Genetics_Long3

Set 1

Set 2

Set 3

Question 1

Set 4

Set 1

Set 2

Set 3

Choose

Set 4

- Genetic Lineage and Pedigree Diagrams (1) -

In man the gene for brown eyes is dominant to the gene for blue eyes. A blue eyed man married a brown eyed woman. They have two children, one has brown eyes and the other has blue eyes.

State the genotypes of the man and the two children. (3)

Man - bb

F1 - Bb ; bb

State the phenotype of each of child. (2)

Bb - brown eyes ; bb - blue eyes

Is the mother homozygous or heterozygous for brown eyes? Give a reason for your answer. (2)

Heterozygous, because she had a blue eyes child – if her child has bb. He must have obtained a b gene from BOTH parents.

Question 2

The diagram below shows the pedigree of two rabbit families. The allele for white fur (b) is recessive. Study the diagram and answer the questions.

Write down the genotype of rabbits A, B, C, D, E, F, G and H. (8)

A: Bb

B: bb

C: Bb

D: Bb

E: bb

F: Bb

G: bb

H: BB or Bb

If rabbit F and rabbit G were crossed, what percentage of the offspring would have: a) Brown fur? and b) White fur? (2)

50%

Question 3

In an experiment with guinea-pigs, a heterozygous black female (B) is crossed with a homozygous white male (b).

Identify the process which takes place at position X and position Y. (1)

meiosis/gametogenesis

Provide genotypes for individuals 1 to 11.(11)

1: Bb

2: bb

3: B

4: b

5: b

6: b

7: Bb

8: bb

9: black

10: white

11: 1 : 1

Question 4

The diagram below shows the inheritance of eye colour in humans. The squares represent men and the circles, women. The individuals represented by shaded symbols have brown eyes and the unshaded symbols blue eyes.

Brown eye colour (B) is dominant to blue eye colour (b).

Use the letters B and b, as indicated, and write down the genotypes of the individuals numbered 1 to 5. (5)

1: bb

2: BB

3: Bb

4: Bb

5: bb

Draw a diagrammatic representation of all the genetic combinations in regard to eye colour, of the children when no. 6 marries a woman with the same genetic constitution as no. 3. Use the letters B and b to show the genetic constitution of the children. (10)

Answer

Question 5

Study the family tree below which shows the inheritance of sex and type of earlobes over four generations of a family. In humans, free earlobes (F) is dominant over attached earlobes (f).

How many members of the family have free earlobes? (1)

What proportion of offspring in the fourth generation are females with attached earlobes? (2)

25% or ¼

If the genotype of person A is Ff, what will be the genotype of person B? Give a reason for your answer. (4)

Ff, because they produced a son with attached ear lobes (ff). Both parents are carrying a recessive gene.

Persons E and F are twins. Were they produced from a single fertilised egg cell or from two separately fertilised egg cells? Explain your answer. (3)

Two separate. One is male and the other is female. Identical twins are identical in every respect/from the same sex.

Is it possible for individuals C and D to have a child with free earlobes? Explain your answer. (3)

No. Since C and D have attached earlobes they have only recessive genes and can therefore have no dominant gene/gene for free earlobes to pass to their offspring.

Set 5

Questions source: DBE (Authorisation 11798)

- Greg Gopaul -