THE CHEMICAL BASIS OF HEREDITY(lesson 2)geenetics hindi pa done Flashcards
hereditary transmission and
variation on the molecular level.
Molecular Genetics
The study of the molecular
structure of genes, involving
DNA and RNA.
We now accepted that
there was genetic transmission of
traits.
From Mendel:
The genetic material must contain the information necessary to construct an
entire organism.
INFORMATION
During reproduction, the genetic material must be passed from parents to
offspring.
TRANSMISSION
Because the genetic material is passed from parents to offspring, and from
mother cell to daughter cells during cell division, it must be copied.
REPLICATION
species, a significant amount of phenotypic variability occurs. The
genetic material must also vary in ways that can account for the known
phenotypic differences within each species.
VARIATION
Conducted experiments that involved the
injection of live and/or heat-killed
bacteria into mice.
Frederick Griffith (1928)
He then observed whether or not the
bacteria caused a lethal infection.
Frederick Griffith (1928)
Discovered that a “transforming factor”
changes harmless bacteria into a
deadly one.
Frederick Griffith (1928)
experiments showed that some
genetic material from the dead bacteria had
been transferred to the living bacteria and
provided them with a new trait.
Frederick Griffith (1928)
Realized that Griffith’s
observations could be used as
part of an experimental strategy
to identify the genetic material.
Oswald Avery, Colin MacLeod,
and Maclyn McCarty (1944)
only one of the extracts, namely, the one
that contained purified DNA from type S bacteria, was able to
convert type R bacteria into type S.
Oswald Avery, Colin MacLeod,
and Maclyn McCarty (1944)
They used radioisotopes to
distinguish proteins from DNA.
Alfred Hershey and Martha Chase
(1952)
Performed the definitive
experiment that showed that DNA
was the genetic
Alfred Hershey and Martha Chase
(1952)
This virus infects Escherichia coli bacterial cells
and is therefore known as a ___, or simply a
phage.
t2, bacteriophage
two types of macromolecules:
DNA
and proteins.
MOST ABUNDNAT FREE NUCLEOTIDE IN MAMMALIAN CELL
ATP-
BUILDING BLOCKS OF NUCLEIC ACIDS
NUCLEOTIDE
Refers to nitrogen-containing heterocyclic ring structures
Nitrogenous Base
2 types of Nitrogenous Base
PURINE PYRIMIDINE
Adenine Cytosine
Guanine Uracil
Thymine
STRUCTURE OF A PURINE RING
- 5 Carbons
2 from Glycine
2 from N10- Formyl-
tetrahydrofolate
1 from CO2 - 4 Nitrogen
1 from Glycine
2 from Glutamine
1 from Aspartate
NUCLEOTIDE =
(Nitrogenous base + Pentose sugar) +
Phosphate
NUCLEOSIDE =
Nitrogenous base + Pentose sugar
serves
as the bond between the
base and sugar (nucleosides
are N-glycosides)
N-glycosidic linkage:
Refers to the combination of
nitrogenous base & pentose
sugar
NUCLEOSIDE
Refers to the combination of
nucleoside + phosphate
NUCLEOTIDE
serves as the bond
between the 5’-OH of pentose
sugar and phosphoryl group
Ester bond
Pentose Sugar
* 2 types:
DNA RNA
2’-deoxy D-Ribose
(Deoxyribose)
D-Ribose (Ribose)
are polymers of
nucleotides joined by a 3’-5’
phosphodiester bond
Nucleic acids
, are known as nucleic
acids.
DNA and RNA
This term is derived from the discovery of
DNA by __ in 1869.
Friedrich Miescher
He identified a novel phosphorus-
containing substance that was isolated
from the nuclei of white blood cells found
in waste surgical bandages. He named this
substance___.
nuclein
Mostly seen in NUCLEUS
Pyrimidine bases: THYMINE,
CYTOSINE
Sugar: DEOXYRIBOSE
Usually DOUBLE-STRANDED
DNA
Mostly seen in CYTOPLASM
Pyrimidine bases: URACIL,
CYTOSINE
Sugar: RIBOSE
SINGLE-STRANDED
RNA
A phosphate group connects two sugar molecules via
ester bonds
For this reason, the linkage in DNA (or
RNA) strands is called a
phosphodiester linkage.
form the backbone of the strand.
phosphates and sugar molecules
Three scientists who worked
together on studying the structure
of DNA
James Watson, Francis Crick,
Rosalind Franklin
The ___ is negatively charged due to a negative charge on each phosphate.
backbone
The proposed model was based on
the X-ray diffraction photographs of
DNA taken
Rosalind Franklin
won a Nobel
Prize in 1962 for their discovery
Watson and Crick
She adjusted her equipment to
produce an extremely fine beam of X-
rays. She extracted finer DNA fibers
than ever before and arranged them in
parallel bundles.
Rosalind Franklin
Right-handed (clockwise) double-stranded DNA helix
COMPOSITION
is STRONGER than A-T bonding
G-C bonding
g-c bonding
a-t bonding
3 hydrogen bonds
2 hydrogen bonds
G-C bonding
major groove, minor groove
often acts as sites of
DNA-protein interaction
Grooves
(Chargaff’s rule):
%G = %C %A = %T
is via
hydrophobic interaction & ionic
bonding
DNA-protein interaction
- discovered the % content of the 4
nucleotides was the same in all tissues of the
same species
ERWIN CHARGAFF
States that the number of
purines = number of
pyrimidines
CHARGAFF’S RULE
All types of DNA are right-
handed,
except Z
6 types have been identified
– A, B, C, D, E and Z, but the
3 more prominent types are
A, B, and Z
- Most abundant chromatin
protein
HISTONES
divided into 2 types:
core histones, linker histones
LEVELS OF DNA ORGANIZATION
*DNA double helix
*10 nm chromatin fibril
*30 nm chromatin fibril
*Supercoiled structure
*Chromosome
shorter
than chromosomal DNA,
RNA STRUCTURE
Different arrangements of base pairing are possible, which result in
structures called
bulge loops, internal loops, multibranched
junctions, and stem-loops (also called hairpins).
