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GENETIC-CONCEPTS
1.Genome
2.Chromosome
3.Gene
4.DNA/RNA
5.Nucleic Acid
6.Protein
7.Amino Acid
Genome
Entirely of an organism’s heredity information
Complete set of instructions for making an organism
All of the hereditary information encoded in an
organism’s DNA.
Master blueprints for all enzymes, cellular structures &
activities
An organism‘s complete set of DNA
All the DNA contained in the cell of an organism
The collection of DNA that comprises an organism
Prokaryotic Organism
• Eubacteria and Archaea. Usually unicellular.
• No internal membrane-bound compartments: DNA
floats free in the cytoplasm.
• 1 circular chromosome (plus optional plasmids, which
are also circular)
• reproduction usually asexual
• sexual processes (mixing DNA from 2 individuals)
occur, but with unequal contributions from the 2
partners
• transcription and translation simultaneous
Prokaryotic genomes
Most have a single, doublestranded circular DNA molecule
 Usually without introns
 Since there is no nucleus, the
DNA floats freely within the cell
 Proteins cause the DNA to coil
tightly forming a nucleoid
region
 Relatively high gene density
 Often indigenous plasmids are
present

Eukaryotic Organism
•
•
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Plants, animals, fungi, protistas. Often multicellular.
DNA contained within a membrane-bound nucleus.
linear chromosomes (usually more than 1)
careful division of chromosomes in cell division:
mitosis and meiosis
• transcription separated from translation
• sexual reproduction: 2 partners contribute equally to
offspring
• life cycle: alternation of haploid and diploid phases
(i.e. 1 vs. 2 copies of each gene and chromosome)
Eukaryotic genomes
 Genetic information is divided in the chromosome.
 The size of genomes is species dependent
 The difference in the size of genome is mainly due to a different
number of identical sequence of various size arranged in sequence
 The gene for ribosomal RNAs occur as repetitive sequence and
together with the genes for some transfer RNAs in several thousand
of copies
 Structural genes are present in only a few copies, sometimes just
single copy. Structural genes encoding for structurally and
functionally related proteins often form a gene family
 The DNA in the genome is replicated during the interphase of
mitosis
Eukaryotic Genome
Chromosome


A DNA – histone
protein thread, usually
associated with RNA,
occurring in the nucleus
of a cell
Chromosomes contain
hundreds of genes
encoded within their
DNA
Chromosome Logical Structure
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Locus
Location of a gene/marker on the chromosome.
Allele
One variant form of a gene/marker at a
particular locus.
Locus1
Possible Alleles: A1,A2
Locus2
Possible Alleles: B1,B2,B3
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Gene

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The material that controls which
traits are expressed in an
organism
Genes come in pairs and
offspring inherit one copy of
each gene from each parent
A section of DNA that codes
for a trait
Material of heredity
Heredity
The passing of traits from parent to offspring
Allele
The different forms
of a trait that a gene
may have. One
form of a gene
Traits
 Ways of looking,
thinking, or being.
 Traits that are genetic
are passed down
through the genes
from parents to
offspring
Recessive

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A trait that is covered over, or dominated, by
another form of that trait and seems to disappear
Hidden when the other copy of the gene
contains the dominant allele.
A recessive allele shows up only when there is no
dominant allele present
Shown with a lower-case letter (a)
Dominant



A trait that covers over, or dominates, another
form of that trait
Trait that always shows up, even when only one
of the two alleles is in the dominant form
Shown by a capital letter (A)
Homozygous


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Both alleles [forms of the gene] are the same
When offspring inherit two dominant genes, (one
dominant gene from each parent) they are said to
be homozygous dominant (AA)
When offspring inherit two recessive genes, (one
recessive gene from each parent) they are said to be
homozygous recessive (aa)
Heterozygous
When alleles occur in different forms
 When offspring inherit one dominant gene
and one recessive gene, they are said to be
heterozygous (Aa)
 Since the dominant gene will be expressed,
they are said to be heterozygous dominant
(Aa)

Genotype
An organism's genetic makeup
Genotype
PHENOTYPE
Outward physical appearance and behavior of an organism
PHENOTYPE
Genes
Segment of DNA which can be transcribed and translated to amino acid
Central Dogma of Biology
DNA, RNA,
and the Flow of Information
Replication
Transcription
Translation
Central Dogma (Modifications)
(2)Ribozymes
Transcription
DNA
RNA
Translation
Protein
(1) Reverse
transcription
Replication
(2)Self Replication
(3)Self Replication
DNA as Genetic Material


DNA encodes all the information in the cell
The composition of the DNA is the same in all cells within an
organism
• Variation among different cells is achieved by reading the DNA
differently

DNA contains four bases that encode all the information to
make an organism’s life
RIBO NUCLEIC ACID
A polymer composed of nucleotides that contain
the sugar ribose and one of the four bases cytosine,
adenine, guanine and uracile
 Polynucleotide containing ribose sugar and uracile
instead of thymine
 Primary agent for transferring information from
the genome to the protein synthetic machinery

Types of RNA
Three types of RNA:
messenger RNA (mRNA)
a)
b)
c)
transfer RNA (tRNA)
ribosome RNA (rRNA)
Remember:
All produced in the nucleus

Codon
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There are 20 different
possible amino acids to
make from different
codons
Amino acids:
the building of protein
3 possible stop codon
1 start codon
TAC on DNA
AUG on RNA
Gene Expression
Production of proteins requires two steps:
Transcription involves an enzyme (RNA polymerase) making an
RNA copy of part of one DNA strand.
There are four main classes of RNA:
i. Messenger RNAs (mRNA), which specify the amino acid sequence of a
protein by using codons of the genetic code.
ii. Transfer RNAs (tRNA).
iii. Ribosomal RNAs (rRNA).
 Translation converts the information in mRNA into the amino
acid sequence of a protein using ribosomes, large complexes of
rRNAs and proteins.
Steps of gene expression
 Transcription –
DNA is read to make
a mRNA in the
nucleus of cells
 Translation –
Reading the mRNA
to make a protein in
the cytoplasm
Poly-peptide
A primary structure of a protein
A sequence of amino acid bonded together by peptide
bonds.
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aa2
aa1
aa3
aa4
aa5
aa199
aa200
Protein


A polymer of amino acids which may consists of one
or more polypeptide chains
Protein may be water insoluble and serve a structural
role or be water soluble with catalytic activity