Download Genetic lab 7

General Genetic
Bio 221 Lab 7
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1-Widow's Peak (W, w) front hairline : Dominant allele in heterozygous or
homozygous individuals results in a V-shaped
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2-Ear lobes (A, a): Ear lobes may be either adherent or free and pendulous.
Homozygous recessives The dominant trait is for lobes to hang free, a bit of
lobe hanging down prior to the point where the bottom of the ear attaches to
the head. With the recessive phenotype, the lobes are attached directly to the
head
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3-Hitchhiker's thumb (H, h): Homozygous recessives
can bend the distal joint of the thumb backward to a nearly
4-Tongue rolling (R, r) : Persons with a dominant allele in
heterozygous or homozygous condition can roll
5-Bent pinky (B, b) inward toward the fourth (ring) finger : Dominant
allele causes the distal segment of the fifth finger to bend distinctly
6-Cleft chin: the dominant gene causes the cleft chin while the
recessive genotype presents without a cleft.
7-Thumb crossing (C, c):
In a relaxed interlocking
of fingers, left thumb over right indicates the dominant
8-PTC tasters (T, t) :
Phenylthiocarbamide (PTC) tastes bitter to heterozygous
or homozygous dominant individuals, but is tasteless to homozygous
recessives
9-Blue eyes (E, e) : Blue-eyed persons are homozygous recessive and lack
pigment in the iris
10-Middigital hair (M, m): People lacking hair in the middle segments of the
fingers are homozygous recessive.
11- clockwise (CW) or counterclockwise (CCW) direction: the allele for
clockwise is dominant to the allele for counterclockwise.
12- Darwin's tubercle:
The allele for Darwin's tubercle is dominant.
13- Toe length:
The big toe is longer than the second
toe ( L), while other people have the
big toe shorter than the second toe
("S"). The allele for S dominant to
the allele for L
Non – Mendelian inheritance : is trait do not segregate in accordance to
Mendel Laws . Some traits are carried on sex chromosomes X and Y . Most
traits carried are present on only the X chromosome while the Y Chromosome
is smaller and very few genes are located on this chromosome .
There are 3 Categories of genes that may have different effects depending on
an individuals gender :
1- Sex – Limited genes .
1-Beard and Breast .
2- Milk Production .
3-White and yellow color of special specie of butterfly .
4-Feathering in birds .
2- Sex – Influenced genes .
1- Baldness .
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3- X– Linked inheritance .
1- Dominant sex – linked traits.
2- Recessive sex linked traitsa-Whit eye (rr) in Drosphilia .
b- Red / Green color blindness .c Example : Hemophilia (hh)
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Definition :
That are inherited by both men and women but are normally only expressed in the
phenotype of one of them .
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Example :
1- Beard and Breast .
Beard and Breast are secondary sexual characters that depend on sex hormones .
In female lacks in beard and male lacks in developed breasts .
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2- Milk Production .
Is trait expressed by cows and affected by gene on Somatic chromosome 14 . Both Bulls
and Cows carry this gene and both contribute an allele to their daughters which affects the
quantity of milk that daughter produces .
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3- White and yellow color of special specie of butterfly .
That male always have yellow color while (WW) the female have in two color white and
yellow (ww) .
WW
Ww
Ww
ww
Male
Yellow
Yellow
Yellow
Yellow
Femal
e
White
White
White
Yellow
Example :
4- Feathering in birds .
Males have long , pointed curved fringed feathers on tail and neck ,
but feathers of female are shorter , rounded , straighter .
t had been early established that hen-feathering is a trait controlled
by a simple autosomic dominant gene, whose expression is limited
to the male sex.
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1-The sex hormones of the animal affect the expression of a trait by the heterozygous
and provide different cellular environments in males and females .
2-The genes behave differently in two sexes .
Ex : amount of body hair and muscle mass.
Example :
1- Baldness (BB).
*In male physiological factors helps in the expression
of hair
( Recessive allele ) in males than females .
*The gene for baldness behaves as a dominant in
males but as a recessive in females .
*Heterozygous males are bald and will pass the
gene to about 50% of their offspring of either sex .
*The amount of thinning of the hair or balding that is
observed depends both on genotype and the amount
of testosterone exposure .
male BB x bb Female
male BB x bb Female
BB
Bb
Bb
bb
Male
Baled
Baled
Baled
Hair
Female
Baled
Hair
Hair
Hair
Information :
That inheritance is different males than females , and That inheritance controlled
by Genes on X – Chromosomes .
- Mother
1- pass X-linked alleles to only sons .
2- Females ( homozygous) have 2 allele for each gene
3-Female can be : Normal , Affected , Carrier .
4-Females have 2 X- Chromosomes that good chance of having the normal gene
on one of the two .
- Fathers
1-pass X-linked alleles to only daughters .
2-Male can be : Normal , Affected .
3- males ( hemizygous) have one X – Chromosomes and have recessive
condition much more commonly than females .
4-Males have 1 X- Chromosome does not carry of the same genes , so there is no
normal gene to counter the defective X .
Probabilities inheritance of sex linked traits
1- Unaffected father with affected mother
2- Unaffected father and carrier mother
3- Affected father and unaffected Mother
3- X-Linked Dominant Inheritance
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A male or female child of a mother
affected with an X-Linked dominant trait
has a 50% chance of inheriting the
mutation and thus being affected with
the disorder.
All female children of an affected father
will be affected (daughters possess
their fathers' X-chromosome). No male
children of an affected father will be
affected (sons do not inherit their
fathers' X-chromosome).
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4-X-Linked Recessive
Inheritance
Females possessing one X-linked
recessive mutation are
considered carriers and will
generally not manifest clinical
symptoms of the disorder.
All males possessing an X-linked
recessive mutation will be
affected (males have a single Xchromosome and therefore have
only one copy of X-linked genes).
All offspring of a carrier female
have a 50% chance of inheriting
the mutation.
All female children of an affected
father will be carriers (daughters
possess their fathers' Xchromosome). No male children
of an affected father will be
affected (sons do not inherit their
fathers' X-chromosome).
Kinds of :
1-Autosomal Dominant Inheritance:
The child of an parent affected with
autosomal dominant inheritance has a
50% chance of inheriting the parent's
mutated allele and thus being affected
with the disorder. A mutation can be
transmitted by either the mother or the
father. All children, regardless of gender,
have an equal chance of inheriting the
mutation.
2-Autosomal Recessive Inheritance
a- An individual will be a "carrier" of
autosomal recessive inheritance if they
possess one mutated allele and one
normal gene copy. There is a 50%
chance that a carrier will transmit a
mutated gene to a child.
b- If two carrier parents have a child there
is a 25% chance that both will transmit
the mutated gene; in this case, the
child will inherit only mutated copies of
the gene from both the mother and the
father and thus will be affected with the
disorder. There is a 50% chance that
one carrier parent will transmit the
mutated gene and the other will
transmit the normal gene; in this case,
the child will have one mutated gene
and one normal gene and will be a
carrier of the disorder. Finally, there is
a 25% chance that both carrier parents
will transmit the normal gene; in this
case the child will have only normal
genes and will not be affected.
Examples:
1-White eye (rr) in Drosophila .
*Consider the red /white eye allele
of Drosphilia .
Red eyes are dominant (Normal)
and codes (RR) , (Carrier ) (Rr)
and White eyes are codes ( rr) .
*The recessive phenotype is more
common in males , because the
R/r locus is on X – Chromosome
that means the males are haploid
, the only genotype have R or r
for that R male has red eyes and r
males have white eyes .
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Examples:
2- Red / Green color blindness .(cc)
* Is condition of color vision . It appears to normal state of animals that active at
night .
Because , the vision is mediated not by cone receptors but by rods which respond to
low intensity of light .
(Normal) code (CC) , (Carrier ) (Cc) and Affected ( cc) .
CC
c
XX
XY
Female
Normal
Male
Affected
1-
Cc
C
Cc
C
XX
XY
XX
XY
Female Carrier
Male Normal
Female Carrier
Male Normal
cc
C
XX
XY
Female
Affected
Male Normal
2-
Cc
c
Cc
c
XX
XY
XX
XY
Female Carrier
Male Affected
Female Carrier
Male affected
Cc
c
XX
XY
Female
Carrier
Male
Affected
3Cc
cc
c
XX
C
XY
XX
XY
Female Carrier
Male Normal
Female Affected
Male Affected
3-Example : Hemophilia (hh)
Most male lethal
1-Male can be : Normal (HH) , Affected (hh) .
2-Female can be : Normal (HH) , Carrier (Hh) , Affected (hh) .
When a female with hemophilia has children , she will pass the gene to each of
her sons. .
Question :
A color blindness man marries a woman with normal vision . Her mother was
color blind .
What kind of :
1- Children would you expect from this marriage ?
2- Which kind of this
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The experiment of today
white eye cross in Drosophila