LECTURE 5: Molecular Basis of Heredity Flashcards
A eukaryotic cell would contain how many molecules of DNA + why?
how about for prokaryotic organisms and viruses? + their genetic material are either… or….?
more than 1 molecules
bc each chromosome has 1 long molecule of DNA
one long molecule of DNA that are either naked or associated with proteins
What is the genetic material of all organisms
DNA
but for some viruses, it’s RNA
Uncoiled DNA of a human chromosome has an average length of?
size of human nucleus?
5 cm
5 x 10^-4 cm
basic unit of the chromatin
+ its composition
nucleosome
- protein core of 8 histone molecules
- molecule of DNA wound around the protein core
Histone molecules contain what histones (4) + how many
each contains 2 of H2A, H2B, and H3, and H4
One nucleosome is connected to another nucleosome by a?
that gives results to what with what kind of appearance?
linker DNA
chromatin fiber = “beads on a string”
length of chromatin fiber
10 nm in diameter
Nucleosomes have a _____ function
packaging
The winding of DNA around the nucleosome core results to a???
6-10 fold reduction in length
How is chromatin folded exactly?
histone molecule H1 connects with copies of itself
What histone molecule is found to be associated with the LINKER DNA
H1
How is chromatin further shortened and packaged?
via successive higher orders of chromatin fiber coiling through the formation of the 30 nm solenoid
once solenoid is formed, the chromatin fiber is packaged along a protein scaffold
DNA and RNA are____, meaning?
polynucleotides: made of repeating units of nucleotides
NUCLEOTIDES
composition (3)
- phosphate group
- pentose sugar
- nitrogen base
PENTOSE SUGAR of:
- DNA
- RNA
+ structure
+ difference
DNA: 2-deoxy-D-ribose
RNA: D-ribose
Cyclopentane (house formation) with O atom at the roof
Carbons 1 - 4 are numbered clockwise
DIFFERENCE:
DNA
- C1 and 3 has 1 OH, and 1 H attached
- C2 has 2 H attached
- C4 has 1 H, and 1 HOCH2 attached
RNA
- C1, 2, 3 has 1 OH and 1 H attached
- C4 has 1 H, and 1 HOCH2 attached
NITROGEN BASES for:
- DNA
- RNA
DNA: adenine, guanine, cytosine, and thymine
RNA: adenine, guanine, cytosine, and uracil
PURINE vs PYRIMIDINE
in terms of nitrogen bases
PURINE: adenine and guanine
PYRIMIDINE: cytosine, thymine, and uracil
PURINE vs PYRIMIDINE
in terms of structure
PURINE: double ring structure (purine ring + 5-membered imidazole ring)
PYRIMIDINE: single ring structure (pyrimidine ring)
the nitrogen base bonds with the sugar with ______ bonds to form a _______
the ______ bonds to the phosphate group with _____ to form a _____
afterward, the _____ bonds with its repeating units with _______ (what bonds?) to form a ______
- N-glycosidic
- nucleoside
- nucleoside
- phosphoester
- nucleotide
- nucleotide
- phosphodiester linkages
- polynucleotide
How does the Carbon (in pentose sugar) bond with the nitrogen base and the phosphate group?
to form a polynucleotide, what bonds to the next nucleotide and where?
- Carbon 1 in sugar attaches to nitrogen base
- Carbon 4 in sugar attaches to the phosphate group
- Carbon 3 attaches to phosphate group of the NEXT nucleotide
How are the ff named?
- nucleoside
- nucleotide
NUCLEOSIDE
- depends on nitrogen base present
- purine: (deoxy)-adenosine or (deoxy)-guanosine
- pyrimidine: (deoxy)-cytidine, (deoxy)-thymidine, or uridine
NUCLEOTIDE
- nucleoside + number of phosphate groups attached
Most common example of nucleotide?
adenosine triphosphate
Strands of DNA are?
- how?
- held together by what bond?
antiparallel
- left strand: 5’ PO4 (upper) and 3’ OH (lower)
- right strand: 3’ OH (upper) and 5’ PO4 (lower)
*orientation of sugar molecule and nitrogen base is also opposite/upsidedown
- HYDROGEN BONDS between paired bases
CHARGAFF’S RULE
- definition
- importance (2)
- conclusion
- a rule that states how nitrogen bases are paired together (A:T and G:C)
- accurate replication of DNA
- complementary of the antiparallel strands of DNA
Therefore, the ratio of purines (A+G) and pyrimidines (C+T) is 1:1 in DOUBLE STRANDED DNA
What is the main characteristic of a DNA molecule?
the arrangement/sequence of the nitrogen bases
the longer the DNA, the ?
and enables it to?
the more complex and varied its base sequence is
enables it to store huge amounts and diverse kinds of biological information
does base sequences vary among different DNA molecules?
yes
FACTORS contributing to stability of genetic material
- covalent bonds (phosphodiester bonds and N-glycosidic bond)
- many H bonds between the base pairs
- hydrophobic interactions between the stacked nitrogen base pairs
Who proposed the double strand 3D DNA structure? + date
+ model name
+ likened to what structure?
James Watson and Francis Crick (1953)
DNA Double Helix
spiral staircase
PARTS of the DNA double helix model
- rails: antiparallel sugar-phosphate backbone
- bars: nitrogen base pairs
the DNA is a _____ (direction) helix wherein a ____ (degrees) turn covers a distance of _______ and _____ (number) base pairs
thus, the base pairs are separated by a distance of ______
the diameter of the molecule is ___
- right-handed (clockwise, going down)
- 360
- 34 angstroms / 3.4 nm
- 10 base pairs
- 3.4 angstroms
- 20 angstroms
