unit 9 Flashcards
What is the role of DNA in heredity?
-Storing genetic information
-Copying genetic information
-Transmitting the genetic information
What are nucleotides made up of?
-5-carbon sugar called deoxyribose
-Phosphate group
-Nitrogenous base
What are the 4 nitrogenous bases in DNA?
Thymine, Adenine, Cytosine, Guanine
What is the macromolecule in DNA?
Nucleic acid
What is the polymer in DNA?
DNA
What is the monomer in DNA?
Nucleotide
What direction do the strands in DNA run?
In opposite directions, they are antiparallel
What are the nucleotides held together by?
Covalent bonds in the backbone
What are the two strands of DNA held together by?
Hydrogen bonds between the nitrogenous bases
What are the base pairings?
A and T = 2 hydrogen bonds
G and C = 3 hydrogen bonds
Which bonds are the strongest?
Covalent bonds
What is the purpose of DNA replication?
New copy of DNA for every cell
What does DNA being semiconservative mean?
1 parent strand and 1 new strand
What is helicase?
The “unzipper”; breaks hydrogen bonds between strands
What is primase?
The “initializer”; makes RNA primer
What is polymerse?
The “builder”; adds nucleotides to the new strand 5’ and 3’
What is ligase?
The “gluer”; create covalent bonds between nucleotides to connect fragments
What are the differences between DNA and RNA?
DNA: Deoxyribose sugar, 2 strand, A = T G = C, stores
RNA: Ribose sugar, 1 strand, A = U G = C, transfers
What is the role of DNA?
Stores information and genetic material
What are proteins made of?
Monomer- Amino acids
What is the role of proteins?
Muscles, transport, stores, enzymes, structural
What do the genes in DNA contain?
Information to make proteins
What is transcription?
Where the cell makes mRNA copies of genes that are needed
Occurs in the nucleus of eukaryotes
What is translation?
Where the mRNA is read by the ribosomes to make proteins
Occurs in the cytosol
What is a gene?
Unit of DNA that carries information to make a proteins
What is mRNA?
Messenger RNA, it carries information from a gene in DNA
What is RNAP
RNA polymerase, the enzyme that reads DNA to make mRNA (5’-3’)
What is the first step of transcription?
RNA polymerase binds to the template strand of DNA at the beginning of a gene called the promoter
What is the second step of transcription?
RNA polymerase moves along the gene unwinding the DNA and creating a complementary strand of RNA stopping when it reaches the terminator. Using the RNA base pairing rules
What is the RNA base pairing rules?
G-C and A-U
What is the initial mRNA that is produced called?
The primary transcript
How does mRNA become mature?
It must go through processing
What are exons?
Coding regions (expressed)
What are introns?
Non-coding regions (interrupting)
Must be removed before primary transcript is mature and can leave nucleus
What is the roles of a ribosome in translation?
It binds mRNA and tRNA to link amino acids together
RIbosome structure:
Contains 2 subunits one small and one large
Made of proteins and RNA (rRNA)
What is tRNA?
Transfer RNA, a type of RNA that matches amino acids to specific sequences of mRNA
What is a codon?
A group of 3 mRNA/DNA that encode a single amino acid
What is the link between mRNA and proteins
tRNA
What is the start codon?
ATG/AUG
What are the stop codons?
UAA, UGA, UAG
What is a mutation?
A change in the DNA sequence
What are the three types of mutations?
Insertion: adding one or more nucleotides
Deletion: removing one or more nucleotides
Substitution: changing a single nucleotide for another
Point: affects only one nucleotide
What is a silent mutation?
The nucleotide change still encodes the same amino acid
What is a missense mutation?
Replaces the original amino acid with a different amino acid
What is a nonsense mutation?
Replaces the original amino acid with a stop codon
What is frame shift?
A mutation caused by the insertion or deletion of a number of nucleotides that is not divisible by 3 disrupting the reading frame, group of codons
What is a virus?
A non-cellular infectious agent that contains genetic material
What characteristics do viruses have?
Reproduce with host, sense + response, evolve, growth + development with host, order
How is a viral infection caused?
Viruses infect host cells by injecting their DNA and they take over the hosts protein synthesis enzymes to make new viruses
What is the lytic cycle?
When the virus injects its DNA into the host cell and it takes over the function of the cell to make more viruses
What is the lysogenic cycle?
The viral DNA is injected and it finds its way into the host genome
What is a retrovirus?
A virus with RNA
What can gen regulation do?
Change the expression of a gene by turning the gene on or off, down or up
What do genes usually have?
Regulatory regions ‘upstream’ of the coding region (the part of the gene that gets translated)
What are activators?
Proteins that increase gene expression
What are repressors?
Proteins that increase gene expression
What are operons?
Multiple genes controlled by one promoter and operator (regulatory region)
What do operons allow?
Many genes to be regulated in the same way
What happens when there is an absence of lactose?
The repressor protein binds to the operator preventing RNAP from binding to the promoter to begin transcription
What happens when there is a presence of lactose?
The repressor protein binds to lactose (inducer) cause the repressor to become inactive. Since the repressor can no longer bind to the operator, RNAP can begin transcription
What is a lac operon?
An inducible operon
What is a trp operon?
A repressible operon
Do eukaryotes have operons?
No
What are eukaryotic genes regulated by?
Proteins called transcription factors
What do transcription factors do?
They are recruited by enhancers and interact with the promoter to help RNAP bind
What happens when DNA is super condensed?
The DNA is less accessible to RNAP. More packing = less transcription
More methylation of histones =
more compact + less transcription
More acetylation histones =
Less compact
What is alternative RNA splicing?
When a single DNA gene can be transcribed into 2 or more alternative mRNA forms
What does alternative RNA splicing lead to?
Leads to multiple proteins that can be made during different conditions
What is micro-RNA (miRNA)?
Very short RNA sequences that bind to complementary mRNA
What happens when miRNA binds to mRNA?
miRNA can stop the translation process of the mRNA strand
What is mRNA degradation?
mRNA that live longer can produce more proteins and it increase the length of the 3’ tail = more stable mRNA
What is initiation of translation?
Inhibitory proteins can stop the ribosome from translating specific mRNAs
What is protein processing?
-Some proteins are only active after ____ by a protease. Insulin
-All proteins eventually get degraded. Protein can be tagged for break down by ubiquitin
What is reception?
Signal molecule (ligand) binds to a receptor in the membrane
-The ligand is specific to the receptor just like and enzyme and substrate
What is transduction?
The receptor passes the message to relay proteins inside the cell. Those proteins pass the message to other proteins
What is response?
A gene is turned on or off by regulatory protein
What leads to fight of flight response?
Epinephrine
How does growth factors lead to cancer?
If a growth factor becomes hyperactive it could lead to uncontrolled cell growth
What are oncogenes?
Genes that have developed a mutation that leads to cancer
What are tumor suppressor genes?
Genes that normally suppress cell division
Pronto
Oncogenes normally cause the cell to go through checkpoints in the cell cycle
Tumor suppressor regulation
Decrease expression of tumor suppressors can lead to cancer
What do tumor suppressors do?
Stop the cell at checkpoints in the cell cycle
What are the causes of cancer?
Inherited
Viruses
Carcinogen: Cancer causing agents found in the environment
