14+15

Question 1

Describe how an ultrasound image is produced?

Answer 1

Ultrasound uses inaudible, high-frequency sound waves to produce an image of the foetus. A probe is placed on the abdomen of the pregnant woman, and the sound waves are reflected by the foetal tissues to obtain a visual ‘echo’ of what is inside the uterus. The doctor feeds these reflected sounds, or echoes, into a computer to produce a screen image of the foetus for study.

Question 2

List six reasons why a foetal ultrasound may be performed.

Answer 2

confirming pregnancy
• estimating the stage of pregnancy
• determining the number of foetuses
• identifying abnormalities of the cervix or uterus
• monitoring the growth of the foetus
• determining the gender of the foetus

Question 3

Describe how an amniocentesis is able to identify chromosomal, genetic or neutral abnormalities.

Answer 3

Approximately 10–20 mL of the fluid is removed. Living cells from the foetus are floating in the fluid. These cells can be examined for biochemical defects and for abnormalities in the number of chromosomes or in the chromosome structure.

Question 4

What does ‘CVS’ stand for?

Answer 4

Chorionic villus sampling (CVS)

is a form of prenatal diagnosis done to determine chromosomal or genetic disorders in the fetus. It entails sampling of the chorionic villus and testing it for chromosomal abnormalities, usually with FISH or PCR

Question 5

State the reason for foetal monitoring.

Answer 5

Foetal monitoring is the regular recording of a baby’s heart rate in order to detect indicators of stress

Question 6

Describe the use of a fibre-optic scope to study the foetus.

Answer 6

fibre-optic scope that looks directly at the foetus through a small, telescope-like instrument with a diameter about the size of a large hypodermic needle. The fibre-optic fetoscope is introduced into the uterus through the abdominal wall. Examination of the outward appearance of the foetus may enable the detection of such conditions as cleft lip and palate, missing or abnormal ears, deformed or absent limbs, and spinal abnormalities, including spina bifida. If detection takes place early in the pregnancy, a decision about termination can then be made. Fetoscopy is also used during foetal surgery.

Question 7

List the places where foetal blood is collected from for testing.

Answer 7

The blood may be taken from:
• the umbilical cord via percutaneous umbilical cord blood sampling (PUBS), where a needle is inserted through the abdominal wall and uterus into the umbilical vein

• a foetal blood vessel, usually the liver or heart, via a fetoscope.

Question 8

Amniocentesis adv and dis

Answer 8

adv: examined for biochemical defects and for abnormalities in the number of chromosomes or in the chromosome structure.
dis: involves a small risk of infection, miscarriage or damage to the baby.

Question 9

Chorionic villus sampling adv and dis

Answer 9

adv: be used to detect genetic disorders and biochemical abnormalities and fast

dis: risk of miscarriage following the procedure is 2%.
cannot diagnose spina bifida.

Question 10

foetal monitoring

Answer 10

detailed foetal heart rate analysis enables medical staff to check whether there is any risk of oxygen deficiency occurring. Oxygen deficiency during birth may result in brain damage, or even a stillbirth

Question 11

Fetoscopy

Answer 11

Fetoscopy is a risky, difficult procedure that is only performed by a specialist doctor, usually after an ultrasound has indicated the possibility of foetal abnormalities such as spina bifida or Duchenne muscular dystrophy.

indicated the possibility of foetal abnormalities such as spina bifida or Duchenne muscular dystrophy.

Question 12

Foetal blood sampling

Answer 12

The results from foetal blood sampling are obtained within a few days, as opposed to a few weeks for other forms of diagnostic testing such as amniocentesis.

However, the risk of miscarriage is higher: 1–2%. There is also a risk of infection, blood loss and premature rupture of the amniotic sac.

Question 13

Biochemical analysis

Answer 13

Detect spinal cord, such as spina bifida.

Blood testing

Question 14

DNA probes

Answer 14

enables the detection of a range of genetic disorders, such as Duchenne muscular dystrophy and thalassaemia.

Question 15

Explain why an ultrasound is often used during an amniocentesis.

Answer 15

ultrasound to guide a needle through the abdominal wall into the amniotic cavity.

Question 16

An amniocentesis is often performed between 16 and 20 weeks of gestation. Suggest why it is not performed at other times.

Answer 16

by which time the foetus is floating in about 130 mL of amniotic fluid

Question 17

Explain why chorionic villus sampling may be preferred over amniocentesis, despite the higher risk of miscarriage.

Answer 17

it is much faster with testing and results which can make termination the baby easier and earlier 10 week

Question 18

Infertility

Answer 18

is defined as being unable to achieve pregnancy despite frequent unprotected sex over the period of at least a year. In Australia, infertility affects approximately one in six couples.

Question 19

For sperm to be able to fertilise an egg, it must be:

Answer 19

produced in sufficient quantities
• able to move in a forward direction
• able to penetrate the corona radiata and zona pellucida.

Question 20

factors affecting male fertility

Answer 20

• Semen, and the sperm it contains, may flow into the bladder, rather than out the urethra
.• The male’s immune system may develop antibodies for their own sperm, altering them and reducing their effectiveness.
• Blockages may occur in the male’s reproductive tract, especially in the vas deferens, which may stop the sperm from leaving the testes.
• Hormonal imbalances can affect sex drive and the production of sperm.

Question 21

Polycystic ovarian syndrome (PCOS)

Answer 21

s another factor affecting the fertility of females. PCOS is a hormonal condition where the ovaries contain many partially formed follicles that fail to mature. This means that the eggs are not released, and therefore cannot be fertilised.

Question 22

Endometriosis

Answer 22

affects approximately 10% of women. It is a painful condition where the cells of the endometrium grow outside the uterus. The resulting scar tissue or distortion of the uterine tubes can affect fertility by blocking the egg’s release or pathway through to the uterus.

Question 23

Fibroids

Answer 23

are benign growths in the muscular part of the uterus. While they are very common, they only affect fertility if their location distorts the uterine cavity or blocks the uterine tubes.Blockages of the uterine tubes will stop the egg passing through to the uterus. This can occur following infections, such as gonorrhoea or chlamydia, or damage – for example, due to ectopic pregnancies.

Question 24

Surgery

Answer 24

Microsurgery can be used to solve some problems of infertility. Blocked uterine tubes and sperm ducts can be opened, and fibroids or endometriosis can be removed.

Question 25

Ovulation tracking

Answer 25

If a couple tracks the ovulation of the female over a number of cycles, it is possible to identify the most effective time to have sexual intercourse.

Question 26

Ovulation induction

Answer 26

In some cases, infertility is due to problems with ovulation resulting from a low level of hormones. These problems may be solved by medications used to correct the problem. Two types of drugs are used, both of which use follicle-stimulating hormone (FSH) to induce the development of follicles.• Clomiphene stimulates the body to make more FSH.• Hormone injections of FSH increase the blood levels of the hormone.Another hormone, human chorionic gonadotrophin (hCG), may also be used to trigger ovulation once the follicle has matured.Females affected by hyperprolactinemia will need to lower their prolactin levels so that ovulation can occur. Correction of the underlying cause is an important consideration. Oral medication is also available to restore normal levels of prolactin and, hence, ovulation.

Question 27

Artificial insemination, or intrauterine insemination (IUI)

Answer 27

is a process where sperm is released into the uterus by a catheter being inserted through the cervix.

UI increases the chance of pregnancy for affected couples by increasing the number of sperm that reach the uterine tubes.

Question 28

Gamete intrafallopian transfer(GIFT)

Answer 28

is a procedure that can be performed when there are normal uterine (or fallopian) tubes and adequate sperm. It involves the following steps:1 Hormonal treatment is used to stimulate the female to produce more than one egg.2 The sperm and egg are collected and analysed.3 The sperm and egg are mixed together in the laboratory.4 The sperm and egg mixture is injected into the woman’s uterine tubes during laparoscopic surgery.It is hoped that the sperm will then fertilise the egg naturally and move down the uterine tube before implanting in the uterus.

GIFT has the disadvantages of having a lower pregnancy rate and requiring surgery. However, as fertilisation occurs naturally, this method is preferred by some couples who are unable to use other techniques due to religious or ethical reasons.

Question 29

In vitro fertilisation (IVF)

Answer 29

It is used to overcome a range of fertility issues, such as blocked uterine tubes, ovulation disorders, endometriosis, fibroids, low sperm quality or production, and unexplained infertility.

Question 30

how ivf works

Answer 30

When the eggs are mature, they are collected by a needle passing through the vagina to the ovaries.Following their retrieval, the eggs are mixed with sperm in a suitable environment at 37°C to maximise their chances of fertilisation and development. Approximately two to six days after collection, an embryo is inserted into the uterus via a catheter passed through the cervix.

Question 31

Intracytoplasmic sperm injection

Answer 31

is very similar to IVF. Once the eggs have been collected, they are examined to ensure that they are suitable. A sperm is then injected into the egg, achieving fertilisation. The resulting cells are then monitored, and any that are developing normally are able to be inseminated.

Question 32

Surgical sperm retrieval

Answer 32

Some men are unable to ejaculate, or very low numbers of sperm are released. In these instances, sperm may be collected during surgery to be used in IVF and ICSI. The surgery may be performed under local or general anaesthetic. In both cases, a needle is used to collect sperm from the epididymis or testis.

Question 33

Donor gametes or embryos

Answer 33

t is possible to use eggs, sperm or embryos from donors to achieve a pregnancy. The donor may be known to the couple, or anonymous. In Australia, there are strict regulations regarding donors, including counselling for both donors and recipients, cooling-off periods and health screening.

Question 34

Surrogacy

Answer 34

If a female is unable to conceive or carry a baby, surrogacy is an option that they may consider. With this arrangement, another woman carries the child for the duration of the pregnancy and then gives the child to the couple to raise as their own.

Question 35

Frozen embryos

Answer 35

Embryos that are produced but not used during an IVF cycle are typically frozen. This process is now highly developed, with the embryos, often in the blastocyst stage, being cooled to –196°C and stored in liquid nitrogen tanks. The embryos stop developing and remain in the same stage until they are

Question 36

homozygous

heterozygous.

Answer 36

the same AA or aa

Different Aa

Question 37

dominant traits

Answer 37

free earlobes
broad lips 
long eyelashes
broad nostrils
abundant body hair
curly hair
Mongolian eye fold
Astigmatism
Roman nose
Huntington’s disease
Achondroplasia
Normal enzyme production
Normal pigmentation
Tongue rolling

Question 38

recessive

Answer 38

Attached earlobes
Thin lips
Short eyelashes
Narrow nostrils
Little body hair
Straight hair
No eye fold
Normal vision
Straight nose
No disorder
Normal build
Phenylketonuria
Albinism
Non-rolling

Question 39

consanguineous union

Answer 39

A union between two close relatives, usually cousins, called a consanguineous union, is shown by double horizontal lines (=).

Question 40

The following are some examples of genetic disorders caused by dominant alleles on the autosomal chromosomes:

Answer 40

Achondroplasia – a form of dwarfism characterised by short limbs, a prominent head, normal intelligence and difficulty walking.

• Facioscapulohumeral muscular dystrophy – a rare form of muscular dystrophy affecting the facial muscles. Other muscles are gradually affected, making it difficult to raise the arms above the shoulders, to lift objects or to walk normally.
• Huntington’s disease – an inherited disorder that results in the death of brain cells, causing changes to mood and mental ability as well as uncoordinated movement

.• Neurofibromatosis – affected individuals exhibit numerous tumours along the peripheral nerves. The tumours are composed of a dense proliferation of nervous and fibrous tissue, and cause abnormalities of the skin and flesh as well as distortions of bone structure.

Question 41

Cystic fibrosis

Answer 41

is another disorder controlled by one recessive allele. Children with the condition suffer from chest infections, lack of digestive enzymes and increased salt los

Question 42

Single-gene disorders

Answer 42

are disorders caused by the inheritance of a single defective gene. The pattern of inheritance of single-gene disorders follows the basic laws of heredity already described

Question 43

The sex of a child is determined by

Answer 43

the sex chromosomes inherited from the parents. A female child gets an X chromosome from each parent, whereas a male child gets an X chromosome from the mother and a Y chromosome from the father.

Question 44

Haemophilia

Answer 44

is another sex-linked characteristic. It is a relatively rare disease in which the blood clots slowly or not at all. The defective allele is recessive to that controlling normal clotting of the blood and is carried on the X chromosome.

Question 45

Co-dominance

Answer 45

is a situation where two or more alleles are equally dominant. This means that, if both the alleles are present, they will both be observed. One example in humans is the BM and BNalleles for the M and N antigens in human blood. Neither allele is dominant to the other, and so three phenotypes are possible: • type M blood−genotype BMBM• type N blood−genotype BNBN• type MN blood−genotype BMBN.

Question 46

multiple alleles

Answer 46

sometimes there are more than two alleles for a particular characteristic. In such cases, they are called multiple alleles and the position of that gene on a chromosome is called multiple allelic

The ABO blood group system is controlled by three alleles, two of which are dominant while the other is recessive. Therefore, this is an example of a multiple allelic, co-dominant trait.

Question 47

genetic counselling

Answer 47

examining the incidence of a disorder in the family tree, the probability that a particular condition will occur can sometimes be determined.

Question 48

electrophoresis.

Answer 48

The DNA pieces were placed on a bed of semi-solid gel and an electric current was passed through the gel via electrodes located at each end, a technique called electrophoresis The DNA, which is negatively charged, moves through the gel towards the positive electrode. The smaller DNA pieces move faster than the larger ones, resulting in a pattern of bands that looks similar to the barcodes on products sold in supermarkets.

Question 49

DNA fingerprint, often called a DNA profile.

Answer 49

DNA fingerprints are frequently used in tracing ancestry and in forensic science. They are also useful in the identification of carriers for hereditary diseases. Using gel electrophoresis, a person who

Question 50

Ethical and social issues

Answer 50

Genetic profiling provides a complete set of genetic information about a person – their genome. It has the potential to provide great benefits for individuals and for providers of health care. A person’s genome could be analysed during infancy, or even before birth, and stored electronically to be used later if required

Genetic counselling and genetic profiling can be used to identify the risk of genetic disorders. However, there are ethical factors to consider when deciding whether to undertake these options.

Question 51

Huntington’s disease

Answer 51

ith symptoms usually appearing after 40 years of age. It is characterised by occasional involuntary flailing movements of the arms and legs. In addition, the person often has difficulty making voluntary movements of the limbs. Other symptoms include writhing movements of the hands, head, trunk and feet, and a progressive loss of the ability to think clearly, referred to as dementia.

Huntington’s disease is a single-gene disorder caused by a dominant allele. Symptoms of the disease are often not present until after the individual has had children, and so the dominant allele may be passed without the parents being aware of the possibility.

Question 52

Phenylketonuria

Answer 52

Many recessive disorders produce serious abnormalities. Phenylketonuria (PKU), which affects approximately 1 in 10 000 people in Australia, is a good example of a disease of this type

the gene concerned controls the production of an enzyme called phenylalanine hydroxylase. This enzyme converts the amino acid phenylalanine to tyrosine. If this enzyme is not present, then phenylalanine will accumulate in the bloodstream and become toxic. The toxicity results in damage to the growing brain, and thus produces extreme mental retardation, as well as a tendency towards epileptic seizures and a failure to produce normal skin pigmentation.

Special diets restricting the intake of phenylalanine and replacing it with substitutes can, if begun early in the child’s life, largely, if not entirely, correct the symptoms.

Question 53

Cystic fibrosis

Answer 53

Cystic fibrosis is another disorder controlled by one recessive allele. Children with the condition suffer from chest infections, lack of digestive enzymes and increased salt loss. Once again, a blood sample is usually taken from the baby’s heel within two to three days after birth. When a child is identified as having the disease, it is given a special diet low in fat and high in carbohydrate and protein. The diet is supplemented with pancreatic extract and large doses of vitamins A, D and K. This does not cure the disease, but it does enable the child to function as normally as possible.

Question 54

electrophoresis.

Answer 54

The DNA pieces were placed on a bed of semi-solid gel and an electric current was passed through the gel via electrodes located at each end, a technique called electrophoresis. The DNA, which is negatively charged, moves through the gel towards the positive electrode. The smaller DNA pieces move faster than the larger ones, resulting in a pattern of bands that looks similar to the barcodes on products sold in supermarkets. This banding pattern is an individual’s DNA fingerprint, often called a DNA profile.

Question 55

Gamete intrafallopian transfer

Answer 55

Gamete intrafallopian transfer(GIFT) is a procedure that can be performed when there are normal uterine (or fallopian) tubes and adequate sperm. It involves the following steps:1 Hormonal treatment is used to stimulate the female to produce more than one egg.2 The sperm and egg are collected and analysed.3 The sperm and egg are mixed together in the laboratory.4 The sperm and egg mixture is injected into the woman’s uterine tubes during laparoscopic surgery.It is hoped that the sperm will then fertilise the egg naturally and move down the uterine tube before implanting in the uterus.

Question 56

In vitro fertilisation (IVF)

Answer 56

In vitro fertilisation (IVF) has been used since the first ‘test tube baby’ was born on 25 July 1978. It is used to overcome a range of fertility issues, such as blocked uterine tubes, ovulation disorders, endometriosis, fibroids, low sperm quality or production, and unexplained infertility.During IVF, hormonal treatment is used to:• stimulate the ovaries so that multiple follicles develop • control ovulation• prepare the uterine lining.

Question 57

intracytoplasmic sperm injection

Answer 57

If there is a problem with the sperm, it is likely that it will not be able to fertilise the egg unassisted. This means that IVF has a low chance of success. Intracytoplasmic sperm injection (ICSI) is very similar to IVF. Once the eggs have been collected, they are examined to ensure that they are suitable. A sperm is then injected into the egg, achieving fertilisation. The resulting cells are then monitored, and any that are developing normally are able to be inseminated.

Question 58

CostAssisted reproductive technologies are very expensive. Some costs involved are:• specialist doctor consultations• initial tests and screenings• medications• fertility treatments such as IVF and ICSI• surgery and/or hospital costs• access to the donor program• frozen sperm, egg or embryo storage.

Answer 58

example, one clinic in Australia states that the cost of IVF is $9828 per cycle, with an out-of-pocket expense of $4991 (

Question 59

Foetal blood may be sampled to:

Answer 59

diagnose chromosomal abnormalities
• diagnose foetal anaemia
• check foetal oxygenation
• identify infections• give medications.