Pack 16 – Genetic and Chromosomal Disorders

Question 1

What are the first 22 pairs of chromosomes

Answer 1

Homologous pairs

Question 2

Homologous pairs are:

Answer 2

• Are the same length
• Have their centromere in the same position
• Have the same genes in the same positions

Question 3

What is the last pair of a chromosome called?

Answer 3

The sex chromosomes

Question 4

Gene

Answer 4

A section of DNA with a specific base sequence, that codes for a protein

Question 5

Allele

Answer 5

A different form of the same gene

Question 6

Homozygus

Answer 6

Genotype with two alleles which are the same (e.g. AA or aa) for a gene

Question 7

Non affected/non-sufferer

Answer 7

A person who does not have a genetic or chromosomal disorder and have two ‘normal’ alleles for a characteristic

Question 8

Heterozygus

Answer 8

Genotype with two different alleles (e.g. Aa) for the same gene

Question 9

Genotype

Answer 9

The alleles a person has for a particular gene

Question 10

Affected/sufferer

Answer 10

A person who has a genetic or chromosomal disorder

Question 11

Phenotype

Answer 11

The observable characteristic or consequence of a genotype

Question 12

Dominant

Answer 12

When the effects of an allele are always seen in the phenotype, even if there is only one copy of the allele

Question 13

Carrier

Answer 13

A person who does not have a genetic or chromosomal disorder, but does have one ‘mutated’ allele for a characteristic and one ‘normal’ allele

Question 14

Recessive

Answer 14

When the effects of an allele are only seen in the phenotype when there are two copies of the allele present

Question 15

Sex linkage

Answer 15

When an allele for a genetic condition is found on the X chromosome (a sex chromosome)

Question 16

Causes of cystic fibrosis:

Answer 16

Cystic fibrosis is caused by a gene mutation in the CF gene, which produces a mutated recessive allele which codes for a non-functional CFTR protein

Question 17

Inheritance of cystic fibrosis:

Answer 17

• F (dominant) = normal allele which codes for a functioning CFTR protein
• f (recessive) = mutated allele which codes for non-functional CFTR protein

Question 18

Cystic fibrosis effects on the human body:

Answer 18

• As the CFTR protein doesn’t work or in some cases is not produced, the water content of mucus cannot be regulated correctly and mucus becomes thicker and stickier
• Mucus has important roles in the digestive, respiratory and reproductive systems
• Mucus lines many of the tubes and ducts in these systems, but it mucus is too thick and sticky, then these tubes become blocked

Question 19

Effectes of people without cystic fibrosis:

Answer 19

The water in mucus can be regulated by the CFTR protein, so that it is not too runny or too thick (it is the correct viscosity)

Question 20

Effects on people with cystic fibrosis:

Answer 20

Mucus becomes too thick and sticky because the CFTR protein doesn’t work properly

Question 21

Causes of huntingtons disease:

Answer 21

• Huntington’s disease is caused by a gene mutation in the Huntingtin gene, which produces the faulty huntingtin protein
• This causes neurone damage in the brain

Question 22

Inheritance of huntingtons:

Answer 22

• H (dominant) = mutated allele which codes for non functional huntingtin protein
• h (recessive) = normal allele which codes for functional huntingtin protein

Question 23

Symptoms of Huntington’s disease:

Answer 23

• Difficulty concentrating and memory lapses
• Depression
• Stumbling and clumsiness

Question 24

Haemophilia causes:

Answer 24

• The production of an abnormal factor 8 or factor 9 blood clotting proteins, or reduces their amount - The altered or missing protein affects blood clotting, so blood clots cannot form properly in response to injury.
• The genes for factor 8 and factor 9 are located on the X chromosome – this means that haemophilia is a sex-linked condition

Question 25

Inheritance of haemophilia:

Answer 25

- XH (dominant) = normal allele which codes for the functional protein - Xh (recessive) = mutated allele which codes for the non-functional protein

Question 26

Effects of haemophilia on the body:

Answer 26

- People with this condition experience prolonged bleeding or oozing following an injury, surgery, or having a tooth pulled - Serious complications can result from bleeding into the joints, muscles, brain, or other internal organs

Question 27

Down's syndrome

Answer 27

A chromosomal disorder caused by having THREE copies of chromosome 21 in the body’s cells

Question 28

Trisomy 21

Answer 28

The most common type of Down’s syndrome - in which all the cells have an extra chromosome 21

Question 29

Effects of down's syndrome on the body:

Answer 29

- A characteristic facial appearance, and weak muscle tone (hypotonia) in infancy - Learning disabilities, delayed development and behavioural problems - Digestive abnormalities, such as a blockage of the intestine, are less common