IMMS

Question 1

Name drugs that target parts of mitosis to treat cancer

Answer 1

Mitotic spindle- taxol and Vinca alkaloids.
Anaphase-Colchicine-like drugs
Spindle poles-Ispinesib

Question 2

Describe sperm production

Answer 2

Primordial germ cells undergo mitosis to produce spermatogonia.
Cytoplasm divides equally to form 4 equal gametes.

Question 3

Describe egg production

Answer 3

Primordial germ cells undergo mitosis to produce oogonia.
Oogonia enters meiosis I by 8th month of intrauterine life
Cytoplasm divides unequally – 1 egg and 3 polar bodies (that apoptose)

Question 4

What is Gonadal Mosaicism

Answer 4

Occurs when precursor germline cells to ova or spermatozoa are a mixture of two or more genetically different cell lines

Question 5

Define Genotype

Answer 5

Genetic constitution of an individual

Question 6

Define Phenotype

Answer 6

The appearance of an individual resulting from the interactions between the genotype and their environment

Question 7

Define Polymorphism

Answer 7

Frequent hereditary variations at a locus

Question 8

Define Penetrance

Answer 8

The proportion of individuals with a certain genotype who express the associated phenotype.

Question 9

Define Hemizygous

Answer 9

only one allele refers to a locus on an X chromosome in a male

Question 10

Define ACMG criteria

Answer 10

formal scoring system to decide if a gene variant is “pathogenic”

Question 11

Define Consanguinity

Answer 11

reproductive union between two relatives

Question 12

Define Recipricol Translocation

Answer 12

When part of one chromosome is exchanged with another.

Question 13

Summarise multifactorial inheritance

Answer 13

Combination of genetic and environmental factors.
If the affected individual is female, males relatives will be more at risk and vice versa.

Question 14

State 2 technologies used to identify chromosomal abnormalities

Answer 14

1. FISH- fluorescence hybridisation
2. Microarrays- investigate the genome at a higher resolution

Question 15

What are oligosaccharides?

Answer 15

Carbohydrate which contains 3-12 monosaccharides.

Question 16

What are phosphoacylglycerols?

Answer 16

Derived from phosphatidic acid.
Formed from fatty acids esterified to glycerol and phosphorylated at C 3.
Examples:
Phosphatidylcholine, Phosphatidylserine

Question 17

Describe the key features of steroids

Answer 17

Formed from cholesterol
Derive our sex hormones from
Fat soluble

Question 18

How are protein structures determined?

Answer 18

X-ray diffraction of protein crystals
-Crystalise pure proteins
-Rays bounce off electrons
-Creates diffraction patterns
-Carry out density calculations on spots

Question 19

How is DNA damaged?

Answer 19

chemicals, UV, radiation, chance

Question 20

How is DNA repaired?

Answer 20

• Base or nucleotide excision
  
  • Mismatch repair

Question 21

Give an example of a tumour suppressor gene and its function.

Answer 21

Pause cell cycle until repair is carried out

Halt cell cycle if DNA not repaired

Apoptosis

Question 22

What are enhancers?

Answer 22

non-coding sequences in the genome that activate the expression of target genes

Question 23

What does methylation of cytosine do?

Answer 23

Inhibits gene expressions

Question 24

Summarise cystic fibrosis

Answer 24

Autosomal recessive condition
Carrier frequency- 1/25
Incidence- 1 in 2500
CTFR gene on chromosome 7q31.2

Question 24

Summarise cystic fibrosis

Answer 24

Autosomal recessive condition
Carrier frequency- 1/25
Incidence- 1 in 2500
CTFR gene on chromosome 7q31.2

Question 25

What is the probability of healthy siblings of someone affected being carriers of the same disease?

Answer 25

2/3

Question 26

What is expressivity?

Answer 26

Refers to the range of phenotypes expressed by a specific genotype

Question 27

What is anticipation?

Answer 27

Whereby genetic disorder affects successive generations earlier or more severely, usually due to expansion of unstable triplet repeat sequences

Question 28

Somatic mosacism

Answer 28

Genetic fault present in only some tissues in body.

Question 29

Gonadal (germline) Mosaicism

Answer 29

Genetic fault present in gonadal tissue. (generally more common in X-linked disorders)

Question 30

Lyonization

Answer 30

X-inactivation
Generally only one of two X chromosomes is active in each female cell. Can be skewed so the number of cells with the X chromosome from their mother and father switched off isn’t 50%

Question 31

What is (genomic) imprinting?

Answer 31

Non-mendelian inheritance
An epigenetic phenomenon that causes genes to be expressed in a parent-of-origin-specific manner

Question 32

What is homoplasmy?

Answer 32

a eukaryotic cell whose copies of mitochondrial DNA are all identical

Question 33

What is heteroplasmy?

Answer 33

there are multiple copies of mtDNA in each cell

Question 34

Define Splice-Site Variant

Answer 34

Affects the accurate removal of an intron

Question 35

Define Non-Sense Variant

Answer 35

A mutation that changes a codon to a stop codon

Question 36

Define a Missense Variant

Answer 36

Single base substitution that changes the type of amino acid in the protein

Question 37

Define Allelic Heterogeneity

Answer 37

Lots of different variants in one gene e.g. cystic fibrosis

Question 38

Define Locus Heterogeneity

Answer 38

Variants in different genes give the same clinical condition e.g. hypertrophic cardiomyopathy

Question 39

Define a loss of function variant

Answer 39

Only one allele of the pair is functioning.
Most loss of function variants are recessive.

Question 40

Define a gain of function variant

Answer 40

A mutation that lead to:
-Increased gene dosage
-Increased protein activity