Extension Of Mendel’s Law Flashcards
Mendelian inheritance describes inheritance patterns that obey two laws
Law of segregation
Law of independent assortment
Simple Mendelian inheritance involves
A single gene with two different____
Alleles display a simple ____\ relationship
alleles
dominant/recessive relationship
Prevalent alleles in a population are termed____
wild-type alleles
These typically encode proteins that
Function normally
Are made in the right amounts
wild-type alleles
Alleles that have been altered by mutation are termed_____
mutant alleles
These tend to be rare in natural populations
mutant alleles
They are likely to cause a reduction in the amount or function of the encoded protein
Mutant alleles
mutant alleles are often inherited in a_____ fashion
recessive
Drosophila dominant allele
Red eyes
Normal wings
Drosophila recessive allele
White eyes
Miniature wings
_____diseases are caused by mutant alleles
Genetic
This prevents the allele from producing a fully functional protein
Mutation
In a simple dominant/recessive relationship, the_____ allele does not affect the phenotype of the heterozygote
recessive
how can the wild-type phenotype of the heterozygote be explained?
There are two possible explanations:
50% of the normal protein is enough to accomplish the protein’s cellular function
The heterozygote may actually produce more than 50% of the functional protein
______ are those that are absolutely required for survival
The absence of their protein product leads to a______ phenotype
Essential genes
lethal
It is estimated that about____ of all genes are essential for survival
1/3
_____ genes are those not absolutely required for survival
Nonessential genes
is one that has the potential to cause the death of an organism
lethal allele
These alleles are typically the result of mutations in essential genes
They are usually inherited in a recessive manner
Lethal allele
Many_____ alleles prevent cell division
These will kill an organism at an early age
lethal
Some lethal alleles exert their effect later in life
_______ disease
Characterized by progressive degeneration of the nervous system, dementia and early death
The age of onset of the disease is usually between 30 to 50
Huntington
________ alleles may kill an organism only when certain environmental conditions prevail
Conditional lethal alleles
Temperature-sensitive (ts) lethals
A developing Drosophila larva may be killed at____
But it will survive if grown at____
30 C
22 C
Kill some individuals in a population, not all of them
SEMI LETHAL ALLELES
Environmental factors and other genes may help prevent the detrimental effects of_______ genes
semilethal genes
A_____ allele may produce ratios that seemingly deviate from Mendelian ratios
An example is the “creeper” allele in chicken
lethal allele
In ________ the heterozygote exhibits a phenotype that is intermediate between the corresponding homozygotes
incomplete dominance
Three or more different alleles
multiple alleles
coat color in rabbits
Has ____different alleles
Four
Partial defect in pigmentation
Cch (chinchilla pattern of coat color)
Pigmentation in only certain parts of the body
ch (himalayan pattern of coat color)
Lack of pigmentation
c (albino)
The himalayan pattern of coat color is an example of a ______conditional allele
temperature-sensitive
The enzyme encoded by this gene is functional only at low temperatures
Therefore, dark fur will only occur in cooler areas of the body
This is also the case in the Siamese pattern of coat color in cats
temperature-sensitive conditional allele
______, the opposite phenotype occurs
The coat in the cooler parts of the body is light-colored
The allele in this case is likely to be cold-sensitive
Its enzymatic product does not work well at lower temperatures
Brown Swiss
The ABO blood group provides another example of____ alleles
multiple
It is determined by the type of antigen present on the surface of red blood cells
ABO blood group
are substances that are recognized by antibodies produced by the immune system
Antigens
Alleles /A and /B are
codominant
Allele i is____ to both /A and /B
recessive
is the phenomenon in which a heterozygote is more vigorous than both of the corresponding homozygotes
Overdominance
Overdominance is also called
heterozygote advantage
Where being heterozygous gives you the best chance of having children and living the best quality of life!
heterozygote advantage (overdominance)
Example = Sickle-cell anemia
Autosomal____ disorder
Affected individuals produce abnormal form of hemoglobin
recessive
Sickle cell
Two alleles:
____→ Encodes the normal hemoglobin, hemoglobin A
____→ Encodes the abnormal hemoglobin, hemoglobin S
HbA
HbS
is caused by a protozoan, Plasmodium
Malaria
In some instances, a dominant allele is not expressed in a heterozygote individual
Incomplete dominance
Example = Polydactyly
Autosomal_____ trait
Affected individuals have additional fingers and/or toes
dominant
A_____ copy of the polydactyly allele is usually sufficient to cause this condition
In some cases, however, individuals carry the dominant allele but do not exhibit the trait
single
The term indicates that a dominant allele does not always “penetrate” into the phenotype of the individual
Incomplete Penetrance
The measure of penetrance is described at the population level
If 60% of heterozygotes carrying a dominant allele exhibit the trait allele, the trait is 60% penetrant
Incomplete penetrance
is the degree to which a trait is expressed
Expressivity
In the case of polydactyly, the number of digits can vary
A person with several extra digits has____ expressivity of this trait
A person with a single extra digit has___ expressivity
high
low
The molecular explanation of _____ and ______may not always be understood
expressivity and incomplete penetrance
In most cases, the range of phenotypes is thought to be due to influences of the
Environment and/or
Other genes
_______ conditions may have a great impact on the phenotype of the individual
Environmental
Phenylketonuria
Autosomal_____ disorder in humans
Caused by a defect in the gene that encodes the enzyme phenylalanine hydroxylase
recessive
PKU patient
Their diet is essentially_______-free
phenylalanine
Some genes can be altered or modified by the effects of one or more other genes.
This effect is called_____
epistasis
The inheritance pattern of certain traits is governed by the sex of the individual
These traits are of 3 main types
8.1 Sex-linked
8.2 Sex-influenced
8.3 Sex-limited
Sex Determination
Humans have 46 chromosomes.
2 of those 46 chromosomes are called_____
sex chromosomes
The other 44 chromosomes are called____.
autosomes
Most of your chromosomes are____ are chromosomes that determine your traits.
autosomes
can determine traits as well, but they also determine gender or sex.
Sex chromosomes
Sex chromosomes can either be X or Y.
If an individual’s sex chromosomes are both X chromosomes, that person will be a____.
If an individual’s sex chromosomes are X and Y, that person will be a____
female
male.
Traits controlled by genes on the sex chromosomes are called
sex-linked traits.
Because______ have only one X chromosome, they are affected by recessive traits found on the X chromosome more than females.
______are less likely to express a recessive trait on an X chromosome, because the other X chromosome may have a dominant allele.
males
Females
How are Sex-linked traits inherited?
This would be the result from a cross between a female_____ (XBXb) for color blindness and ____ male (XBY).
½ of the children would be normal
½ would either be color blind or be carriers
carrier
normal
Hemophilia is another ______ trait that causes delayed blood clotting.
sex-linked trait
Most sex-linked traits like color blindness and hemophilia affect____ more than_____.
males
females
Calico cats are always______ because the gene for coat color is on the X chromosome.
If a_______ is heterozygous, it will be a calico cat.
females
Male pattern baldness is technically an autosomal trait, but it acts like a_____ trait
sex-linked trait.
Eye color in Drosophila Fruit flies is a _____ trait
sex-linked trait
Calico Cats
_____can either be black or orange
______can be black, orange, or calico.
This is caused by one of the X chromosomes becoming inactive in female cats.
Males
Females
Traits where an allele is dominant in one sex but recessive in the opposite sex
Thus, _____ is a phenomenon of heterozygotes
Sex-influenced Traits
Male Pattern Baldness
The gene for baldness is recessive in____, but dominant in____.
females
males
______can either be heterozygous or homozygous dominant.
______must be homozygous recessive to be bald.
Males
Females
Traits that occur in only one of the two sexes
Sex-limited Traits
Type of trait
Breast development is normally limited to females
Sex-limited Traits
Type of trait
Beard growth is normally limited to males
Sex-limited Traits
Sex-limited Traits
Hen-feathering is controlled by a dominant allele expressed in ____
Cock-feathering is controlled by a recessive allele only expressed in____
both sexes
males
occur when two or more different genes influence the outcome of a single trait
Gene interactions
The term_____ describes the situation in which a gene Can porns mask the phenotypic effects of another gene
epistasis
_______ often arise because two (or more) different proteins participate in a common cellular function
Epistatic interactions
