Molecular Genetics Flashcards
What do nucleotides consist of?
A 5 carbon cyclic structure called deoxyribose
A phosphate group
One of 4 nitrogenous bases
What are the four nitrogenous bases?
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
What is DNA Replication?
The process in which DNA makes an exact copy of itself
Occurs during interphase
What happens in the Splitting phase of DNA replication?
DNA is split in half and each half is used as a template strand to make a new copy
DNA helicase unwinds the DNA strand by breaking hydrogen bonds between the complimentary base pairs (like a zipper)
The point at which the two DNA strand are separated is called the replication fork
What happens during the building complimentary strands phase of DNA replication?
New strands are synthesized by DNA polymerase III
It works by linking together free nucleotides to appropriate complimentary base pairs
A short piece of RNA called a primer attaches to the template strand and gives the DNA polymerase a place to start
DNA polymerase III adds nucleotides on the side towards the replication fork
DNA Polymerase I then cuts out the primers and replaces them with nucleotides
DNA Ligase then joins the backbones of these fragments together
What is the leading strand?
DNA Polymerase III adds nucleotides on the side towards the replication fork
What is the lagging strand?
DNA polymerase III is synthesized in short Okazaki fragments
What happens during the DNA Repair phase in DNA Replication?
Proofreading: polymerase backtracks and cut out any incorrect nucleotides
What does DNA Helicase do?
Unwinds double helix
What does DNA Polymerase III do?
Synthesizes complimentary strand
What does DNA Polymerase I do?
Removes RNA primers and replaces with nucleotides
What does DNA Ligase do?
Joins DNA fragments together
What is gene expression?
The conversion of a gene into a specific trait through the production of a particular polypeptide
A polypeptide is a long chain of amino acids, polypeptides make up proteins, proteins for many structures such as skin, muscle, and enzymes
This is done with the help of RNA
What is the difference between DNA and RNA?
RNA is single stranded
RNA contains ribose sugar (one more oxygen than deoxyribose)
Uracil instead of thymine
What is transcription?
DNA is converted to RNA
What is translation?
Converts RNA to protein
During translation RNA is read in groups of 3 nucleotides called codons
Each codon calls for a specific amino acid to be placed in the polypeptide chain
Redundant but not Ambiguous
Redundant: several amino acids are coded for by different codons
Not Ambiguous: certain codons code for certain amino acids
What happens during the initiation phase of transcription?
RNA polymerase binds to a segment of DNA called the promoter
This sequence tells the enzyme where transcription should begin
The promoter will sit upstream of the DNA sequence to be transcribed
What happens during the elongation phase of transcription?
RNA polymerase starts building single-stranded in RNA (messenger RNA) in the 5’ to 3’ direction
Thymine (T) in DNA are replaced with Uracil (U) in mRNA
Exons are expressed, introns are not
What happens during the termination phase of transcription?
RNA polymerase will continue to transcribe DNA until it reaches a termination sequence
RNA polymerase falls off DNA molecule and the mRNA separates from DNA
What happens during the initiation phase of translation?
Ribosome recognizes a specific sequence on the mRNA and binds to it
In eukaryotes, the ribosomes consists of two subunits: large and small, the subunits clamp the mRNA between them
The ribosome read the mRNA 5’ to 3’
What happens during the elongation phase of translation?
tRNA (transfer RNA) bring amino acids to the ribosome, tRNA molecules have an anticodon that is complimentary to the codon in the mRNA
Amino acids continue to be added
What are mutations?
Mutations are changes in the sequence of DNA
Mutations are a source of new genetic variation and can be acted upon by natural selection
Mutations can be seen at the chromosomal level involving large segments of DNA
What is a point mutation?
A mutation at a specific base pair (substitution)
What is a gene mutation?
A mutation that changes the coding for amino acids (missense)
What is a silent mutation?
Does not result in a charge in amino acid coded for (same sense)
What is a nonsense mutation?
Converts a codon for an amino acid into a stop codon
What is a frame shift mutation?
A mutation that causes the reading frame of codons to change (insertion or deletion)
What causes mutations?
Spontaneous mutations: a mutation occurring as a result of errors made in DNA replication
Induced mutation: a mutation caused by a chemical agent or radiation
What is phylogeny?
Proposed evolutionary history of a species or group of organisms
Closer DNA sequence, closer evolutionary relationship
What is mitochondrial DNA (mtDNA)?
Can be used to provide clues about the evolutionary history of modern humans
What is DNA Sequencing?
Determines the exact sequence of based pairs for a particular DNA fragment or molecule
What is recombinant DNA?
A fragment of DNA composed of sequences originating from at least two different sources
