Transcript Genetics Student

Mr. Drake
 The nucleotides are made of a ________, and
_____________ group and a ______________
 The four bases are:
 Adenine, Thymine, Guanine, and Cytosine
 Adenine and Guanine are ________________
 Thymine and Cytosine are ____________________
 Base-Pairing Rule
 Adenine always hooks to Thymine
 Guanine always hooks to Cytosine
 The nucleotides hook together
in the form of a _____________
 Twisted like a spiral staircase
 Different segments of DNA
code for different traits
 Scientist who worked with plants and studied their
traits
 Founded the study of _________________: how
characteristics are transferred from generation to
generation
 ___________: all of the traits we receive
from our parents
 He observed 7 traits of pea plants such as height, color,
 He recorded these characteristics
 After planting and growing more and
more pea plants he noticed that these
traits showed up randomly
 He carefully controlled how these plants reproduced,
or “pollinated”
 ___________________:
same plant
 ____________________:
two different plants
 He chose “true breeding” plants– pure bred for one
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trait (example: color, height, etc.)
These were the parent generation or _______________
He then took pollen from these plants and used it to
fertilize another type of pea plant
The result of this was the first family or _____________
He allowed these F1 plants to “self pollinate” into the
_____________
 Certain traits get passed on through chromosomes,
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one from each parent.
The different forms of a trait , Dominant or recessive,
are called ______________
The segment of DNA that codes for an allele is called a
___________.
Capital letters for Dominant; Lower case recessive
Each parent gives an allele for a trait
Father gives F for freckles and mother gives f for
freckles it will be Ff= dominant trait gets expressed.
 He found that the F1 or first generation where all one
color
 The second generation 75% were one color (purple)
and 25% were another color (white)
 “Alleles” are different forms of a gene
 Example: There is the purple allele and the white allele
 Purple= dominant (B) – BB or Bb
 Dominant alleles are represented with a capital letter
 White = recessive (b)– bb
 Recessive alleles are represented with a lower case letter
 ____________: The genetic makeup of an individual
 Represented by letters (BB, Bb, bb)
 “Gg” would be the genetic makeup of a pea plant with
green pods, green being dominant.
 The ___________: the appearance of the organism and
the traits that gets shown.
 For the pea plant with “Gg”, the phenotype is “green”.
 ______________: When the alleles are the same.
Either both dominant “PP” or both recessive “pp”.
 ______________: When there is a dominant and a
recessive “Pp”. This is the carrier organism.
 Traits are controlled by chromosomes, which separate
during cell division (meiosis)
 How traits separate is random
and independent
 Every time an offspring is
produced the traits that control
the appearance are determined
randomly by luck.
 Very important in determining
variety of a species
Self fertilizes
 This means that while someone may be dominant for
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one trait, they may be recessive for others
Blonde hair is recessive
Brown eyes are not
These combinations may occur because traits are
independent of one another.
We Like this Law
 Y is Brown
eyes
 Y is Blue eyes
 R is Brown
hair
 r is Blonde
hair
 Brown is
dominant is
both hair
and eyes
 When two organisms reproduce, their traits get passed
on randomly to their offspring.
 To determine the probability of the offspring getting
certain traits, test crosses are done.
 These determine the genetic makeup and also what
the individual will look like.
 This is done to predict probability of offspring from
two different parents with one trait
 Use a Punnett square.
 Simple but very effective in predicting genotypes and
phenotypes
 Using a Punnett square helps you predict the
probability of each genotype and phenotype.
 Likelihood of something happening
 Number of times something is expected occur over the
number of chances
 I grow 100 pea plants. 75 of them are green 25 are
yellow.
 There is a 75% chance of these plants turning out to be
green and a 25% chance for yellow.
 Dominant parent and recessive parent
 Parents are GG x gg
 Will result in a genotype of Gg
 The phenotype will demonstrate the Dominant traits
of the individual
 Dominant parent and either dominant or recessive
parent.
 Either Hh x HH or Hh x hh
 The results will be 50% homozygous and 50%
heterozygous
 2 parents with the dominant phenotype and
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heterozygous genotype: Bb
Bb x Bb: resulting in 1 BB, 2 Bb and 1 bb.
This is a 3:1 ratio: 3 dominant and 1 recessive
25% homozygous dominant, 50% Heterozygous, and
25% homozygous recessive.
This is known as the phenotypic ratio and is how many
recessive traits get overlooked because the parents
show dominant traits
 When we do not know the genotype of an individual
 Cross the individual with homozygous recessive
individual
 This will determine if the unknown is homozygous or
heterozygous for the specific trait
Unknown
allele
 Incomplete Dominance
 Codominance
 Sex-linked
 Polygenic
 Multiple allele
 A phenotype that is located between dominant and
recessive
 RR=red rr= White Rr=pink
 This occurs when two or more alleles affect a trait
 Very common in nature, eye color in humans
Brown=Dom. Blue= Recessive Green= mix
 Occurs when both genes are expressed in a
heterozygous offspring
 In chickens, R= black feathers and r= white feathers.
 A chicken that is Rr will have black and white feathers.
 This is very common in nature
 Genes that are found on the sex-chromosomes
 Males will express traits found on
X chromosome since they only have
one X.
 Ex: More males are colorblind
because it is linked to the X
chromosome.
 Traits that are controlled by two or more genes.
 Show a wide range of phenotypes.
 Skin color in humans
 Controlled by at least
four different genes
 Genes that have more than two alleles
 Example: Rabbit fur color
 A rabbit’s coat color is determined by a single gene that
has at least four alleles;
Possible alleles
C-dominant to all
alleles
cch –dominant to ch
and c alleles
ch-dominant to c
alleles
c-recessive to all
other alleles
cch ch,cch c,
cch cch
 Dihybrid crosses involve parents with two or more
traits
 More complicated and involves more results and
outcomes for the offspring
 The Punnet square is more involved and more difficult
to figure out.
 First you must set up the punnet square with 16
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squares.
You must determine the parents genotypes, they now
have 4 traits instead of 2.
R= round peas r= wrinkled peas, Y=yellow peas,
y=green peas
RrYy would be made into 4 parents RY, Ry, rY and ry.
rrYy would be made into rY, ry, rY, ry.
Then the same rules apply as 4 square Punnet squares