DNA Structure and Replication, Protein Synthesis, Mutations & Genetic Engineering Flashcards
State Stargaff’s Rule
The amount of 4 bases are not equal
Bases are present in a characteristic are not a equal ratio
A=T and G=C (All in percentages)
Summarize Rosalind Franklin’s contribution to determining the structure of DNA
She used X-ray photography to analyze the structure of DNA and found that it is a helix w/ 2 repeating patterns. She found that nitrogen bases were on the inside and the sugar-phosphate was on the outside
Describe the double helix structure DNA discovered by Watson and Crick
The discovered it was like a twisted ladder. The handrails on the outside are the sugar-phosphate backbone. The rungs or steps of the ladder are the nitrogen bases that are arranged in complementary pairs (A-T and C-G). The two stands are NOT IDENTICAL and they are ANTI-PARALLEL (they run the opposite of one another- one strand is pointed up and the other down
Describe the antiparallel strands (twisted ladder)
The 5’ to 3’ ends run in opposite directions on each strand of nucleotides in a double strand DNA molecule the 5’ end points up strand and down the other
Compare DNA to RNA- sugar, nitrogen bases, # of stands and where it occurs
DNA: Deoxyribose, A-T and C-G, two strands, nucleus
RNA: Ribose, A-U and C-G, one stand, cytoplasm
Define gene:
A functional sub-unit of DNA that directs the formation of a protein (or polypeptide) molecule
Define genome:
is all of the DNA in each organism’s cells. It includes genes and non-coding sequences of DNA that do not direct the information of a protein
What is the first step for semi-conservative replication?
- Two stands of template DNA before replication in S Phase of interphase
What is the second step for semi-conservative replication?
- The DNA unwinds due to the helicase enzyme cutting the H bonds between matching nitrogen bases and the DNA polymerase enzyme adds in matching new bases to the template strand
What is the third step for semi-conservative replication?
- The ligase enzyme glues the DNA up to make two daughter strands: half old and half new
What does helicase do?
It breaks the weak H bonds between nitrogen bases to unwind the DNA molecule
What does DNA polymerase do?
Adds complementary bases to the template DNA to make a new stand
What does Ligase do?
Glues up the bases on the newly made DNA strands to join them together
In what way is the structure of a protein related to the genetic code?
The sequence (order) of the base pairs in a DNA molecule, the genetics code, decides the sequence of amino acids in a protein
Summarize the steps in Central Dogma or Transcription and Translation:
Transcription (Step 1): Occurs in the nucleus. Genes on DNA are made into an mRNA copy
Translation (Step 2): Occurs in the cytoplasm at a ribosome: the sequence of bases on the mRNA molecule determines the sequence of amino acids in a protein
Define Codon:
A set of three bases that codes for an amino acid or a stop codon. 3 bases= 1 codon
What is a redundant characteristic of a genetic code?
More than one codon can code for the same amino acid. Only 3 codons do not code for any amino acids (they code for stop codons instead)
What is a continuous characteristic of a genetic code?
There is no spaces, punctuation or overlap in the genetic code
What is a universal characteristic of a genetic code?
All living organisms build proteins w/ the same genetic code
Describe the role of RNA polymerase in transcription?
It unravels a section of the DNA that is to be made into mRNA. It works in the 5’ to 3’ direction to add complementary mRNA bases to the template DNA strand that is being transcribed
Define anti-codon
A stretch of 3 nucleotides found on the tRNA molecule that is complementary to the mRNA codon. If the mRNA codon is CGA then the anticodon is GCU
What is a mutaiton?
A permanent change in the genetic material (base sequence of DNA) of an organism- it is inheritable
How can mutations be inherited?
They are copied during DNA replication (S phase of interphase) and passed onto daughter cells
What is a mutagen?
Substance/ event that causes an increased rate of mutation in an organism
What is a carcinogen?
A cancer causing factor (mutagens associated with one or more types of cancer)
How can mutations lead to: cancer?
Mutations accumulate within cells and combinations of mutations can lead to cancer
How can mutations lead to: Genetic variation?
Accumulation of mutations over time provides diversity (variation) and gives different characteristics of organisms
In which two parts of a cell is DNA found, besides the nucleus?
Mitochondria and chloroplasts
How are mitochondrial and chloroplast DNA different from nuclear DNA?
- Slightly different genetic code
- Can replicate, transcribe/ translate independently of nuclear DNA
Why is mitochondrial DNA identical to the mtDNA of your mother, not your father?
- At fertilization the egg contributes to the cytoplasm of the zygote,sperm from dad does not contribute any cytoplasm
- mtDNA/ mitochondria are found in the cytoplasm = it is inherited from mom
What is genetic engineering?
Recombinant DNA technologies: manipulating genetic material to alter genes and blend plants, animal and bacterial DNA together
What is recombinant DNA?
Genetic material that comes from different sources
What are restriction enzymes? (Also called restriction endonuclease)
Cleave (cut) DNA at specific nucleotide sequences. They are like molecular scissors
How are restriction enzymes used in genetic engineering?
They cut DNA at specific recognition its, which produces a “sticky end”- this end can be joined onto another strand of DNA to form base pairs
What is the role of DNA ligase in genetic engineering?
Ligase splices or joins pieces together to make a recombinant DNA molecule
Describe how restriction enzymes and DNA ligases work together in recombinant DNA technology?
Restriction enzymes act as molecular scissors to cut DNA from one organism and DNA ligase joins the DNA strands together
What is a gel electrophoresis?
A method used to separate molecule (like DNA) according to mass, charge and size
What is a DNA fingerprint?
A pattern of bonds that shows the fragments of DNA in a sample (longest fragments do not move far-> smallest fragments move furthest)
What are two real life uses for DNA fingerprints?
Forensics: match suspect to crime scene
Paternity test: child have half DNA from mom and half from dad
What process is the polymerase chain reaction (PCR) process like?
DNA replication
What is a transgenic organism (genetically modified organism or GMO)?
An organism who’s genetic material includes DNA from different species
