DNA structure test Flashcards
What is the full name of DNA?
Deoxyribonucleic acid
What are the 4 nitrogenous bases
Adenine (A), Thymine (T), Guanine (G), Cytosine (C)
What is meant by the term antiparallel?
strands are opposite
mRNA
- Messenger RNA
- Carries genetic information from the DNA in the nucleus to the ribosome in the cytoplasm to make proteins
tRNA
- Transfer RNA
- Each tRNA transfers a different amino acid to the ribosome during protein synthesis
rRNA
- Ribosomal RNA
- Helps form large and small subunits of ribosomes
What are start codons and stop codons?
- Start codons- Protein translation is initiated
- Stop codons- Termination of the translation site
Components of a nucleotide
Deoxyribosugar, phosphate, and Nitrogenous bases.
Hydrogen bonding - which base pairs are held with 3 H bonds vs. 2 H bonds?
5’ to 3’ and 3’ to 5’
Purines are held with 2 bonds
Pyrimidines are held with 3 bonds
Complementary base pairing - which ones pair together and why?
Adenine matches with thinine
Guanine matches with cytosine
Topoisomerase
- Works in a position just ahead of the helicase
- Untwists the DNA and holds it steady so that helicase can move down the replication bubble
What makes DNA twist? - hydrophobic vs. hydrophilic
Alternating deoxyribose and phosphate molecules
Helicase
Disrupts by
- Unzips the double helix by disrupting hydrogen bonding between nitrogenous bases
- Creates two single strands with free nitrogenous bases that can be used as a template for free nitrogenous bases to be added
- Moves in both directions from the origin of replication
Single Stranded Binding
- Holds the single strand still and stable
- Prevents the two strands from rejoining so that additional proteins may do their jobs of adding new nitrogenous bases
Primase (Primer)
- Attaches a short complementary RNA strand to the DNA template - this is a start code, which is a primer that allows the next protein to begin working
- Works only in the 5’ to 3’ direction
- 1 primase is needed for the leading strand (continuous replication)
- Multiple primase is needed for the lagging strand (fragmented synthesis)
DNA Polymerase III
Identifies opposite of DNA
- Identifies the RNA primer and attaches to the strand at that location
- Continuously moves in the 5’ to 3’ direction adding free nucleotides from the environment within the nucleus to the template strand
- Releases from the template when two replication forks meet
DNA Polymerase I
- Fills in the gaps between Okazaki fragments by adding the correct nucleotides (ones with complementary nitrogenous bases)
Okazaki fragments
There are gaps between the fragments of new DNA that must be filled in as replication continues down the lagging strand
Ligase
- This joins the fragments into one continuous complementary strand of DNA by synthesizing phosphodiester bonds
Nuclease
* ______Bonds
* Helps with….
- Phosphodiester bonds
- play crucial roles in various DNA repair processes, which involve DNA replication, base excision repair,
CODons
Codes for a specific amino acid
AnTicodons
Found in tRNA and pairs with codon on a strand of mRNA during translation
Location of transcription
Nucleus of human cells
What is a complementary mRNA gene sequence
A,C,G,U
IniTiation (Translation step 1)
- Transcription factors (helper proteins) bind to a promoter region somewhere on the DNA double helix
- In humans, our promoter region (TATA box)
Elongation (Translation step 2)
The mRNA strand is synthesized
* RNA Polymerase III attaches to the double helix
* It untwists the double helix to create a transcription bubble
* It moves down the template strand in the 3’–>5’ direction , adding complementary RNA nucleotides to the growing mRNA in the 5’–>3’ direction and securing the RNA sugar-phosphate backbone
Termination (Translation step 3)
- RNA Polymerase III adds complementary RNA nucleotides to the DNA template until a stop code is reached
- termination code is called polyadenylation (a string of A’s) - it tells the polymerase to stop transcribing and the enzyme releases the DNA double helix and the new mRNA strand
Termination code
polyadenylation (a string of A’s)
Promoter region
TATA box
Replication bubble
- Two replication forks are formed at the replication bubble
- DNA replication occurs in both directions.
Replication fork
A Y-shaped region where the parent DNA splits into two strands
What sugar is in RNA? How is the sugar different from DNA?
RNA- Ribose
DNA- Deoxy, No ribose
Purines vs. pyrimidines
Purines: adenine and guanine
Pyrimidines: cytosine and thymine
Hydrogen bonding - which base pairs are held with 3 H bonds vs. 2 H bonds?
Purines: Adenine and guanine form 2 bonds
Pyrimidines: Cytosine and thymine form 3 bonds
5’ to 3’ and 3’ to 5’
Count the amount of sugars starting with oxygen and going clockwise
What is the job of DNA? And where is DNA stored?
To store and transmit genetic info. It is stored in the nucleus
Leading strand
- Runs from 5’ to 3’ direction in the replication fork
- Can be replicated continuously
Lagging strand
- The strand opens in 3’ to 5’ direction toward the replication fork
- Replication is fragmented
Transcription
the process of building a complementary RNA copy of a DNA strand
Translation
is the process of building a protein based on the sequence of the RNA copy
