Gabriella Goudeau Ch.4-DNA and Gene Expression

What is DNA

Genetic material for all life forms

What is DNA made up of?

Two long chains of nucleotides wound around each other

What is the shape of DNA?

Double helix

What is each nucleotide made up of?

Phosphate group, deoxyribose sugar, nitrogenous base

What is the backbone of DNA?

The sugar and phosphate

How are the rungs of the ladder connected together?

Hydrogen bonds

What are the four nitrogen bases?

ATCG

How do the nitrogenous bases of DNA pair?

AT CG

What do the sequence of bases code?

Instructions for building proteins

How does Biotech use DNA’s stability and reproductability?

PCR, gene sequencing, and genetic engineering

WHat does understanding the structure of DNA allow?

Helps us better understand its function

When does DNA replication occur?

In the S phase

What does semiconservative replication mean?

Half of the material is saved and used to make another

How does the DNA double helix unwind?

DNA polymerase

What is the replication fork?

Split in strand where Helicase is unzipping DNA

What is the leading strand?

Strand that is built continuously

What is the lagging strand?

Strand that is build in fragments

What type of DNA does bacteria have?

Circular

What is DNA polymerase?

Enzyme that unwinds DNA

What is the origin recognition complex?

Detects and binds to origin of replication, marks beginning of replication

What is helicase?

Enzyme that unzips DNA

What is the purpose of the template DNA?

Guide for building complementary strands

What is the replication bubble?

Where DNA strands separate, expands as replication proceeds in both directions

What is the replication fork?

Y-Shaped region where DNA is unwound and copied

What are topoisomerases?

Prevent DNA from unwinding ahead of the fork by making temporary cuts

What are single-strand binding proteins?

Bind to unpaired DNA strands to keep them from reattaching

What are RNA primers?

Short RNA sequences made to start DNA synthesis

What is primase?

DNA polymerase, enzyme that synthesizes RNA primers on both strands

What are okazaki fragments?

Short stretches of newly synthesized DNA joined later into a continuous strand

What is DNA ligase?

Enzyme that joins O. fragments, final step ensuring a complete strand

What are histone proteins?

Small, positively charged proteins that bind DNA, allowing it to coil tightly

What are histones?

Positively charged proteins that bind DNA, allowing it to coil tightly

What are nucleosomes?

Basic unit of chromatin, consisting of DNA wrapped around histones, “beads on a string”

What is chromatin?

Entire DNA-protein complex seen in nucleus

What are euchromatin?

Loosely packed, active

What are heterochromatin?

Tightly packed, inactive

Who discovered transformation?

Fredrick Griffith

When was transformation discovered?

1928

What was the end conclusion of DNA transformation?

Genetic info could be transferred between bacteria

What is transcription?

From DNA to mRNA

What is mRNA?

Single stranded RNA copy of DNA that carries genetic info to ribosomes

What is a ribose phosphate backbone?

RNA’s sugar-phosphate structure (ribose, not deoxyribose)

What is a codon?

Sequence of 3 RNA bases that code for a specific amino acid

What is a polypeptide?

Chain of AA linked by peptide bonds, folds into functional protein

What is an enzyme?

Protein that speeds up chemical reactions

What is the central dogma of molecular biology?

DNA>mRNA>Protein>Trait

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

Because RNA molecules are critical intermediaries between DNA and proteins

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

By manipulating RNA to treat diseases and develop therapies

What makes RNA unstable?

Extra oxygen atom

What is the ribose-phosphate backbone?

Repeating sugar-phosphate chain that forms RNA’s structural framework

What makes DNA more stable?

Lacks one oxygen atom

When does uracil pair with adenine?

RNA

What are the three differences between RNA and DNA?

DNA has: double helix, thymine, deoxyribose

What is messenger RNA?

RNA that carries genetic info from RNA to ribosomes (code copied from DNA during transcription)

What is a codon?

3 base sequence on mRNA, codes for one amino acid

What are amino acids?

building blocks of proteins

What is an anticodon?

3 base sequence on tRNA complementary to mRNA codon

What do tRNA molecules do?

Read mRNA and deliver corresponding amino acid (cloverleaf structure)

What does the cloverleaf shape of tRNA allow?

Allows binding to both specific amino acids and complementary codons on mRNA

What is the small ribosomal subunit?

Helps positions mRNA and tRNA correctly during protein synthesis

What is the large ribosomal subunit?

Connects amino acids together to form protein chains, contains catalytic site for forming peptide bonds

What do ribosomes do?

Reads mRNA codons, matches them with tRNA anticodon, links amino acids into polypeptide chains, folding them into proteins

Why is it important to understand transcription?

Because when it messes up it can cause genetic diseases

What is RNA polymerase?

Enzyme that catalyzes transcription

What is pre-MRNA?

Initial RNA transcript product produced directly from DNA

What are exons?

“Good” regions, parts of pre-mRNA that will be kept

What are introns?

“Bad” regions, non-coding regions that will be removed

What is the 5’-cap?

Modified guanine nucleotide added to 5’ end of mRNA, protects from degradation

What is a Poly-A tail?

String of adenines, helps increase stability and lessen degradation

What percent of human genetic diseases is due to improper RNA splicing?

15%

What is the ribosomal complex?

Molecular machine that reads mRNA and assembles proteins

During translation, what happens at initiation?

Ribosome assembles on mRNA at start codon

During translation, what happens at elongation?

Ribosome reads each codon, tRNA w/ complementary anticodon binds, AA added to growing chain via peptide chains, ribosome moves to next codon

During translation, what happens at termination?

At stop codon, completed polypeptide releases

Why is gene regulation important?

Allows scientists to control when proteins are produced

What is the regulator gene?

Encodes the repressor protein, located away from operon

What is the promoter region?

DNA binding site for RNA polymerase, where transcription begins

What is the operator region?

Control switch for gene expression, repressor protein binds here to block transcription

What is an inducer?

molecule that binds to repressor

What is the repressor protein?

Lactose-bound form cannot attach to operator, prevents DNA binding

What is the TRP operon?

What happens when tryptophan is absent?

Operon is on

What happens when tryptophan is abundant?

Operon is on

What is a point mutation?

Single base change

Why is it important to understand point mutation?

essential for precision medicine