E2 Chapter 16/17: Inheritance and Gene Expression Flashcards
Exam 2
Copying DNA is also called
DNA replication
Type of DNA replication where the replicated double helix consists of one old strand (from the parent molecule) and one new strand
Semiconservative model
The two parent strands reassociate after acting as templates for new strands, thus restoring the parental double helix
Conservative model
Each strand of both daughters contains a mixture of old and new DNA
Dispersive model
What model of DNA replication is the most commonly regarded as true?
Semiconservative model
Each somatic cell has how many DNA molecules in its nucleus?
46
short stretches of DNA that have a specific sequence of nucleotides; “start here”
Origins of replication
a Y-shaped region where the parental strands of DNA are being unwound
Replication fork
Proteins that initiate DNA replication recognize this sequence and attach to the DNA, separating the two strands and opening up
a replication bubble
enzymes that untwist the double helix at the replication forks, separating the two parental strands and making them available as template strands
Helicases
A protein that binds to the unpaired DNA strands during DNA replication, stabilizing and holding strands as they get ready for complimentary strands
Single-strand binding protein
a short polynucleotide with a free 3′ end, which is bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication.
Primer
The primer is synthesized by what enzyme (it is really obvious lol)
Primase
enzymes that catalyze the synthesis of new DNA strands by adding nucleotides to a pre-existing chain.
DNA Polymerase
The two strands in DNA replication are anti-________. What does this mean?
Anti-parallel; the 3’ end of one attaches to the 5’ end of the other
A DNA strand can only elongate in which direction?
5’-3’
short segments of DNA synthesized on the lagging strand during DNA replication.
Okazaki Fragments
one of the two new strands of DNA synthesized during DNA replication.
Lagging strand
What is a lagging strands main characteristic?
It is synthesized discontinuously in short segments
Lagging strands are _______________ to the template strands and synthesized in the _______ direction
Anti-parallel; 3-5
Where do Okazaki fragments start synthesizing?
Origins of Replication
crucial for maintaining DNA integrity and preventing mutations that could lead to diseases.
Mismatch Repair
In many replications, a segment of the strand containing the damage is cut out (excised) by a DNA-cutting enzyme called
Nuclease
The exact way in which this complex of DNA and protein fits together
Chromatin
The less condensed form of eukaryotic chromatin that is available for transcription
Euchromatin
Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed
Heterochromatin
A change in nucleotide sequence of an organism’s DNA or in the DNA/RNA of a virus
Mutations
A change in a SINGLE nucleotide pair in a gene
Point mutation
What are the two types of small-scale gene mutations? (2)
- Single nucleotide-pair substitutions
- nucleotide-pair insertion/deletion
the replacement of one nucleotide and its partner with another pair of nucleotides
Nucleotide-pair substitutions
a mutation that has no observable effect on the phenotype
Silent-mutations
Substitutions that change one amino acid to another one
Missense mutations
mutations that cause translation to be terminated prematurely
non-sense mutations
Additions or losses of nucleotide pairs in a gen
Insertions/deletions
occurs whenever the number of nucleotides inserted or deleted is not a multiple of three
Frameshift mutation
A chemical or physical agent that interacts with DNA and can cause a mutation
Mutage
Mi mato con la pistola
i’m going to shoot myself
altering genes in a specific, predictable way
Gene editing
The moving ends of each bubble – where the
double-stranded DNA is getting pulled apart &
copied – are called
The Replication Fork
where there
are now two identical sets of double-stranded DNA
Replication bubble
One origin of replication on a circular DNA.
Opposite replication forks eventually meet, resulting in two
separate double-stranded DNAs
Prokaryotic Replication
Multiple origins of replication on each non-
circular DNA double helix. The multiple replication bubbles
eventually connect, resulting in two separate double-
stranded DNAs
Eukaryotic Replication
What are the 4 major enzymes?
- Helicase
- Primase
- DNA polymerase
- DNA Ligase
Enzyme that separates the two parental strands of
the DNA double-helix so that they can be
replicated
Helicase
What are the two ways DNA polymerase helps to build a new DNA strand?
- Helping lone nucleotides base-
pair with nucleotides on the
parent strand - Catalyzing phosphodiester
bonds between incoming
nucleotides so they’re
connected to each other
synthesizes a short
primer in replication
Primase
A short stretch of RNA base-
paired to the DNA parental strand. It
is a starting block for DNA
polymerase to build a new complimentary
strand.
Primer
Daughter strands are always built in what direction?
5’-3’
Is DNA’s double strand parallel or antiparallel?
Antiparallel
The daughter strand IS the
leading strand
The lagging strand is built in what direction?
3’-5’
What are the 5 steps of DNA replication?
- Unzip the DNA
- Add primers
- Build new complimentary strands
- Replace primers
- Join the Okazaki Fragments
A _____________ elongates the new strands by adding DNA nucleotides
DNA polymerase
Once the fragments of the new strands touch,
_______________ cuts out the RNA
primers and replaces them with DNA
nucleotides.
DNA polymerase
joins together the remaining adjacent
nucleotides where the primers have been
replaced
Ligase
Are Okazaki fragments continuous or discontinuous
Discontinuous
Eukaryotic DNA is packaged into multiple
Chromosomes
One long strand of DNA wrapped around histone proteins
Chromosome
Protein “beads” around which DNA is wrapped
Histones
Histones help to do what?
Help a cell package and organize its extremely long DNA into a small space
DNA + Histones; the stuff of chromosomes
Chromatin
Is chromatin loosely packed or tightly packaed?
Can be both
What does loosely packed chromatin do?
Leaves enough room between the “beads” for transcription and replication enzymes to access the DNA
What does tightly packed chromatin do?
Allow for genomes to not be transcribed
