Which of the following structures is directly involved in the passage of electrical signals between cells as, for example, in the vertebrate heart?
a) anchoring junctions
b) tight junctions
c) chemical synapses
d) gap junctions

The correct answer is d) gap junctions

Explanation:

Animals have gap junction in many places in their body like in cardiac muscles, nerves, epithelial cells, smooth muscles. It connects cell to cell through cytoplasm and helps in transferring of many molecules and electric signals between these cells.

Vertebrate heart is made up of mainly muscle tissue in which electric signals are transferred through these gap junctions throughout the heart.

These gap junction plays important role in contraction of all the muscle cells in the heart together which is an important process called systole.

Therefore, the correct answer is d) gap junctions.

an individual’s sex (i.e., whether they are a male or female) is determined by the sex chromosomes. most people have two sex chromosomes, one that is inherited from their mother and one that is inherited from their father. typically, females have two x chromosomes (xx) and males have one x chromosome and one y chromosome (xy). conditions caused by changes (“mutations”) in genes located on the x chromosome are considered x-linked.

x-linked recessive inheritance

most x-linked conditions are recessive. this means that in a person with two x chromosomes (most females), both copies of a gene (i.e., one on each x chromosome) must have a change or mutation whereas in a person with one x chromosome (most males), only one copy of a gene must have a mutation. a female with a mutation in one copy of a gene on the x chromosome is said to be a “carrier” for an x-linked condition. a male with a mutation in a gene on the x chromosome is typically affected with the condition. because females have two copies of the x chromosome and males have only one x chromosome, x-linked recessive diseases are more common among males than females. however, x-linked recessive diseases can occur in both males and females.

for x-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the x chromosome can transmit either the x chromosome with this mutation or a “normal” x chromosome to her children. if the father is unaffected, none of her daughters will be affected and all of her daughters will be unaffected—since they will inherit at least one normal x chromosome from their father. however, each daughter will have a 50% chance of being an unaffected carrier like her mother and a 50% chance of both x chromosomes being normal.