Pts 1 dif m ref 506 key remembering 22 ans a the

PTS: 1 DIF: M REF: 506 KEY: REMEMBERING
22. ANS: A
The location of a specific gene on a chromosome is called a locus, and the locus of each gene does not vary
from one person to another. This allows the genes supplied by the egg to align with similar genes supplied by
the sperm. The locus of a gene does not influence whether a mutation occurs. It also does not affect whether
fertilization occurs. Gender is determined by sex chromosomes.
PTS: 1 DIF: M REF: 507 KEY: UNDERSTANDING
23. ANS: C
A dominant allele overshadows the effect of a recessive allele, so it will be expressed even if only one
chromosome in a pair carries it.
PTS: 1 DIF: E REF: 507 KEY: REMEMBERING
24. ANS: A
Because the alleles are different, the individual will be heterozygous for the trait. Also, because brown eyes
are a dominant trait, that trait will overshadow the recessive blue eye trait. A person is homozygous for a trait
when both alleles are the same.
PTS: 1 DIF: M REF: 507 KEY: APPLYING
25. ANS: C
Sex-linked disorders are recessive and are carried on the X chromosome. Because the X chromosome is so
much larger than the Y chromosome, a male does not have a matching dominant allele to overpower the X-
linked recessive trait. Therefore, he would express the disorder. In contrast, a female, who would have a
matching dominant allele, would only be a carrier of the trait. (It’s possible, however, for a female to express
the disorder if she carries a matching recessive allele on her other chromosome, but this is rare.) Turner
syndrome results from nondisjunction of sex chromosomes.
PTS: 1 DIF: D REF: 508 KEY: UNDERSTANDING
26. ANS: B
Two copies of the defective allele must be inherited for the disorder to manifest itself; therefore, with only one
allele, children can carry the disorder and pass it along to their children, but they will not personally manifest
the disorder.
PTS: 1 DIF: M REF: 509 KEY: UNDERSTANDING
27. ANS: C
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Because each child receives one copy of the gene from the mother and one from the father, he or she has a 50
percent chance of inheriting the defective gene and manifesting the disorder.
PTS: 1 DIF: M REF: 509 KEY: APPLYING
28. ANS: D
Multifactorial disorders result from many contributing factors, including multiple genes in combination with
lifestyle and environmental factors. None of the other answers is correct.
PTS: 1 DIF: E REF: 511 KEY: REMEMBERING
Copyright © 2020 F. A. Davis Company