Match each sex determination mechanism or sex-linked inheritance phenomenon on the left wi… — JAMB UTME

Match each sex determination mechanism or sex-linked inheritance phenomenon on the left with its corresponding biological characteristic or inheritance pattern on the right.

XX-XO sex-determination system in grasshoppers (*Melanoplus* species)Males are heterogametic possessing a single sex chromosome ( $X0$ ) and producing two types of gametes, whereas females are homogametic ( $XX$ ).
ZZ-ZW sex-determination system in birds (*Gallus gallus*)Females are the heterogametic sex ( $ZW$ ) producing two distinct egg types, whereas males are the homogametic sex ( $ZZ$ ).
X-linked recessive phenotypic expression in Turner syndrome females ( $45, X$ )A single copy of a recessive mutant allele results in phenotypic expression due to female hemizygosity caused by monosomy X.
Holandric (Y-linked) trait inheritance in humansExpressed exclusively in males and passed directly from an affected father to all of his sons without skipping generations or involving female carriers.

Answer

XX-XO in grasshoppers matches males being heterogametic (

X0

) and females homogametic (

XX

); ZZ-ZW in birds matches females being heterogametic (

ZW

) and males homogametic (

ZZ

); X-linked recessive expression in Turner syndrome females matches hemizygosity due to monosomy X; Holandric inheritance matches exclusive father-to-son transmission without female carriers.

Each mechanism accurately corresponds to its defining chromosomal configuration or inheritance pattern: XX-XO grasshoppers have

X0

heterogametic males; ZZ-ZW birds have

ZW

heterogametic females; Turner syndrome females are hemizygous (

45, X

) expressing X-linked recessives directly; holandric Y-linked traits transmit exclusively from fathers to sons.

Step-by-Step Solution

Analyze the sex determination system in grasshoppers (XX-XO).

Identify that grasshopper females are

XX

(homogametic) and males are

X0

(heterogametic).

The absence of a Y chromosome means males have 23 chromosomes (

22 + X0

) while females have 24 (

22 + XX

Analyze the sex determination system in birds (ZZ-ZW).

Identify that female birds are

ZW

(heterogametic) and male birds are

ZZ

(homogametic).

This reverses the male heterogametic pattern seen in mammals.

Evaluate the genetic condition of Turner syndrome females (

45, X

) regarding X-linked traits.

Determine that monosomy X creates a hemizygous state in females.

Without a second X chromosome to mask a recessive allele, a single X-linked recessive allele is expressed phenotypically.

Evaluate holandric (Y-linked) inheritance in humans.

Determine that Y-linked genes pass strictly from male parent to male offspring.

Females do not inherit a Y chromosome and therefore cannot carry or pass on holandric traits.

Key Concept

Chromosomal mechanisms of sex determination (XX-XY, XX-XO, ZZ-ZW) and hemizygous expression of sex-linked genes.

Estimated Time:2m 0s

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