happy thursday bell work: in 33 words, explain how a girl with blue eyes could have two parents with...
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HAPPY THURSDAY
BELL WORK:In 33 words, explain how a girl with blue eyes could have two parents with brown
eyes.
**Turn in your HW – The 2 handouts**
Standard: B6F - Predict possible outcomes of genetic combinations
such as monohybrid crosses.
Essential Question: How can I predict genetic outcomes?
Genetics is the scientific study
of heredity.
Gregor Mendel is the Austrian monk who was
particularly important to
understanding biological
inheritance.
From his experiments, Mendel concluded that biological inheritance is
determined by factors that are passed from one
generation to the next.
The chemical factors that determine traits are called
genes.
The different forms of a gene are called alleles.
When mating two organisms, the original pair of organisms is known as the P
generation.
The “P” in P generation stands for parental.
The offspring of the P generation is the F1 generation.
“F1” in F1 generation stands for first filial.
Filius and filia are the Latin words for son and daughter.
The offspring of crosses between parents with different traits are
called hybrids.
The principle of dominance states that
some alleles are dominant while others
are recessive.
The dominant allele will always be expressed.
A capital letter is used to represent a dominant
allele.
Y = Dominanty = Recessive
When Mendel crossed the F1 generation with itself,
one fourth of the F2 plants showed the trait controlled
by the recessive allele.
The recessive allele will only be expressed when the
dominant allele for the trait is not present.
A lower case letter is used to represent a recessive
allele.
Y = Dominanty = Recessive
The way in which alleles separate during meiosis does not follow a pattern. It is completely random.
The results of genetic crosses can be
explained by the principles of probability.
Probability is the likelihood that a
particular event will occur.
Probabilities predict the average outcome of a large number of events.
Probabilities cannot predict the exact outcome of an individual event.
In probability, sample size eventually determines how close resulting numbers get to the expected values.
In probability, past outcomes do not affect future ones.
The gene combinations that might result from a genetic cross can be determined by
drawing a diagram known as a Punnett square.
The types of gametes produced by each F1 parent are shown
along the top and left sides of a Punnett square.
The possible gene combinations for the F2
offspring appear in the 4 boxes that make up the square.
The letters in the Punnett square
represent alleles.
Punnett squares are used to predict and
compare the genetic variations
that will result from a cross.
Organisms that have two of
the same alleles for a trait are homozygous
Organisms that have two
different alleles for a trait are heterozygous.
Homozygous organisms are true-breeding/purebred for a trait.
Heterozygous organisms are hybrid for a trait.
BB Bb bb
BB Bb bb
A phenotype is an organism’s physical
characteristics.
A genotype is an organism’s genetic
makeup.
Two organisms can have the same phenotype but
different genotypes.
BB Bb bb
Brown Eyes vs Blue eyes
Mendel’s assumptions
about segregation predicted a
phenotypic ratio of 3:1.
Mendel’s assumptions
about segregation predicted a
genotypic ratio of 1:2:1.
The fact that genes that segregate independently
do not influence each other’s inheritance is
known as independent assortment.
The principle of independent assortment
states that genes for different traits can
segregate independently during the formation of
gametes.
Independent assortment helps account for the many
genetic variations observed in many
organisms.
Punnett Square Steps1st Step = Identify what letter is being
usedWhat would be the possible outcomes for the
offspring of a cross between pink flower (PP) and a white flower (pp)?
“P” and “p”
Punnett Square Steps2nd Step = Assign the trait for each letter.
What would be the possible outcomes for the offspring of a cross between pink flower (PP) and a white flower (pp)?
P= PINK p = WHITE
Punnett Square Steps3RD Step = Match what letters are being
used for each parent/gender.What would be the possible outcomes for the
offspring of a cross between pink flower (PP) and a white flower (pp)?
= PP = ppMOMDAD
Let’s sum it up…..1st = Identify what letters are being used.
2nd = Assign the trait for each letter.
3rd = Match what letters are being used for each parent/gender.
4th = Now fill in your Punnett Square.
Punnett Square practice…1. What would be the possible outcomes for the offspring of a cross between pink flower (PP) and a white flower (pp)?
P P
p
p
Pp Pp
Pp Pp
P = Pink p = White
DAD = PPMOM = pp
**When using the letters like “P and p” OR “C and c”, draw the lowercase letter in cursive or just make sure you make them look different. Otherwise, you might
confuse the dominant for the recessive **
2. Long fingers are dominant (F) to short fingers (f). Complete the Punnett square for a homozygous
recessive mom and a heterozygous dominant dad.
F f
f
f
Ff ff
Ff ff
F = Longf = Short
DAD = FfMOM = ff
3. In a plant, long stems are dominant (L) to short stems (l). If a homozygous dominant flower and a homozygous recessive
plant are crossed, what would be the phenotypic ratio of their offspring?
L L
l
l
Ll Ll
Ll Ll
L = LongL = Short
DAD = LLMOM = ll
4. Straight hair (C) is dominant to curly hair (c). What would be the probability that a child would have curly
hair if both parents are heterozygous dominant?
C c
C
c
CC Cc
Cc cc
C = Straightc = Curly
DAD = CcMOM = Cc
5. Having a hitchhiker's thumb is a dominant trait (T). If a woman with a straight thumb has a child with a man who is heterozygous for the trait, what are the chances
their child will have a hitchhiker's thumb?
T t
t
t
Tt tt
Tt tt
T = Hitchhikert = Straight
DAD = TtMOM = tt
6. What would the phenotypic and genotypic ratios be for two purple (Pp) flowers that were bred together?
P p
P
p
PP Pp
Pp pp
P = Purplep = White
DAD = PpMOM = Pp
Can you identify your own genotypes and phenotypes?
Hairline:
Widow’s peak is dominant tostraight hairline
Eye Shape:
Almond eyes is dominant to round eyes
Tongue Rolling:
CAN roll the tongueis dominant to cannot
Eyelash Length:
Long eyelashes is dominant toshort eyelashes
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