The CDC conducted a survey with the Ministry of Health in Uganda to evaluate the prevalence of filariasis among the local population. Skin snips and blood specimens were collected and sent to a regional laboratory for preparation. Thick blood films were made and stained with Giemsa, and then forwarded to the CDC in Atlanta for evaluation. The objects seen in Figures A–D were seen in low numbers on several of the patients’ smears. The object in Figure A measured 325 micrometers in length; Figure B shows a close-up of one of its ends. The object in Figure C measured 237 micrometers in length. The object in Figure D measured 225 micrometers in length. Fig. A Fig. B Fig. C Fig. D

1. What class of organisms does this parasite belong? (1)

2. Knowing where this organism was found, what is your best guess as to its identity? (1)

3. How are these organisms transmitted? (1)

4. How can this organism be differentiated from the others of this class? (2)

identify the dna change shown in the diagram and explain how that change can result in the increased genetic diversity often seen among siblings.

nucleus

would be most reasonable answer tbh

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.