Sickle cell anaemia is an inherited autosomal recessive
condition caused by a mutation in the haemoglobin
subunit beta (HBB) gene. A male and female who are
phenotypically normal, discover through genetic testing
that they are both carriers of a HBB mutant allele. What is
the probability that their first child will be biologically
female and phenotypically normal?

Answer:

1/8 (12.5%)

Explanation:

An autosomal recessive disease is an inherited disease in which an individual need to receive both defective alleles at the same gene locus to be expressed in the phenotype. In this case, both parents are carriers of the recessive mutant allele associated with the sickle cell anaemia trait, thereby both parents are heterozygous, ie., each parent has one copy of the normal allele 'H' and one copy of the defective mutant allele 'h' associated with this condition. In consequence, their first child has a 1/4 (25%) chance of having sickle-cell anaemia. Moreover, the chance of having a girl is 1/2 and the chance of having a boy is 1/2, thereby the final chance of having a girl sickle cell anaemia individual is 1/4 x 1/2 = 1/8 (12.5%).

- Parental cross for sickle cell anaemia trait = Hh x Hh >>

- F1 = 1/4 HH (normal); 1/2 Hh (normal); 1/4 hh (sickle cell anaemia) >>  

- Sex proportion of sickle cell anaemia individuals =  1/8 female sickle cell anaemia individuals + 1/8 male sickle cell anaemia individuals (1/8 + 1/8 = 1/4)

A forest fire destroys an area. A small population of trees and a large population of birds are both affected. Which type
of limiting factor causes this?
density dependent
density independent
population dependent
population independent

The oxidation of a chemical occurs when

It loses electrons
It gains electrons
It shares electrons
All the above

Plyometrics can help a person maintain cardiorespiratory fitness true or false

Shondra takes notes in class.
Three entries in Shondra's notes are not in the right
place. What can Shondra do to correct her notes?
1. Energy
A Definition - the energy of moving objects
B. Main categories of energy
1. Kinetic - the ability to do work
2 Potential - the energy stored in objects
3. Chemical -- the energy in chemical bonds
C. Forms of energy
1. Gravitational - the energy of a rock on a hill
2 Elastic - the energy in a spring
3. Nuclear - the energy in the nuclei of atoms
4. Electromagnetic wave - the energy from the Sun
5. Electrical - the energy of flowing electrical charges
O Switch "the energy of moving objects" and "the
ability to do work" and place chemical energy under
"Forms of energy."
O Switch "the energy of flowing electrical charges" and
"the energy in a spring" and place kinetic energy
under "Forms of energy."
O Switch "the energy in the nuclei of atoms" and "the
energy stored in objects" and place nuclear energy
under "Main categories of energy."
O Switch "the energy from the Sun" and "the energy of
a rock on a hill" and place electrical energy under
"Main categories of energy."
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