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Genetics
Genetics
The branch of biology that deals with the process of
inheritance and variation.
Gene
It is the basic physical and functional unit of heredity.
DNA (DeoxyriboNucleic Acid)
The letters A, G, T and C correspond to the nucleotides
found in DNA
Nucleotide
the basic building block of nucleic acids (RNA and DNA).
RNA (RiboNucleic Acid)
a nucleic acid present in all living cells that has structural
similarities to DNA. Unlike DNA, however, RNA is most often
single-stranded.
Alleles
These are forms of the same gene with small di erences in
their sequence of DNA bases.
Chromosomes
These are the tiny coiled structures in the cell that contain
the DNA material.
Law of Dominance
In a cross of parents that are pure for contrasting traits,
only one form of the trait will appear in the next generation.
Law of Segregation
It is the first division of meiosis in which the homologous
chromosomes with their di erent versions of each gene are
separated into daughter nuclei.
Law of Independent Assortment
It describes how di erent genes individually separate from
one another when reproductive cells develop.
Codon
It is a trinucleotide sequence of DNA or RNA that
corresponds to a specific amino acid.
Peptide bond
It is a chemical bond formed between two molecules when
the carboxyl group of one molecule reacts with the amino
group of the other molecule, releasing a molecule of water
(H2O).
Protein synthesis
It is the process in which cells make proteins.
C terminus
It connects to the N terminus of an amino acid.
Homologous chromosomes
These are two pieces of DNA within a diploid organism
which carry the same genes, one from each parental
source.
N terminus
It connects to the C terminus of an amino acid.
Nucleus
An organelle found in eukaryotic cells.
Genetic code
It is required in the process of Translation, through which
the information contained in the nucleic acid sequence is
expressed to produce a specific sequence of amino acids.
Nucleolus
(noo-KLEE-uh-lus) An area inside the nucleus of a cell that
is made up of RNA and proteins and is where ribosomes
are made. Ribosomes help link amino acids together to
form proteins. The nucleolus is a cell organelle.
Protein
Refers to the essential molecules produced by DNA.
This acts as instructions to make molecules.
Protein is found throughout the body—in muscle, bone,
skin, hair, and virtually every other body part or tissue. It
makes up the enzymes that power many chemical reactions
and the hemoglobin that carries oxygen in your blood. At
least 10,000 di erent proteins make you what you are and
keep you that way.
Base pairs
These are chemically-bonded nitrogenous structures that
make up the DNA material.
Mucus
This is a slippery substance that lubricates and protects
the linings of the airways, digestive system, reproductive
system, and other organs and tissues.
Cystic fibrosis
This is an inherited disease characterized by the buildup of
thick, sticky mucus that can damage many of the body's
organs.
Specific codon
It always codes for the same amino acid.
Translation
The pathway of protein synthesis is called translation.
Universal
In all living organisms Genetic code is the same.
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Facts:
DNA replication is the process by which DNA
makes a copy of itself during cell division.
RNA is a single stranded chain of amino acids.
DNA is a double helix structure of amino acids.
In DNA replication, each strand of the original DNA
serves as a template for the synthesis of a
complementary strand.
The process by which DNA is copied to RNA is
called transcription, and that by which RNA is used
to produce proteins is called translation.
The Central Dogma of Molecular Biology states
that DNA makes RNA and makes proteins.
The process by which DNA is copied to RNA is
called transcription, and that by which RNA is used
to produce proteins is called translation.
Therefore, Translation and transcription in the
Central Dogma are the gene expression.
Ribosomes are the molecular machine of living
cells designed for decoding mRNA-encoded
genetic
information
into
protein.
Being
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sophisticated machinery, both in design and
function, the ribosome not only carries out protein
synthesis, but also coordinates several other
ribosome-associated cellular processes. The set of
instructions occurs in Translation.
The information in mRNA is then read by a
machine called the ribosome, which builds or
“translates” a protein one amino acid at a time.
Note: Not DNA
Translation takes place on ribosomes in the cell
cytoplasm, where mRNA is read and translated into
the string of amino acid chains that make up the
synthesized protein.
According to the conservative model, after one
round of replication, half of the new DNA double
helices would be composed of completely old, or
original, DNA, and the other half would be
completely new.
Then, during the second round of replication, each
double helix would be copied in its entirety.
One of the most important concepts of DNA
replication is that it is a semi-conservative process.
This means that every double helix in the new
generation of an organism consists of one
complete “old” strand and one complete “new”
strand wrapped around each other.
During the elongation stage, the ribosome
continues to translate each codon in turn. Each
corresponding amino acid is added to the growing
chain and linked via a bond called a peptide bond.
Elongation continues until all of the codons are
read.
RNA, like DNA, is a sugar-phosphate chain with
pyrimidines and purines. In RNA the sugar is
ribose, and uracil replaces the thymine found in
DNA.
What connects sugar and phosphate in DNA?
DNA and RNA are composed of nucleotides that are linked
to one another in a chain by chemical bonds, called ester
bonds, between the sugar base of one nucleotide and the
phosphate group of the adjacent nucleotide.
A phosphate group is attached to the sugar molecule in
place of the -OH group on the 5' carbon.
Where does the connection between the phosphate group
and the sugar occur?
The phosphate group is attached to the 5′ carbon atom of
the sugar, and the base is attached to the 1′ carbon atom.
There is an additional free hydroxyl group (–OH) attached
to the 3′ carbon atoms.
A=T/C=G
T=A/G=C
A=U/C=G
U=A/G=C
Mutation
Somatic Mutations
Mutations can lead to genetic conditions that a ect your
health.
Why does mutation occur in some organisms?
somatic mutations (that occur in body cells) are not passed
on. Egg and sperm cells are called germ cells, in contrast
to the other cells of the body, which are called somatic
cells.
Mutations can result from errors in DNA replication during
cell division, exposure to mutagens or a viral infection.
Somatic mutations are changes to your DNA that happen
after conception to cells other than the egg and sperm.
Mutagen
A mutagen is a chemical or physical agent capable of
inducing changes in DNA called mutations. Examples of
mutagens
include
tobacco
products,
radioactive
substances, x-rays, ultraviolet radiation and a wide variety
of chemicals.
How protein is made using information from DNA
During transcription, the enzyme RNA polymerase (green)
uses DNA as a template to produce a pre-mRNA transcript
(pink). The pre-mRNA is processed to form a mature mRNA
molecule that can be translated to build the protein
molecule (polypeptide) encoded by the original gene.
Germline Mutations
(that occur in eggs and sperm) can be passed on to
o spring. Germ line refers to the sex cells (eggs and sperm)
that sexually reproducing organisms use to pass on their
genomes from one generation to the next (parents to
o spring).
Germline mutations are changes to your DNA that you
inherit from the egg and sperm cells during conception.