Transcript RRYY

Genetics
Chapter 9 and 12
Gregor Mendel
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1842
Studied hereditythe transmission
of characteristics
from parents to
offspring.
Studied garden
peas- Pisum
sativum
Mendel's Work
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Looked at peas’ traits
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Height (tall or short)
flower position (axial or terminal)
pod appearance (inflated or
constricted)
pod color (green or yellow)
seed texture (smooth or wrinkled)
Flower color (purple or white)
Mendel’s Methods
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Pollination - from anther to stigma
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Self-pollination
Cross-pollination
Types of Pollination
His experiments
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Mated pure plants through self
pollination.
Created strains of plants.
Created P1 or parent generations.
Crossed the plants to get F1 or first
filial generations. AKA 1st offspring.
Then crossed F1 plants to create F2
Plants. AKA 2nd generation
offspring.
Conclusions (pg 167-168)
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Axial + terminal = axial
Green + yellow = green
Purple + white = purple
THEREFORE….
Found factors – pairs for each trait.
2 Alleles per trait (ex Gg)
Recessive vs Dominant Traits
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Dominant = controlling or over
powering allele.
Recessive= overpowered not
controlling allele. Can be masked
Law of segregation= pair of factors
is segregated, or separated, during
the formation of gametes.
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AKA one from dad, one from mom ->
join to make a pair.
Chromosomes and Genes
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Molecular genetics= study of
structure and function of genes.
Alleles- one half of a pair of genes
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ex. Aa, “A” is an allele. “a” is an allele.
Probability- the likelihood that a
specific event or trait will occur.
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ratios
Genotype and Phenotypes
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Genotype= genetic makeup of an
organism. (Gg)
Phenotype= Physical appearance of
organism as a result of its
genotype. (green)
Homozygous= both alleles are the
same (GG)
Heterozygous= alleles are different
(Gg)
Punnett Squares and Crosses
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Monohybrid
Crosses- cross for
ONE pair on
contrasting traits.
Homozygous
Dominant (PP) x
Homozygous
Recessive (pp)
B
B
B
BB
BB
B
BB
BB
Monohybrid Cont.
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Homozygous (BB)
x heterozygous
(Bb)
B
b
B
BB
Bb
B
BB
Bb
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Heterozygous (Bb)
x heterozygous
(Bb)
B
b
B
BB
Bb
b
Bb
bb
Test Crosses
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Unknown
genotypes of
parents
Known phenotypes
of offspring
BB=black, Bb=
black, bb=brown
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2 black:2brown
One parent is
brown (bb)
?
?
b
Bb
bb
b
Bb
bb
Incomplete Dominance
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Two or more alleles
influence the
phenotype. AKA
“mixing”
Neither allele is
dominant
EX: RR=red, Rr=pink,
rr=white
Geno=1RR:2Rr:1rr
Pheno=1red:2pink:
1white
R
r
R
RR
(red)
Rr
(pink)
r
Rr
rr
(pink) (white
)
Co dominance
Page 176
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Both alleles are
expressed in
heterozygous
offspring.
Example- a horse
has a gene for
both red and white
hair. Therefore he
has strands of
white hair and
strands of red
hair.
Dihybrid Crosses
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Involves two pairs of contracting
traits.
EX= seed texture and seed color
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Homo Dom x Homo Recessive
R (round) is dominant over r (wrinkled)
Y (yellow) is dominant over y (green)
Cross rryy (homogenous wrinkled
green) with RRYY (homogenous round,
yellow)
RRYY X rryy
(Homozygous dominant X recessive)
ry
ry
ry
ry
RY
RrYy
RrYy
RrYy
RrYy
RY
RrYy
RrYy
RrYy
RrYy
RY
RrYy
RrYy
RrYy
RrYy
RY
RrYy
RrYy
RrYy
RrYy
Heterozygous X Heterozygous
RrYy X RrYy
RY
Ry
rY
ry
RY
RRYY
RRYy
RrYY
RrYy
Ry
RRYy
RRyy
RrYy
Rryy
rY
RrYY
RrYy
rrYY
rrYy
ry
RrYy
Rryy
rrYy
rryy
Hetero X Hetero Results
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Genotypic ratio
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1RRYY: 2RRYy: 2RrYY: 4 RrYy:
1RRyy: 2Rryy: 1rrYY: 2rrYy: 1rryy
Phenotypic Ratio
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Always 9:3:3:1 (total 16)
9 dominant for both traits
1 recessive for both traits
Results Continued
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9/16
3/16
3/16
1/16
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**Remember**
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round and yellow
round and green
wrinkled and yellow
wrinkled and green
9:3:3:1
Sex determination of Offspring
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Cross XX (mom)
with XY (dad)
Geno Always =
2XX:2XY
Pheno Always=
2females:2males
X
X
X
XX XX
Y
XY
XY
Sex Linkage
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Genes that are found only on the “X”
chromosome or the “Y” chromosome.
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color blindness (inherited from mom)
hemophilia
Ex Fly eye color (Morgan)
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F1= all red eyes
F2= 3 red: 1white
 White was ALWAYS male
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THUS, eye color is carried on the “X”
chromosome.
Results
X
Y
r
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F1- all red eye
because they all
carry “R”
XR
XR X
r
XRY
XR
XR Xr
XRY
XR
Y
XR
XR XR
XRY
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Xr
XR Xr
XrY
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F23 red eyed (carry
“R”
1 white (does not
carry “R” )
X- Influenced
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Traits influenced by
sex hormones.
Phenotypes differ
even is genotypes are
the same.
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Pattern baldness
B=bald
B’=non bald
Dominant in males,
Recessive in females
**Females only show
if both alleles are
dominant. **
XB
XB’
XB
XBXB
XBXB’
(Bald
(not
because bald)
both BB)
YB’
XBYB’
(Bald)
XB’YB’
(Bald)
Blood Type
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Controlled by
multiple alleles
 iA, iB, and i (iO).
 A and B are co
dominant.
 A and B are
dominant to O.
Genotype Phenotype
IAIA
A
IaI
A
IBIB
B
IBI
B
IAIB
AB
II
O
Pedigrees
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(see page 227)
Record of how a trait is inherited
over several generation.
Determines carriers- organisms that
have the gene but do not show the
phenotypic trait.
Used to determine genetic
disorders.
Additional Info
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Chromosome Map- diagram that
shows a linear sequence of genes
on a chromosome.
Mutation- some sort of change in
the gene sequence. Can be good or
bad.
Chromosome Map
Trisomy 21
Great Apes Karyotype
Mutations Cont.
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Chromosome Mutations
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Deletion- loss of part of a chromosome.
Inversion- break off and reattach in
reverse.
Translocation- break off and attaches
to another chromosome.
Gene Mutations
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Point Mutation- substitution,
addition, or removal of a single
nucleotide.
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Ex sickle cell anemia (A for T)
Substitution- nucleotides switch
Frame Shift- caused by deletion or
addition.
Ways to detect genetic Disorders.
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Genetic Screening
Genetic Counseling
Amniocentesis
Chorionic villi sampling
Pedigrees
Genetic Traits and Disorders
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Huntington’s Disease- (single allele)
Blood Type- (multiple alleles)
Skin Color- (polygenic alleles)
Non-disjunction (addition or
subtraction of chromosomes)
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Monosomy- One chromosome
Trisomy- Three chromosomes
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Trisomy-21 – Down Syndrome
Huntington’s Disease