Medical laboratory technician
Medical laboratory technicians carry out routine laboratory tests and other procedures for use in the diagnosis and treatment of diseases and disorders of the human body.Medical laboratory technicians can be involved in: • setting up equipment used in the laboratory and
maintaining it in a clean condition
• preparing and staining slides of micro-organisms for examination
• testing and analysing blood, tissue or other body samples to determine blood types and composition, and to identify diseases
• analysing DNA samples to screen for diseases • communicating the results of tests to the medical
officers who have requested them.
A good medical laboratory technician will be able to: • work as part of a team with doctors, scientists and
laboratory assistants
• work accurately and with minimal supervision • do repetitive work without losing concentration
• keep accurate records and communicate well with others • apply scientific method to problems.
Fig 4.2.11
A medical laboratory technician preparing DNA for analysis
Human inheritance
UNIT
UNIT
4.2
4.2
4.2
UNIT
[
Questions ]
Checkpoint
Simple human inheritance
1 List three human conditions inherited through a single
gene.
2 Two ‘normal’ parents produce a child with a recessive
genetic characteristic being expressed. Identify whether the parents have homozygous or heterozygous genotypes.
3 State the probability of a recessive characteristic being
expressed in the child of parents who are:
a both homozygous for that characteristic and are
themselves affected by it
b both heterozygous for that characteristic
Blood groups
4 Describe the type of inheritance involved when Rh
blood groupings are inherited.
5 Outline the type of inheritance for the ABO blood group
system.
6 List the alleles of the ABO system.
7 Identify the codominant ABO allele, and the recessive
allele of the ABO system.
Other types of human inheritance
8 State the number of gene pairs thought to influence
eye colour.
9 Distinguish between continuous and discontinuous
variation.
10 List the two influences on intelligence.
Studying human inheritance
11 Studying human inheritance is complex. Identify the
main method of gathering information.
12 Draw the symbols used in pedigrees for a female,
identical twin boys, non-identical twin girls, and parents.
Sex-linked inheritance
13 Modify the following statements to make them correct. a The X chromosome is responsible for female
characteristics only.
b Males have the genotype XX.
c The Y chromosome carries more genetic coding than
the X chromosome.
d Sex-linked diseases occur because the Y
chromosome has fewer genes than the X.
e Diseases like haemophilia are inherited through males
in a family.
14 a Clarify what is meant by the term ‘a carrier’ of the
disease haemophilia.
b Explain whether a male can be a carrier of
haemophilia.
Think
15 Listed here are some characteristics:
height, ability to roll the tongue, skin colour, blood group
a From the list, identify two examples of characteristics
that show discontinuous variation within a population.
b From the list, identify two examples of characteristics
that show continuous variation within a population.
16 Cystic fibrosis is a disease carried by a single recessive
gene. Two unaffected parents have a child who suffers from the disease. Predict whether they will produce a child without the disease.
17 For each of the blood group genotypes listed below, identify the blood group phenotype.
a IA IA c IA IB e IB IO
b IA IO d IB IB f IO IO
18 An albino female and a non-albino male have two
children. One is non-albino, one is albino. Using the letters A for the dominant gene and a for the recessive gene, identify the genotypes of each of the children.
19 a If two albino people partner and produce a child, predict whether the child will be albino.
b If an albino person partners a person heterozygous
for albinism, predict the chances of their children being albino.
20 Explain why approximately half the human population
is female.
21 A genetic abnormality occurs where a person has the
genotype XXY. Would the person be male or female?
Justify your answer.
22 The ability to roll the tongue is a dominant characteristic.
Two people who cannot roll their tongue have four children. Predict how many of these children would be likely to be able to roll their tongue.
23 A child has blood group AB. The mother has blood
group A.
a Identify the possible blood group genotypes of the
father.
b Identify the possible blood groups of the father.
Analyse
24 ‘Sperm are either male or female’. Analyse this
statement, explaining whether the writer is correct, incorrect, or a bit of both, and justifying your answer.
>>>
26 Some people can roll their tongue into a U-shape.
Tongue rolling is controlled by a dominant gene (R) and a recessive gene (r). A pedigree for tongue rolling is shown in Figure 4.2.12. Identify the genotypes of each of these individuals.
a I male (generation I male) b II 1 c III 1 2 1 1 2 3 4 2 1 3 I II III IV Fig 4.2.12
Pedigree for tongue-rolling ability
Symbol Meaning
A Mating of a male and female
B Male with the inherited characteristic
C Identical twin boys
D Female without the inherited characteristic
E Deceased male
25 Identify the meaning that matches the pedigree symbol.
Skills
27 Construct a pedigree from the following information.
Jim and Jean are partners. They have four children: Scott, James, Natasha and Alan. James has a partner, Kylie.
[
Extension]
Investigate
1 a Gather information about the pedigree of a
champion horse or show dog.
b Construct a pedigree for your chosen animal. c Discuss the factors and outcomes that were
important when matings were chosen at each stage of the pedigree.
2 a Research the genetics of human blood groups,
and the problems raised by blood transfusions.
b Present a case study on one problem that has
occurred with a transfusion, explaining why the problem arose.
3 a Research some studies that have been conducted
concerning twins.
b Evaluate the evidence, summarising whether
heredity or environment is the major factor responsible for patterns of inheritance.
They have two children: Susan and Alison. Susan has a partner, Paul. They have three children: Anne, Emma and Colin. James, Natasha, Susan and Anne are all albino.
28 A man with blood group B and a woman with blood
group A produce a child. Predict the possible blood groups of the child by constructing a Punnett square.
29 Colour blindness is an X-linked recessive condition.
The symbols used to show the relevant genes are
Xn for the recessive allele on the X chromosome and XN for the normal gene on the X chromosome.
a Identify the genotypes of a non-colour-blind female,
a colour-blind female, a non-colour-blind male and a colour-blind male.
b If a colour-blind female partners a non-colour-blind
male, predict the chances of:
i their daughters being colour blind ii their sons being colour blind
30 Haemophilia is an X-linked recessive disease.
A heterozygous female does not show the disease. Her genotype is XHXh.
a Identify the genotype of: i a haemophiliac male
ii a non-haemophiliac male
b If the heterozygous female partners a non-
haemophiliac male, predict whether their sons will be haemophiliacs.