AQA A LEVEL BIOLOGY EXAM REVIEW
UPDATED COMPLETE QUESTIONS AND
ANSWERS GRADED A+
◉ cell cycle. Answer: · Prophase
o Chromosomes condense
o Nucleolus becomes less prominent
o Nuclear membrane breaks down
· Metaphase
o Chromosomes move to equator
o Spindle fibres produced by centrioles
o Spindle fibres join to centromere
· Anaphase
o Chromosomes pulled to opposite poles of the cell as spindle fibres
contract
· Telophase
o New nuclear membrane reforms
o Cytokinesis
◉ binary fission. Answer: · Circular DNA and plasmids replicate by
semi-conservative replication
· Cell grows larger
· Circular DNA moves to opposite poles
,· Cytoplasm divides and cell wall forms
· 2 daughter cells - same circular DNA variable number of plasmids
◉ meiosis. Answer: · Meiosis 1
o Prophase 1
§ Chromosomes condense
§ 2 chromatids joined by centromere
§ Homologous pairs form bivalents
o Metaphase 1
§ Pairs of homologous chromosomes line up on equator
o Anaphase 1
§ Spindal fibres contract
§ Homologous chromosomes are pulled to opposite poles of the cell
o Telophase 1
§ Nuclear membrane reforms
§ Cytokinesis occurs
· Meiosis 2
o Prophase 2
§ Spindle fibres form again
o Metaphase 2
§ Pairs of chromosomes attach to spinal fibres and line up along
equator
o Anaphase 2
, § Spindle fibres contract and chromatids pulled to opposite poles of
the cell
o Telophase 2
§ Nuclear membrane forms
§ 4 genetically different haploid cells
◉ transcription. Answer: · DNA helicase separates 2 strands
· Hydrogen bonds broken
· Bases are exposed
· 1 strand used as a template to make an mRNA copy
· Free nucleotides line up along complementary bases on template
strand
· RNA polymerase attaches to DNA at beginning of gene
· RNA polymerase joins adjacent RNA nucleotides together by
catalysing the formation of phosphodiester bonds to form the sugar-
phosphate backbone and a new strand of mRNA
· RNA polymerase stops making mRNA when reaches a stop codon
· Once mRNA has been made, DNA recoils and hydrogen bonds
reform
· mRNA moves out of nucleus and attaches to ribosome
◉ translation. Answer: · tRNA carries amino acids with anticodon
complementary to codon on mRNA
· Ribosome moves to next triplet
· Amino acids joined by peptide bond
UPDATED COMPLETE QUESTIONS AND
ANSWERS GRADED A+
◉ cell cycle. Answer: · Prophase
o Chromosomes condense
o Nucleolus becomes less prominent
o Nuclear membrane breaks down
· Metaphase
o Chromosomes move to equator
o Spindle fibres produced by centrioles
o Spindle fibres join to centromere
· Anaphase
o Chromosomes pulled to opposite poles of the cell as spindle fibres
contract
· Telophase
o New nuclear membrane reforms
o Cytokinesis
◉ binary fission. Answer: · Circular DNA and plasmids replicate by
semi-conservative replication
· Cell grows larger
· Circular DNA moves to opposite poles
,· Cytoplasm divides and cell wall forms
· 2 daughter cells - same circular DNA variable number of plasmids
◉ meiosis. Answer: · Meiosis 1
o Prophase 1
§ Chromosomes condense
§ 2 chromatids joined by centromere
§ Homologous pairs form bivalents
o Metaphase 1
§ Pairs of homologous chromosomes line up on equator
o Anaphase 1
§ Spindal fibres contract
§ Homologous chromosomes are pulled to opposite poles of the cell
o Telophase 1
§ Nuclear membrane reforms
§ Cytokinesis occurs
· Meiosis 2
o Prophase 2
§ Spindle fibres form again
o Metaphase 2
§ Pairs of chromosomes attach to spinal fibres and line up along
equator
o Anaphase 2
, § Spindle fibres contract and chromatids pulled to opposite poles of
the cell
o Telophase 2
§ Nuclear membrane forms
§ 4 genetically different haploid cells
◉ transcription. Answer: · DNA helicase separates 2 strands
· Hydrogen bonds broken
· Bases are exposed
· 1 strand used as a template to make an mRNA copy
· Free nucleotides line up along complementary bases on template
strand
· RNA polymerase attaches to DNA at beginning of gene
· RNA polymerase joins adjacent RNA nucleotides together by
catalysing the formation of phosphodiester bonds to form the sugar-
phosphate backbone and a new strand of mRNA
· RNA polymerase stops making mRNA when reaches a stop codon
· Once mRNA has been made, DNA recoils and hydrogen bonds
reform
· mRNA moves out of nucleus and attaches to ribosome
◉ translation. Answer: · tRNA carries amino acids with anticodon
complementary to codon on mRNA
· Ribosome moves to next triplet
· Amino acids joined by peptide bond
