Answer:
recessive
Explanation:
A lethal allele is a gene variant associated with a mutation in an essential gene, which has the potential to cause the death of an individual. In general, lethal genes are recessive because these alleles do not cause death in heterozygous individuals, which have one copy of the normal allele and one copy of the allele for the lethal disease/disorder. In recessive lethal diseases, heterozygous individuals are carriers of the recessive lethal allele and can eventually pass the 'defective' allele on to offspring even though they are unaffected; whereas dominant lethal diseases are caused by dominant lethal alleles, which only need to be present in one copy to be fatal. In consequence, the frequency of recessive lethal alleles is generally higher than dominant lethal alleles because they can be masked in carrier individuals. Some examples of human diseases caused by recessive lethal alleles include, among others, Tay-Sachs disease, sickle-cell anemia, and cystic fibrosis.
Answer:
Within double-stranded DNA, the nitrogenous bases on one strand pair with complementary bases along the other strand; in particular, A always pairs with T, and C always pairs with G. Then, during DNA replication, the two strands in the double helix separate.
Explanation:
The four nitrogenous bases of DNA are thymine, adenine, guanine, and cytosine. Guanine and cytosine are bound together by three hydrogen bonds; whereas, adenine and thymine are bound together by two hydrogen bonds. This is known as complementary base pairing.
Answer:
Hyperimmunoglobulinemia E Syndrome
Explanation:
Hyperimmunoglobulinemia E Syndrome or Job syndrome is an immunodeficiency disorder in which the white blood cells are incapable of producing an inflammatory response to infectious organisms. It is an autosomal dominant disorder. It is characterized by recurring bacterial infections, specially of lung and skin. There are also other symptoms like abromalities in vascular or skeletal system and elevated IgE level.
Symptoms like frequent formation of pus pockets in skin, lungs or joints usually begin during infancy. These pus pockets are formed due to infection by staphylococcal bacteria. Treatment usually consists of antibiotics to fight infection and anti histamines to relieve the symptoms like rash and itching. Sometimes drugs can also be administered to modify immune system.
Answer:
The mechanisms of transport across the cell membrane are as follow: 1- simple diffusion, 2- facilitated diffusion, 3- primary active transport and 4-secondary active transport
Explanation:
The cell membrane is a selectively permeable structure capable of transporting substances by different mechanisms. Simple diffusion is a type of passive transport (i.e. does not require energy) where non-polar molecules (e.g. O2, CO2) pass across the membrane by a process that does not require energy from the cell. Facilitated diffusion is another type of passive transport where larger polar molecules (e.g., glucose and amino acids) pass across the membrane by using specific transmembrane integral proteins. On the other hand, primary active transport is a type of active transport that uses chemical energy (e.g., ATP) to move substances such as metal ions (Na+, K+, Ca2+) across the cell membrane against their concentration gradient. Finally, secondary active transport is another type of active transport where transporter proteins are used to couple the movement of ions (e.g., H+ protons) down their electrochemical gradient to the transport of another ions/solutes against their concentration/ electrochemical gradient.
