worksheet 3
DESCRIPTION
hkfhlhlTRANSCRIPT
1
BLUEPRINT OF LIFE – WORKSHEET 3
1. A heterozygous male is bred with a homozygous recessive female. What is the percentage chance
that the offspring will be homozygous recessive?
a. 1:1 heterozygous to homozygous recessive
b. 50%
c. 0.25
d. 75%
2. A particular enzyme X is found in both organisms Y and Z, which are distantly related. There is only
a difference of two amino acids between the two enzymes. What is this an example of?
a. Comparative embryology
b. Comparative anatomy
c. Biochemistry
d. DNA - DNA hybridisation
3. Susan has blue eyes but both of her parents have brown eyes. Why might this be the case?
a. Susan's blue eye alleles (b) are recessive, and both her parents are heterozygous brown eyes
(Bb)
b. Susan's blue eye alleles (B) are carried by her grandparents, and they skipped a generation
c. Her twin sister, Geraldine, took the brown eye alleles from her during gestation
d. It is impossible for Susan to have blue eyes if her parents do not
4. The main parts of the embryo that comparative embryology concentrates on are:
a. Gill slits, embryonic cage, fins
b. Fins, gill slits, tail
c. Tail, gill slits, spinal column
d. Tail, gill slits, muscle blocks
5. An allele is considered dominant if:
a. It is more prevalent in a population
b. It is always passed down and expressed in offspring
c. It has the capability to mask another allele
d. It completely removes the possibility for other alleles to be phenotypically expressed in
offspring
2
Question 6 (2 marks)
Distinguish between the terms allele and gene, giving examples of each.
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
Question 7 (5 marks)
A homozygous pea plant with purple flowers is crossed with a pea plant with white flowers, producing
all purple offspring (generation F1).
a. Which colour is dominant? Justify your answer. (2 marks)
__________________________________________________________________________________
__________________________________________________________________________________
b. Two offspring from generation F1 are then bred together. Calculate the probabilities of each
genotype. (3 marks)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
3
Question 8 (5 marks)
Samantha is planning on having babies in the near future. She makes this prediction:
”Even though I have blue eyes, both my mother and father have brown eyes. That must mean that blue
eyes are recessive. Therefore, my babies have blue eyes by a 50% chance, because recessive genes
skip a generation.”
a. Is Samantha correct in saying that the allele for blue eyes is recessive? Justify your answer with an
appropriate Punnett square. (2 marks)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
b. Through genetic testing, Samantha finds out her husband is heterozygous for the gene for eye
colour. Assess the accuracy of her prediction for her babies’ eye colour. (3 marks)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
4
Question 9 (7 marks)
A family is considering their history of hemophilia, and have consulted you to help them.
a. Explain why pedigrees are useful in a scenario like this. (2 marks)
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
b. Draw the standard symbols for:
i. A man affected by hemophilia (1 mark)
ii. A woman who is a carrier of hemophilia (1 mark)
iii. Twins, one affected male and one unaffected female (1 mark)
c. Identify 2 non-human uses of pedigrees. (2 marks)
__________________________________________________________________________________
__________________________________________________________________________________