Sweat, tears, skin, and mucous membranes are among the physical defenses that keep a person from being sick.
<h3>What causes infectious diseases?</h3>
Coming into contact with a person or an animal who has the virus is one of the most straightforward ways to obtain the most contagious or infectious diseases. Direct contact, such as person-to-person contact, can transfer contagious diseases. Direct transmission of bacteria, viruses, or other germs from one person to another is the primary method by which contagious diseases are typically disseminated. If someone who is unaffected touches, kisses, coughs, sneezes, or has the virus or bacterium on them, this could happen. Additionally, these pathogens can disperse through sexual contact and the exchange of bodily fluids. The person who spreads the infection may only be a carrier and not exhibit any signs of the illness.
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Answer: B (Color blindness)
Explanation:
Typical red-green color blindness in human patients is caused by mutations on genes located in the X chromosome. These mutations act in a recessive manner. Since females have two X chromosomes, the presence of a mutation in a single one of them does not normally result in color blindness. Males, in contrast, have a single X chromosome and therefore the presence of a mutation is likely to cause the disease.
About the other options: Down‘s syndrome is a numerical chromosomal anomaly, not related to sex. Human blood type is a codominant trait. Finally, tail length in dogs is a polygenic trait not amenable to classic Mendelian analysis.
Answer:
The three genes in coupling are in repulsion.
Explanation:
Coupling happens when the dominant alleles and the recessive alleles are on the same homologous chromosome, while the repulsion happens when one chromosome has one dominant allele and one recessive allele and another homologous chromosome also has dominant and recessive alleles.
If the progeny has:
nb+ ls+ a/nb ls a ⇒ nb+ ls+ a
nb ls a+/nb ls a ⇒ nb ls a+
Where nb+ ls+ a is the dominant alleles and nb and nb+ is in middle.
ls+ nb+ are on the same chromosome (both dominant)
ls nb are on the same chromosome (both recessive)
ls nb, these two are in coupling with each other, but ls+ and a are on the chromosome and ls+ or nb+ are dominant, while nb+ and a are recessive on form a, thus, ls and nb, they are in repulsion with a.
