Genetics

Question 1

Which bases have 2 carbon - nitrogen rings and are known as purines?

Answer 1

A and G

Question 2

Which bases have a single carbon - nitrogen ring and are known as pyrimidines?

Answer 2

C and T

Question 3

What are the base pairings?

Answer 3

A pairs with T

C pairs with G

Question 4

Which bases have the strongest bond?

Answer 4

The bond between C and G is stronger than that of A and T

Question 5

How many bases and genes are there in the human genome?

Answer 5

30,000 genes

3,000,000,000 bases

Question 6

What are the stages of the cell cycle?

Answer 6

Prophase 
Metaphase 
Anaphase 
Telophase 
Cytokinesis
(these all make up mitosis) 
Then; 
G1, S, G2

Question 7

Where are the checkpoints in the cell cycle?

Answer 7

G1 checkpoint towards the end of G1
G2 checkpoint at the end of G2
M check point during mitosis

Question 8

What is mitosis and what is meiosis?

Answer 8

Mitosis is when one diploid parent cell forms two identical diploid daughter cells
Meiosis is when one diploid parent cell forms 4 haploid daughter cells

Question 9

What is the difference between a mutation and a polymorphism?

Answer 9

A mutation is a gene that causes a genetic disorder

A polymorphism is any variation in the human genome that doesn’t necessarily cause disease but can predispose to one

Question 10

Are all mutations harmful?

Answer 10

NO - not necessarily if they don’t affect the coding part of the DNA

Question 11

Normal number of female and male chromosomes

Answer 11

Female 46 XX

Male 46XY

Question 12

What is an acrocentric chromosome?

Answer 12

A chromosome in which the centromere is situated at or very near one end

Question 13

What symbols are used for the long and short arm of a chromosome?

Answer 13

Short arm - p

Long arm - q

Question 14

What is meant by a ‘Robertsonian Translocation’ ?

Answer 14

Two acrocentric chromosomes are stuck end-to-end.

Question 15

What is meant by balanced and unbalanced chromosome changes?

Answer 15

Balanced - There is rearrangement of the chromosomes but all material is still present
Unbalanced- Rearrangement in which there is extra or missing material

Question 16

Define the term ‘ANEUPLOIDY’

Answer 16

Whole extra or missing chromosomes

Question 17

Down’s Syndrome

Answer 17

Trisomy 21

Question 18

Edward’s Syndrome

Answer 18

Trisomy 18 (death a few days post-birth)

Question 19

Turner’s Syndrome

Answer 19

45 X
Female
Mild learning difficulties
Appearance abnormalities

Question 20

Klinefelter Syndrome

Answer 20

47 XXY 
Male 
Infertility 
Lack of testosterone 
Poor development of sexual features

Question 21

Genetic tests

Answer 21

FISH (examines genes)
Microarray CGH (Detects missing/extra chromosomes)
PCR
NGS

Question 22

What is meant by ‘MOSAICISM’ ?

Answer 22

A disease that affects part but not all of the body

Question 23

List 5 types of mutations that can occur in DNA sequences and what term describes the normal/natural sequence

Answer 23

Wild Type (normal/natural) 
Premature stop 
Missense 
Deletions
Insertions 
Triplet Expansion

Question 24

What does ‘PENETRANCE’ mean?

Answer 24

The likelihood of having a disease if you have a gene mutation

Question 25

What are the differences between mendelian and multifactorial diseases?

Answer 25

Mendelian diseases are high penetrance with a high genetic contribution. Multifactorial diseases are common but have low penetrance and are caused by both genes and the environment!

Question 26

What is an SNP? What is a CNV?

Answer 26

Single Nucleotide Polymorphism Copy number variation - Extra or missing stretches of DNA

Question 27

What is meant by driver and passenger mutations?

Answer 27

Driver mutations drive carcinogenesis | Passenger mutations are incidental and occur because the tumour becomes unstable

Question 28

What is meant by the 'Philadelphia Chromosome' and what does it cause

Answer 28

a 9 to 22 translocation | it drives leukaemia development

Question 29

What is meant by 'imprinting'

Answer 29

Differences in gene expression depending on whether a gene is maternally or paternally inherited

Question 30

What 4 stages make up the central dogma?

Answer 30

Transcription Splicing Translation Post transcriptional modification

Question 31

What is a promotor mutation?

Answer 31

A mutation which stops the action of the 'on switch' involved in producing proteins - this leads to no/reduced transcription

Question 32

What is somatic mosaicism? Does it affect the entire body?

Answer 32

Two populations of cells within an individual due to post-zygotic mutations, it may only affect parts of the body

Question 33

What kind of inheritance would involve a condition only being transmitted from an affected mother to her children?

Answer 33

Mitochondrial Inheritance

Question 34

What kind of inheritance would involve no male to male transmission of the condition?

Answer 34

X-linked inheritance

Question 35

Describe autosomal recessive inheritance?

Answer 35

Involves heterzygous parents having a 1 in 4 chance of having an affected child

Question 36

At which stage of the cell cycle does DNA synthesis occur?

Answer 36

S phase! | G1- S- G2-M...

Question 37

What is the 1st line test for looking at chromosomes?

Answer 37

Microarray CGH

Question 38

What genes stop cells dividing if they are switched on? Which genes cause cells to start diving if they are switched on?

Answer 38

Tumour suppressors Oncogenes

Question 39

Is penetrance higher for mendelian or multifactorial diseases?

Answer 39

Mendelian

Question 40

What does angel man syndrome involve and which chromosome is affected?

Answer 40

Patients have developmental delay and intellectual disability Chromosome 15

Question 41

What is meant by heteroplasmy?

Answer 41

Different daughter cells contain different proportions of mutant mitochondria