BiologyChapter 12: Inheritance
Sex-Linked Inheritance — Work A Carrier Cross
XHXh x XHY. Daughters: XHXH or XHXh.
Learning objectives
- Define work a carrier cross using accurate biology terms.
- Explain why work a carrier cross matters within sex-linked inheritance.
- Apply the learning unit to an FBISE-style example, comparison, diagram, or calculation.
Definition
XHXh x XHY. Daughters: XHXH or XHXh. Sons: XHY or XhY. Phenotype: all daughters typical; half sons show the trait. Write X superscripts: X^H X^h (carrier female) × X^H Y (normal male). Sons: X^H Y or X^h Y. Daughters: X^H X^H or X^H X^h. State phenotype for each. This page separates the idea from the wider topic “SEX-LINKED INHERITANCE” so it can be revised and assessed on its own.
Important terms
- WORK A CARRIER CROSS
- XHXh x XHY.
- SEX-LINKED INHERITANCE
- Genes on X (most school examples) show in males if recessive, because males have one X (hemizygous).
Overview
Study this learning unit in three steps:
Key Idea
XHXh x XHY. Daughters: XHXH or XHXh. Sons: XHY or XhY. Phenotype: all daughters typical; half sons show the trait. Write X superscripts: X^H X^h (carrier female) × X^H Y (normal male). Sons: X^H Y or X^h Y. Daughters: X^H X^H or X^H X^h. State phenotype for each.
Examples Write XH not just H · Y has no allele in the school grid · Rare female affected if XhXh
Exam Application
Worked: carrier mother x typical father. Mother gametes: XH or Xh. Father gametes: XH or Y. Sons: XHY typical, XhY shows the trait. Daughters: XHXH or XHXh (carrier).
Examples Write XH not just H · Y has no allele in the school grid · Rare female affected if XhXh
WHAT — SEX-LINKED INHERITANCE — WORK A CARRIER CROSS
XHXh x XHY. Daughters: XHXH or XHXh. Sons: XHY or XhY. Phenotype: all daughters typical; half sons show the trait. Write X superscripts: X^H X^h (carrier female) × X^H Y (normal male). Sons: X^H Y or X^h Y. Daughters: X^H X^H or X^H X^h. State phenotype for each. This page separates the idea from the wider topic “SEX-LINKED INHERITANCE” so it can be revised and assessed on its own.
WHY — Why this topic matters
SEX-LINKED INHERITANCE — WORK A CARRIER CROSS is an independent FBISE learning unit because students must connect its structures and processes with their biological functions and examples.
HOW — How it works
XHXh x XHY. Daughters: XHXH or XHXh. Sons: XHY or XhY. Phenotype: all daughters typical; half sons show the trait. Write X superscripts: X^H X^h (carrier female) × X^H Y (normal male). Sons: X^H Y or X^h Y. Daughters: X^H X^H or X^H X^h. State phenotype for each. Examples: Write XH not just H; Y has no allele in the school grid; Rare female affected if XhXh. Exam use: Worked: carrier mother x typical father. Mother gametes: XH or Xh. Father gametes: XH or Y. Sons: XHY typical, XhY shows the trait. Daughters: XHXH or XHXh (carrier).
Explanation
XHXh x XHY. Daughters: XHXH or XHXh. Sons: XHY or XhY. Phenotype: all daughters typical; half sons show the trait. Write X superscripts: X^H X^h (carrier female) × X^H Y (normal male). Sons: X^H Y or X^h Y. Daughters: X^H X^H or X^H X^h. State phenotype for each. Examples: Write XH not just H; Y has no allele in the school grid; Rare female affected if XhXh. Exam use: Worked: carrier mother x typical father. Mother gametes: XH or Xh. Father gametes: XH or Y. Sons: XHY typical, XhY shows the trait. Daughters: XHXH or XHXh (carrier).
In simple words
Federal Board Class 11 Biology learning unit. Easy wording; no provincial-board material added.
Key points
- half the sons
- half sons
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Sex-Linked Inheritance — Work A Carrier Cross
Sticky Notes · Quick Revision
Core idea
- XHXh x XHY. Daughters: XHXH or XHXh. Sons: XHY or XhY. Phenotype: all daughters typical; half sons show the trait. Write X superscripts: X^H X^h (carrier female) × X^H Y (normal male). Sons: X^H Y or X^h Y. Daughters: X^H X^H or X^H X^h. State phenotype for each. This page separates the idea from the wider topic “SEX-LINKED INHERITANCE” so it can be revised and assessed on its own.
WHAT
- XHXh x XHY.
WHY
- SEX-LINKED INHERITANCE — WORK A CARRIER CROSS is an independent FBISE learning unit because students must connect its structures and processes with their biological functions and examples.
HOW
- XHXh x XHY. Daughters: XHXH or XHXh. Sons: XHY or XhY. Phenotype: all daughters typical; half sons show the trait. Write X superscripts: X^H X^h (carrier female) × X^H Y (normal male). Sons: X^H Y or X^h Y. Daughters: X^H X^H or X^H X^h. State phenotype for each. Examples: Write XH not just H; Y has no allele in the school grid; Rare female affected if XhXh. Exam use: Worked: carrier mother x typical father. Mother gametes: XH or Xh. Father gametes: XH or Y. Sons: XHY typical, XhY shows the trait. Daughters: XHXH or XHXh (carrier).
Common misconception
- Do not treat work a carrier cross as the same as every other part of sex-linked inheritance; define this unit and use its own evidence, steps, or conditions.
FBISE exam check
- Define sex-linked inheritance — work a carrier cross, explain how it works, and support the answer with one relevant example.
60-second revision
- XHXh x XHY.
- Write XH not just H
- Exam link: half the sons.
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