| Date | May 2022 | Marks available | 1 | Reference code | 22M.1.SL.TZ1.16 |
| Level | Standard level | Paper | Paper 1 | Time zone | Time zone 1 |
| Command term | Question number | 16 | Adapted from | N/A |
Question
Huntington’s disease is an autosomal dominant genetic disease. What are the chances of two parents that are heterozygous for the gene having a child with Huntington’s disease?
A. 25 %
B. 50 %
C. 75 %
D. 100 %
Markscheme
C
Examiners report
Syllabus sections
- 22M.2.SL.TZ1.4a: State the probability that Edward had hemophilia.
- 17N.1.SL.TZ0.16: An allele for lactase persistence allows humans to digest milk as adults. People who lack...
- 18M.2.SL.TZ1.3a: Using the Punnett grid, explain how two parents can have children with any of the different...
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16N.2.HL.TZ0.5a:
Using the pedigree chart, deduce the type of allele that causes hypophosphatemia.
- 21N.1.SL.TZ0.15: In humans, male pattern baldness is caused by a recessive sex-linked gene found only on the X...
- 17M.1.HL.TZ1.11: What proves that the inheritance of the condition shown in this pedigree chart is autosomal...
- 21M.1.SL.TZ1.18: Which genotype would be normally found in a gamete? A. Rr B. RS C. rStt D. TUt
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19M.1.SL.TZ2.14:
The pedigree chart shows a family affected by cystic fibrosis.
[Source: © International Baccalaureate Organization 2019]
What is the genotype of the affected boy’s father?
A. AA only
B. Either AA or Aa
C. Aa only
D. aa only
- 16N.2.HL.TZ0.5b: Identify the genotype of the individual marked with a star in the pedigree chart, using...
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18M.2.HL.TZ1.3b.i:
Distinguish between sex-linked genes and genes with linked loci.
- 17M.2.SL.TZ2.4a.i: State one type of environmental factor that may increase the mutation rate of a gene.
- 18M.1.SL.TZ1.21: What explains the presence in living humans of DNA sections which are identical to DNA found...
- 18M.1.HL.TZ1.40: What contributes to the total DNA content of a zygote?
- 17M.1.SL.TZ2.16: The diagram shows a pedigree of cystic fibrosis, in which the black colour indicates the...
- 18N.1.SL.TZ0.15: In cats, black coat colour is dominant over gray. A female black cat, whose mother is gray,...
- 19N.2.SL.TZ0.6b: Outline how two parents could have a child with any of the four ABO blood groups.
-
19M.1.SL.TZ1.16:
Which pedigree chart is consistent with the inheritance of red-green colour blindness?
[Source: © International Baccalaureate Organization 2019]
- 19M.2.SL.TZ2.4b: Explain one cause of mutation.
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19N.1.SL.TZ0.16:
A pair of alleles controls the secretion of antigens corresponding to blood group in saliva. Examine the pedigree chart.
[Source: © International Baccalaureate Organization 2019]
Based on this pedigree chart, which best describes the allele conferring antigen secretion in saliva?
A. Dominant
B. Recessive
C. Sex-linked
D. Co-dominant
- 21N.1.HL.TZ1.12: Huntington’s disease can develop in middle age and leads to death of brain cells. It is...
- 17M.1.SL.TZ2.27: The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive...
- 17N.1.HL.TZ0.12: A dominant autosomal allele for lactase persistence allows humans to digest milk as adults....
- 18M.1.SL.TZ2.15: What is the percentage risk of a child inheriting Huntington’s disease if only one parent has...
-
18M.1.HL.TZ2.20:
Nail patella syndrome is a rare disease that causes abnormalities of the nails and some bones. Its alleles are linked to the blood group alleles on the same chromosome. The pedigree chart shows the inheritance of these two characteristics over three generations.
[Source: Copyright © 1998. Phillip McClean]
Which descendant represents a recombinant phenotype?
- 21N.2.HL.TZ0.2a.ii: Deduce the genotype of Queen Victoria’s daughter Alice.
- 19N.1.SL.TZ0.15: A variety of Pelargonium has yellow leaves. When plants of this variety are crossed, the...
- 19N.2.HL.TZ0.2a: State the type of inheritance shown.
- 19N.2.HL.TZ0.7b: Outline how two parents could have a child with any of the four ABO blood groups.
-
18M.2.HL.TZ1.3b.ii:
Outline how it can be shown that the genes for shell base colour (Cc) and presence or absence of bands (Bb) are linked.
- 17M.1.SL.TZ1.21: Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is...
-
22M.2.SL.TZ1.4b:
Explain the reasons for none of the females in the pedigree chart having hemophilia.
- 22M.1.SL.TZ2.17: A group of students used quadrat sampling to gather data on the presence of two plant species...
-
22M.2.SL.TZ2.6b:
A family has a history of hemophilia that is caused by a sex-linked recessive allele. A woman from this family is a carrier and marries a man who does not have the allele. Showing your working, determine the probability of their children having the disease.
- 18N.2.SL.TZ0.6a: Isolated communities in rural Finland, Hungary and some of the Scottish islands have a high...
-
21M.2.HL.TZ2.5b:
Outline how sperm are produced from diploid cells in the testis and how this production can be sustained over many decades of adult life.
- 19M.1.SL.TZ2.15: The children in a family have blood groups A, B and O. What are the genotypes of their...
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19M.1.SL.TZ1.15:
Creeper in chickens is a condition in which the chickens are born with very short legs. The creeper allele (C) is dominant over the normal allele (c). Embryos which are homozygous for the dominant allele fail to develop into viable chickens and die before they hatch. What phenotypic ratio would you expect in the live offspring of a cross between two creeper chickens?
A. All creeper
B. 1 creeper; 2 normal
C. 2 creeper; 1 normal
D. 3 creeper; 1 normal
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19N.1.HL.TZ0.12:
The pedigree chart shows the inheritance of hemophilia in some of the descendants of Queen Victoria. Which letter points to a family member certain to be heterozygous?
[Source: © International Baccalaureate Organization 2019]
-
16N.2.SL.TZ0.4b:
Explain reasons that mules cannot reproduce.
-
21N.2.HL.TZ0.2a.i:
Draw a Punnett square to show all the possible genotypes of Queen Victoria’s children.
- 20N.1.SL.TZ0.13: In the pedigree chart, individuals affected by a genetic disease are shown as shaded symbols....
- 17M.2.HL.TZ1.1f.ii: Suggest a reason for the greater expression of the gene for the urea transporter after an...
- 18N.2.HL.TZ0.7a: Isolated communities in rural Finland, Hungary and some of the Scottish islands have a high...
-
21M.2.HL.TZ1.7a:
Outline the inheritance of blood types in the ABO blood system in humans.
-
18M.2.HL.TZ2.3b:
The genes for cystic fibrosis and blood group are not linked. Two parents are heterozygous for cystic fibrosis. One parent has blood group O and the other has blood group AB. Using a Punnett square, determine the probability that their child will have both cystic fibrosis and blood group A.
- 20N.1.SL.TZ0.15: What are all the possible phenotypes of children born to a mother with blood group AB and a...
- 17M.2.SL.TZ1.1c: Estimate how much smaller drilled oysters raised in seawater at a high CO2 concentration were...
- 17M.1.SL.TZ2.15: Some breeds of dogs are characterized by the presence of a melanistic mask, which is a...
- 18N.1.SL.TZ0.14: A human gene has two alleles. One allele, P, is dominant over the recessive allele p. Embryos...
- 17M.1.SL.TZ1.13: A child has blood group A. The father of the child has blood group B. What are the possible...
- 22M.1.SL.TZ2.15: The pedigree chart shows the inheritance of hemochromatosis, a genetic disease which causes...
- 16N.2.SL.TZ0.4d: A mule was born at the University of Idaho in the USA with 64 chromosomes. Suggest a...
- 18N.1.SL.TZ0.12: The image shows the chromosomes in four cells of an insect at the end of meiosis. What is...
- 19M.2.HL.TZ2.7b: Mendel found the same pattern of inheritance in all the crosses that he performed. Outline,...
- 16N.1.HL.TZ0.11: What is the major health issue resulting from the Chernobyl nuclear accident in 1986? A....
- 20N.1.SL.TZ0.14: Tall heterozygous pea plants were crossed and the resulting seeds grown. Out of 360 plants,...
- 21M.1.SL.TZ2.15: A woman with blood type A has three children with a man who has blood type AB. The first...
