Download Support worksheet – Chapter 4 - Cambridge Resources for the IB

Cambridge Biology for the IB Diploma
Support worksheet – Chapter 4
1
The table below compares the processes of mitosis and meiosis. Place a tick () in the box if
the description applies to the process or a cross () if it does not.
(7)
Description of process
Mitosis
Meiosis
involves two nuclear divisions
occurs in a haploid cell
involves the formation of chiasmata
leads to random assortment of chromosomes
occurs during gamete formation in animals
daughter nuclei have identical genetic content
DNA replicates before cell division
2
Assume that in humans the allele for brown eyes (B) is dominant over the allele for blue eyes
(b). A blue-eyed man, both of whose parents had brown eyes, marries a brown-eyed woman.
They have one child who has blue eyes.
What are the genotypes of the man, his parents, his wife and the child?
3
(5)
Alkaptonuria is a rare, autosomal genetic condition in humans that affects the metabolism of
phenylalanine. The family tree below shows a family who are affected by this condition.
a
Is alkaptonuria a dominant or recessive condition?
b
Which individuals in the family are definitely heterozygous for the alkaptonuria allele? (2)
c
Alkaptonuria occurs as a result of a point mutation. Outline what this term means and
give another example of a condition that is caused by a point mutation.
(2)
Copyright Cambridge University Press 2011. All rights reserved.
(1)
Page 1 of 2
Cambridge Biology for the IB Diploma
4
Hemophilia is an example of a condition that is sex-linked. A woman who is a carrier
for hemophilia and a man who does not have the condition have two children, a boy
and a girl. Complete the Punnett grids below using the correct notation to show the
inheritance of the condition and the probability of:
a
their son
b
their daughter
having the condition or being a carrier of it.
Son’s alleles
Daughter’s alleles
Mother
Father
Father
Mother
5
(4)
The diagram below shows DNA profiles for a paternity test and for a forensic investigation.
a
Which of the two alleged fathers is the father of the child?
(1)
b
i
Is suspect 1 or suspect 2 more likely to be implicated in the crime?
(1)
ii
Why was a sample of the victim’s DNA taken in this case?
(1)
Copyright Cambridge University Press 2011. All rights reserved.
Page 2 of 2