Ch. 9 Flashcards
Nucleotide
a single building block composed of a deoxyribose sugar, a phosphate group, and a nitrogenous base
Nitrogenous bases
Adenine, Guanine = purines
cytosine, thymine = pyrimidines
Sugar phosphate backbone
chained nucleotides
5’ ends w phosphate group on backbone
3’ ends w hydroxyl group
Which DNA fragment is more resistant to heat?
GC fragments bc it has 3 hydrogen bonds, while AT has 2 hydrogen bonds
Chromatin
chromosome substance where DNA is wrapped in several layers
protein DNA complex that makes up eukaryotic chromosomes
Semiconservative
two identical double helices are formed from one original, parental double helix, and each DNA double helix has half original and half kinda new strand
DNA Replication (in S phase)
- Parent DNA molecule
- Parental strands unwind and separate at several points
- Parental strand has template where DNA polymerase binds complementary bases (A-T and G-C)
Enzymes in DNA Replication
Helicase
unwinds parental double helix
Enzymes in DNA Replication
Binding proteins
stabilize separate strands
Enzymes in DNA Replication
Primase
adds short primer to template strand
Enzymes in DNA Replication
DNA polymerase
binds nucleotides to form new strands
Enzymes in DNA Replication
Ligase
joins Okazaki fragments and seals other nicks in sugar-phosphate backbone
Polymerase Chain Reaction (PCR)
DNA amplification technique
DNA polymerase replicate specific DNA sequence in test tube
Sequencing DNA
deduces a DNA sequence by aligning pieces that differ from each other by the end base
reverse transcription
Reading a DNA sequence
- DNA fragments are ordered by size on sequencing gel (by longest to shortest)
- Laser highlights end base
- Sequence is derived
Histone
individual proteins that DNA is wrapped around
Nucleosome
structure resembling beads on string
metaphase chromosome
highly compacted replicated DNA
The copying of the information in DNA is straightforward because
each strand of a DNA molecule carries complementary information.
Replication occurs at a
replication fork
The DNA double helix is separated into single strands by the enzyme
helicase
Short segments of RNA, called ___ , are synthesized.
RNA primers
Newly-exposed, unreplicated DNA is protected by
binding proteins
The enzyme that synthesizes the short segments of RNA is called a
primase
New DNA is synthesized in the ___ direction.
5’ to 3’
The enzyme that catalyzes new DNA synthesis is
DNA polymerase
Fragments of discontinuous DNA synthesis are called
Okazaki fragments
Gaps in the sugar-phosphate backbone of DNA are closed by
DNA ligase
What components are needed to perform PCR?
target DNA, DNA primers, DNA nucleotides, and Taq1 polymerase.
Imagine you are able to watch DNA replication under a microscope in a mutant strain of bacteria. DNA replication appears to proceed normally, but at the end of the replication cycle, there are some regions of the DNA that appear to be fragmented and not joined together along the backbone of the DNA molecule.
Which enzyme is most likely missing in this bacterial strain?
ligase
You are performing PCR for the first time in the lab. You have all your reagents ready, but you forgot to add adenine.
What will be the result of your reaction?
DNA synthesis will occur until the polymerase reaches a thymine in the template strand, and then it will halt.
You are working with a novel organism with double-stranded DNA and you discover that this organism has 20% adenine in its DNA.
What percentage of cytosine do you expect that this organism has in its DNA?
30%; in DNA the amount of adenine equals the amount of thymine, and the amount of cytosine equals the amount of guanine. If the percentage of adenine is 20%, we also expect the % of thymine to be 20%. This leaves 60% of the DNA for cytosine and guanine. Because we expect equal amounts of each of these, we expect 30% cytosine.
