Genetic Diseases - Genetic Inheritance

Question 1

What is a genetic disease?

Answer 1

Disease that is caused by an abnormality in an individual’s DNA

Question 2

About genetic diseases:

Answer 2

1. Most genetic disorders are quite rare
2. Genetic disorders may or may not be inherited (passed down from the parents to offspring)
3. In non-heritable genetic disorders, defects may be caused by somatic mutations - changes to the DNA of somatic cells after the birth
4. The defect can only be heritable if genetic disorder occurs in the germ line

Question 3

Types of genetic disorders

Answer 3

1. Single gene defects
2. Chromosome abnormalities
3. Multifactorial disorders
4. Cancer (progressive accumulation of mutations in different genes and different chromosomes abnormalities, usually in somatic cells)

Question 4

RECAP DNA to proteins:

Answer 4

1. DNA sequence transcribed into RNA
2. Mature mRNA is translated into proteins.

RNA sequence is read consecutively in groups of three consecutive nucleotides (codons), from the start codons

3. Codons are nonoverlapping and the message has no gaps
4. There are stop codons that block the translation

Question 5

Gene (unit of heredity)

Answer 5

encodes the synthesis of a gene product, usually a protein (or RNA), according to its nucleotide sequences, following the genetic code

Question 6

Single gene disorders

Answer 6

Group of over 10,000 diseases caused by changes or mutations that occur in the DNA sequence of a single gene, producing either an altered protein or no protein at all

Question 7

Mutations can lead to…

Answer 7

a) a gain-of-function but also to a loss-of-function (conferring abnormal or enhanced protein activities)

b) The resulting protein alteration/deficiency is responsible for the disease symptoms

c) A condition that is present from birth (congenital

Question 8

The gene mutation may be passed between generations:

Answer 8

If present at birth or arise in germ cells of a parent

Question 9

Different mechanism of inheritance:

Answer 9

• autosomal dominant
• autosomal recessive
• X-linked recessive or dominant

Question 10

autosomal dominant

Answer 10

if a single mutated allele is sufficient to cause the disease (heterozygosis)

Question 11

autosomal recessive

Answer 11

• if both mutated allele must be inherited to be affected (homozygosis)

Question 12

X-linked recessive or dominant

Answer 12

mutated gene is present on the X chromosome

Question 13

Mutations alter the coding information of genes, in different ways:

Answer 13

• Missense mutations
• Nonsense mutations

Question 14

Missense mutations

Answer 14

These are base changes that alter the codon for an amino acid resulting in its replacement with a different amino acid

Question 15

Nonsense mutations

Answer 15

Base changes that convert an amino acid codon to a stop codon, resulting in a premature termination of translation and the production of a shortened protein

Question 16

Silent mutations-

Answer 16

do not cause any change in an amino acid

Question 17

Frameshift mutations

Answer 17

These mutations result from the insertion or deletion of one or more bases causing the alteration of the reading frame of the gene and a different set of codons, leading to an altered protein

Question 18

Promoter mutations or mutations on other regulatory sequences

Answer 18

Affect the way gene transcription is regulated, often abnormally reducing or enhancing the expression of certain genes

Question 19

Promoter mutations or mutations on other regulatory sequences

Answer 19

Affect the way gene transcription is regulated, often abnormally reducing or enhancing the expression of certain genes

Question 20

Sickle cell Anaemia

Answer 20

Autosomal recessive

Question 21

Caused by homozygosity (sickle cell Anemia)

Answer 21

both alleles - for a point mutation in the beta-globin gene within the chromosome 11

Question 22

Normal Red Blood Cell

Answer 22

• Red blood cells shaped like a disk
• Haemoglobin (protein) carries oxygen to all parts of the body

Question 23

Sickle Red Blood Cell

Answer 23

• Red blood cells form an abnormal crescent shape
• Haemoglobin (protein) is abnormally shaped
• Don’t move easily through your blood vessels

-Form clumps and get stuck in the blood vessels

Question 24

What does sickle cell Anaemia cause?

Answer 24

Blockage in blood vessel by blood cells preventing flow

Question 25

Cystic fibrosis

Answer 25

autosomal recessive