Chapter4: DNA & Gene Expression/ Ava Resendez

What is DNA?

the molecule that contains the genetic code for all living organisms

What is DNA made up of?

two long strands of nucleotides, each composed of a sugar-phosphate backbone and a nitrogenous base

What shape is DNA?

double helix/ ladder shape

What is each nucleotide made up of? 

a five-carbon sugar (either ribose or deoxyribose), a phosphate group, and a nitrogenous base

What is a backbone of DNA?

the sugar-phosphate chain that runs along the sides of the double helix

How are the rungs of the ladder connected together?

a physical ladder's rungs are often attached to the side rails by welding or using a locking mechanism

What are the four nitrogen bases?

adenine (A), guanine (G), cytosine (C), and thymine (T)

How do the nitrogenous bases of DNA pair?

held together by hydrogen bonds, with A-T having two and G-C having three. This complementary base pairing ensures that the two strands of the DNA double helix are matched and have a predictable relationship

What do the sequence of bases code? 

the order of amino acids in a protein

How does Biotechnology use DNAs stability and reproductive?

By inserting specific genetic sequences into plasmid DNA, scientists can induce bacterial or mammalian cells to produce high-value proteins

What does understanding the structure of DNA allow?

scientists to explain how genetic information is stored and copied

When does DNA replication occur?

during the S (synthesis) phase of the cell cycle

What is semiconservative replication?

the process where each new DNA molecule is a hybrid of one original "parental" strand and one newly synthesized strand

How does the DNA double helix unwind? 

through a process involving enzymes called helicase and topoisomerase.

What is the replication fork?

the Y-shaped structure formed during DNA replication where the double helix is unwound by enzymes like helicase

What is the leading strand? 

one of the two new DNA strands synthesized during replication that is made continuously in the 5' to 3' direction, following the movement of the replication fork

What is the lagging strand?

one of the two DNA strands replicated during DNA synthesis

What type of DNA does bacteria have?

a main, circular, double-stranded genomic DNA

What is DNA polymerase?

a crucial enzyme that synthesizes new DNA molecules by reading an existing strand and creating a complementary one

What is the Origin Recognition Complex?

a protein complex essential for initiating DNA replication in eukaryotes by binding to origins of replication

What is Helicase?

an enzyme that unwinds double-stranded nucleic acids, like DNA and RNA, by breaking the hydrogen bonds that hold them together

What is the purpose of the template DNA?

to act as a guide for the synthesis of a new, complementary strand of DNA or RNA during processes like replication and transcription

What is the Replication bubble? 

an unwound and open region of a DNA double helix where replication is taking place

What is the replication fork?

the Y-shaped structure formed during DNA replication where the double helix is unwound by enzymes like helicase

What are topoisomerases?

enzymes that regulate DNA's structure by managing supercoiling and tangles through transiently breaking and rejoining DNA strands

What are single-strand binding proteins?

bind to and protect single-stranded DNA (ssDNA) to maintain genome stability

What are RNA primers?

short segments of RNA that serve as the starting point for DNA synthesis

What is primase? 

an enzyme that synthesizes short RNA primers

What are Okazaki fragments?

short, discontinuous segments of DNA synthesized on the lagging strand during DNA replication

What is DNA ligase?

an enzyme that joins two DNA fragments by forming a phosphodiester bond between the 5' phosphate and 3' hydroxyl groups at the ends of the strands

What are histone proteins?

the primary protein components of chromatin, the complex that makes up chromosomes in eukaryotic cells

What are histones?

small, positively charged proteins that act as spools for DNA to wind around

What are nucleosomes? 

the basic structural units of DNA packaging in eukaryotes, consisting of a segment of DNA wound around a protein core made of histones

What is chromatin?

the complex of DNA and proteins (primarily histones) that forms chromosomes in the nucleus of eukaryotic cells

What are euchromatin?

a loosely packed form of chromatin in eukaryotic cells that is rich in genes and is actively transcribed

What are heterochromatin?

tightly packed, condensed regions of DNA within chromosomes that are transcriptionally inactive

Who discovered transformation?

Frederick Griffith

When was transformation discovered?

1928

What was the end conclusion of DNA transformation?

DNA is the genetic material

What is transcription?

the process of converting one form of information into another

What is MRNA?

Messenger RNA (abbreviated mRNA) is a type of single-stranded RNA involved in protein synthesis. mRNA is made from a DNA template during the process of transcription.

What is a ribose phosphate backbone?

the structural framework of RNA, composed of alternating ribose sugar molecules and phosphate groups linked together

What is a codon? 

a three-nucleotide sequence in mRNA that acts as a "word" in the genetic code

What is a polypeptide?

a long chain of amino acids linked together by peptide bonds, which forms the basic structure of proteins

What is an enzyme?

a biological catalyst, typically a protein, that speeds up chemical reactions in living organisms without being consumed

What is a central dogma of molecular biology?

the principle that genetic information flows in one direction: from DNA to RNA to protein

Why is it important to understand the structure of RNA in biotechnology? 

a molecule's function is determined by its structure

How are RNA used to treat disease and create new therapies? 

by being engineered to carry genetic instructions, prevent protein production, or modify existing RNA sequences

What makes RNA unstable?

the 2'-hydroxyl group on its ribose sugar

What is the ribose-phosphate backbone?

the structural framework of RNA, consisting of alternating ribose sugar molecules and phosphate groups linked by phosphodiester bonds

What makes DNA more stable?

primarily due to its double-stranded structure, the deoxyribose sugar it uses, and the presence of thymine instead of uracil

When does uracil pair with thymine?

Uracil does not pair with thymine

What are three key differences between RNA and DNA? 

sugar type, base structure, and strand formation

What is messenger RNA?

a single-stranded molecule that carries genetic instructions from DNA in the nucleus to ribosomes in the cytoplasm, where they are used to synthesize proteins

What is a codon?

a three-nucleotide sequence in mRNA that acts as a "word" in the genetic code

What are amino acids?

organic compounds that are the building blocks of proteins

What is an anticodon?

a three-nucleotide sequence in a transfer RNA (tRNA) molecule that binds to a complementary three-nucleotide codon on a messenger RNA (mRNA) molecule during protein synthesis

What do tRNA molecules do? 

act as an adaptor in protein synthesis, linking the genetic code on messenger RNA (mRNA) to the specific amino acids that build a protein

What does the cloverleaf shape of tRNA allow? 

simultaneously hold a specific amino acid at one end and display a three-base anticodon at the other

What is the small ribosomal subunit?

the part of a ribosome that binds to messenger RNA (mRNA) and decodes the genetic information it carries

What is the large ribosomal subunit?

the larger of a ribosome's two components and is responsible for catalyzing peptide bond formation during protein synthesis

What do ribosomes do?

synthesize proteins by reading genetic instructions from messenger RNA (mRNA)

Why is it important to understand transcription?

it is the process of making RNA from DNA, which is central to life

What is RNA polymerase? 

a crucial enzyme in all living organisms that synthesizes RNA from a DNA template in a process called transcription

What is pre-MRNA?

the initial, immature RNA transcript produced from a protein-coding gene that must undergo processing before it can be translated into a protein

What are exons?

non-coding sequences of DNA that are initially transcribed into a messenger RNA (mRNA) precursor but are then removed during a process called RNA splicing before the mRNA is translated into a protein

What are introns?

a modified guanine nucleotide that is added to the 5' end of eukaryotic messenger RNA (mRNA) during transcription

What is the 5’ cap?

a series of adenine (A) nucleotides added to the end of an mRNA molecule to increase its stability, aid in its export from the nucleus, and enhance translation

What percent of human genetics disease is due to improper RNA splicing?

15-20%

What is the ribosomal complex?

a large ribonucleoprotein complex that synthesizes proteins

During translation, what happens at initiation?

the small ribosomal subunit binds to the mRNA, and a specific initiator tRNA carrying the amino acid methionine binds to the start codon (AUG)

During translation, what happens at elongation? 

the ribosome moves along the mRNA, adding amino acids to a growing polypeptide chain

During translation, what happens at termination? 

a release factor protein binds to a stop codon (UAA, UAG, or UGA) on the mRNA when it reaches the ribosome

Why is gene regulation important?

it ensures genes are expressed at the right time, in the right amounts, and in the right cells, which is crucial for normal development, cell differentiation, and adapting to environmental changes

What is the regulator gene?

genes that control the expression of other genes by producing proteins that can turn them on or off

What is the promoter region?

a region of DNA located upstream of a gene that controls the initiation of transcription by acting as a binding site for RNA polymerase and other proteins

What is the operator region?

a segment of DNA in a prokaryotic operon that serves as a binding site for regulatory proteins, such as repressors or activators, to control gene expression

What is an inducer? 

a substance that triggers a process, most commonly activating genes within a cell

What is the repressor protein?

a DNA-binding protein that inhibits gene transcription by binding to a specific DNA sequence, typically an operator region, to prevent the RNA polymerase from binding or moving along the DNA

What is the TRP operon?

a group of genes in bacteria that are responsible for synthesizing the amino acid tryptophan

What happens when tryptophan is absent?

the activator protein will not bind and transcription will not occur

What happens when tryptophan is abundant?

its production is halted through a process called feedback inhibition in bacteria, where it acts as a corepressor

What is a point mutation? 

a genetic alteration where a single nucleotide base in a DNA or RNA sequence is changed, inserted, or deleted

Why is it important to understand point mutation?

they are a primary source of genetic variation that drives evolution, and they are also the cause of many diseases, such as sickle cell anemia and some types of cancer