Which bases are purines?
Which bases are pyrimidines? - Answer- Adenine (A) and Guanine (G) are purines
Cytosine (C) and Thymine (T) / Uracil (U) are
... [Show More] pyrimidines
What kind of structure do purines have?
What kind of structure do pyrimidines have? - Answer- purines have a double ring structure
pyrimidines have a single ring structure
The phosphate group in a nucleotide is expected to be found on which position of the sugar? - Answer- 5th carbon
The nitrogen base in a nucleotide is expected to be found on which position of the sugar? - Answer- 1st carbon
What is the sugar in DNA? What is the sugar in RNA? - Answer- deoxyribose in DNA
ribose in RNA
Which nucleotides pair with each other? - Answer- Guanine (G) and Cytosine (c) pair together
Adenine (A) and Thymine (T) / Uracil (U) pair together
Where do you find hydrogen bonds? - Answer- they form between nucleotides on different strands
A forms two bonds with T / U
C forms three bonds with G
Where do you find phosphodiester bonds? - Answer- they form the backbone of DNA. There is a linkage between the 3' carbon of one sugar molecule and the 5' carbon atom of another
Where do you find ionic bonds? - Answer- they form the bond between DNA and histones.
DNA is negatively charged and histones are positively charged
Where do you find glycosidic bonds? - Answer- they form the bond between the nitrogenous base and ribose sugar group in RNA
What happens in a missense mutation? - Answer- the altered codon now corresponds to a different amino acid. As a result an incorrect amino acid is inserted into the protein being synthesized
What happens in a nonsense mutation? - Answer- instead of tagging an amino acid, the altered codon signals for transcription to stop. Thus a shorter mRNA strand is produced and the resulting protein is truncated or nonfunctional
What happens in a silent mutation? - Answer- Since a few different codons can correspond to the same amino acid, sometimes a base substitution does not affect which amino acid is picked. Everything remains the same in the resulting protein and the mutation would go undetected, or remain silent.
What happens in a frameshift mutation? - Answer- Sometimes a nucleotide is inserted or deleted from a DNA sequence during replication. Or, a small stretch of DNA is duplicated.
Since a continuous group of three nucleotides forms a codon, an insertion, deletion or duplication changes which three nucleotides are grouped together and read as a codon. In essence it shifts the reading frame.
Frameshift mutations can result in a cascade of incorrect amino acids and the resulting protein will not function properly.
What happens in DNA replication? - Answer- the parent molecule unwinds, and two new daughter strands are built based on base-pairing rules
When does DNA replication occur? - Answer- S phase of interphase
What are the four steps of DNA replication? - Answer- 1. Replication fork formation
2. Primer binding
3. Elongation
4. Termination
What is attached to the 5' end of a DNA strand? - Answer- a phosphate group
What is attached to the 3' end of a DNA strand? - Answer- a hydroxyl group
Replication progresses in which direction? - Answer- the 5' -----> 3' direction
Which strand is oriented in the 3' -----> 5' direction? - Answer- the leading strand
Which strand is oriented in the 5' -----> 3' direction? - Answer- the lagging strand
What is the function of primase? - Answer- it catalyzes the synthesis of short RNA primers required for priming DNA synthesis. The primer is the starting point for replication.
What is the function of helicase? - Answer- it unwinds and separates double stranded DNA. It breaks the hydrogen bonds between nucleotide pairs.
What is the function of topoisomerase / gyrase? - Answer- they unwind and rewind DNA strands to prevent the DNA from becoming tangled or supercoiled. They relieve strain.
What is the function of DNA polymerases? - Answer- they synthesize new DNA molecules by adding nucleotides to leading and lagging DNA strands
What prokaryotic polymerase repairs, removes RNA primers from okazaki fragments, fills up gaps, works on the lagging strand, synthesizes in the 5' -----> 3' direction, and has 3' -----> 5' AND 5' -----> 3' exonuclease activity?
Replication - Answer- DNA polymerase I
What prokaryotic polymerase repairs gaps and discontinuities and has 3' ------> 5' exonuclease activity?
Replication - Answer- DNA polymerase II
What prokaryotic polymerase is the main polymerizing enzyme, can synthesize and and degrade simultaneously, has 3' -----> 5' exonuclease activity, acts on the leading strand, and cant start a new strand on its own (ORI sites) ?
Replication - Answer- DNA polymerase III
What Eukaryotic polymerase synthesizes the RNA primer, initiates synthesis on lagging strand, and is found in the nucleus?
Replication - Answer- Polymerase alpha
What Eukaryotic polymerase is found in the nucleus and does base excision repair?
Replication - Answer- Polymerase beta
What Eukaryotic polymerase works on mitochondrial DNA replication, is involved in nonhomologous end-joining, and has 3' -----> 5' exonuclease activity?
Replication - Answer- Polymerase gamma
What Eukaryotic polymerase fills in gaps, works on leading strand synthesis, and has 3' -----> 5>' exonuclease activity?
Replication - Answer- Polymerase delta
What Eukaryotic polymerase completes synthesis, repairs, and has 3' -----> 5' exonuclease activity?
Replication - Answer- Polymerase epsilon
What are Okazaki fragments? - Answer- Short fragments of DNA synthesized on the lagging strand during DNA replication. The lagging strand begins replication by binding with multiple primers. Each primer is only several bases apart. DNA polymerase then adds pieces of DNA, called Okazaki fragments, to the strand between primers. This process of replication is discontinuous as the newly created fragments are disjointed.
What are exonucleases? - Answer- they are enzymes that remove all RNA primers from the original strands. These primers are then replaced with appropriate bases. Exonucleases also "proofread" the newly formed DNA to check, remove and replace any errors. This happens after the continuous and discontinuous strands are formed.
What is the function of DNA ligase? - Answer- it connects two strands of DNA together by forming a bond between the phosphate group of one strand and the deoxyribose group of another. It joins the okazaki fragments.
What are telomeres and what is their function? - Answer- They are noncoding, repetitive DNA sequences at the end of chromosomes; they protect the coding sequence from degradation. Telomerase enzyme catalyzes the synthesis of telomere sequences at the ends of the DNA.
Which DNA form is the most common? - Answer- B form, right handed
Why is replication semiconservative? - Answer- each strand in the DNA double helix acts as a template for the synthesis of a new, complementary strand.
What is transcription? - Answer- It is the first step in gene expression. It's the process of copying a gene's DNA sequence to make an RNA molecule.
What are the steps of transcription? - Answer- 1. Initiation
2. Elongation
3. Termination
What initiates transcription? - Answer- When RNA polymerase binds to the promoter, found near the beginning of a gene. Once bound, RNA polymerase separates the strands.
What direction does transcription move in? - Answer- A 5' ---------> 3' direction
(polymerase can only move along the template in a 3' --------> 5' direction)
The DNA strand being copied in transcription is? - Answer- the antisense / noncoding / template strand
The RNA transcript carries the same information as which strand? - Answer- The sense / coding / non-template strand
(except it contains U instead of T) [Show Less]