DNA Flashcards
1
Q
nucleic acids
A
- biological molecules (biopolymers)
- their monomers are nucleotides
- 3 main types are DNA, RNA and ATP (a modified nucleotide)
2
Q
nucleotide structure
A
- contains a phosphate group, a pentose sugar and a nitrogen base
3
Q
5 types of nitrogen bases
A
- adenine, thymine/uracil, cytosine and guanine
4
Q
pyrimidines
A
- 1-ringed nitrogen bases (C, T, and U)
5
Q
purines
A
- 2-ringed nitrogen bases (A and G)
6
Q
what is DNA acronym for
A
- deoxyribonucleic acid
7
Q
DNA measurements
A
- one turn = 3.4 nm
- between rungs = 0.34 nm
- across= 2.0 nm
8
Q
hydrogen bonds in DNA
A
- there are 2 between A and T
- there are 3 between C and G
9
Q
are the 2 strands of polynucleotides in DNA antiparallel to each other?
A
- yes. this means that they are parallel to each other but face opposite directions
10
Q
in DNA:
adenine can only pair with ___
cytosine can only pair with___
A
- thymine
- guanine
11
Q
Chargaff’s rule
A
- no. of A = no. of T. A = T.
- no. of C = no. of G. C = G.
- named after the chemist, Erwin Chargaff.
- total amount of purines = total amount of pyrimidines.
- ratio of purines to pyrimidines in DNA of every cell = 1:1
- A + G = T + C
12
Q
cell theory
A
- all living organisms are made up of cells which reproduce to make new cells like themselves and cells come only from pre-existing cells
- cell has life cycle of its own; is made from a pre-existing cell (“born”), grows, becomes specialized, performs their functions and die
13
Q
chromosomes consist of
A
- DNA and proteins
14
Q
what is an important cell function related to the cell theory?
A
- to make daughter cells (which have same no. and types of chromosomes) which are exactly like parent cells
- when cell is ready to divide, it grows larger; the number of organelles doubles and the amount of DNA doubles as well, which is due to DNA replication
15
Q
the doubling of the amount of DNA results from ___
A
- DNA replication
16
Q
DNA replication
A
- making copy of DNA. DNA is only biomolecule capable of making its own copy!
- occurs in nucleus
- occurs on both strands of DNA (all the genes replicate)
- result is 2 identical copies of o.g. DNA
17
Q
steps of DNA replication
A
- double stranded DNA unwinds and unzips
- the complementary bases pair on each unzipped strand
- adjacent nucleotides join
18
Q
talk about step 1: “double stranded DNA unwinds and unzips”
A
- after unwinding, hydrogen bonds still exist. after unzipping, hydrogen bonds break
- DNA helicase does the unzipping
19
Q
talk about step 2: “the complementary bases pair on each unzipped strand”
A
- in the nucleoplasm, there is an abundance of free nucleotides. these can bond with the complementary exposed nucleotides on the replicating DNA molecule
- “new” and “old” nitrogen bases join by hydrogen bonds, but new nucleotides are not joined to each other yet
- enzyme at this stage is DNA polymerase
20
Q
talk about step 3: “adjacent nucleotides join”
A
- the complementary base pairings result in the pairing of each base, but sugar and phosphate are not connected to make backbone
- so, adjacent sugar and phosphates are sealed by the enzyme DNA polymerase to make a continuous strand
- DNA ligase is also active at this stage. it spots any errors in replication, proofreads and corrects mistakes and errors
