IB Biology HL Theme D: Continuity and change questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

Type
Multiple choiceWritten
Difficulty
EasyMediumHard

Question 1

Multiple choiceMedium1 mark

At a replication fork moving to the right, the upper parental template runs 3′→5′ from left to right, and the lower template runs 5′→3′. Which description of new-strand synthesis is correct?

Show answer and explanation

Answer: D. DNA polymerase extends a new strand at its 3′ end, so synthesis proceeds 5′→3′. The upper template allows continuous synthesis toward the fork from one primer. The lower template is copied away from the fork in Okazaki fragments, requiring repeated primers. A: reverses which template supports leading-strand synthesis toward the fork. B: reverses the direction of DNA synthesis; new DNA is made 5′→3′. C: reverses primer frequency: continuous synthesis uses one primer, whereas discontinuous synthesis requires repeated primers. Remember: the lagging strand is made discontinuously as Okazaki fragments.

Question 2

Multiple choiceMedium1 mark

The diagram shows the base sequences in two cell lineages. Which interpretation correctly identifies the offspring that inherited the germ-cell mutation and the fate of the somatic-cell mutation?

C–G–A–TReference sequenceC–G–G–Tchanged baseMutated sequenceGerm-cell lineageParent germ cell/ C–G–G–TGamete/ C–G–G–TOffspring P: body cells/ C–G–G–TSomatic-cell lineageParent somatic cell/ C–G–G–TTumour cells/ C–G–G–TParent germ cell/ C–G–A–TGamete/ C–G–A–TOffspring Q: body cells/ C–G–A–T
Show answer and explanation

Answer: D. A mutation in a germ cell can pass through a gamete to the offspring, as shown by the mutated sequence in offspring P. The somatic-cell mutation is present in the tumour cells, while the separate germ-cell lineage and offspring Q retain the reference sequence.

A: swaps the offspring labels and incorrectly assigns the somatic mutation to offspring P.
B: selects Q rather than P as the offspring with the inherited germ-cell mutation.
C: reverses the somatic-cell pathway, placing its mutation in offspring Q rather than the tumour cells.
Remember: mutations in germ cells can be inherited; mutations in somatic cells can be associated with cancer but are not passed to offspring.

The best questions are still waiting

Unlock every question in this topic, then type, photograph or draw your answer and have it marked against the markscheme. Find out where you are dropping marks.

Unlock all questionsCompare Student and Student Plus