Zadanie 7, Paper 2, maj 2023, TZ1, Biologia IB HL
Wzorowane na: Biology HL Paper 2, May 2023, TZ1, pytanie 7. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Polecenie
(a) Outline the chromosome changes during prophase I of meiosis.
(b) Describe processes performed by enzymes that bind to DNA.
(c) Explain how environmental conditions can affect DNA and its expression in living organisms.
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Odpowiedź z klucza
(a)
Homologous chromosomes pair to form bivalents. ✔
Crossing over occurs OR chromatids break and rejoin to non-sister chromatids. ✔
DNA/alleles are transferred between chromatids. ✔
This creates recombinant allele combinations. ✔
Chromosomes condense and become shorter and thicker. ✔
Chiasmata mark connections where exchange occurred. ✔
(b)
Helicase unwinds the DNA double helix. ✔
Helicase disrupts hydrogen bonds OR separates the strands. ✔
Topoisomerase can relieve torsional strain ahead of an unwinding region. ✔
Primase supplies RNA primers that provide a starting point for synthesis. ✔
DNA polymerase replicates DNA OR adds nucleotides to a new strand. ✔
DNA polymerase I replaces RNA primer regions with DNA. ✔
Ligase seals gaps in the sugar-phosphate backbone, joining adjacent fragments. ✔
RNA polymerase carries out transcription. ✔
RNA polymerase binds a promoter OR unwinds/separates DNA locally. ✔
It makes an RNA copy using a DNA template sequence. ✔
Restriction endonucleases can cut DNA at particular recognition sequences. ✔
Telomerase extends chromosome ends or makes telomeres. ✔
(c)
Environmental agents can induce mutations. ✔
A mutation changes the DNA base sequence. ✔
Ultraviolet or ionizing radiation can damage DNA and lead to sequence changes. ✔
Mutagenic chemicals, such as compounds in tobacco smoke, can cause DNA changes. ✔
Environmental conditions can alter gene expression without changing the sequence. ✔
They can change DNA or histone methylation patterns. ✔
Methylation can inhibit transcription OR acetylation can promote transcription. ✔
Diet, stress or temperature can influence expression patterns. ✔
Quality of communication: The whole response is clear on a first reading and concise, with little repetition or irrelevant material. ✔
Schemat punktowania
Part (a): Award any 4 of the listed points; maximum 4 marks. Part (b): Award any 7 of the listed points; maximum 7 marks. Part (c): Award any 4 of the listed points; maximum 4 marks. Award 1 independent quality mark for clear, concise communication across the whole response. Maximum 16 marks. Accept alternative scientifically equivalent examples where the source allows examples; do not require every item joined by OR.