2-4852-bd1d-3be74c9a0139","revisionId":"8801fe9d-0cbf-494a-bfab-ca1124e6ab2b","questionNumber":null,"questionType":"LA","specification":"","difficulty":4,"difficultyBand":"medium","totalMarks":11,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"d9a9ec84-c832-4592-8967-1785d6c91c39","label":"a","content":"A certain chemical used as a mouse poison targets and destroys red blood cells in the blood.\n\nDescribe the function of red blood cells in the blood.","markscheme":"- States that red blood cells contain haemoglobin which binds (reversibly) to oxygen B1\n- Explains that they transport oxygen from the lungs to respiring tissues or cells B1","marks":2,"order":0,"markingRubric":null,"explanation":null,"options":[]},{"id":"cd150326-3ab2-4d56-9f86-fc297d85c0c9","label":"b","content":"Some mice are resistant to this chemical. Scientists found that the resistance is due to a dominant allele, \$D\$.\n\nTwo resistant mice containing the heterozygous genotype \$Dd\$ mate.\n\nComplete the genetic diagram to find the expected ratio of resistant mice to non-resistant mice among their offspring.\n\n| | ... | ... |\n| :---: | :---: | :---: |\n| **D** | ... | ... |\n| **d** | ... | ... |\n\nRatio of resistant to non-resistant mice =","markscheme":"- Correctly identifies column gametes as $D$ and $d$ B1\n- Completes the offspring genotypes in the Punnett square as $DD$, $Dd$, $Dd$, and $dd$ B1\n- Gives the ratio of resistant to non-resistant mice as $3 : 1$ A1","marks":3,"order":1,"markingRubric":null,"explanation":{"methods":[{"id":"punnett_square","label":"Punnett square","steps":[{"type":"text","order":0,"title":"Identify the parent alleles","content":"Each mouse has genotype $Dd$, so each parent can pass on either allele: $D$ or $d$.\n\nThe allele $D$ is **dominant**, meaning any offspring with at least one $D$ allele will be resistant. Only $dd$ mice are non-resistant.","highlights":[{"text":"the resistance is due to a dominant allele, \$D\$","location":"specification"},{"text":"heterozygous genotype \$Dd\$","location":"specification"}]},{"type":"drawing","order":1,"title":"Set up the square","width":644,"height":364,"shapes":[{"id":"poly-1","type":"line","color":"black","points":[{"x":42,"y":42},{"x":602,"y":42},{"x":602,"y":322},{"x":42,"y":322},{"x":42,"y":42}]},{"id":"seg-V1TV1B","type":"line","color":"grey","points":[{"x":228.7,"y":42},{"x":228.7,"y":322}]},{"id":"seg-V2TV2B","type":"line","color":"grey","points":[{"x":415.3,"y":42},{"x":415.3,"y":322}]},{"id":"seg-H1LH1R","type":"line","color":"grey","points":[{"x":42,"y":135.3},{"x":602,"y":135.3}]},{"id":"seg-H2LH2R","type":"line","color":"grey","points":[{"x":42,"y":228.7},{"x":602,"y":228.7}]},{"x":313.3,"y":48.2,"id":"label-2","text":"D","type":"text"},{"x":500.3,"y":48.2,"id":"label-3","text":"d","type":"text"},{"x":96.7,"y":165.5,"id":"label-4","text":"D","type":"text"},{"x":96.9,"y":258.8,"id":"label-5","text":"d","type":"text"}],"caption":"Each heterozygous parent produces gametes carrying either $D$ or $d$. Writing $D$ and $d$ as the column headings earns B1.","diagramSpec":{"points":[{"at":[0,3],"name":"TL"},{"at":[6,3],"name":"TR"},{"at":[6,0],"name":"BR"},{"at":[0,0],"name":"BL"},{"at":[2,3],"name":"V1T"},{"at":[2,0],"name":"V1B"},{"at":[4,3],"name":"V2T"},{"at":[4,0],"name":"V2B"},{"at":[0,2],"name":"H1L"},{"at":[6,2],"name":"H1R"},{"at":[0,1],"name":"H2L"},{"at":[6,1],"name":"H2R"},{"at":[3,2.5],"name":"CTD"},{"at":[5,2.5],"name":"CTd"},{"at":[1,1.5],"name":"RLD"},{"at":[1,0.5],"name":"RLd"}],"elements":[{"kind":"polygon","points":["TL","TR","BR","BL"]},{"to":"V1B","from":"V1T","kind":"segment","color":"grey"},{"to":"V2B","from":"V2T","kind":"segment","color":"grey"},{"to":"H1R","from":"H1L","kind":"segment","color":"grey"},{"to":"H2R","from":"H2L","kind":"segment","color":"grey"},{"dir":"above","kind":"label","text":"D","nextTo":"CTD"},{"dir":"above","kind":"label","text":"d","nextTo":"CTd"},{"dir":"left","kind":"label","text":"D","nextTo":"RLD"},{"dir":"left","kind":"labe

Inheritance

Question 12

Inheritance Questions

Inheritance

Question 12

Inheritance Questions