2+3 Non-disjunction and ploidy + Gene Interaction Flashcards
what is mendels first law
Alleles of a single gene segregate independently from each other
what is mendelas second law
Alleles of different genes segregate independently from each other
If a male is affected by an X-linked trait, then all his daughters are ______ and all his sons ______
-carriers
- will not be affected (father doesn’t give son his X chromo)
TF Nearly all affected people are male
T
If a female is a carrier of an X-likned trait then ___ of her sons are affected and _____ her daughters are carriers
-half
-half
for dominant x-linked diseases, Affected males transmit their trait to all the _______ and none of their _____
-daughters
-sons
TF x-linked affected heterozygous females transmit the trait to all of their children regardless of sex
F, transmit to 1/2 their children
what is an allopolyploid
the containment of the multiple copies of chromosomes of different species.
what is an aneuploid
having mismatched number of chromos
what is an autopolyploid
the containment of multiple copies of chromosomes in the same parent.
what is an autosome
any chromosome that is not a sex chromosome.
what is a chromatid
One of the two daughter strands of a duplicated chromosome
what is a chromosome
2 sister chromatids
what is a diploid
2n - normal for most eukaryotes
what is euploidy
having a normal number of each chromosome
What is polyploidy
extra copies of each chromosome
- triploid = 3n
- tetraploid = 4n
what is a haploid
missing copies of all chromosomes ( only 1 set of chromos)
- monoplod = 1n
what does hemizygous mean
they have only one copy of it present in their organism. For example, in mammals, males are hemizygous for genes on the Y chromo
what is a karyotype
the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.
what is monosomy
Imbalance in chromosome
Monosomy is an example of aneuploidy, which is an imbalance in chromosome numbers.
what is nondisjunction
the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes
what are intra-allelic effects
○ Multiple alleles of the same gene affecting the phenotype together
what does haplosufficent mean
More formal form to say dominance
○ Only requires one copy for its phenotype to be produced
what does haploinsufficent mean
○ Formal way to say recessive
○ Genes that require more than 1 copy to produce the phenotype
what is incomplete dominance
blended phenotypes
○ Heterozygote has a third phenotype
- New phenotype not presented in parents
○ Third phenotype is a blending of the first 2
what is codominance
Shared dominance
○ Not a blend but a 50/50 of the first 2 phenotypes
○ Ex) the A B O blood group
what is a null allele
a nonfunctioning allele
what is a hypomorphic allele
has partial function
what is pleiotropy
Single alleles has more than 1 phenotypic effect
A 2:1 ratio in a punett square indicates a _______ copy
lethal
what is variable penetrance
Same mutant genotype may or may not show the phenotype (all or nothing)
- What determines penetrance (if the phenotype is shown)
○ Modifier genes
○ Environmental factors
○ Allelic variation
what is variable expressivity
all or some
what is variable penetrance and expressivity
all, some, or none
what are interallelic effects
○ multiple genes affecting the same phenotype
what is a monogenic trait
1 gene accounts for 1 phenotype
what is a pleiotropic gene
1 gene has multiple effects (phenotypes)
what is a polygenic trait
multiple genes coding for 1 phenotype
how can we test for a monogenic vs polygenic trait
compliment test
what does a compliment test do
hide the mutations and find the WT phenotype
how do we do a compliment test
cross homozygous recessive mutants
in a compliment test, if both alleles of 1 gene are still mutant and have the recessive mutant phenotype, that means that
the mutations are on the same gene
in a compliment test, if 1 allele of a gene is WT and have the WT phenotype, that means that
mutations are on different genes
what is complimentary gene interaction
- compliment test
- 2 loci, 1 trait, 2 phenotypes
○ Will get genotypic ration 9;7 (9; 3+3+1) after crossing F2 generation
(white and blue flowers)
what is additive gene action
○ 2 loci, 1 trait, 4 phenotypes
- Alleles of 2 genes generate 4 phenotypes
(orange and black snake)
is additive gene action mendelian ? why ?
not mendelian
4 phenotypes for 1 trait
what is duplicate gene action
○ 2 loci, 1 trait, 2 phenotypes
○ Ratio of dominant phenotype is many more than the recessive
Only way to get the recessive phenotype is is both genes are double recessive
(no dominance presence will give a recessive phenotype)
what is epistasis
○ Allele of one gene overrides the other gene in the phenotype
- If one gene is present the other gene is ignored and sits under the first gene
what is dominant epistasis
- Dominant allele of 1 gene masks the effect of the second one (dominant or recessive)
- 2 loci, 1 trait, 3 phenotypes
- 12:3:1 phenotypic ratio
(think of eggplants)
what is recessive epistasis
- Recessive allele of 1 gene masks the effect of the second one (dominant or recessive)
- 2 loci, 1 trait, 3 phenotypes
- Phenotypic ratio : 9;3;4
(think of the labradoodles)
give the phenotypic ratios for the following gene interactions
- additive
- complimentary
- recessive epistasis
- dominant epistasis
- duplicate
9:3:3:1
9:7
9:3:4
12:3:1
15:1
if we have 1 gene and the ratio is 3:1 it is ____
1:2:1 is ____
2:1 is ___
- Mendelian
- Co-dominance
- Lethal
what is a hypostatic gene
one whose phenotype is altered by the expression of an allele at a separate locus, in an epistasis event.
Example: aa bb In labrador retrievers
