Transcript Genetics Lecture I

Lecture I
Intro to
Genetics & DNA Replication
with a review in
DNA, RNA, & Protein Synthesis
Standards Covered
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4a~ students know the general pathway by which
ribosomes synthesize proteins, using tRNA’s to
translate genetic information in mRNA
4b~ students know how to apply the genetic
coding rules to predict the sequence of amino acids
from a sequence of codons in RNA
4e~ students know proteins can differ from one
another in the number and sequence of amino
acids
Standards Covered
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5a~ students know the general structures and
functions of DNA, RNA, and proteins
5b~ students know how to apply base-pairing rules
to explain precise copying of DNA during semiconservative replication and the transcription of
information from DNA into RNA
Important Vocabulary
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Heredity – the passing on of characteristics from
parents to offspring
Traits – characteristics that are inherited (for
example your eye color)
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Genes – a piece of DNA that provides a code or
instructions to make a certain protein
A gene’s specific location within your DNA code
is called its locus
 This is like a “home address”
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Important Vocabulary
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Genotype – the genetic makeup of an individual or
referring to a specific gene or trait
Phenotype – the physical expression of a gene or
trait as “coded for” by the Genotype
Allele – any alternative form of a gene that can be
possible for a specific gene at a specific locus
Dominant – the allele that is expressed when two
different alleles are present
Recessive – the allele that is expressed only when
two copies of that allele are present
Genotype vs. Phenotype
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Your DNA is the genetic
blueprint for all of your
physical characteristics we
call “traits”
The DNA code for a trait is
called the genotype and the
trait that is expressed is the
phenotype
Important Vocabulary
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DNA Polymerase – a special enzyme responsible for
a process called DNA Replication
Semi-conservative replication – the process of
making a copy of a DNA strand by using each
complimentary half as a “template” for two new
strands
The Cell Cycle
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Cells go through
the cell cycle
during their
lifetime
MOST of the
life of a cell is in
Interphase
DNA is packed
into
chromosomes
during late G1
DNA Arranged in a Chromosome
S Phase & DNA Replication

A cell makes copies of its DNA during the S-Phase
of the cell cycle where the chromosomes
“duplicate” and the cell prepares for cell division
The Structure of DNA
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DNA is a long molecule
made up of nucleotides
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Each nucleotide is
made up of three parts:
5-carbon sugar called
deoxyribose
 Phosphate group
 Nitrogen Base
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The Nucleotides
Nitrogen Bases
A- adenine
G- guanine
Adenine Guanine
Cytosine Thymine C- cytosine
T- thymine
Phosphate group
(Deoxyribose)
5-Carbon Sugar
Chargaff ’s Rules
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According to Erwin Chargaff:
 Adenine
always pairs with Thymine
 Cytosine
always pairs with Guanine
Central Dogma Review
The term central dogma is used in science to describe
the “making of proteins” from instructions coded in
the DNA
 An equation to remember for Central Dogma would
be:
DNA
mRNA
Amino Acid Chain
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Transcription
Translation
Transcription inside the Nucleus
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA
polymerase
RNA
DNA
Central Dogma
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Proteins are assembled into polypeptides
 These
are long chains of amino acids
 There
are 20 different types of amino acids
 The
properties of proteins are
determined by which order these amino
acids are joined
Transcription & Translation
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Each of these amino acids that mRNA “codes” for
recognizes the three base pair sequence
A codon consists of “three nucleotides in a row” that
code for a single amino acid
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AUG codes for the amino acid Methionine
The (20) Amino Acids
Methionine is the
universal “start
codon” for all
proteins