Lecture 6 Flashcards
(50 cards)
What is the wild type allele?
The most commonly found allele in a population
If identical alleles are present on both homologous chromosomes, the organism/cell is said to be ______ for that allele
Homozygous
If one allele is wild type and the other allele is not (I.e mutant allele) the organism/cell is said to be _______ for that allele
Heterozygous
The known mutant alleles for a given gene plus its wild type allele are referred to as an ________ or _________
The known mutant alleles for a given gene plus its wild type allele are referred to as an allelic series or Multiple alleles
Define homozygotes
A cell/organism with identical alleles of a gene of interest
-Two copies of the same allele
Define Heterozygotes
A cell/organism with one wild type copy and one mutant allele of a gene of interest
If an individual has two mutant alleles that are different from each other, what is this referred to as?
- Hereroallelic - general term
or
-Transheterozygous (drosophila community)
or
-Compound heterozygotes (mice community)
Define Hemizygous
A situation where a cell/organism has only one copy of a gene/locus/chromosomal region
What are two examples of when a hemizygote might be observed?
Example 1: deletion - corresponding gene/locus/region is deleted on the homologous chromosome
Example 2: the gene/locus/region occurs naturally in one copy (true for most genes on X or Y chromosomes in an XY individual)
i.e. males are hemizygous for most genes found on sex chromosomes given that they have one X and one Y
Complex traits are typically _______ (involving multiple genes)
Complex traits are typically Polygenic (involving multiple genes)
-likely derived from multiple genes = exibit large variety of phenotypes
Simple traits may be linked to a single gene with multiple alleles. Single gene traits are called ______
Monogenic
What is complete dominance
Type of dominance in which the same phenotype is expressed in homozygotes (AA) and in heterozygotes (Aa); only the dominant allele is expressed in a heterozygote
What is haplosufficiency?
Simply that one functional copy is sufficient for a wild type phenotype
What is incomplete dominance?
Type of dominance in which the phenotype of the heterozygote falls in between the phenotypes of the two homozygotes = blending (i.e both alleles contribute to phenotype
Define codominance
Type of allelic interaction in which the heterozygote simultaneously expresses the phenotypes of both homozygotes
Eg Sickle Cell Anemia: point mutation in haemoglobin
Eg2: Blood type of AO X BO:
Offspring: AO | AB | BO | OO (AB is codominance)
Define Haploinsufficiency
One functional copy is NOT sufficient for a wild type phenotype
Give an example of a heterozygous advantage
Hb^S allele: identical to Hb^S except for a missense mutation that provides some protection against malaria
What three mechanisms explain how a mutated allele can be dominant:
- Haploinsufficiency: one wt copy is not sufficient to produce a wt phenotype
- Dominant Negative Effect
- Gain of Function Effect
What is The dominant-negative effect
the gene product from the mutant allele interferes with the gene product from the WT allele (muller’s morph: “antimorph”), thus blocking the wildtype function
What is the Gain of Function effect?
the mutant allele acquires a new property not present in the WT allele and this new property causes a phenotype (mullers morph - “hypermorph” and “neomorph”
Who came up with five classes of mutant alleles?
H.J. Muller
Muller’s Morphs
Muller’s name for a morph that results in a complete loss of function:
“Amorph”
(Modern day called “Null mutation”)
What causes an amorph (null mutation)?
Provide three examples
Any mutation abrogating the function of a gene:
- complete deletion of entire gene
- missense point mutation that abolishes all functions of the protein
- A nonsense point mutation yielding a truncated, non-functional protein
What is Hypomorph?
Muller’s term for an allele with partial loss of function.
The allele is still partially functional but not at the level of the wild type gene
