MODERN GENETICS

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Transcript MODERN GENETICS

GENETICS
What do you remember about genetics?
List key terms that come to mind….
The branch of human Biology that deals
with inheritance
Often referred to as the science of
heredity and variation in living
organisms.
TWO MAJOR DIVISIONS
OF GENETICS
Mendelian Gentics
•Founded by Gregor Mendel
•Developed the basic concepts of
heredity by applying knowledge of
inheritance of characteristics
Modern Genetics
•Currently being studied today
•Seeks to understand the
mechanisms( reasons/modes)
for inheritance
DNA and its Structure
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DNA stands for
Deoxyribonucleic acid
Located in the nucleus
of each cell.
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Video
Role: to maintain genetic
continuity and carry all
genetic info of the cell
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Aim: How are genetic traits passed from
parent to offspring?
DN:
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What is an organelle – give an example.
What is an active site? What is it specific to?
Which reproductive structure is responsible for the
“exchange of materials” between mother and
fetus?
What type of molecule is capable of mutating?
HW: Review book pages 50-51 q’s 23-31
Chromosomes: package DNA
DNA:
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Code of Life
Housed in nucleus
Controls all cell
activities
Is replicated when
passed from one
generation to the
next or when cells
divide (mitosis)
The structure of DNA was discovered by
two scientist known as
Watson and Crick.
How would you describe a DNA molecule?
A DNA MOLECULE LOOKS
LIKE A TWISTED LADDER.
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This Twisted ladder
structure is known
as a double helix.
Job Description of DNA
Must store information
 Must be “copy-able”
 Must be strong and stable
 Must be capable of mutating, or
changing, slightly to produce
variation – which leads to
evolution
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Some History…
Mendel performed experiments on
pea plants
 Discovered “Genes” are located at a
specific area on a chromosome.
 Alleles  two genes associated with
a specific trait – (one from mom, one
from dad)
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Aim: How are genetic traits
passed from parent to offspring?
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DO NOW:
Review book p 9 #20-35
Homework:
Castle learning “Genetics 1 & 2”
DNA
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is a polymer
(large molecule)
made up of
repeating
chemical units
called
nucleotides.
Nucleotide
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Composed of three
separate subunits:
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Phosphate group
Deoxyribose: 5 carbon
sugar
Nitrogenous bases:
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
What is a gene?
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A gene
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gene
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Is a section of
the DNA
molecule that
codes for the
production of a
specific protein.
Determines
characteristics
of the organism.
Inherited
What are Genes?
Genes = code language for protein, and
proteins give you your physical traits
 A chromosome contains many genes
 A gene is made up of lots of DNA.
Put the following terms in order from
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Big----------------Small:
Nucleus, Cell, DNA, Genes, Chromosomes
An Allele Can Either be:
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Dominant  the
expressed allele
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CAPITAL LETTER
Recessive  the
covered up allele
(unless both
alleles are
recessive)
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lowercase letter
Let's Test Your Ability to See Colors?
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Phenotype  physical traits (observable) an
organism has
Genotype  the actual alleles (genes) an
organism has
Homozygous person has two identical
alleles for a particular trait (TT or tt)
(“purebred”)
Heterozygous  person has two different
alleles for a particular trait (Tt) (“hybrid”)
Polygenic Inheritance  a trait controlled by
two or more genes (ex. Eye color, skin color,
blood group)
Summary of Genetics:
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During fertilization there is random
recombination of traits from each parent
Random separation and distribution of
paired chromosomes occurs during
1.
2.
3.
4.
cleavage
mitotic cell division
fertilization
meiotic cell division
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1.
2.
3.
4.
Two genes for two same traits
located on the different chromosome
are said to be
homozygous
independently assorted
mutagenic agents
linked
The diagram below represents the
organization of genetic information
within a cells nucleus.
The circle labeled Z most likely
represents
a.) chromosomes
Nucleus
b.) amino acids
Z
c.) vacuoles
Genes
d.) molecular base
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4 Nitrogenous Bases
1.
2.
3.
4.
Adenine
Thymine
Guanine
Cytosine
Base Pair Rule:
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Adenine (A) bonds
to Thymine (T)
 A-T or T-A
Guanine (G) bonds
to Cytosine (C)
 G-C or C-G
DNA Chains are
COMPLEMENTARY
Practice
More Practice:
If a DNA chain
consists of the sequence
ATTACGGCA
What is its complementary
sequence?
Answer…
When Can You Best See
Your Chromosomes?
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During Mitosis – all DNA is tightly coiled for
accurate cell division!
What is DNA Replication?
Process that
creates an exact
copy of DNA
before a cell
divides.
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DNA Replication
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Start with an original “template”
Untwist “template”
Template “unzips” by DNA Polymerase
(enzyme) breaking hydrogen bonds that
hold bases together
Free-floating bases in nucleus attach to
exposed bases
Result  two identical double strands –
each made up of one ‘old’ and one ‘new’
strand
DNA unwinds, unzips and base
pairs match up.
DNA Replication
Remember:
Untwist
Unzip
Add the Bases
Re-Twist!
Aim: How do the DNA and
RNA molecule differ?
Do Now:
Which of the following arrangements lists
the structures from largest to smallest?
a chromosome
a nucleus
a gene
1. gene - chromosome - nucleus
2. gene - nucleus - chromosome
3. nucleus - gene - chromosome
4. nucleus - chromosome - gene
A researcher recently discovered a new species of bacteria
in the body of a tubeworm living near a hydrothermal vent.
He compared the DNA of this new bacterial species to the DNA
of four other species of bacteria.
The DNA sequences came from the same part of the bacterial
chromosome of all four species.
According to these data, the unknown bacterial
species is most closely related to
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2.
3.
4.
species
species
species
species
I
II
III
IV
RNA - RiboNucleicAcid
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nucleotides
ribose instead of deoxyribose
Uracil(U) instead of Thymine (T)
3 types
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messenger (mRNA)
 carries info from DNA
transfer (tRNA)
 carries amino acids
ribosomal (rRNA)
DNA vs. RNA
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DNA
•Double stranded
molecule
Sugar = deoxyribose
• Bases:
A= adenine
T= thymine
G= guanine
C= cytosine
RNA
•Single stranded
molecule
•Sugar = ribose
•Bases:
A= adenine
U= uracil
G= guanine
C= cytosine
DNA vs. RNA
Protein Synthesis
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Protein synthesis is the process by which a
cell synthesizes (makes) proteins from
DNA (deoxyribonucleic acid).
Process begins in the nucleus of the cell.
Happens with the help of RNA (ribonucleic
acid)
The synthesis of the proteins takes place
outside the nucleus in the ribosomes
Types of RNA
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There are different types of RNA
present in the cell
Messenger RNA (mRNA)
and transfer RNA (tRNA)
* Predict the functions of these
types of RNA.
Transcription
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The copying of a genetic message into a
molecule of messenger RNA (mRNA) is
called transcription.
Reads the message on the DNA molecule in
groups of 3 bases called CODONS while in
the nucleus.
mRNA then Carries the message to the
ribosome in the cytoplasm.
Transcription
For the following DNA base sequences, write the
complimentary messenger base sequence:
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DNA: TAT CGT AAC GGA TCG
RNA: ____________________
Answer:
DNA: TAT CGT AAC GGA TCG
RNA: AUA GCA UUG CCT AGC
***Identify a codon?
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DNA: CCG ATA GGG TAA GCT
RNA: ____________________
Answer:
DNA: CCG ATA GGG TAA GCT
RNA: GGC UAU CCC AUU CGA
*Now Identify the Codon
Transfer RNA (tRNA)
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Transfer RNA (tRNA)
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Brings amino acids to the ribosome.
Dependent on the codon sequence of
mRNA
Steps of Protein Synthesis
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Begins in the nucleus
DNA is copied and a strand of mRNA is made.
(transcription)
mRNA travels to the ribosomes in the cytoplasm.
The codons are “read” by the ribosomes. This
process is called translation.
tRNA transfers the proper amino acid (based on the
codon sequence) to the ribosome for protein
assembly.
A protein (could be hundreds or thousands of amino
acids long) is made.
Protein Synthesis
Protein Synthesis
w
x
v
Identify the parts.
Is this transcription or
translation?
Translation
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The language of mRNA consists of 4 letters:
A, U, C, G.
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Each word is only made up of 3 letters or bases.
Every three bases is called a codon.
A CODON codes for a specific amino acid
that must be added to the polypeptide chain
or protein.
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There are 64 different codons for 20 amino
acids.
mRNA CODONS
Translation
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The START CODON is AUG and it codes for
Methionine, which signals the beginning of
translation.
3 STOP CODONS: UAA, UAG, UGA. DO NOT CODE
FOR AN AMINO ACID.
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They signal the end of a protein chain.
tRNA (transfer) is responsible for deciphering the
codon and transferring the amino acid to the
protein.
Each tRNA contains an anti-codon attached to one end
and three bases called an anti-codon that are
complimentary to the codon on the mRNA.
Protein Synthesis
Transcription
Translation
DNA --------- RNA --------- Protein
Analogy:
Pair the correct
genetics term with
the construction
site examples given.
Construction Site Analogy
Blueprint to build house
tRNA
DNA
Workers carrying
materials to house
mRNA
The construction site
Ribosome
Messenger who brings
instructions to worksite.
Changes in DNA:
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Changes occur due to
recombination, mutations &
genetic engineering