Review Flashcards
a linear, unbranched polymer having the monomeric subunits- four chemically distinct nucleotides
DNA
Why are positions on the pentose given a prime
To avoid ambiguity between the numbering systems of the heterocyclic rings (bases) and the sugar
provides the structural support for the DNA double helix
sugar-phosphate backbone
how many base pairs in DNA make a complete turn
10
refers to the over- or under-winding of a DNA strand and is an expression of the strain on that strand.
DNA supercoiling
-important for compacting DNA for packaging within all cells
-reduces the space and allows for much more DNA to be packaged.
supercoiling of DNA
When the DNA helix has the normal
number of base pairs per helical turn it is in the _______________ state
relaxed
the number of times one strand crosses over (or wraps around) the other
linking number
why is thymine used in DNA instead of uracil
thymine has a higher resistance to photochemical mutation, which makes genetic message more stable.
A single substitution in base that leads to
production of stop codon and terminate protein synthesis.
Nonsense mutation
Mutations that insert or delete individual bases cause a shift in the triplet sets after the site of mutation
frameshift mutation
___________ has the least effect; will affect only one amino acid while ____________mutations have huge effects
substitution
frameshift
the sequence of mRNA that is complementary to the sequence of one strand of DNA
antisense or template strand
The mRNA that is identical (apart from the replacement of T with U) to the other strand of DNA
coding or sense strand
The convention for writing DNA sequences is that the top strand is the ________ strand and runs 5′ to 3′.
coding
the sequences in the DNA molecule that code for the
amino acid sequences of corresponding proteins.
exons
the DNA sequence in a eukaryotic gene that is not
translated into a protein.
introns
why is alternative splicing done
to remove introns
the overall length of a gene is determined largely by its _____________
introns
The exons of some genes appear homologous to the exons of others suggesting a common
exon _______________________
ancestry
a change in the nucleotide sequence of the genome, caused by a replication error or by a mutagen
mutation
-no change in coding function of genome
-A substitution mutation that does not change the amino acid sequence of the polypeptide product is a silent mutation
synonymous change
-mutation altering the codon
-A mutation in the coding region alter the amino acid sequence of the polypeptide product, resulting in either a missense codon (for a different amino acid) or a nonsense (termination) codon
nonsynonymous change
having no effect on the phenotype of the organism
neutral mutation
regions where mutations occur most frequently
hotspots
capsid
protein coat containing nucleic acid of viral genomes
nucleoid
bacterial genome organized as multiple loops compacted by nucleoid associated proteins such as H-NS (histone-like, nucleoid structuring protein)
-Very long duplex of DNA is packaged into thread like
structures called chromosomes
-ensures that DNA is replicated and distributed
appropriately during cell division.
chromosomes
- The region of the chromosome that is responsible for its
segregation at mitosis and meiosis
centromere
-seal the chromosome ends and facilitate meiotic chromosome reorganization for efficient pairing and recombination of homologous chromosomes.
-use reverse transcriptase to extend the very ends of chromosomes and solves the shortening of chromosomal ends during replication.
telomere
DNA is packaged in the nucleus by association with DNA binding proteins called ________________proteins in chromatin
histone
fundamental subunit of chromatin
nucleosome
how many histone proteins are present on a nucleosome
8
the histone proteins form a barrel shaped ___________ with the DNA wound _________ around the outside
octamer
twice
what are the core histones
H2A, H2B, H3, and H4.
what amino acid residues are present in histones
arginine and lysine residues, resulting in a high affinity for DNA
Histones ____________ are among the most conserved proteins
known, and the core histones are responsible for DNA
packaging in all eukaryotes.
H3 and H4
Each of the core histones has a histone fold domain that contributes to the central protein mass of the nucleosome, sometimes referred to as the ___________________
globular core
The positive charge on lysine is neutralized upon _____________________, whereas methylated lysine and arginine retain their positive charges.
acetylation
In eukaryotic cells, replication of DNA occurs in what phase?
S phase
In ____________phase everything except DNA begins to be doubled: RNA, protein, lipids, and carbohydrates.
G1
