Gene expression

Question 1

What is a gene?

Answer 1

A length of DNA on a chromosome that codes for production of one or more polypeptide chains and functional RNA

Question 2

What is meant by genotype?

Answer 2

The genetic makeup of an organism which includes the different alleles which the organism possesses

Question 3

What is the phenotype

Answer 3

An organism’s observable characteristics.

Question 4

What are alleles?

Answer 4

Different versions of the same gene

Question 5

What is a dominant allele?

Answer 5

A version of a gene where only one copy is needed for it to be expressed

Question 6

What is a recessive allele?

Answer 6

A version of a gene where two copies are needed for it to be expressed

Question 7

What is meant when an organism is homozygous?

Answer 7

It has two copies of the same allele (2 dominant or 2 recessive)

Question 8

What is meant when an organism is heterozygous?

Answer 8

When it has two different versions of the same gene, one dominant and one recessive

Question 9

What is codominance?

Answer 9

Two dominant alleles that both contribute to the phenotype. The characteristics either blend together or show up both

Question 10

What is an autosome?

Answer 10

A chromosome that is not an X or Y chromosome

Question 11

What is a sex chromosome?

Answer 11

A chromosome that determines the sex of an organism. X and Y

Question 12

Define monohybrid inheritance

Answer 12

Where one phenotypic characteristic is controlled by a single gene

Question 13

What do family pedigrees show?

Answer 13

The inheritance of an allele over multiple generations

Question 14

What is a sex-linked characteristic?

Answer 14

A characteristic where the gene responsible is located on a sex chromosome. This makes it more common in one sex than in the other

Question 15

Give one example of a sex-linked trait

Answer 15

Red/green colorblindness is inherited on the X chromosome and is much more common in males

Question 16

What is red/green colorblindness?

Answer 16

An X-linked condition which makes the individual unable to distinguish between red and green due to a lack of red or green photoreceptors

Question 17

Why is red/green colorblindness significantly more common in males?

Answer 17

The faulty gene which causes it is located on the X chromosome. Men only inherit one copy of the X chromosome so they cannot inherit another non-faulty copy.

Question 18

What is cystic fibrosis?

Answer 18

An inherited autosomal recessive genetic condition. It impairs the functioning of the gaseous exchange, digestive and reproductive systems. It produces a faulty copy of a protein involved in producing mucus

Question 19

What is the genotype of individuals with cystic fibrosis?

Answer 19

Homozygous recessive

Question 20

Why is the genotype of carriers of cystic fibrosis?

Answer 20

Heterozygous

Question 21

What is meant by genetic screening?

Answer 21

Determining if an individual’s DNA contains a certain allele. This can allow prenatal diagnosis and earlier start of treatment

Question 22

What is pre-implantation genetic diagnosis? (PGD)

Answer 22

The determination of genetic diseases during IVF before implantation of the embryo into the uterus

Question 23

Describe the process of chorionic villus sampling

Answer 23

A sample of embryonic tissue is taken from the placenta at 8-12 weeks. It is screened for various disorders.

Question 24

Describe the process of amniocentesis

Answer 24

A sample of amniotic fluid is taken at 14-16 weeks. The results are slower than CVS because the fetal cells have to be grown for 2-3 weeks before screening

Question 25

Give some social and ethic issues surrounding prenatal genetic screening

Answer 25

-procedures carry risk of harming fetus
-may result in spontaneous miscarriage
-high cost of bringing up a baby with a genetic disorder
-emotional and mental stress on parents

Question 26

Outline how genetic screening can be used to improve healthcare (3)

Refers to adults, not prenatal screening

Answer 26

-enables awareness of potential risks and introduction of lifestyle changes to reduce these risks
-enables treatment to begin early
-prediction of a patient’s reaction to certain drugs

Question 27

Outline the drawbacks of genetic testing in healthcare (2)

Answer 27

Discrimination by employers if a person is likely to develop a disease. Person may develop anxiety, depression, etc.