D1.3.6—Consequences in germ vs. somatic cells

Germ-line mutations can be inherited, whereas somatic mutations affect body-cell descendants and may contribute to disease in one individual only.

The consequence of a mutation depends on whether it occurs in the germ line or in a somatic cell lineage.

Location	Who can receive the mutation?	Important consequence
Germ-line cell or gamete	Offspring, if the mutated gene is transmitted at fertilization	The mutation can be inherited and enter the descendant's cell lineages
Somatic cell	Descendant body cells produced by mitosis	A clone of altered cells can form; mutations affecting growth control can contribute to cancer

A mutation in a sperm cell may be inherited by a child, whereas a mutation acquired in one skin cell can spread through a local clone but is not normally passed to offspring.

Somatic does not mean harmless: a non-inherited mutation can still cause cancer or other serious effects in the individual.

How it is assessed

This objective is assessed through multiple choice, commonly using Distinguish.

Command terms

Distinguish

What earns marks

Build the answer around this relationship: Only germ-line mutations can normally be passed to offspring.

Watch for

Saying any mutation can automatically be inherited regardless of cell type.

Representative question

[Maximum number: 1]

A mutation in which type of cell could be inherited?

Beta cell in the pancreas

T-cell in the lymph

Sperm cell in the testis

Skeletal muscle cell in the diaphragm

Gene mutations are changes in the base sequence of DNA; main types are substitution, insertion, deletion, and duplication. Base substitutions can create SNPs and change codons; degeneracy can make substitutions silent, missense, or nonsense. Insertions or deletions not in multiples of three cause frameshifts that alter downstream codons and often disrupt protein function. Mutations can arise from replication errors, repair errors, or chromosome damage; mutagens include chemicals, ionizing radiation, and ultraviolet radiation. Mutations occur randomly with respect to organism need or advantage; mutation rate varies with DNA sequence, gene expression, repair, and mutagen exposure. Germ-line mutations can be inherited by offspring; somatic mutations affect only descendant body cells and can contribute to cancer. Mutation is the original source of new alleles and genetic variation; many are neutral or harmful, but variation supplies material for natural selection.

Concept essentials

Only germ-line mutations can normally be passed to offspring.
Somatic mutations affect body cells and their descendant cells.
Somatic mutations can contribute to cancer without being inherited by children.
Germ-line gene therapy raises heritable-change concerns.

D1.3.6—Consequences in germ vs. somatic cells

Germline and Somatic Mutations Have Different Reach

Consequences in germ vs. somatic cells

Assessment in practice

Core Mutation Effects

Concept essentials

Question 1