Download Unit VII: Genetics

Unit VII: Genetics
Basic Genetics
Modern Genetics
Understanding our genes and the ways
they are passed to the next generation.
A. Basic Genetics
Genetics = study of heredity
understanding of how characteristics get passed from
parent to offspring, generation to generation
1. Gregor Mendel
Monk - studied pea plants in the 1800’s
a) True breeding = _____________
b) Traits = specific characteristic
Trait
Seed Shape – round or wrinkled
Allele =
Seed Color – yellow or green
Seed Coat – gray or white
Pod Shape – smooth or constricted
Pod Color – green or yellow
Flower Position – axial or terminal
Flower Color – purple or white
Plant Height – tall or short
c) Generations
P = parent generation – original plants
F1 = first filial generation = offspring of the original plants
F2 = second filial generation = offspring of F1
d) Crosses – for each trait
Mendel crosses true breeding plants
and makes observations of the
offspring
ex:
P  Tall Pea Plant x Short Pea Plant
F1  All tall pea plants
Only 1 characteristic showed in the F1 generation
Why not a blend of the parent plants?
_________ – cross between parents with different
traits
All tall
plants
e) Conclusions
1. biological inheritance is determined by factors that are
passed from one generation to the next
____________
____________ = different forms of genes
2. _____________________ – some alleles are
dominant over recessive alleles. The recessive trait will
only show if the dominant trait is not present.
f) Segregation
What about the F2 generation?
What happens next?
Were the recessive alleles still present in the pea plant?
Cross - F1 x F1
Ex: Hybrid Tall Pea Plant x Hybrid Tall Pea Plant
F2 – Mostly Tall; some Short;
Short trait reappeared
Some how the short trait
_________ from the tall trait
1. __________________________________________
When gametes are formed during meiosis there is a
segregation/separation of alleles on homologous
chromosomes.
As a result of fertilization, __________________________.
As a consequence, _____________________ are likely to
be produced.
Short separated
from tall
2. Probability and Inheritance
a) ________ = genetic make up / two alleles of an individual
___________________ = same alleles (TT or tt)
__________________ = different alleles (Tt) = Hybrid
b) _______________ = physical characteristic (Tall or Short)
Usually determined by the genotype –
sometimes the ___________ can affect the phenotype.
Can two organisms have the same phenotype but
different genotypes?
c) Punnett Square
representation of parental gametes and
the different allelic combinations of the offspring
ex: Cross: True breeding Tall x True breeding Short
TT
tt
1. Determine the genotypes of
the parents
2. Determines the possible
gametes of the parents
T
3. Write the gametes on the
outside of the box
t
Tt
4. Combine the parents
gametes
t
Tt
Remember only 1 gamete
from each parents
T
Tt
Tt
All the offspring are genotype Tt – heterozygous
The genotype tells the phenotype – Tt  Tall
In the heterozygous the recessive allele is hidden
ex: Cross: Heterozygous Tall x Heterozygous Tall
Tt x Tt
What is the genotype ratio?
What is the phenotype ratio?
Through his knowledge of
math and detailed record
keeping, with 10,000s of pea
plants Mendel always had this
ratio in the phenotypes.
d) _________________________________
If the genes for two different traits are located on different
Chromosomes (____________________ chromosomes), they
segregate randomly during meiosis and, therefore, may be
_________________________ of each other.
Not only did Mendel look at
single traits, he observed
the probability of the
inheritance of multiple
traits at the same time.
What if the plants are tall
with round seeds and
short with wrinkled seeds
what allelic combinations
will occur in successive
generations?
ex: Dihybrid
Cross
the organisms
are
heterozygous
for two traits.
(Use letters that
are easy to tell
the difference)
TR
Tr
tR
tr
T
R
TTRR
TTRr
TtRR
TtRr
T
r
TTRr
TTrr
TtRr
Ttrr
t
R
TtRR
TtRr
ttRR
ttRr
t
r
TtRr
Ttrr
ttRr
ttrr
Phenotype Ratio:
9 Tall Round
3 Tall Wrinkled
3 Short Round
1 Short Wrinkled
3. Other Patterns of Inheritance
Not all genes come with dominant and recessive alleles
a) Incomplete Dominance – neither allele is dominant
heterozygous results in a mix of characteristics
ex: Flower Color in Snap Dragons
R = red; W = white
Red Flower x White Flower
R
W
W
R
Genotype Ratio:
Phenotype Ratio:
b) Codominance
both alleles show in the phenotype
some cells produce one allele other cells produce the other
ex: Roan Colored Cattle
R = red coat; W = white coat
RW = Roan = Some red hair some white hair in the coat
What is the
probability that
the offspring of
two roan colored
cattle would be
roan colored?
c) Multiple Alleles
genes that have more than two alleles
the individual only has 2 alleles, but more than two exist in
the population
ex: Blood Types
IA = type A; IB = type B; i = type O
IA & IB are codominant but both are dominant over i
Who is the Daddy?
A woman with type A blood has a
child with type O blood, but she is
unsure of the father. Bob has type
AB blood and Bill has type A
blood.
Who is the baby’s daddy?
Bill is the father
d) Polygenic Traits
traits produced by the interaction of many genes
Show a wide range of phenotypes
Ex: Skin color, Eye Color, Height
e) _________________________
genes that occur on the sex chromosomes
X and Y chromosomes  XX = female; XY = male
X chromosome is larger and carries more genes
Since males only have 1 X chromosome, what ever allele is
on the chromosome shows up in the phenotype
Females have two alleles for the gene
ex: color blindness and hemophilia
Ex: Color Blindness
A normal man and a woman that is a carrier for
colorblindness have children.
X Y x X Xn
a) What is the chance they will
have a colorblind child?
b) If they are having a girl
what is the chance she will be
colorblind? A boy?
Watch for the wording of the question
4. Human Inheritance
a) Pedigree
a diagram of family
relationships that uses
symbols to represent
people and lines to
represent genetic
relationships.
easier to visualize
relationships within
families
Pedigrees are often used
to determine the mode of
inheritance (dominant,
recessive, etc.) of genetic
diseases.
b) Karyotype and Amniocentesis
picture of chromosomes
22 pairs of autosomes, 1 pair of sex chromosomes
Used to determine
gender
and chromosomal
disorders
c) Human Genetic Diseases / Disorders
1) Albinism
recessive allele
lack pigment in skin, hair, eyes
2) ____________________
recessive allele
excess mucus in lungs;
increases susceptibility to infections;
death in childhood unless treated
3) _____________________ (PKU)
recessive allele
accumulation of phenylalanine
(amino acid) in tissue
body can not break down the
amino acid
mental retardation if they eat
phenylalanine
4) ________________ Disease
recessive allele
higher occurrence (1/100 vs
1/100,000) in Jewish families
of eastern European ancestry
lipid accumulation in brain
cells, nervous system break
down  death in early
childhood
5) Achondroplasia Dwarfism
dominant allele
bones fuse and stop growth
6) ________________________
codominant allele
red blood cells have a crescent
shape
misshapen hemoglobin
can not carry O2 as well
7) Polydactyl
dominant allele
extra toes and fingers
not always expressed
8) ____________________
chromosomal disorder
extra 21st chromosome cause
by nondisjunction
B. Modern Genetics
1. Griffiths’ Experiments – 1920s
2 Strains of
bacteria
One strain is
deadly
Even when
killed, the
deadly strain
can pass
something to
the nondeadly strain
to make it a
killer!
2. Avery’s Experiments – 1940s
Repeats Griffith’s experiments but adds enzymes that
break down different compounds in the cells
Not until he
destroys
DNA that the
mice live!
DNA =
molecule
that stores
and
transmits
genetic
information
3. Watson and Crick – 1950’s
Used Rosalind Franklin’s x-ray pattern
of DNA to build its 3-D structure
Double helix with complimentary
base pairs
a) DNA Structure
Nucleotides
A = _______________
B = _______________
C = _______________
__________________________ ________________
From the human to the DNA – PBS Flash
DNA
STRUCTURE
MOVIE
4. DNA Replication
a) Occurs inside the ______  during S phase of cell cycle
b) DNA molecules separate into ___ strands, then produces
two new complimentary strands following the rules of base
pairing
c) Each original strand serves as a __________ for the new
strand
Original DNA
DNA “Unzips” Enzymes fill in nucleotides
TAC
A
AT
TG
G
CGG
G
GC
CC
C
ACC
T
TG
GG
G
CGT
G
GC
CA
A
AGG
T
TC
CC
C
C AA
G
GT
TT
T
TAG
A
AT
TC
C
TAC
CGG
ACC
CGT
AGG
C AA
TAG
Easy Version of DNA Replication
Check out this site on your own for a more detailed
explantation
More Complicated but explains the process really well.
http://207.207.4.198/pub/flash/24/menu.swf
5. Protein Synthesis
a) _________ = Ribo Nucleic Acid
single stranded nucleic acid
contains Ribose as the sugar not __________ as in DNA
has the base _______ instead of _________ as in DNA
Types of RNA
_______ = messenger RNA 
carries gene out of the nucleus
_______ = ribosomal RNA 
makes up ribosome
_______ = transfer RNA 
brings in amino acid
b) Transcription
1st step of protein synthesis; similar to replication
DNA  ______________
Occurs in the ______________
“Unzip” DNA – uses 1 side of DNA as a template
RNA polymerase fills in complimentary RNA bases
mRNA detaches from DNA
mRNA leaves nucleus
Simple Trasncription Animation
Just another Trancription animation
Original
DNAEnzymes
DNA
“Unzips”fill inRNA
RNA
DNA
breaks
nucleotides
reconnects
from DNA
TAC
A
AT
UG
G
CGG
G
GC
CC
C
ACC
TG
U
GG
G
CGT
G
GC
CA
A
A G G C AA TA G
T
UC
CC
C G
G TUTU AATUCC
The groups of 3 bases on the mRNA is called a CODON
The codon codes for specific amino acids when making a
protein
c) Translation
2nd step of protein synthesis
mRNA  ______  __________  ___________
occurs in the ______________ at the _______________
Ribosome reads ___________ on mRNA
Matches the codon to an anticodon on tRNA
Ribosome reads next codon
and brings in next tRNA with
matching anticodon
Since tRNA is attached to
Amino Acids – two amino
acids are located next to
each other
This proximity allows the
____________________
Makes a peptide
Repeats until mRNA says
stop
More than 1 ribosome can attach to the mRNA at a time
Makes multiple peptides
Translation Animation
d) Protein Synthesis Overview
To see it in some more
detail check out the
following website on
protein synthesis
http://learn.genetics.utah.edu/content/begin/dna/
e) Genes code for peptides
generally a protein is the
combination of more than
1 peptide
Try this website as an interactive for
replication and protein synthesis
http://www.pbs.org/wgbh/aso/tryit/dna
/shockwave.html
6. Mutations
___________ in the _________ sequence
Some are ____________
Some are ____________
Most are _____________
Mutations are only passed to the next generation if they occur in _________
Mutations in somatic cells are not passed – acquired characteristics are not
passed
a) Gene Mutations
changes in a single gene
1) Point Mutations – involve just one nucleotide
substitution = change one nucleotide for another
ex:
TAC G C G AC C C GA
becomes
TAC G C C AC C C GA
the change may or may not change the amino acid
2) __________________ Mutations
insertion or deletion of a single nucleotide
changes the codons read by the ribosome
usually affects _________ amino acids after the mutation
ex: DNA:
TAC C G G AC C C GA
mRNA:
AUG GCC UGG GCU
Amino A:
Met
Ala
Try
Cys
Insertion
DNA:
TAC G C G
GAC CCG
A
mRNA:
AUG CGC
CUG GGC U
Amino A:
Met
Arg
Leu
Gly
The order of amino acids changed  changes protein (big
time)
Ex:
delete 1 letter
THE FAT CAT ATE THE RAT 
THE FTC ATA TET HER AT ????
Completely change everything after the deletion
No longer makes sense
The same thing happens with the protein
The order of the letter (amino acids) determines the structure of the
words and sentence (protein)
One little mistake can completely change the meaning
b) Chromosomal Mutations
changes the structure of a chromosome
rearrange the genes on a chromosome
1) Deletion
2) Addition / Duplication
3) Inversion – rearrange the genes
4) Translocation – move a piece of a
chromosome to a non homologous chromosome
Chromosomal
Mutations
c) Mutagenic Agents
factors that cause mutations
1) Radiation –
X-rays
ultraviolet
radioactive substances, and cosmic rays
2) Chemicals –
formaldehyde, benzene, asbestos fibers
THC
nicotine
7. DNA Technology
ways in which the knowledge of DNA can help benefit
society
a) Selective Breeding
choosing specific traits in organisms, mating the organisms,
and hoping some of the offspring have the combinations of the
traits
ex: dogs,
cattle, crops
selective breeding
has been occurring
for 1000s of years
b) Genetic Engineering
recombinant DNA; transfer DNA from one organism to
another
isolate gene 
cut DNA with restriction enzymes 
combine DNA of organisms 
place recombinant DNA in a new organism
*restriction enzymes = cut DNA at very specific sequences
can be used to make a variety of products
bacteria that can make:
Insulin, Human Growth
Hormone
crops that resistant to
disease and insects
livestock with extra copies
of growth hormone gene
c) Cloning
making an exact genetic copy
Remove the nucleus of an egg cell
Use the nucleus of a body cell 
Insert the nucleus into the egg cell 
Grow the egg cell 
Identical genetic copy of the body cell
organism
Click and Clone
d) Gel Electrophoresis
making “DNA Fingerprints”
use restriction enzyme to cut DNA
into fragments 
place DNA into a porous gel 
electrify gel and DNA fragments
move 
small pieces move the farthest 
DNA banding pattern = finger print
Gel Electrophoresis - Learning Center
Gel Electrophoresis Virtual Lab
e) Human Genome Project
sequence all human DNA
map and locate all the
human genes  about
3,000,000,000 base pairs in
order
help to find and cure diseases
Gene Therapy
find defective gene and
replace it with a healthy gene