D3.2 Inheritance

Scientists sequenced the genes in each chromosome of chimpanzees (Pan troglodytes) and humans (Homo sapiens). The graph shows the mean divergence between the genes of these species by chromosome.

_{[Source: Material from: Mikkelsen, T.S. et al, Initial sequence of the chimpanzee genome and 
comparison with the human genome, 2005 Nature, reproduced with permission of SNCSC.]}

What can be deduced from this data?

A.  Autosomes are more similar than Y chromosomes.

B.  There is the same number of chromosomes in humans and chimpanzees.

C.  Humans are more closely related to chimpanzees than to other species.

D.  Smaller chromosomes are more similar than larger chromosomes.

Scientists sequenced the genes in each chromosome of chimpanzees (Pan troglodytes) and humans (Homo sapiens). The graph shows the mean divergence between the genes of these species by chromosome.

_{[Source: Material from: Mikkelsen, T.S. et al, Initial sequence of the chimpanzee genome and 
comparison with the human genome, 2005 Nature, reproduced with permission of SNCSC.]}

What can be deduced from this data?

A.  Autosomes are more similar than Y chromosomes.

B.  There is the same number of chromosomes in humans and chimpanzees.

C.  Humans are more closely related to chimpanzees than to other species.

D.  Smaller chromosomes are more similar than larger chromosomes.

Scientists sequenced the genes in each chromosome of chimpanzees (Pan troglodytes) and humans (Homo sapiens). The graph shows the mean divergence between the genes of these species by chromosome.

_{[Source: Material from: Mikkelsen, T.S. et al, Initial sequence of the chimpanzee genome and 
comparison with the human genome, 2005 Nature, reproduced with permission of SNCSC.]}

What can be deduced from this data?

A.  Autosomes are more similar than Y chromosomes.

B.  There is the same number of chromosomes in humans and chimpanzees.

C.  Humans are more closely related to chimpanzees than to other species.

D.  Smaller chromosomes are more similar than larger chromosomes.

Scientists sequenced the genes in each chromosome of chimpanzees (Pan troglodytes) and humans (Homo sapiens). The graph shows the mean divergence between the genes of these species by chromosome.

_{[Source: Material from: Mikkelsen, T.S. et al, Initial sequence of the chimpanzee genome and 
comparison with the human genome, 2005 Nature, reproduced with permission of SNCSC.]}

What can be deduced from this data?

A.  Autosomes are more similar than Y chromosomes.

B.  There is the same number of chromosomes in humans and chimpanzees.

C.  Humans are more closely related to chimpanzees than to other species.

D.  Smaller chromosomes are more similar than larger chromosomes.

Using a Punnett grid, explain the results of this cross.

Suggest a reason for the F₂ generation not corresponding exactly to the expected ratio of purple-flowered and white-flowered plants.

The pedigree chart shows the inheritance of three generations of Duane syndrome, a condition caused by a dominant allele that affects alignment of the eyes.

_{[Source: Yang, M.-M., Ho, M. et al., 2013. Pedigree of a Chinese family with Duane retraction syndrome. [diagram online]
Available at: https://www.researchgate.net/figure/Pedigree-of-a-Chinese-family-with-Duane-retraction-syndrome-
Squares-men-circles_fig1_236921765 [Accessed 5 October 2021]. Public domain.]}

If individuals II:1 and II:2 had a third child, what is the probability that the child would have Duane syndrome?

A.  25 %

B.  50 %

C.  75 %

D.  100 %

The pedigree chart shows the inheritance of three generations of Duane syndrome, a condition caused by a dominant allele that affects alignment of the eyes.

_{[Source: Yang, M.-M., Ho, M. et al., 2013. Pedigree of a Chinese family with Duane retraction syndrome. [diagram online]
Available at: https://www.researchgate.net/figure/Pedigree-of-a-Chinese-family-with-Duane-retraction-syndrome-
Squares-men-circles_fig1_236921765 [Accessed 5 October 2021]. Public domain.]}

If individuals II:1 and II:2 had a third child, what is the probability that the child would have Duane syndrome?

A.  25 %

B.  50 %

C.  75 %

D.  100 %

Using a Punnett grid, explain the results of this cross.

Suggest a reason for the F₂ generation not corresponding exactly to the expected ratio of purple-flowered and white-flowered plants.

Using a Punnett grid, explain the results of this cross.

Suggest a reason for the F₂ generation not corresponding exactly to the expected ratio of purple-flowered and white-flowered plants.

The pedigree chart shows the inheritance of three generations of Duane syndrome, a condition caused by a dominant allele that affects alignment of the eyes.

_{[Source: Yang, M.-M., Ho, M. et al., 2013. Pedigree of a Chinese family with Duane retraction syndrome. [diagram online]
Available at: https://www.researchgate.net/figure/Pedigree-of-a-Chinese-family-with-Duane-retraction-syndrome-
Squares-men-circles_fig1_236921765 [Accessed 5 October 2021]. Public domain.]}

If individuals II:1 and II:2 had a third child, what is the probability that the child would have Duane syndrome?

A.  25 %

B.  50 %

C.  75 %

D.  100 %

The pedigree chart shows the inheritance of three generations of Duane syndrome, a condition caused by a dominant allele that affects alignment of the eyes.

_{[Source: Yang, M.-M., Ho, M. et al., 2013. Pedigree of a Chinese family with Duane retraction syndrome. [diagram online]
Available at: https://www.researchgate.net/figure/Pedigree-of-a-Chinese-family-with-Duane-retraction-syndrome-
Squares-men-circles_fig1_236921765 [Accessed 5 October 2021]. Public domain.]}

If individuals II:1 and II:2 had a third child, what is the probability that the child would have Duane syndrome?

A.  25 %

B.  50 %

C.  75 %

D.  100 %

Autosomal genes are located in chromosomes that are not sex chromosomes. The inheritance of autosomal genes is affected by whether the genes are linked or unlinked. Explain the two types of inheritance, using the example of parents that are heterozygous for two genes A and B.

Autosomal genes are located in chromosomes that are not sex chromosomes. The inheritance of autosomal genes is affected by whether the genes are linked or unlinked. Explain the two types of inheritance, using the example of parents that are heterozygous for two genes A and B.

Autosomal genes are located in chromosomes that are not sex chromosomes. The inheritance of autosomal genes is affected by whether the genes are linked or unlinked. Explain the two types of inheritance, using the example of parents that are heterozygous for two genes A and B.

Congenital lactase deficiency is a type of lactose intolerance that occurs in infants. It is inherited in an autosomal recessive pattern. Calculate the chance of congenital lactose intolerance in a child whose parents are both carriers for the disorder, showing fully how you reached your answer.

Congenital lactase deficiency is a type of lactose intolerance that occurs in infants. It is inherited in an autosomal recessive pattern. Calculate the chance of congenital lactose intolerance in a child whose parents are both carriers for the disorder, showing fully how you reached your answer.

Congenital lactase deficiency is a type of lactose intolerance that occurs in infants. It is inherited in an autosomal recessive pattern. Calculate the chance of congenital lactose intolerance in a child whose parents are both carriers for the disorder, showing fully how you reached your answer.

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

Deduce reasons for the difference between the results of Cross 2 and Cross 3.

Identify, using one recognition feature visible in the photo, the phylum in which D. plantarius is classified.

Deduce reasons for the difference between the results of Cross 2 and Cross 3.

The pedigree chart shows the inheritance of three generations of Duane syndrome, a condition caused by a dominant allele that affects alignment of the eyes.

_{[Source: Yang, M.-M., Ho, M. et al., 2013. Pedigree of a Chinese family with Duane retraction syndrome. [diagram online]
Available at: https://www.researchgate.net/figure/Pedigree-of-a-Chinese-family-with-Duane-retraction-syndrome-
Squares-men-circles_fig1_236921765 [Accessed 5 October 2021]. Public domain.]}

If individuals II:1 and II:2 had a third child, what is the probability that the child would have Duane syndrome?

A.  25 %

B.  50 %

C.  75 %

D.  100 %

The pedigree chart shows the inheritance of three generations of Duane syndrome, a condition caused by a dominant allele that affects alignment of the eyes.

_{[Source: Yang, M.-M., Ho, M. et al., 2013. Pedigree of a Chinese family with Duane retraction syndrome. [diagram online]
Available at: https://www.researchgate.net/figure/Pedigree-of-a-Chinese-family-with-Duane-retraction-syndrome-
Squares-men-circles_fig1_236921765 [Accessed 5 October 2021]. Public domain.]}

If individuals II:1 and II:2 had a third child, what is the probability that the child would have Duane syndrome?

A.  25 %

B.  50 %

C.  75 %

D.  100 %

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

Deduce reasons for the difference between the results of Cross 2 and Cross 3.

Identify, using one recognition feature visible in the photo, the phylum in which D. plantarius is classified.

Deduce reasons for the difference between the results of Cross 2 and Cross 3.

Identify, using one recognition feature visible in the photo, the phylum in which D. plantarius is classified.

Deduce reasons for the difference between the results of Cross 2 and Cross 3.

Deduce reasons for the difference between the results of Cross 2 and Cross 3.

The pedigree chart shows the inheritance of three generations of Duane syndrome, a condition caused by a dominant allele that affects alignment of the eyes.

_{[Source: Yang, M.-M., Ho, M. et al., 2013. Pedigree of a Chinese family with Duane retraction syndrome. [diagram online]
Available at: https://www.researchgate.net/figure/Pedigree-of-a-Chinese-family-with-Duane-retraction-syndrome-
Squares-men-circles_fig1_236921765 [Accessed 5 October 2021]. Public domain.]}

If individuals II:1 and II:2 had a third child, what is the probability that the child would have Duane syndrome?

A.  25 %

B.  50 %

C.  75 %

D.  100 %

The pedigree chart shows the inheritance of three generations of Duane syndrome, a condition caused by a dominant allele that affects alignment of the eyes.

_{[Source: Yang, M.-M., Ho, M. et al., 2013. Pedigree of a Chinese family with Duane retraction syndrome. [diagram online]
Available at: https://www.researchgate.net/figure/Pedigree-of-a-Chinese-family-with-Duane-retraction-syndrome-
Squares-men-circles_fig1_236921765 [Accessed 5 October 2021]. Public domain.]}

If individuals II:1 and II:2 had a third child, what is the probability that the child would have Duane syndrome?

A.  25 %

B.  50 %

C.  75 %

D.  100 %

Outline one example of a human disease caused by an autosomal recessive allele.

Outline one example of a human disease caused by an autosomal recessive allele.

Outline one example of a human disease caused by an autosomal recessive allele.

Outline one example of a human disease caused by an autosomal recessive allele.

Outline the inheritance of blood types in the ABO blood system in humans.

Outline the inheritance of blood types in the ABO blood system in humans.

Outline the inheritance of blood types in the ABO blood system in humans.

Autosomal genes are located in chromosomes that are not sex chromosomes. The inheritance of autosomal genes is affected by whether the genes are linked or unlinked. Explain the two types of inheritance, using the example of parents that are heterozygous for two genes A and B.

A couple have four children whose blood groups are A, B and AB. What is the likely combination of the parents’ genotypes?

A.  I^Ai and I^Bi

B.  I^Ai and I^BI^B

C.  I^AI^B and ii

D.  I^AI^A and I^BI^B

Autosomal genes are located in chromosomes that are not sex chromosomes. The inheritance of autosomal genes is affected by whether the genes are linked or unlinked. Explain the two types of inheritance, using the example of parents that are heterozygous for two genes A and B.

Autosomal genes are located in chromosomes that are not sex chromosomes. The inheritance of autosomal genes is affected by whether the genes are linked or unlinked. Explain the two types of inheritance, using the example of parents that are heterozygous for two genes A and B.

A couple have four children whose blood groups are A, B and AB. What is the likely combination of the parents’ genotypes?

A.  I^Ai and I^Bi

B.  I^Ai and I^BI^B

C.  I^AI^B and ii

D.  I^AI^A and I^BI^B

Which pedigree chart is consistent with the inheritance of red-green colour blindness?

[Source: © International Baccalaureate Organization 2019]

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

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.

The system of sex determination in chimpanzees (Pan troglodytes) is the same as in other mammals. A chimpanzee has 48 chromosomes in the nuclei of its body cells.

What can be deduced from this information?

A. The sex of the chimpanzee

B. The number of genes in each chromosome

C. Whether non-disjunction has occurred

D. The number of autosomes in a diploid cell

Explain how the presence of a Y chromosome in the cells of a human embryo causes it to develop as a male.

Which pedigree chart is consistent with the inheritance of red-green colour blindness?

[Source: © International Baccalaureate Organization 2019]

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

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.

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.

The system of sex determination in chimpanzees (Pan troglodytes) is the same as in other mammals. A chimpanzee has 48 chromosomes in the nuclei of its body cells.

What can be deduced from this information?

A. The sex of the chimpanzee

B. The number of genes in each chromosome

C. Whether non-disjunction has occurred

D. The number of autosomes in a diploid cell

Explain how the presence of a Y chromosome in the cells of a human embryo causes it to develop as a male.

Explain how the presence of a Y chromosome in the cells of a human embryo causes it to develop as a male.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Draw a Punnett square to show all the possible genotypes of Queen Victoria’s children.

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.

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]

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Draw a Punnett square to show all the possible genotypes of Queen Victoria’s children.

Draw a Punnett square to show all the possible genotypes of Queen Victoria’s children.

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.

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.

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]

Explain the reasons for none of the females in the pedigree chart having hemophilia.

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

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]

Draw the symbol for individual X on the diagram.

Calculate the probability of male Y having an allele for the disorder.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

Explain the reasons for none of the females in the pedigree chart having hemophilia.

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

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]

Draw the symbol for individual X on the diagram.

Calculate the probability of male Y having an allele for the disorder.

Draw the symbol for individual X on the diagram.

Calculate the probability of male Y having an allele for the disorder.

Explain the reasons for variation in human height.

A total of 271 164 people were tested for blood groups in Mexico. The pie chart summarizes the ABO blood group distribution.

^{[Source: Canizalez-Román, A. et al., 2018. Blood Groups Distribution and Gene Diversity
of the ABO and Rh (D) Loci in the Mexican Population.
BioMed Research International, (Article ID 1925619).
http://dx.doi.org/10.1155/2018/1925619. Public domain.]}

What can be concluded from the ABO blood group distribution in Mexico?

A.  Allele frequencies are not the same for all blood group alleles.

B.  The majority of the Mexican population shows a co-dominant phenotype.

C.  Most of the Mexican population can receive blood from all blood groups.

D.  Only 2 % of the Mexican population have a heterozygous genotype for blood groups.

Explain the reasons for variation in human height.

Explain the reasons for variation in human height.

A total of 271 164 people were tested for blood groups in Mexico. The pie chart summarizes the ABO blood group distribution.

^{[Source: Canizalez-Román, A. et al., 2018. Blood Groups Distribution and Gene Diversity
of the ABO and Rh (D) Loci in the Mexican Population.
BioMed Research International, (Article ID 1925619).
http://dx.doi.org/10.1155/2018/1925619. Public domain.]}

What can be concluded from the ABO blood group distribution in Mexico?

A.  Allele frequencies are not the same for all blood group alleles.

B.  The majority of the Mexican population shows a co-dominant phenotype.

C.  Most of the Mexican population can receive blood from all blood groups.

D.  Only 2 % of the Mexican population have a heterozygous genotype for blood groups.

William Bateson and Reginald Punnett used the sweet pea (Lathyrus odoratus) in genetics studies in the early 20^th century. Pure-breeding plants that produced purple flowers and long pollen grains were crossed with pure-breeding plants that produced red flowers and round pollen grains. The resulting offspring all produced purple flowers and long pollen grains. Two of the F₁ generation plants were crossed. The table shows the ratio of phenotypes in the F₂ generation. 

What is an explanation for these experimental results?

A. Purple flowers and long pollen grains are dominant and the alleles have assorted independently.

B. The genes for flower colour and pollen shape are linked and all plants producing long pollen grains are recombinants.

C. The genes for flower colour and pollen shape are linked and all plants producing red flowers are recombinants.

D. Plants producing purple flowers and round pollen grains arose through crossing over.

In fruit flies (Drosophila melanogaster), grey bodies (b⁺) are dominant to black bodies (b) and normal wings (vg⁺) are dominant to vestigial wings (vg). Homozygous vestigial winged, black bodied flies were crossed with individuals that were heterozygous for both traits. 2300 individuals were counted and the phenotypes observed were recorded as shown.

965 normal wings, grey bodies
944 vestigial wings, black bodies
206 vestigial wings, grey bodies
185 normal wings, black bodies

Which statement is valid?

A. The predicted phenotypic ratio was 9:3:3: 1.

B. There is independent assortment of wings but not body colour.

C. The expected number of vestigial winged, grey bodied flies was 575.

D. The traits are on different chromosomes.

Explain whether these results fit the predicted Mendelian ratios for this cross.

Explain whether these results fit the predicted Mendelian ratios for this cross.

William Bateson and Reginald Punnett used the sweet pea (Lathyrus odoratus) in genetics studies in the early 20^th century. Pure-breeding plants that produced purple flowers and long pollen grains were crossed with pure-breeding plants that produced red flowers and round pollen grains. The resulting offspring all produced purple flowers and long pollen grains. Two of the F₁ generation plants were crossed. The table shows the ratio of phenotypes in the F₂ generation. 

What is an explanation for these experimental results?

A. Purple flowers and long pollen grains are dominant and the alleles have assorted independently.

B. The genes for flower colour and pollen shape are linked and all plants producing long pollen grains are recombinants.

C. The genes for flower colour and pollen shape are linked and all plants producing red flowers are recombinants.

D. Plants producing purple flowers and round pollen grains arose through crossing over.

In fruit flies (Drosophila melanogaster), grey bodies (b⁺) are dominant to black bodies (b) and normal wings (vg⁺) are dominant to vestigial wings (vg). Homozygous vestigial winged, black bodied flies were crossed with individuals that were heterozygous for both traits. 2300 individuals were counted and the phenotypes observed were recorded as shown.

965 normal wings, grey bodies
944 vestigial wings, black bodies
206 vestigial wings, grey bodies
185 normal wings, black bodies

Which statement is valid?

A. The predicted phenotypic ratio was 9:3:3: 1.

B. There is independent assortment of wings but not body colour.

C. The expected number of vestigial winged, grey bodied flies was 575.

D. The traits are on different chromosomes.

Explain whether these results fit the predicted Mendelian ratios for this cross.

Explain whether these results fit the predicted Mendelian ratios for this cross.

Explain gene linkage and its effects on inheritance.

Explain gene linkage and its effects on inheritance.

Explain gene linkage and its effects on inheritance.