DNA Flashcards
What is the central dogma of molecular biology
DNA –> RNA –> Protein
What are the nucleotide bases
Adenine, guanine, cytosine, thymine
Which bases are purines
Adenine and guanine
Which bases are pyrimidine
Cytosine and thymine
How are nucleotides in a strand connected to each other
Phosphodiester bonds
What is Chargaff’s Rule
% A = % T
%C = %G
What is the ratio of C+A:G+C?
It varies!
How many DNA bp per helical turn?
10
What is the most basic level of DNA packaging?
Nucleosome
What is a nucleosome
DNA wrapped around octameric histone complex
“beads on a string”
What are sister chromatids
Identical copies of a chromosome
WHich are larger–purines or pyrimidines
Purines
Where is the centromere
In the middle of the replicated chromosome
Why is the centromere important
Where the mitotic spindle attaches, densest DNA
What is the telomere
Region of DNA at ends of chromatids
Euchromatin:
less condensed, more accessible
Heterochromatin:
highly condensed, not rich in genes, low levels of gene expression
What are the types of heterochromatin
Constitutive and facultative
What are the differences between the subtypes of heterochromatin
Constitutive: always tightly packed
Facultative: can be opened up
What is a gene?
region of DNA that controls discrete hereditary characteristics, usually corresponding to single protein or RNA
What makes up mobile DNA elements
DNA trasposons, retroviral-like retrotransposons, non-retroviral retrotransposons
Why di we care about simple sequence repeats?
Help with gene mapping, some are specific to diseases such as Huntingtons
About how much fo the human genome is repeated vs unique sequences
50-50
Define synteny
The presence of two or more loci on the same chromosome
What are the 3 basics of DNA metabolism
Replication, Recombination, Repair
What is the mechanism of DNA replication
Semiconservative
What catalyzes DNA replication
DNA polymerases
What directing does DNA replication happen?
5’-3’
Leading strand:
replicated in same direction as helix is being unwound
Lagging strand:
Replicated in the opposite direction of unwinding
Many small fragments generated
Who connects the fragments of the lagging strand
DNA ligase
Who unwinds the DNA
DNA helicase
Who prevents the unwound DNA from reconnecting
Single strand DNA binding protein
Who makes the RNA primer
DNA polymerase/primase
Who synthesizes the new DNA strand
DNA polymerase
Draw a schematic of the replication fork
What is the problem with ending replication
lagging strand cannot finish replicating the parent strand
How is the end replication problem fixed
Telomerase. Uses RNA template to synthesize a DNA copy of telomeric portion
What is DNA methylation
Methyl group added to cytosine
What does methylation do
Influences regulatory proteins, usually in transcriptionally silent regions
Is methylation hereditary
Yes
