary Mullis

Inventor of the Polymerase Chain Reaction (PCR) technique in 1983, revolutionizing molecular biology by allowing for the amplification of DNA sequences.

DNA (Deoxyribonucleic Acid)

A nucleic acid that contains the genetic instructions for the development and function of living organisms, typically double-stranded with a deoxyribose sugar.

RNA (Ribonucleic Acid)

A nucleic acid that plays crucial roles in coding, decoding, regulation, and expression of genes; usually single-stranded with a ribose sugar.

Structure of DNA

DNA has a double helix structure formed by two long strands of nucleotides, held together by complementary base pairing (adenine with thymine, and guanine with cytosine).

Structure of RNA

RNA is typically single-stranded and can fold into complex three-dimensional shapes; it contains uracil instead of thymine, pairing with adenine.

Function of DNA

Serves as the long-term storage of genetic information; it is replicated and passed on during cell division.

Function of RNA

Involved in protein synthesis (mRNA), gene regulation (miRNA), and catalyzing biochemical reactions (ribozymes).

Location of DNA

Primarily found in the nucleus of eukaryotic cells, while in prokaryotes, it is located in the cytoplasm.

Location of RNA

Found in the nucleus and the cytoplasm; mRNA, tRNA, and rRNA play roles in protein synthesis in the cytoplasm.

Stability of DNA

DNA is more stable due to its deoxyribose sugar and double-stranded structure, making it less prone to degradation.

Stability of RNA

RNA is less stable than DNA because it is single-stranded and contains ribose sugar, which makes it more susceptible to hydrolysis.

Double Helix

The molecular structure of DNA, consisting of two strands twisted around each other, resembling a spiral staircase.

Nucleotides

The building blocks of DNA, each consisting of a phosphate group, a deoxyribose sugar, and a nitrogenous base (adenine, thymine, guanine, or cytosine).

Base Pairing

The specific pairing of nitrogenous bases in DNA, where adenine pairs with thymine, and guanine pairs with cytosine through hydrogen bonds.

Phosphodiester Bond

The covalent bond that links the phosphate group of one nucleotide to the sugar of another, forming the backbone of the DNA strand.

Antiparallel Orientation

The orientation of the two strands of DNA, where one strand runs in the 5' to 3' direction and the other runs 3' to 5', allowing for proper base pairing.

Major and Minor Grooves

The spaces formed by the twisting of the DNA double helix; the major groove is wider and provides access for proteins to bind, while the minor groove is narrower.

Minor and Major Groove

Refer to the gaps formed by the twisting of the double helix of DNA, with specific protein binding properties influencing gene regulation.