Genetics

Question 1

What are some essential features of cell division

Answer 1

• Faithfully replicate genetic material

- Accurately segregate into daughter cells

Question 2

How long does it take to replicate the human genome?

Answer 2

8 hours

Question 3

How long does it take to segregate the replicated genome?

Answer 3

2 hours

Question 3

How long does it take to segregate the replicated genome?

Answer 3

2 hours

Question 4

How is the cell division cycle controlled?

Answer 4

Cyclin dependent kinases

Question 5

What is down syndrome?

Answer 5

A genetic disorder that involves having 3 copies of chromosome 21

Question 6

What happens if there is a promotor or splice site sequence change?

Answer 6

Stop transcription or cause abnormal splicing

Question 7

What could happen if there is a base change within a gene?

Answer 7

• Change in protein sequence
• Not every base change causes disease
• May or may not reduce protein function
• Some missense mutations make a protein work faster
• May cause a premature stop codon

Question 8

What could happen if there is an insertion or deletion of bases in a gene?

Answer 8

Frame shifts possible so mutations can be in frame or out of frame

Question 9

Describe disorders with mendelian inheritance

Answer 9

A change in a single gene, sufficient to cause clinical disease, is inherited in a fashion predicted by Mendel’s law

Question 10

What shape represents males in inheritance diagrams?

Answer 10

Square

Question 11

What shape represents females in inheritance diagrams?

Answer 11

Circle

Question 12

What is nonpenetrance?

Answer 12

Failure of a genotype to manifest

Question 13

Describe mitochondrial DNA

Answer 13

• 16,559 base pairs
• Many copies in a cell (because of many mitochondria)
• Contains important genes for mitochondrial metabolic pathways and ribosomal RNAs
• Inherited almost exclusively maternally
• Point mutations and deletions occur

Question 14

What are some different types of growth?

Answer 14

• Multiplicative/replicative growth - cell replication
• Auxetic growth - cell size increase
• Accretionary growth - extracellular space increases
• Combined pattern of growth

Question 15

Define hyperplasia

Answer 15

Increase in number of cells

Question 16

Define hypertrophy

Answer 16

Increased cell size

Question 17

What term is used to describe decreased/regressed growth?

Answer 17

Atrophy

Question 18

What factors can be underlying causes for systemic growth disorders?

Answer 18

• Hormones and growth factors
• Genetics
• Nutrition
• Environmental factors
• Secondary effects of disease

Question 19

Describe turner’s syndrome

Answer 19

• 45 chromosomes
• Missing X chromosome
• Female
• Very short

Question 20

Describe Beckwith-Wiedemann syndrome

Answer 20

• Inheriting two copies of a chromosome from one (paternal) parent and none from the other is bad news
• Increased expression of IGF-II
• Decreased expression of H19
• Overgrowth in early childhood

Question 21

What factors influence differentiation?

Answer 21

• Location
• Growth factors
• Hormones
• Adjacent cells
• Autocrine factors

Question 22

What is metaplasia?

Answer 22

• Change of differentiated cell type
• Response altered cellular environment
• Often epithelial or mesenchymal cells

Question 23

Describe dysplasia

Answer 23

• Increased cell proliferation
• Atypical morphology
• Decreased differentiation
• Often premalignant

Question 24

Describe neoplasia

Answer 24

- Abnormal uncoordinated excessive cell proliferation | - Persists after initiating stimulus withdrawn

Question 25

What is agenesis?

Answer 25

Failure to develop an organ or structure

Question 26

What is atresia?

Answer 26

Failure to develop a lumen

Question 27

What is hypoplasia?

Answer 27

Failure of an organ to develop to a normal size - may only apply to a segment of an organ

Question 28

What is ectopia/heterotopia?

Answer 28

Small areas of mature tissue from one organ present in another

Question 29

What is maldifferentiation?

Answer 29

- Failure of normal differentiation | - Persistence of primitive embryological features

Question 30

How is a chromosome recognised?

Answer 30

- Banding pattern with specific stains - Length - Position of centromere

Question 31

What is a key feature of acrocentric chromosomes?

Answer 31

The short arm doesn't really matter

Question 32

Which chromosomes are acrocentric?

Answer 32

13, 14, 15, 21, 22

Question 33

What are aneuploidies?

Answer 33

Whole extra or missing chromosomes

Question 34

What are translocations?

Answer 34

Rearrangement of chromosomes

Question 35

What is another name for down syndrome?

Answer 35

Trisomy 21

Question 36

What is another name for Edward syndrome?

Answer 36

Trisomy 18

Question 37

What is another name for Patau syndrome?

Answer 37

Trisomy 13

Question 38

What is robertsonian translocation?

Answer 38

Two acrocentric chromosomes stuck end to end

Question 39

What are the reproductive risks involved in reciprocal translocations?

Answer 39

- For most translocations, ~50% of conceptions will have either normal chromosomes or the balanced translocation - Unbalanced products result in: miscarriage (large segments) or dysmorphic delayed child (small segments)

Question 40

Which chromosomes are involved in the production of a philadelphia chromosome?

Answer 40

9 and 22

Question 41

What are the 3 single chromosome mutations?

Answer 41

- Deletion - Duplication - Inversion

Question 42

What is quantitative inheritance?

Answer 42

Complex disorder & continuous traits are influenced by multiple genes and multiple environmental factors

Question 43

Describe the threshold model

Answer 43

For a discontinuous phenotype with an underlying continuous distribution, a threshold exists above which the abnormal phenotype is expressed. Population incidence is the proportion beyond the threshold in the general population. Among relatives, the proportion beyond the threshold is the familial incidence

Question 44

Describe heritability

Answer 44

- Heritability of a trait or disease is the proportion of the total variance that is genetic - The overall variance of the phenotype is the sum of the environmental and genetic variance - Heritability provides information on the importance of genetic factors in the causation of the disease

Question 45

Describe disease causing mutations

Answer 45

A gene change that causes a genetic disorder

Question 46

What is synonymous polymorphism?

Answer 46

Changes DNA sequence but not the amino acid or subsequent protein produced

Question 47

What is non-synonymous missense polymorphism?

Answer 47

Changes DNA sequence and the amino acid and protein produced

Question 48

What is non-synonymous nonsense polymorphism?

Answer 48

Changes DNA sequence to code a premature stop codon

Question 49

What are two possible definitions of polymorphism?

Answer 49

- Any variation in the human genome that has a population frequency of greater than 1% - Any variation in the human genome that does not cause a disease in its own right. It may however, predispose to a common disease

Question 50

What percentage of genes do different types of twins share?

Answer 50

Monozygotic - 100% | Dizygotic - 50%