Human Genetic Disease

Question 1

Congenital

Answer 1

Disorder present at birth

Question 2

Single gene disorders can be…

Answer 2

Autosomal dominant

Autosomal recessive

X-linked dominant

Question 3

Mono genic defect

Answer 3

Single-gene disorder

Question 4

Types of aetiological disorders

Answer 4

Single gene/monogenic

Mitochondrial

Chromosomal imbalance

Or multifactorial (includes enviro)

Question 5

Examples of single gene disorders

Answer 5

Cystic fibrosis

phenylketonuria

Question 6

Autosomal dominant disorders can be…

Answer 6

Gain of function or loss is function

Question 7

Examples of autosomal dominant disorders

Answer 7

Huntington’s

Familial breast cancer (BRCA1)

Question 8

_____ are more likely to suffer from x linked disorders

Answer 8

Males

Question 9

Anticipation

Answer 9

When a disorder gets worse with each generation

Question 10

Females may show c-linked diseases less severely due to

Answer 10

X-chromosome inactivation

Question 11

Examples of x-linked diseases

Answer 11

Fragile x syndrome

Duchenne muscular dystrophy

Question 12

Complexity in single gene disorders

Answer 12

Generic heterogeneity:
Same phenotype, different genetic loci

Penetrance: when a phenotype is not expressed regardless of presence of allele

Expressivity: degree of expression

Mosaicisism: when not all cells are genetically identical

Phenology: when an environmental factor can lead to the same phenotype as a genetic disorder

Genomic imprinting: when expressivity depends on which parent the disease allele was inherited from

Question 13

Multifactorial vs complex diseases

Answer 13

Multifactorial = affected by enviro

Complex = affected by multiple genes

Question 14

Types of chromosomal mutations

Answer 14

Non-disjunction

Translocation (balances or unbalanced)

Question 15

Functions encoded in mitochondrial DNA

Answer 15

13 Respiratory chain subunits

tRNA for each amino acid

12S and 16S rRNA for mitochondrial ribosomes

Question 16

Mitochondrial disorders could be due to mutations in___

Answer 16

Mitochondrial or nuclear DNA

Question 17

homoplasmic vs heteroplasmic

Answer 17

Homoplasmic: all the mitochondria in the cell have the same DNA

Question 18

Population bottleneck of heteroplamia

Answer 18

Due to the small number of mitochondria passed from mother to oogonia

Return to homoplamic after a few generation be

Question 19

Genetic disorders that may have been selected for

Answer 19

Cystic fibrosis - have fewer attachment points for cholera therefore immunity

Sickle cell anaemia: helps prevent malaria

Both are advantageous when heterozygous but deadly when homozygous

Question 20

Molecular basis of recessive vs dominant traits

Answer 20

Recessive: takes two non-functioning gene copies to be below threshold
*haplosufficient

Dominant: only takes one non functioning gene to be below threshold
*haploinsufficient

Question 21

Allelic vs non-allelic genetic heterogeneity

Answer 21

Allelic: mutations in same gene but different phenotypes (ie. dif alleles = dif phenotype)

Non-allelic: mutations in different genes but similar phenotypes

Question 22

Methods for observing genetic basis of a trait/disorder

Answer 22

Compare incidence in a family compared to general population

Compare monozygotic twins

Question 23

Ploidy of mitochondrial genome

Answer 23

2-10

Question 24

Mitochondrial genome transplant

Answer 24

In vitro fertilization > removal of pronuclei > pronuclei added to cell with healthy mitochondria

Or

Spindle chromosomes are removed from unfertilized egg > added to egg with good mitochondria and no genome > in vitro fertilization