What phenotypic ratio would you expect as a result of a test cross between a dihybrid organism and one that is homozygous recessive for alleles at two independent loci?
a. 3:1
b. 9:3:3:1
c. 1:1:1:1
d. 1:2:1
e. 9:4:2:1
Answer:
c. 1:1:1:1
Explanation:
When a heterozygous individual for two genes is test crossed with a double homozygous recessive individual, the progeny is obtained in 1:1:1:1 phenotypic ratio. This occurs as the heterozygous dominant individual forms four types of gametes in 1:1:1:1 ratio while the homozygous recessive individual would form only one type of gamete having one recessive allele for each gene.
For example, a test cross between TtRr (tall and red) and ttrr (short and white) would produce a progeny in following ratio=
1 tall, red: 1 tall, white: 1 short, red: 1 short, white
Here, T= tall, t= short, R= red, r= white
Hello. The answer is zinc.
I am guessing R is pink and W is white so RR an RW is pink so it would be 3 out of every four seeds.
Answer:
Multiple Sclerosis is an inflammatory disease in which myelin sheath of nerve cells of brain and spinal cord are damaged.
Explanation:
Cause:- (Exact cause of inflammation is not known)
- But damage is caused due to attack by autoimmune cells or antibodies against myelin sheath.
Types of tissues attack:-
- Oligodendrocytes and myelin sheath is damaged and stripped away from axon and the process is known as demyelination.
- Myelin sheaths are made up of fatty tissues and help in transmission of electric impulse.
Result of immune system attack:-
- Damaged myelin sheath stop forming whIte matter of central nervous system.
- Hence disrupt coordinating communication between different brain regions.
Signs and symptoms:- vary from person to person
- Diminished eyesight.
- Disrupt motor coordination.
- Weak sensory perception.
- Fatigue and dizziness.
- Speech disorder.
- Muscle weakness and spasticity.
- Difficulty in urination and stool.
Diagnosis and treatment:-
- Diagnosis include MRI T2 findings and cerebrospinal fluid specific oligoclonal bands.
#SPJ2
Gene, as such traits are passed down through genes
