3: Genetics and children

Question 1

How is information stored in genes?

Answer 1

Amino acid sequences

i.e DNA

Question 2

In which arrangement do DNA strands bind together?

Answer 2

Anti-parallel

Question 3

What is the sugar forming the backbone of

a) DNA
b) RNA?

Answer 3

a) 2-deoxyribose

b) Ribose

Question 4

Which bases pair in DNA?

And in RNA?

Answer 4

A-T; C-G

A-U; C-G

Question 5

DNA strands are bound to which proteins?

Answer 5

Histones

Question 6

Tons of DNA strands combine to form what?

Answer 6

Chromosome

Question 7

How many base pairs are there in the human genome?

Answer 7

3 000 000 000

3 billion

Question 8

How many genes does each human have?

Answer 8

30 000

30 thousand

Question 9

How many polymorphisms does each person have on average?

Answer 9

3 000 000

3 million

Question 10

Which genetic testing technique is used to find

a) large changes affecting the entire genome (e.g extra chromosomes)
b) tiny changes affecting one or a few bases (e.g point mutation)?

Answer 10

a) Array genomic hybridisation (aCGH)

b) Next generation sequencing (NGS)

Question 11

How does aCGH work?

Answer 11

Detects BIGGER changes (e.g big deletions, chromosome duplications)

Compare sample to control DNA and ask “Is there more or less DNA?”

Question 12

If aCGH finds half as much DNA as the control, a ___ mutation has occurred.

Answer 12

deletion

Question 13

If aCGH finds 50% more DNA than the control sample, a ___ mutation has occurred.

Answer 13

duplication

Question 14

aCGH can only detect (balanced / unbalanced) chromosome changes.

Answer 14

unbalanced changes

Question 15

Which genetic disorder is caused by a deletion in chromosome 22?

Answer 15

Digeorge syndrome

Question 16

What are the symptoms of Digeorge syndrome?

Answer 16

Developmental delay

Vision / hearing problems

Mouth deformities e.g cleft palate

Congenital heart disease

Hypoparathyroidism causing seizures

Question 17

Which genetic test is used to identify Digeorge syndrome?

Why?

Answer 17

aCGH

Picks up bigger genome changes (e.g deletions or duplications)

Digeorge syndrome is caused by a deletion in chromosome 22

Question 18

• The cat sat on the mat
• The cat
• The car sat on the mat
• The cat spa to nth ema t
• The cas ato nt hem at
• The cat on the mat
• The cat cat sat on the mat

Name each type of mutation.

Answer 18

Normal

Stop mutation

Missense mutation

Insertion mutation

Deletion mutation (out of frame >>>>)

Deletion mutation (in frame)

Triplet expansion mutation

Question 19

When is NGS used?

Answer 19

Small changes to genome

e.g a mutation in one gene

Question 20

What is an example of a disease which could be identified by NGS?

Answer 20

Kabuki makeup syndrome

wouldn’t worry about remembering it

Question 21

What does de novo mean?

Answer 21

An acquired mutation

Arising spontaneously in the patient

Question 22

What is the percentage chance of finding a de novo mutation in a child with a developmental disorder?

Answer 22

> 30%

Question 23

For children with non-specific developmental disorders, which genetic test should be done first?

Answer 23

NGS

to try and find a small mutation

Question 24

Although genetic tests are useful in diagnosing disease, what information is essential?

Answer 24

History

Examination

because there are too many genes to analyse