Nucleus and nucleic acids Flashcards
What are the building blocks of DNA?
Phosphoric acid
Deoxyribose sugar
Nitrogenous bases
Which nitrogenous bases are purines?
Adenine and Guanine
Which nitrogenous bases are pyrimidines?
Thymine and Cytosine
what is the double helix called? and what forms this double helix?
It’s called the sugar-phosphate backbone, formed by the pentose sugar and phosphoric acid
What is adenine complimentary to?
Thymine
What is Cytosine complimentary to?
Guanine
What is the difference between a nucleoside and a nucleotide?
Nucleoside: Pentose sugar + Nitrogenous base
Nucleotide: Pentose sugar + Nitrogenous base + phosphate
What’s the difference between DNA and RNA
DNA is double stranded while RNA is single stranded
DNA has a deoxyribose sugar, RNA has a ribose sugar
DNA has a nitrogenous base pair, RNA has a single nucleobase
DNA has Thymine; RNA has Uracil
RNA has an OH group in carbon 2; while DNA does not have that OH
Which nucleic acid is the most abundant in cells?
RNA is the most abundant
Approximately 90% of the nucleic acid within cells is RNA, and the remainder is DNA, which is the repository of genetic information
Which bonds contribute to the stability of the sugar-phosphate backbone? (double helix)?
Hydrogen bonds
Van der Waals forces
Hydrophobic interactions
How many hydrogen bonds does adenine form with thymine?
2 bonds
How many hydrogen bonds does Cytosine form with Guanine?
3 bonds
How is DNA packaged in the nucleus?
-DNA strands, which are negatively charged, become tightly wound around a positively charged protein called histones. They are then packaged in chromosomes
What enzyme is responsible for unwinding DNA?
Helicase
What enzyme is responsible for unwinding DNA?
Helicase
What stabilizes the unwound parental DNA during replication? (to prevent the strands from winding up again)
Single Strand Binding Protein
In which direction is the DNA synthesized?
5’——> 3’ direction
What enzyme is responsible for synthesizing DNA?
DNA polymerase enzyme
How is the lagging strand synthesized?
The lagging strand is synthesized discontinuously. The primase enzyme synthesizes a short RNA primer, which is extended by DNA polymerase to form an Okazaki fragment. After the RNA primer is replaced by DNA, DNA ligase joins the Okazaki fragment to the growing fragment.
Describe the process of DNA replication.
- Helicase unwinds the double helix
2.Single Strand Binding Protein stabilizes the DNA stands, preventing them from winding up. - DNA polymerase then synthesizes the leading strand continuously in the 5’ to 3’ direction.
- The lagging strand is synthesized discontinuously. The primase enzyme synthesizes a short RNA primer which is extended by DNA polymerase, creating an Okazaki fragment.
- After the RNA primer is replaced by DNA, the enzyme DNA ligase binds the Okazaki fragment to the growing strand.
The high fidelity and accuracy of DNA replication is due to?
- Substrate specificity and proofreading function of DNA polymerase
- Efficiency of post-replication DNA mismatch repair
What is the difference between leading and lagging strand?
The leading strand is synthesized from 5’ to 3’ direction, while the lagging strand is synthesized from 3’ to 5’ direction
List the stages of mitosis in their order
Interphase
Prophase
Metaphase
Anaphase
Telophase
IPMAT :)
What happens during interphase?
DNA replication in preparation for cell division
What happens during prophase?
-Spindle fiber formation
-Chromosomes become condensed
What happens in prometaphase?
Spindle fibers attach to centromeres
What happens during metaphase
Chromosomes align at the equator
What happens during anaphase?
The chromatids of each chromosome are pulled to the poles of the cell
What happens in Telophase
Cytokinesis occurs
What is the period of cell growth that occurs before DNA replication?
G1 (growth) phase
What is the period in which DNA is synthesized/replicated?
S (synthesis) phase
What is the period after DNA replication but before cell division?
G2 phase
What is the period of cell division called?
M (mitosis) phase
The quiescent phase that a cell can enter after the M phase, when growth + replication cease, is called_______________
G-0
