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GENETICS
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Mendel
Vocab
Practice
Mono-crosses
Di-crosses
Sex crosses
Non-Mendel
Pedigrees
Genetic Engineering
Gregor Mendel
“Father of Genetics”
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Born in Czechoslovakia in 1822
Died in 1884
Studied math and statistics (Biology was a hobby)
Entered monastery in Austria at age 21 so he
didn’t have to pay for college
• Between 1856-1863 he studied over 30,000 pea
plants he grew in the monastery garden…(lots of
offspring really fast and yummy)
• Mendelian Genetics
Flower Parts
Cross pollination vs. Self pollination
Mendel’s Laws
• Law of Segregation: random separation of
homologous pairs of chromosomes during
Anaphase 1 of meiosis.
• Law of Independent Assortment (Dihybrid
cross): the separation of the alleles of one
allelic pair is independent of the segregation
of the alleles of another allelic pair
• Law of Dominance: One trait trumps another,
so, if Dominant trait (capitol letter) is present
it will show!!!
Basic VOCAB!!!!! Foundation of
Genetics
• Gene: short segment of DNA, located on a
chromosome, that codes for a protein to show a
trait.
• Trait: a characteristic that can be passed from
parent to offspring. Ex: blonde hair
• Sex-trait: a characteristic that can be passed from
parent to offspring on sex chromosome (pair #23,
X or Y). Ex: blonde hair
• Heredity: the passing of traits from parent to
offspring.
• Genetics: The study of Heredity
More vocab!!!! THE IMPORTANT
STUFF
• Allele: form of a gene…2 alleles per trait
– Dominant- stronger, expressed if present, represented by a
capitol letter (F)
– Recessive- weaker, not expressed if alone, Only expressed
if both alleles are recessive, represented by a lower case
letter (f)
• Genotype: combination of 2 alleles
– Homozygous (pure)- (FF or ff)- can be dominant or
recessive, both alleles the same
– Heterozygous (hybrid)- Ff- the alleles are different
• Phenotype: How it physically looks…..ex. Tall, white,
short
Practice naming and what trait will it
show (dominant or recessive)
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RR
Tt
PP
Rr
rr
Homozygous Dominant--------------- dominant trait
Heterozygous-----------------------------dominant trait
Homozygous Dominant--------------- dominant trait
Heterozygous-----------------------------dominant trait
Homozygous recessive--------------- recessive trait
Word Problem Steps
1st- Write the two traits
2nd- Figure out which one is dominant and which
is recessive
3rd- Pick a letter to use, assign the dominant trait
the uppercase of that letter and assign the
recessive the lowercase of that letter…………
1 trait = 1 letter
2 traits = 2 letters
• A person is heterozygous for curly hair which is
the dominant trait over straight hair. What is his
genotype?
C- curly
c- straight
Cc
• A person has blue skin which is dominant to
green. What are the possible genotypes and
BB- blue
what phenotype will it show? B- blue
b- green
Bb- blue
bb- green
• A person has Brown eyes which is dominant to
hazel. He is homozygous, what is his genotype?
B-brown b- hazel
BB
• A person has red hair which is recessive to blonde
hair. What is his genotype?
B-blonde
b- red
bb
Genetic Cross Punnett Square
• Punnett Squares are used to solve genetic
problems. They show the probability that a
certain trait will be inherited by the offspring.
MOM’s alleles
25%
25%
DAD’s alleles
25%
25%
THE BOXES ARE THE
POSSIBLE
OUTCOMES OF THE
OFFSPRING
Mono Crosses
• 1 trait involved in a cross. So only 1 letter, the
uppercase and lowercase of it.
• Steps:
1st Follow your previous steps for naming
2nd Draw your Punnett Square
3rd Put the parents alleles on the outside
4th Down and over (fill in boxes)
• In pea plants, round seeds is dominant and
wrinkled is the recessive trait. Show a cross
between a homozygous round and a
homozygous recessive. What are the possible
genotypes and phenotype ratios?
• Short fur in rabbits is dominant to long fur.
What phenotype ratio and genotype ratio
would you expect from a heterozygous female
and a male with long fur?
• Pink hair in trolls is more powering than green
hair. If two heterozygous pink haired trolls
made a baby troll, what are the possible
genotypes and phenotype ratios?
• In guinea pigs, rough hair is dom over straight
hair. If two heterozygous pigs are crossed, the
largest number of any one genotype of
offspring would probably be ?
If a yellow heterozygous flower was mated with
a white recessive flower, what could the possible
outcomes be?
THINK!!!!!!!
I buy a dog with Red fur. Red is the dominant
trait over golden. I wanna know what genotype
my dog is for breeding purposes. How would I
go about doing that?
TEST CROSSES
• Test cross = the cross of an organism with an
unknown dominant genotype (heterozygous
and homozygous dominant) with a (known)
genotype (homozygous recessive)
So remember,
AN ORGANISM WITH A RECESSIVE TRAIT
ALWAYS HAS A HOMOZYGOUS RECESSIVE
GENOTYPE (two lowercase letters).
• To summarize a little, here are the "Key Points" to remember
about a TEST CROSS.
LOOK AT THE OFFSPRING!!!!!!!!!!!!!
• I buy a dog with Auburn (red) fur. Red is the
dominant trait over blue. What are the
possible genotypes for this red dog and how
would I go about finding out which one he is?
I have a brown bunny. For bunnies, brown fur is
dominant to white fur. I would like to know which
genotype my bunny is. So I mated him with a white
bunny and came out with all brown bunnies. What
genotype is my bunny? Show the cross to prove it!!!!
SEX-linked traits
• Carried on the sex chromosomes (mostly on X) X and Y
• Still have a dominant and recessive allele that is written
as a superscript only on the X chromosome. ex: Xr Xr
• Must also specify if a man/ woman
– Females XX
– Males XY
• Males show most sex-linked traits because only has 1 X
chromosome
• Most diseases carried on the X chromosome
• Females can be carriers (heterozygous)
Punnett Squares are the same, just have to bring
down/over everything
Lets practice
• Eye color is a sex-linked trait carried on the X
chromosome. Red is dominant to white.
- Female with white eyes
- Female that is heterozygous for red eyes
- White eyed male
- Red eyed male
Cross 1: Cross a White eyed male and
a Homozygous red eyed female.
Cross 2: Cross a Red-eyed male and a
white eyed female.
1) A colorblind man marries a normal, non-carrier woman.
Colorblindness is a recessive disorder. What are the chances that they
will have a:
a. normal son
b. colorblind son?
c. colorblind daughter?
d. daughter who is a carrier?
2) A normal-vision man marries a colorblind woman. What are the
chances that they will have a:
a. normal son
b. colorblind son?
c. colorblind daughter?
d. daughter who is a carrier?
Dihybrid Cross (Mendel’s Rules)
• Looking at 2 traits (ex: color and size) so 2
different letters—each with a dominant and
recessive allele
• Still follows Mendel’s “LAW OF DOMINANCE”
Steps to solve a punnett square dihybrid cross
1. Write down the parents genotype (TtHh) (TTHh)
2. Formula : 2n (n = # of heterozygous traits) for each parent
gametes
3. to figure out the possible gamete separation, DANCE method
4. Draw a punnett square with correct number of boxes
5. Down and over keeping letters together in box (4 letters per
box….2 for each trait)
6. total up phenotypes
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Question:
How many gametes will be produced for the following
allele arrangements and what are they?
If round is dominant to smooth and Yellow is dominant
to blue
• Remember: 2n (n = # of heterozygotes) then
DANCE
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1.
Both parents are heterozygous for each trait
RrYy
2n = 22 = 4 gametes
• RY
2.
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3.
Ry
rY
ry
Homozygous round and heterozygous yellow
RRYy
Shows both recessive traits
rryy
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If round is dominant to smooth and Yellow
is dominant to blue
DO STEPS 1-4.....do not complete square,
but set it up!!!
1) Parent 1: Homozygous round and blue
Parent 2: Heterozygous for both traits
2) Parent1: Shows both recessive traits
Parent 2: Smooth and heterozygous for color
What r the possible offspring for two parents
one of which is heterozygous for height and
color hair, and the other shows the recessive
trait for height but is heterozygous for color. Tall
is dominant to short, and brown in dominant to
yellow.
• TtBb
ttBb
TB
Tb
tB
tb
tB tb
Now put into the Punnett Square How
many boxes will we have??? 4 across
and 2 down= 8
In trollville, having pink hair for trolls is dominant over
yellow hair. Having a green belly ring is dominant over
a blue belly ring. If a troll that is pure for pink hair and
heterozygous for ring color marries a heterozygous troll
for both traits, what possible phenotypes can their
children be?
Being Blue is a dominant trait to yellow. Being wrinkled
is dominant to being smooth. One parent is pure blue
and heterozygous for wrinkled. The other parent is
yellow and heterozygous for being wrinkled as well.
Show the possible offspring and analyze the phenotype
ratios.
Purple is dominant to yellow in plant color.
Starchy plants are dominant to sweet in taste.
Cross a heterozygous purple, sweet plant with a
yellow, pure starchy plant.
White wolves are dominant to black wolves. Brown
eyes are dominant to green eyes. Cross a black
coated, pure brown eyed wolf with a Heterozygous
wolf for both traits
3 Dominance Types
• Complete dominance
– Only 1 phenotype is shown
– Only one letter, dominant and recessive
– Ex. – Tall (T) short (t)
• Incomplete dominance
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Phenotype is blended in
Always using dominant allels
No recessive
Ex. - white flowers mate with red flowers pink flowers
• Codominance
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2 or more phenotypes are shown together
Both equally dominant
No recessive
Ex. – Roan Horse (has patches), calico cats
EX- White flower mate with red flower white/red flower
Trix to figuring out if an Incomplete or
Co-dominant cross
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2)
3)
4)
Read the question
Punnett squares will look the same
Look at the possible phenotypes given
2 dominant alleles of different letters: 1 for
each trait.
5) Genotype will be homozygous dominant
ALWAYS!!!!!!!!!
Practice
Co-dom or Incomplete
Write genotypes
• Red flower + white flower= Pink flower
– RR + WW= RW
• Striped + Spotted = Striped/spotted
– SS + TT = ST
• Square + round= Oval
– SS + RR = SR
• Stared eyes + Circle eyes= Star/circled eyes
– SS + CC = SC
Practice Incomplete dom.
• In Oompa loompa’s, hair color is incomplete
dominance. Blue-haired oompa crossed with a
red-haired oompa. What would the
phenotypes be, show your cross.
B
R
B
(BR)
(BR)
(BR)
(BR)
R
So, what would
the offspring
look like if I
crossed 2 purple
haired oompas?
• A bug that has stripes is mated with a bug that
has spots. Stripes and spots are codominant.
What would the offspring look like?
• A Stripe/spotted bug mates with a striped
bug. What would the offspring look like?
IB i
-type AO,and
universal
2 Dominant:
B and donor
-type: O
AB, universal receiver
1 Recessive
Blood types: mix on Mendel and Co-dominance
BCT Practice
1) Which organisms are chiefly responsible for the recycling
of dead matter?
a. parasites b. viruses
c. decomposers
d. producers
2) A characteristic shared by both predators and parasites
is that they
a. feed on decomposing plant material b. capture and kill animals for food
c. live inside their host
d. attack a living food source
3) In guinea pigs, rough hair is dominant over straight hair.
If two heterozygous pigs are crossed, the largest number of
any one genotype of offspring would probably be
a. Homozygous straight hair
c. Heterozygous straight hair
b. Homozygous rough hair
d. Heterozygous rough hair
1) In squirrels, the gene for gray fur (G) is dominant over the gene
for black fur (g). Fifty % of a large litter of squirrels is gray. Which
parental cross most likely produced this litter?
a. GG x gg b. GG X GG c. Gg x gg d. gg x gg
2) Compared to that of a body cell, a sperm cell has this many
chromosomes?
a. The same b. twice c. half d. four times
3) An exact duplication of chromosomes, followed by the separation
of these sets into 2 cells is known as
a. Meiosis b. mitosis c. fertilization d. differentiation
4) One characteristic of all living organisms is that they
a. make food
b. live on land
c. maintain homeostasis d. move from place to place
5) The basic raw materials of photosynthesis are
a. Glucose and CO2 b. Oxygen and water c. Water and CO2
d. oxygen and sugar
Practice
• A heterozygous parent for blue eyes and
brown hair marries a homozygous recessive
parent with green eyes and blond hair. What
are the possible phenotypes of their children?
QUESTION: Pretend that Brad Pitt is homozygous
for the type B allele, and Angelina Jolie is
heterozygous for type “A.” What are all the
possible blood types of their baby?
IB
IB
IA
IAIB
I AI B
i
IB i
IB i
Based on the information in this table,
which men can not be the father of the
baby? The mother is heterozygous for type
A. Justify your answer with Punnett
squares showing all possibilities.
Het
Homo
GEORGE
Cable Guy
I (B)
Sammy the Player can not be
the babies father. He has
blood type O so if he mated
with this mother, than all
children would have type A.
The waiter can also not be the
father. The children would
either have type A or O.
HINT: MAKE a cross
between mother and each
possible fathers!!!!!
"Could a man with type B blood and a
woman with type AB produce a child with
type O blood?"
Practice:
• Stewie and his family all have purebreed oval
heads which is the dominant trait in Family
Guy world. He recently married Ellie, also
from Family Guy world, but she has a square
head. What are the genotype and phenotype
ratios of their possible children for head
shape.
• A genetic disorder is sex linked and is caused by a
recessive allele (e). The allele for the unaffected
condition (E) is dominant. A woman who is a carrier
of this disorder married an unaffected man. The
couple would like to have a child but they are
concerned that their child will inherit the disorder.
X
E
X
E
E
XX
X
E
e
E
XX
e
Female unaffected
Female Carrier
Male Unaffected
Male affected
E
Y
XY
e
XY
1)
Enzyme molecules are synthesized primarily from
a. monosaccharides b. amino acids c. fatty acids d. phopholipids
2) The science of naming and classifying organisms is called
a. Ecology
b. taxonomy c. synthesis d. homeostasis
3) Cells are to tissues as organs are to
a. cells b. genes c. organ system d. organelles
4) The top of a food chain is usually a
a. Autotroph
b. plant
c. herbivore
d. carnivore
PedigreeA family history
of a trait
male
female
married
offspring in order of birth,
from left to right
Individual showing
trait being studied
Carrier for trait, but does not
show it (heterozygous)
I, II, III, IV...
generation
How many women? Diseased women?
How many men? Diseased men?
How many children did couple 1&2 of generation 2 have?
How many children did couple 7&8 of generation 2 have?
How many marriages are there?
= Huntington’s
Disease
1. Which members of the family above are afflicted with Huntington’s Disease? _________________________________
2. There are no carriers for Huntington’s Disease- you either have it or you don’t.
With this in mind, is Huntington’s disease caused by a dominant or recessive trait? ____________________________
3. How many children did individuals I-1 and I-2 have? _______________________________________________
4. How many girls did II-1 and II-2 have? ______________ How many have Huntington’s Disease? ________________
5. How are individuals III-2 and II-4 related? ________________________ I-2 and III-5? _________________________
12. The pedigree to the right shows a family’s pedigree for colorblindness. Which sex can be carriers of
colorblindness and not have it? ______________________
13. With this in mind, what kind of trait is colorblindness? ______________________
14. Why does individual IV-7 have colorblindness, show the punnett square?
_________________________________________________
15. Why do all the daughters in generation II carry the colorblind gene? ____________________________________
16. Name 2 IV generation colorblind males. _________
• Mutations can involve an entire chromosome
or a single section of a DNA molecule
• Mutations can have a positive effect, a
negative effect, or a neutral (no) effect on the
organism
• MUTATIONS CAUSE EVOLUTION!!!!!!!
CHROMOSOME MUTATIONS
• Change in structure of chromosome or the loss of entire chromosome
– DELETION
• Loss of a piece of a chromosome due to breakage…all info carried by missing piece
may be lost
– INVERSION
• Segment breaks off and then reattaches in reverse order to that same chromosome
– TRANSLOCATION
• A segment breaks off and then reattaches to a different chromosome
– NONDISJUNCTION
• Alter the # of chromosomes found in the cell
• Failure to separate during meiosis
• A zygote with 45 Chromosomes …one copy of a particular chromosome= monosomy
• three chromosomes on a spot in a karyotype= trisomy…a zygote with 47
chromosomes
– Ex: Down Syndrome (trisomy-21)….on chromosome 21
GENE MUTATIONS
• May involve large segments of DNA or a single
nucleotide within a codon
– POINT MUTATIONS
• Substitution, addition, or removal of a single nucleotide
– SUBSTITUTIONS
• One nucleotide is replaced with a different one…can cause
problems or may not…What if sub is for a STOP
codon….YIKES!!!!
– Ex: Sickle Cell Anemia….substi A (adenine) for T (Thymine)
– FRAMESHIFT MUTATIONS
• Since codons are read in threes…..if an addition or deletion
occurs….the FRAME OF 3 gets err…..SHIFTED
ACGTTA ACTTA
ACGTTA ACCTTA
DNA Technology
Rosalind Franklin
• 1950's.
• Took X-ray picture of DNA
Watson and Crick
• Watson and Crick made
a model of the DNA
molecule and proved
that genes determine
heredity
Genetic code
• 1966
• The Genetic code was
discovered; scientists
are now able to predict
characteristics by
studying DNA. This
leads to genetic
engineering, genetic
counseling.
DNA Fingerprinting
• The late 1980's.
• An international team
of scientists began the
project to map the
human genome.
• The first crime
conviction based on
DNA fingerprinting, in
Portland Oregon.
Barbara McClintock
• 1983
• Barbara McClintock
(1902-1992) of the U.S.
was awarded the Nobel
Prize for her discovery
that genes are able to
change position on
chromosomes.
“crossing-over”
Dr. Kary Mullis
• 1993
• Dr. Kary Mullis
discovered the PCR
procedure, for which
he was awarded the
Nobel prize.
Copying DNA
• Polymerase Chain Reaction
• Also called PCR
• A method of making many
copies of a piece of DNA
Gel Electrophoresis
The fragments of DNA cut by restriction enzymes
are separated by gel electrophoresis
STEPS:
a. DNA fragments are loaded at one end of a gel
tray
b. A current is applied to the gel
c. DNA molecules are negatively charged
and move toward positive end of gel
d. The fragments separate because
smaller molecules move faster than
larger ones. This results in a pattern
of bands
e. Photographic film is used to visualize the
DNA fragments. This pattern can serve as
a person’s DNA fingerprint
Cloning Begins
• 1997.
• Dolly the sheep - the
first adult animal clone.
Biotechnology Breakthroughs
• Potatoes with higher solid content
• Garlic that lowers cholesterol
• Fruits and vegetables that reduce
risks of cancer and heart disease
Human Genome Project
• Started in 1990
• Research effort to sequence
all of our DNA (46
chromosomes)
• Over 3.3 billion nucleotides
• Mapping every gene location
(loci)
• Conducted by scientists
around the world