L8: DNA AND THE FLOW OF GENETIC INFO Flashcards
What is the real word for DNA?
Deoxyribonucleicacid
DNA lives…
inside the nucleus
Amino acids live…
outside the nucleus in the cytoplasm
Characteristics of the structure of DNA
- double helix
What scientist discovered the structure of DNA?
Watson and Crick
What are the two strands called in DNA and what are they held together by?
- nucleotides
- held together by base pairing - hydrogen bonds
Differences in DNA sequence lead to …
genetic variation
When is DNA replicated?
-during the cell cycle in S phase
Whats the first thing that happens when DNA is being replicated?
-hydrogen bonds are broken.
- uncoils
Whats the name of the protein/ enzyme that replicates DNA?
DNA polymerase
What does DNA polymerase do to replicate the DNA?
The enzyme adds the nucleotides using the sequence of the parent strand
What is an old strand of DNA referred to as?
template strand
Can mistakes be made during the DNA replication process?
Yes, there called DNA
- errors
-mismatches
-mutations
Whats the error rate of DNA replication?
1 in 10,000 nucleotides
What rate has DNA polymerase reduced the error rate to?
1 in 10 000 000 000 nucleotides
What is a mismatch error?
occurs when the proofreading abilities of DNA polymerase fails
Example: c matches with a
Does a cell have the ability to fix a mismatch error?
-yes
- with the mismatch repair enzymes
When do we see a DNA mutation?
When the mismatch repair was not able to be fixed.
What is a DNA mutation?
A permanent error in the DNA sequence
What are the 3 steps in DNA repair?
- recognition
- removal
- replacement
How can a segment of DNA become damaged? Cause mutations?
- chemicals
- radiation
- ultraviolet light
Explain the stages of DNA repair:
Recognition- the damaged or mismatched area is detected
Removal- the region is removed by enzymes, cuts out damaged area
Replace- DNA polymerase fills in the gap with new nucleotides, by re-reading and filling the template strand
Why is it important to repair either mutations or damaged DNA?
- if you have failed DNA mechanisms it can result in disease
Whats an example of a disease that can result from failed DNA mechanisms?
- xeroderma pigmentosum
- more prone to skin cancer
- if they are exposed to ultraviolet light it will cause two T”s that are side by side to bond together, creating thymine dimers
What do genes code for ?
ribonucleic acid molecules
What info makes a protein?
RNA molecules
What is a gene?
A sequence of DNA that is used to make a copy of an RNA molecule used to eventually make proteins
BLANK –> BLANK —> BLANK —>
DNA -> RNA -> Protein
Differences with RNA compared to DNA
- single-stranded
-the base uracil takes the place of thymine - ribose sugar is used
3 types of RNA molecules:
- ribosomal RNA = rRNA
- messenger RNA= mRNA
- transfer RNA = tRNA
Function of mRNA:
the code that specifies the order of amino acids that are used to make proteins
Function of rRNA:
- a major component of ribosomes
- their job is to make covalent bonds that link the amino acids together
Function of tRNA:
- transports the correct amino acid to the ribosome using the information found on the mRNA molecule
- brings it to the site of amino acid assembly
What are the two steps of making proteins?
- transcription
- translation
Transcription
-produces mRNA copy from the DNA sequence of a gene
- once made the mRNA moves from the nucleus to the cytoplasm
Translation
- assembles the amino acids of proteins
Transcription begins when…
RNA polymerase binds to a region of DNA called a promoter
What two things do you need for transcription to occur?
- DNA sequence of a gene
- RNA polymerase
Transcription starts at the ——
and ends at the ——–
promoter region, terminator sequence
Transcription
-mRNA Polymerase finds promoter, begins unzipping DNA and reading the template strand and adding the complimentary nucleotides
End point of transcription:
Terminator sequence
How is transcription different from DNA replication?
- only one strand of DNA is used in as a template
- the product is a single-stranded RNA, not double stranded
- specific segments are transcribed into RNA not the entire DNA molecule
- transcription occurs all the time
Transcription occurs —– the time while DNA replication only happens during —–
all the time, cell division
What has to happen after transcription before translation?
the RNA molecule needs to move from inside the nucleus to the cytoplasm
Formula of Translation
mRNA into proteins
A group of three nucleotides are called…
codons
What do we used to make sense of the meaning of codons?
We can use the genetic code.
What is the genetic code?
A chart that specifies all the codons needed to make certain proteins
T/F : more then one codon can code for a single amino acid.
True
What codon is the starting point for mRNA translation?
AUG - METHIONINE
What is the stop codon for mRNA translation:
UAA
UAG
UGA
What does a stop codon symbolize?
the end of translation
What four things do you need for the construction of a protein?
- The mRNA molecule
- Ribosomes: made up of rRNA and proteins
- amino acids
- tRNA molecules: that will bring the amino acids to the mRNA and ribosomes
A tRNA molecule is really just a ….
RNA molecule folded on its self
What important aspect does the tRNA molecule bring to translate?
the anti codon
What is the anticodon?
a codon complimentary to the original codon
Example of DNA mutation
-Sickle-cell anemia
-caused by a single nucleotide mutation in the hemoglobin gene
