DNA structure And Replication Flashcards
Genome DNA is in the form of
Chromatin
Genome DNA is bound to which proteins
Histones and non Histones
Histones bind DNA mainly as nucleosomes
composed of 2 copies of each
H2A
H2B
H3
H4
Amino acids in Histones are subject to______ which regulate the activity of underlying genomic regions
posttranslational modifications (PTMs)
_________are required for normal
chromosome segregation in mitosis and
meiosis
Centromeres
a substantial proportion of
human pathology stems from
abnormalities of
Chromosome segregation
The primary sequence of cenromeres are
Alpha satellite DNA
______________are DNA
sequences that have the ability to
change their position within a genome
Transposons (DNA)
retro (RNA) transposons.
Transposable elements drive______ of genomes by
facilitating the translocation of genomic
sequences, the shuffling of exons, and the
repair of double-stranded breaks
Evolution
DNA transposons move by
Cut and paste
Retrotransposons move
Copy and paste
Retrotransposotion takes place in both
The nucleus and cytoplasm
Each nucleotide is composed of
1) a phosphate group, (2) a five-carbon sugar, or
pentose, and (3) a cyclic nitrogen-containing
compound called a base.
In DNA the sugar associated is
2-deoxyribose
in RNA, the sugar is
Ribose
The DNA backbone is a polymer
with an
Alternating sugar phosphate sequence
Deoxyribose sugars are joined at both the _______to phosphate groups in ester links called _______
3’ and 5’ hydroxyl groups; phospodiester bonds
Nucleotides are arranged in what shape
Double helix
In the DNA The two polynucleotide strands are held together
in their helical configuration by
hydrogen bonding
Adenine and thymine form how many hydrogen bonds
2
Cytosine and guanine form how many hydrogen bonds
3
Chargaffs rule states
%A = %T and %G = %C.
Purine bases are
Adenine and guanine
Pyramiding bases are
Cytosine and thymine and uracil
Thymine and uracil differ in that
Thymine has a methyl group and uracil does not
DNA replicates in what phase of the cell cycle
S phase
Each strand of DNA serves as a template for
DNA polymerase
What does DNA polymerase do
Catalyze the addition of the correct bases during the synthesis of the new strand
Which strand is continuously synthesized by DNA polymerase
Leading strand
Synthesis of the lagging strand is done by
Okazaki fragments
DNA polymerase can only synthesize DNA in what direction
5’ to 3’
What are ORC proteins
enzymes that recognize the origin of replication
What is the function of topoisomerase
Relieves stress of the supercoils
What is the function of primate
Synthesizes RNA primers
What does DNA ligaments do
Seals Okazaki fragments into a continuous strand
All polymerases require
Pre existing DNA and a free 3’-hydroxyl
What does exonuclease do
Proofreading
In eukaryotes, initiator proteins are
ORC
Cdc6
Cdt1
Initiator proteins recruit the______
Helicase
Heliscase is activated in which phase
S phase
Polymerase and primate are added to the complex only when
Helicase is activated
Helicase is only activated when________activity begins
CDK/DDK kinases
Telomeres prevent ______during replication
DNA degration
The repeated sequence of telomeres is
TTAGGG
Synthesis of telomeres is done by
The reverse transcriptase telomerase
Cell senescence is when
The cell is unable to divide and triggers apoptosis
Cell senescence occurs when
Telomeres are progressively shortened after each cell division
telomeres length and telomerase activity are crucial for
Cancer initiation and the survival of tumours
Helicase is a complex of proteins containing
CDC6, Mcm2-7 and GINS
3’ exonuclease activity is involved in
Proofreading
5’ exonuclease activity is involved in
Primer removal
