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SBI4U - Molecular Genetics

Terms in this set (83)

Double Helix
two strands of nucleotides wound about each other; structure of DNA
Deoxyribose sugar
sugar used in DNA to make up the "backbone"
Nitrogenous base
An organic base that contains nitrogen, a subunit of a nucleotide in DNA and RNA
Purine
double-ring nitrogenous base; adenine and guanine
Pyrimidines
Cytosine and Thymine/uracil, single ring
phosphate group
Component of DNA and RNA backbone along with 5-C sugar
Nucleotide
monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base
Glycosyl Bond
nitrogenous base is attached to 1' carbon
phosphodiester bond
a bond that is responsible for the polymerization of nucleic acids by linking sugars and phosphates of adjacent nucleotides
3' end of DNA
Unbound OH on the 3' carbon of deoxyribose
5' end of DNA
Unbound OH on the 5' carbon of deoxyribose
4 bases of DNA
Adenine, Thymine, Cytosine, Guanine
4 bases of RNA
Adenine, Uracil, Cytosine, Guanine
initiation of transcription
Attachment of RNA polymerase to the promoter. Unwinds the DNA and breaks the H bonds between strands. RNA polymerase binds to the template (3'-5') strand of DNA.
elongation (transcription)
RNA polymerase reads 3'-5', starts mRNA synth when it finds beginning of the gene. mRNA is synthesized w/ uracil in 5'-3' direction forming phosphodiester bonds.
template strand
The DNA strand that provides the template for ordering the sequence of nucleotides in an mRNA transcript. 3'-5'.
coding strand
the strand of DNA that is not used for transcription and is identical in sequence to mRNA, except it contains uracil instead of thymine. Genetic code version. 5'-3'.
termination of transcription
rna polymerase finds terminator sequence in template dna. single strand of mrna and rna poly released. dna h bonds reform, dna recoils
Post Transcription Processing of pre-mRNA
Splicing occurs - introns removed, exons spliced together. Capping & tailing to protect pre-mRNA from enzyme degradation in cytoplasm.
Capping
Modified guanosines attached to 5' end
Needed for mRNA to exit nucleus and bind ribosome
Tailing
~200 adenines added to 3' tail of mRNA. Poly-A tail.
RNA polymerase
Enzyme similar to DNA polymerase that binds to DNA and separates the DNA strands during transcription and links together mRNA nucleotides
DNA helicase
Recognizes the ORI (origin of replication) and begins unwinding the DNA
Single stranded binding proteins (SSBs)
bind to each side of the DNA ladder keeping it from bonding back together during DNA replication
Topoisomerases (DNA gyrase)
Keeps DNA from recoiling by alleviating tension
RNA Primase
An enzyme that creates an RNA primer for initiation of DNA replication. Creates template that DNA can be formed from.
DNA polymerase I
Removes RNA primers and replaces them with DNA nucleotides
RNA primer
Sequence of RNA nucleotides bound to a region of single-stranded DNA to initiate DNA replication.
DNA ligase
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain. Forms recombinant DNA when DNA with matching sticky ends is inserted.
DNA polymerase II
Proofreads/edits new DNA, looks for distortions in BPs
DNA polymerase III
synthesizes new DNA only in the 5' to 3' direction
Okazaki fragments
Small fragments of DNA produced on the lagging strand during DNA replication by DNA polymerase III, joined later by DNA ligase to form a complete strand.
leading strand
the new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5' to 3' direction
lagging strand
A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.
replication fork
A Y-shaped region on a replicating DNA molecule where new strands are growing.
origin of replication
Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.
Proofreading
mispaired nucleotide is removed by DNA polymerase II
Introns
Noncoding segments of nucleic acid that lie between coding sequences.
Exons
Coding segments of eukaryotic DNA.
Nucleus
A part of the cell containing DNA and RNA and responsible for growth and reproduction
promoter
Upstream from 5' end of gene. TATA box binding site, binding site for RNA polymerase & transcription factors (up or down regulation). Controls transcription of all genes in an operon
Gene
sequence of DNA that codes for a protein and thus determines a trait
Protein
An organic compound that is made of one or more chains of amino acids and that is a principal component of all cells
Polypeptide
A polymer (chain) of many amino acids linked together by peptide bonds.
RNA
A single-stranded nucleic acid that passes along genetic messages
mRNA
A type of RNA, synthesized from DNA, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.
tRNA
An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA
initiation complex
Transcription factors bind to promoter region. Trigger the binding of RNA Polymerase to DNA.
spliceosome
Several snRNPs (small nuclear RNA proteins). Recognize splice site sequence. "Cut and paste" gene.
TATA box
A promoter DNA sequence crucial in forming the transcription initiation complex.
The Central Dogma of Molecular Biology
Codon
three-nucleotide sequence on mRNA that codes for a single amino acid
Anticodon
group of three bases on a tRNA molecule that are complementary to an mRNA codon
Ribosome
site of protein synthesis. Facilitate coupling of tRNA anticodon to mRNA codon.
Ribosome structure
ribosomal RNA (rRNA) & proteins, 2 subunits: large & small. Large looks like hand emoji. A, P, E sites
tRNA structure
cloverleaf form,
anticodon end is opposite 3' (clover leaf) end. aminoacyl (amino acid) on 3' end.
Methionine
AUG start codon
A site (Acceptor site, aminoacyl-tRNA site)
Holds tRNA carrying next amino acid to be added to chain
P site (peptidyl-tRNA binding site)
Holds tRNA carrying growing polypeptide chain
E site (exit site)
empty tRNA leaves ribosome from exit site
initiation of translation
Brings together mRNA, ribosome subunits, initiator tRNA
elongation (translation)
adding amino acids based on codon sequence
termination of translation
occurs when a stop codon in the mRNA reaches the A site of the ribosome (end codon)
Peptide bond
covalent bond formed between amino acids
Release factor
Proteins that can trigger termination of RNA translation when a ribosome reaches a stop codon.
Prokaryotes vs. Eukaryotes DNA
Prokaryote: DNA in cytoplasm, naked, no introns, circular chromosome, transcr. & transl. are simultaneous, no mRNA editing, ribosome read mRNA as it is being transcribed

Eukaryote: DNA in nucleus, linear chromosome, introns & exons, DNA wound on histone proteins,
Point mutation
change in a single nucleotide within a gene. substitution, insertion, deletion, and inversion
subsitution
replacement of one bp for another
nonsense mutation
premature stop codon. ex beta-thalassemia
silent mutation
does not alter the resulting sequence of amino acids
frameshift mutation
shift in the reading frame, many missense/nonsense mutations. insertion/deletion always lead to this. ex Tay-Sachs disease
gene duplication (Amplification)
Group of genes is copied to multiple regions of chromosomes. Compounds the effect of the gene. Important in evolution.
Operon
group of genes operating together. transcribed as one unit, a single mrna is made for all of them.
restriction endonucleases
Molecular "scissors" that cut DNA at a specific bp sequence (recognition site, usually 4-9 bp long.)
palindromic sequence
Nucleic acid sequence: read the same 5'-3' as complementary 3'-5'
polymerase chain reaction (PCR)
A technique for amplifying DNA in vitro by incubating with special primers, DNA polymerase molecules, and nucleotides while heating every few minutes to separate DNA strands.
Plasmid
A small ring of DNA that carries accessory genes separate from those of the bacterial chromosome
antibiotic resistance
the ability of bacteria to withstand the effects of an antibiotic
recombinant plasmid
plasmid that has had a particular gene inserted into it using restriction enzymes
Reporter gene
A genetic marker included in recombinant DNA to indicate the presence of the recombinant DNA in a host cell. Ex: GFP (green fluorescent protein, glows green under UV light)
DNA fingerprinting
analysis of sections of DNA that have little or no known function, but vary widely from one individual to another, in order to identify individuals
gel electrophoresis
Restriction enzyme is used to fragment cells. Gel electrophoresis separates the fragments based on size, can be used to determine genetic relatedness.
Transformation
Cells take in recombinant plasmid through their cell membranes, incorporating it into their DNA.
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