I assume that this is your question with the options:
Proteins scan chromosomes for damage during:
A) the G1 checkpoint
B) Beginning of the synthesis phase
C) Apoptosis phase
D) G2 checkpoint
E) Metaphase checkpoint.
Answer:
The answer is option A): G1 checkpoint.
Explanation:
During the internal checkpoints for regulation of a cell cycle, proteins usually scan chromosomes for damage to DNA and evaluate other external factors at the G1 checkpoint in order to ascertain whether conditions are inadequate. If conditions are inadequate and damages exist, cells will not be allowed to continue to the next phase.
C. Anaphase
Anaphase is the briefest stage of mitosis. The centromeres begin to separate, being pulled to the poles by the spindle fibers. As the centromeres seperate the chromatids split.
Answer:
Considering the <u>whole progeny</u> (100%), there will be
- 25% Black male kittens, XBY
- 0% Calico Male kittens
- 25% Calico female kittens, XBXR
Explanation:
<u>Available data:</u>
- The gene for Calico (multicolored) cats is an x-linked trait and codominant
- Calico Females receive a "B" and an "R" gene, and have black and orange splotches on white coats. Their genotype is XBXR.
- Males can only be black or orange, but never calico. Their genotype is XBY and XRY
Cross: a female calico cat with a black male
Parentals) XBXR x XBY
Gametes) XB XR XB Y
Punnett square) XB XR
XB XBXB XBXR
Y XBY XRY
F1) Among the whole progeny:
- 2/4 = 50% will be black (female XBXB and male XBY)
- 1/4 = 25% will be Calico (female XBXR)
- 1/4 = 25% will be Orange (male XRY)
Among females:
- 1/2 = 50% of females will be black, XBXB
- 1/2 = 50% of females will be Calico, XBXR
Among males:
- 1/2 = 50% of males will be black, XBY
- 1/2 = 50% of males will be orange, XRY
Traits that are passed down on an X or a Y chromosome are sex-linked traits. Most of the time males are affected by sex-linked traits because males only have one X and a Y. The Y is the chromosome that makes a man, a man.
