gen2 Flashcards
Mendelian pea plants
- easy to grow & breed
- self-fertilized
- easy to cross breed and propagate
Mendel’s postulate of inheritance
genetic characteristics are controlled by unit factors existing in pairs in individual organisms.
Mendel’s 2nd postulate of inheritance
when 2 unlike unit factors responsible for a single characteristic are present in an individual, 1 unit factor is said to be dominant to the other, which is said to be recessive.
Mendel’s 3rd postulate of inheritance
When gametes form, the paired unit factors separate, or segregate randomly so that each gamete receives 1 or the other with equal likelihood.
Genes
mendel’s unit factors, a unit of heredity that can be passed from parent to offspring and produce a given trait.
Alleles
Variations of a given gene
There are ___ alleles for every trait
2
A punnet square for an unknown phenotype
2 punnet squares
Dihybrid cross
looks at 2 traits at once
True breeding
They are homozygous for their trait
Mendel’s 4th postulate
During gamete formation, segregating pairs of genes, assort independently of each other
product law of possibility
the probability of 2 or more independent events occurring simultaneously is equal to the product of their individual probability.
Wild type
The most commonly produced phenotype in a population
Neutral/ silent mutation
protein/ DNA gets mutated but nothing happens
loss of function mutation
- gene product may be diminished
- confirmation of a certain protein may be completely changed so that it cannot function
- the gene product may not be produced at all
Gain of function mutation
gene is turned on all the time. Never turns off
threshold effect
A minimum of gene product is needed to meet a normal phenotypic expression
Incomplete dominance
Shows a mixture of genes and phenotypes
- neither trait is truly dominant
Tay- Sachs disease
No activity in hexosaminidase A, resulting in abnormal lipid storage that slowly destroys the brain and spinal cord cells.
Homozygous dominant
100% of enzyme produced, okay
Homozygous recessive
0% of enzyme produced, diseased
Heterozygous
50% of enzyme produced, okay
Factor 5 leiden
a liver enzyme responsible for the conversion of prothrombin into thrombin (needed for blood clotting)
Homozygous for factor 5
disproportionate risk of deep thrombolytic events and pulmonary clots
Heterozygous for factor 5
Huge array of phenotypes
codominance
2 alleles of a certain gene can produce 2 distant and independent gene products. Both alleles are fully expressed
Monohybrid cross
occurs when 2 pure individual parental strains are mated that contrast only in the trait that is being observed. 1 trait at a time.
Gene interaction
where a single phenotype is affected by more than a single gene
wild type
allele for any given gene that exists most predominantly in a population
incomplete/ partial dominance
the phenomenon of an intermediate phenotype of the parental strains
Consider the following 4 independent traits in pea plants. Use the product law to predict the likelihood of inheriting 3 dominant traits (tall, yellow, and round) and recessive trait (white).
3 dominant and 1 recessive
3/4* 3/4 * 3/4 * 1/4 = 27/ 256
explain why an individual who is heterozygous for a genetic disorder may go for a very long time as a carrier of that disorder without realizing that they have it.
The threshold effect. they will need a certain level of gene activity in order to get a normal phenotype. A low amount of gene product is required to observe that genotypic trait
The presence of the ABO antigens on the surface of blood cells is an example of codominance. If a mother is type AB(AB) and the father is type A(AO), what are the possible combos for the child’s blood type?
type A(AA or AO)
type B(BO)
Type AB(AB)
A person can only be homozygous or heterozygous for a given gene?
True
What is the purpose of a test cross and how is it done?
Used to determine whether a plant that is exhibiting a dominant phenotype is homozygous or heterozygous for that trait.
The organism with unknown genotype and dominant phenotype is crossed with a known homozygous organism
A homozygous individual will yield all dominant phenotypes whereas a heterozygous individual will yield a 1:1 mix of phenotypes.
Law of segregation
Each parent contributes only one of their two alleles to each offspring
Law of Independent Assortment
Genes for different traits assort independently, resulting in various combinations.
Homozygous
2 alleles that are the same
Traits
Distinguished characteristics of an organism
Heterozygous
2 different alleles for a given trait
Test cross
An individual that has the dominant phenotype, but unknown genotype is crossed with a known homozygous recessive individual
Gene interaction
A single phenotype is affected by more than a single gene.
Null allele
The mutation and a gene results in a total loss of the gene function
