Biochemical Basis of Heredity Flashcards
What are chromosomes made of?
DNA and protein
DNA consists of a lot of _______________ but no _____________.
- phosphorus
- sulfur
Proteins contain _____________ but very little _______________.
- sulfur
- phosphorus
Rough strain Griffith experiment
the rough strain is nonvirulent so the mouse lives
Heated killed smooth strain Griffith experiment
mouse lives
smooth strain Griffith experiment
the smooth strain is virulent so the mouse dies
rough strain and heated killed smooth strain Griffith experiment
all mice die
What happened when the rough strain and heated killed smooth strain were injected into a mouse?
all mice died and the living bacteria was found of S type so this implies that R bacteria were transformed into S
Transforming principle
carried genetic information, there is a chemical in one cell that is genetically changing the other
What did Phoebus Levene do?
isolated nucleotide and figured out what they were made of
What are nucleotides made of?
a sugar molecule, phosphate group, and a nitrogen-containing base
Nitrogen containing bases
Adenine, guanine, cytosine, thymine
What did Erwin Chargaff do?
found out how base pairs pair to each other
What base pair corresponds to A?
T
What base pair corresponds to G?
C
What did Maurice Wilkins and Rosalind Franklin do?
took an X ray diffraction which showed that DNA was a helix
Watson and Crick
created a DNA model showing how DNA is a double helix
How is DNA orientated?
3’ – 5’ and 5’ – 3’
What holds together base pairs?
hydrogen bonds
Central Dogma
a theory stating that genetic information flows only in one direction from DNA to RNA to proteins or RNA directly to protein
Three steps of the central dogma
- replication
- transcription
- translation
Replication occurs in the ….
DNA
After DNA is replicated it resides in the __________.
nucleus
Helicase
unwinds and holds apart DNA section to be replicated
Primase
begins new DNA molecule with RNA primer
DNA polymerase
brings in new DNA nucleotides to existing strand
Exonuclease
removes RNA primer
Ligase
seals sugar phosphate backbone
What do binding proteins do?
stabilize separated strands of DNA
Step one of DNA replication
helices binds to origin and separates strands
Step two of DNA replication
binding proteins prevent single strands from rejoining
Step three of DNA replication
primate makes a short stretch of RNA on the DNA template
Step four of DNA replication
DNA polymerase adds DNA nucleotides to the RNA primer
Step five of DNA replication
DNA polymerase proofreading activity checks and replaces incorrect bases just added
Step six of DNA replicaiton
enzymes remove RNA primer and ligase seals sugar phosphate backbone
What is the overall direction of DNA replication?
‘5 to 3’
What strand replicates smoothly?
the leading or continuous strand
What does the discontinuous strand must do?
produces Okazaki fragments on the 5’ to 3’ template
Where does transcription occur in?
the nucleus
Where does translation occur?
the cytoplasm
In transcription what serves as a template for RNA synthesis?
DNA
What does RNA polymerase do in transcription?
begins at promoter region and adds nucleotides until a stop codon is reached
What are the RNA nucleotides?
A, U, G, C
rRNA
ribosomal RNA
-forms the ribosomes with protein
mRNA
messanger RNA
-carries the code for protein synthesis (codons)
tRNA
transfer RNA
-picks up amino acid for the growing polypeptide chain (anticodons)
What happens during transcription?
- base sequence of new RNA strand is complementary to the template DNA strand which is the mRNA molecule
- mRNA detaches
How many nucleotide bases are on a codon?
3
How many codons make up the genetic code?
64
What does redundancy mean in the genetic code?
that more than one codon corresponds to one amino acid
Start codon
AUG
Stop codons
UAA, UAG, UGA
What does tRNA do?
translates the genetic code anticodon base pairs with codon on mRNA and tRNA has a hook that allows the correct amino acids to pair
How are genes expressed?
they are either on or off
Name some ways genes are expressed:
- some switched on/off throughout lifetime
- some turned on only at certain times
- some turned off permanently before birth
Posttranscriptional modifications
- introns are cut out
- exons are joined together
- the mRNA transcript is transported to cytoplasm for translation
What do regulatory proteins do?
-speed up or halt transcription
-may bind with noncoding DNA sequences and affect the transcription of a neighboring gene
Positive regulation
if activator is on operator then transcription occurs
Negative regulation
if a repressor is on an operator then no transcription occurs
If no activator is present does transcription occur?
no
If no repressor is present does transcription occur?
yes
