Key Concepts - Week 2 - Nucleotides and nucleic acids Flashcards
What distinguishes nucleotides from nucleosides?
nucleosides lack the phosphate group
(Nucleoside is a nitrogenous base linked to a pentose)
A nucleotide of DNA may contain (explain answer)
a. ribose, uracil, and a phosphate group
b. deoxyribose, uracil and a phosphate group
c. deoxyribose, thymine, and a phosphate group
d. ribose, thymine, and a phosphate group
c.
The pentose in DNA is a deoxyribose. Thymine is a nitrogenous base that only exist in DNA nucleotides, whereas Uracil only exists in RNA nuleotides. All nucleotides contain at least one phosphate group.
Which of the following nitrogenous base is a purine (and explain)
a. uracil
b. adenine
c. cytosine
d. thymine
b.
(Adenine and Guanine are purines (double ring). Cytosine, Uracil and Thymine are pyrimidines (single ring))
The nucleotide sequence of DNA is which level of structure: primary, secondary, tertiary, or quaternary? Why?
Primary
The sequence of nucleotides and their respective Nitrogenous bases are the primary structure of DNA.
The secondary structure is the double helix, tertiary structure relates to supercoiling of the helix (normally occurs in Prokaryotic DNA) and quaternary structure refers to the association of DNA with histones
How does the double helix structure of DNA support its role in encoding the genome? Explain
Complementary base pairing allows easy editing of both strands of DNA.
(Complementary base pairing in DNA is important to allow easy editing of both strands of DNA to avoid mutations, so the genome is safely kept. Double helix also supports DNA duplication, and transcription of genes into mRNA. Complementary base pairing is important for DNA stability and for its function in the genome.)
DNA double helix does not have which of the following?
a. antiparallel configuration
b. complementary base pairing
c. major and minor grooves
d. uracil
Uracil
In eukaryotes, DNA is wrapped around…?
Histones
If the sequence of the 5’-3’ strand is AATGCTAC, the complementary sequence has the following sequence:
3’-TTACGATG-5’
Select which one is true about structural differences between RNA and DNA and explain:
a. bases, pentose, and the phosphodiester linkage
b. bases, pentose and the secondary structure
c. bases, pentose, and the glycosidic bond
d. bases, pentose, and number of phosphate groups
b.
Structurally DNA and RNA differ in their pentose (deoxyribose vs ribose), in the nitrogenous bases (Thymine vs uracil) and in the secondary structure (double helix vs mostly single-strand).
mRNA splicing is required to remove ___________ from pre-mRNA and initiate_________
introns, translation
How many nucleotides contain 12 mRNA codons? Why?
36
Each codon has 3 nucleotides (3 bases); therefore, a mRNA with 12 codons has 36 nucleotides.
Match the following list of RNAs with their functions
- rRNA
- mRNA
- tRNA
a. codes for proteins
b. components of the ribosome
c. is linked to a specific amino acid
- b
- a
- c
Select the statements that are correct. Explain.
a. Codon is a sequence of three bases in mRNA that codes for one amino acid
b. The initiation codon is AUG and codes for isoleucine
c. Each codon specifies more than one amino acid
d. Some amino acid acids may have two or more codons
e. The genetic code, the number and size of chromosomes differ for each species
a. d.
The initiation codon is AUG and codes for the amino acid methionine. Each codon specifies only one amino acid. The number and size of chromosomes differ for each species, but the genetic code is universal.
Ribosomes are complex particles containing rRNA and ___________ where protein synthesis take place. ________ molecules bind to mature ___________ and transfer ____________ one by one to start and elongate the polypeptide chain.
proteins, tRNA, mRNA, amino acids
Key concept: describe the structure of nucleotides
