Genetics Lecture I

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Transcript Genetics Lecture I

Lecture I
Intro to
Genetics & DNA Replication
with a review in
DNA, RNA, & Protein Synthesis
Standards Covered
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
Standards Covered
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
Heredity – the passing on of characteristics from
parents to offspring
Traits – characteristics that are inherited (for
example your eye color)
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”
Important Vocabulary
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
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
Important Vocabulary
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
The Cell Cycle
Cells go through
the cell cycle
during their
MOST of the
life of a cell is in
DNA is packed
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
DNA is a long molecule
made up of nucleotides
Each nucleotide is
made up of three parts:
5-carbon sugar called
 Phosphate group
 Nitrogen Base
The Nucleotides
Nitrogen Bases
A- adenine
G- guanine
Adenine Guanine
Cytosine Thymine C- cytosine
T- thymine
Phosphate group
5-Carbon Sugar
Chargaff ’s Rules
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
Amino Acid Chain
Transcription inside the Nucleus
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
Central Dogma
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
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
AUG codes for the amino acid Methionine
The (20) Amino Acids
Methionine is the
universal “start
codon” for all