Term
|
Definition
neither of the two traits
are seen in the F1 of a cross of two pure breeding traits. Examples: flower colors, blooming time in peas |
|
|
Term
|
Definition
both alternative traits are
expressed in the F1 of a cross of two pure example: spotted or dotted lentil plants.
breeding parents. |
|
|
Term
There may be deviations from ______
and ________
• Variants are not restricted to two ______.
• A single gene may affect _______
• A single phenotype may be the result of __________
actions and _________. |
|
Definition
complete dominance, recessivness. allelic forms. Multiple phenotypes.
multiple gene actions, environmental factors. |
|
|
Term
In a given individual, there can be only ___________ for
a given gene _______.
• The dominance relationships are between the_________, and need not be the same for each
allele pair of a given locus. |
|
Definition
| 2 alleles, locus. 2 coexisting alleles. |
|
|
Term
| Three different alleles for blood type in humans |
|
Definition
|
|
Term
There are 4 different blood group
phenotypes: |
|
Definition
|
|
Term
| Biochemical basis for blood type in humans |
|
Definition
– Complex membrane anchored molecules that
cause a variation in the structure of the sugar
polymer on the cell surface.
– Three possibilities: Sugar type A, B or none. |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
This is a large multiple allele series: involves three
different loci and several alleles at each locus. |
|
|
Term
Polymorphism antigens:
• These antigens are carried |
|
Definition
| HLA A, B and C. by most human cells. |
|
|
Term
Polymorphic antigens
_______at each locus, the relationship
between any two alleles at a given locus is always
______ |
|
Definition
| 20-100 alleles, codominance |
|
|
Term
| Polymorphism, HLA antigens create... |
|
Definition
| a powerful source of variation in human populations. |
|
|
Term
|
Definition
Chance alterations arise spontaneously.
• Gamete producing cells can transmit mutations to
offspring. |
|
|
Term
| Mutations for new alleles. Mutattions make it possible to follow.... Stability of a mutation depends on it's... A mutation may take hold in the population to become a... |
|
Definition
...the pattern of
transmission.
... functional
consequences.
...polymorphism. |
|
|
Term
An allele frequency greater than 1% is a ________;
less than 1% is a_______ |
|
Definition
|
|
Term
Each individual carries ....
• The number of copies of alleles in a population
• The percentage of a given allele in the population.... |
|
Definition
...two copies of a gene.
... = 2 x #of individuals in population.
... is its allele frequency. |
|
|
Term
Sometimes several alleles exist...
example: agouti gene in mouse.
– A= brown (agouti)
– a= black
– at= black with yellow belly.
• Both a and at are prone to predator attacks... |
|
Definition
... but most are mutant:
..., hence
frequency never gets to greater than 1%. |
|
|
Term
The phenomenon of a single gene determining
multiple distinct traits is known as |
|
Definition
|
|
Term
|
Definition
One gene may contribute towards several visible
characteristics.
• E.g: coat color in mice
• In addition to coat color, a specific allele at this
locus also causes lethality. |
|
|
Term
Pleotropy may be the result of ...
• Example: |
|
Definition
a single gene
product (protein)giving rise to multiple functional
characteristics.
Sickle cell syndrome |
|
|
Term
Lethality can be....
Examples of latter |
|
Definition
Prenatal or Postnatal...
– Tay-Sachs Disease: paralysis, deteriorating
nervous system, mental retardation etc.
– Deficiency in enzyme Hexosaminidase A
– Prevalent in Eastern European Jews
– Death of infants before they reach ~3 years of
age. |
|
|
Term
Vast majority of traits are determined by multiple
factors:___________
• Gene interactions between ...
• Example: |
|
Definition
-Genetic as well as environmental
-two or more genes
-Lentil Seed color |
|
|
Term
Multifactorial Inheritance
F1 all same,
F2: __________
• F2 phenotypic ratio is ______
same as in Mendel’s original crosses).
• Difference: in original crosses, two independent
traits; here: |
|
Definition
All different phenotypes
9:3:3:1
multiple phenotypes of single trait |
|
|
Term
| Dominance relationship for Multifactoral Inheritance |
|
Definition
Tan is dominant to green
– Gray is dominant to green
– Brown is dominant to gray, green and tan.
– Tan and Gray are incompletely dominant,
giving rise to brown. |
|
|
Term
| Genotypic classes for Multifactorial traits |
|
Definition
Genotypic classes:
– Brown: A_B_
– Tan: A_bb
– Gray: aaB_
– Green: aabb |
|
|
Term
Each genotypic class may not always
dictate a
• Two or more genotypic classes may display an...
• Example: |
|
Definition
-unique phenotype
-identical phenotype.
-Two lines of pure breeding white flowered pea plants falling into different genotypic classes:
AAbb & aaBB |
|
|
Term
Complimentary Gene action
Biochemical basis: two genes work in tandem to _____
• A dominant allele of both _____
• Now the phenotypic ratio is altered from 9:3:3:1 to_____ |
|
Definition
-produce color.
-essential to produce color
- 9:7. (can also be 15:1) |
|
|
Term
Complementary Gene Action in Humans
• Example _____
• At least one ______ each of _____ is required for hearing.
• Here, we see a situation where only two
genes are considered.
• Two deaf parents can give rise to a
_______ |
|
Definition
-deafness.
-dominant allele, fifty
different genes
-normally hearing offspring. |
|
|
Term
Epistasis
• One gene’s allele masks the phenotype of the
• Four genotypic classes produce.... |
|
Definition
- other gene’s alleles.
- fewer than four
phenotypes. |
|
|
Term
|
Definition
when the recessive allele of
one gene masks the effects of either allele of the
second gene. |
|
|
Term
|
Definition
when the dominant allele of
one gene masks the effects of either allele of the
second gene. |
|
|
Term
Recessive epistasis
Example 1:
• Example 2:
• Phenotypic ratios are . |
|
Definition
-Coat color of Labrador retriever
-ABO blood groups: Bombay
phenotype.
9:3:4 in F2 |
|
|
Term
Dominant Epistasis
• caused by the dominant allele
• Example... |
|
Definition
...of one gene,
masking the action of either allele of the
other gene.
-Summer Squash and Feather color of chicken |
|
|
Term
|
Definition
: Genotype does not necessarily define
phenotype. The proportion of individuals with a given
genotype express the phenotype |
|
|
Term
... all individuals show phenotype. ....half the individuals show phenotype.
• Example: |
|
Definition
100% penetrance...50%
penetrance.
retinoblastoma: only 75% individuals affected. |
|
|
Term
• Expressivity:
• Retinoblastoma: |
|
Definition
the degree or intensity with which a
particular genotype is expressed in a phenotype in a given
individual.
some have both eyes affected, some only
one |
|
|
Term
|
Definition
they have a subtle, secondary effect
which alters the phenotypes produced by the primary
genes.
• E.G. Tail length in mice. The mutant allele t causes a
shortening of the tail. Not all short tails are of the same
length: another gene affects the actual length. (Variable
expressivity). |
|
|
Term
|
Definition
The environment may influence
the effect of a genotype on the phenotype.
• E.G.: Siamese cats: temperature dependent color of coat.
Color shows up only in extremities, where the temp is
lower (enzyme for pigment formation is active only at
lower temp.) |
|
|
Term
Continuous Traits
• Variation of the same trait...
• Multiple genes affect a single trait...
• Example: Height: _____adds 6 inches to a base. a...
____adds 3 inches to a base. b
height of 5 ft. Allele a adds nothing. Allele B adds
3 inches. Allele b adds nothing |
|
Definition
...different intensities of
skin color; different gradations in height etc.
...phenotype
depends on how many dominant alleles of each trait
one has.
-A...adds nothing
-B...adds nothing |
|
|
Term
AABB =
• AaBb =
• Aa BB =
• AAbb = |
|
Definition
6.5 ft
5 ft, 9 inches
6 ft.
6 ft. |
|
|
