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question 21 1 pts a mutation that occurs in a diploid cell can be inher…

Question

question 21
1 pts
a mutation that occurs in a diploid cell can be inherited only if the
mutated allele is recessive.
mutation occurs in a cell that produces gametes.
same mutation also occurs on the homologous chromosome.
mutated allele is dominant.
question 22
1 pts
among children with parents who are both carriers of tay - sachs, an autosomal recessive disorder, chances are that
50 percent will die in a few years.
50 percent will be carriers.
75 percent will be carriers.
75 percent will not carry the recessive tay - sachss allele.

Explanation:

Question 21
Brief Explanations

To determine when a mutation in a diploid cell is inheritable, we analyze each option:

  • "Mutated allele is recessive": Recessiveness alone doesn’t determine inheritance (e.g., dominant mutations in gametes can also be inherited). Eliminate.
  • "Mutation occurs in a cell that produces gametes": Gametes (sperm/egg) pass genetic info to offspring. A mutation in a gamete - producing cell (germ - line cell) can be passed to the next generation. This makes sense.
  • "Same mutation on homologous chromosome": Not required—mutations in one chromosome of a gamete - producing cell can still be inherited. Eliminate.
  • "Mutated allele is dominant": Dominance alone doesn’t ensure inheritance (e.g., dominant mutations in somatic cells aren’t inherited). Eliminate.
Brief Explanations

For Tay - Sachs (autosomal recessive, let allele be \( T \) (normal) and \( t \) (mutant)), parents are carriers (\( Tt \)). The Punnett square for \( Tt\times Tt \) gives: \( TT \) (25%), \( Tt \) (50%), \( tt \) (25%).

  • "50 percent will die in a few years": \( tt \) (25%) has the disorder and may die, not 50%. Eliminate.
  • "50 percent will be carriers": \( Tt \) (carriers) is 50% of offspring. Correct.
  • "75 percent will be carriers": Carriers are 50%, not 75%. Eliminate.
  • "75 percent will not carry the recessive allele": \( TT \) (25%) and \( Tt \) (50%)—\( Tt \) carries \( t \), so only 25% ( \( TT \)) don’t carry \( t \). Eliminate.

Answer:

B. mutation occurs in a cell that produces gametes.

Question 22