Genetics - Genetic Variation and how it causes Diseases

Question 1

What does SNP stand for?

Answer 1

Single Nucleotide Polymorphisms. Slide 2.40

Question 2

What would the chances of a female carrier’s children have?

Answer 2

Half of male children will be affected, half of female children will be carriers. Slide 2.27

Question 3

What are the temperature cycles of PCR?

Answer 3

100, 50, 72. Slide 18-22

Question 4

What are the ways a child can get mutations?

Answer 4

1. If one parent has a mutation
2. No parents have it, new mutation occurs in gametogenesis
3. One parent is mosaic
4. Mutation is post-zygotic. Slide 57

Question 5

Why might a carrier female show mild features of the disease?

Answer 5

Due to only one X chromosome is active, so some affected genes might be turned off and some normal ones might be randomly inactivated. Slide 2.30

Question 6

What is a multifactorial disease?

Answer 6

When more than one environmental or genetic factors influence the disease. Slide 2.55

Question 7

What is usual about common disorders?

Answer 7

They have a rather small effect but are very common. Slide 2.56

Question 8

What are CNVs?

Answer 8

They are extra or missing stretches of DNA. Slide 2.49

Question 9

What do SNPs do?

Answer 9

Most have no effect, some that do are expected to have smaller effects than a rare disease causing mutation and some completely destroy the gene without causing disease. Slide 2.48

Question 10

What is a mutation?

Answer 10

A genetic variation that causes a disease. Slide 11

Question 11

What is X linked recessive?

Answer 11

When the gene fault lies on the X chromosome. Slide 2.25

Question 12

What would the chances of an affected male’s children have?

Answer 12

All male children would be normal, all of female children would be carriers. Slide 2.27

Question 13

Are all females who carry a faulty gene on their X chromosome affected?

Answer 13

No, due to X inactivation, they are often a carrier but not affected. Slide 2.25

Question 14

Where is mitochondrial DNA inherited from?

Answer 14

The maternal side. Slide 2.76

Question 15

What are the pedigree drawing basic symbols of male, female, affected and not, miscarried and dead?

Answer 15

Male - box
Female - circle
Affected - coloured
Unaffected - white
Miscarried - Triangle
Dead - Line through shape. Slide 2.9

Question 16

What does autosomal dominant mean?

Answer 16

If you have the mutation then you’ll have the disease with 100% penetrance. Slide 2.11

Question 17

What happens when there are mutations in a gene before a stop codon?

Answer 17

A stop codon may be kept in by accident and will cause it to be finished early so the protein will be short or absent. Slide 40

Question 18

What is each temperature for in PCR?

Answer 18

100 - denature DNA strands
50 - for primers to bind
72 - optimum temp. for taq. polymerase to replicate. Slide 21

Question 19

What are the 4 types of Mendelian Inheritance?

Answer 19

Autosomal Dominant
Autosomal Recessive
X linked
Mitochondrial. Slide 2.5

Question 20

What happens when there are mutations in a gene between exons and introns?

Answer 20

An intron my be left in or a exon may be left out of the mature mRNA. That creates an abnormal or absent proteins. Slide 39

Question 21

What is common about Mendelian disorders?

Answer 21

They have a big effect but are very rare. Slide 2.56

Question 22

Can different mutations have different effects on the protein produced and can they be predicted?

Answer 22

Yes. Slide 2.17

Question 23

What happens when the promotor has a mutation?

Answer 23

There is no or reduced transcription, therefore there are no or reduced protein. Slide 38

Question 24

In a ‘rare’ genetic disorder, what has more of an impact to the genetic disorder; genotype or environment?

Answer 24

Genotype (single mutation). Slide 2.36

Question 25

What is penetrance?

Answer 25

It is the likelihood of having a disease if you have the gene mutation. E.g. 100% penetrance means you will always have the disease if you have the mutation. Slide 2.3

Question 26

What is autosomal recessive?

Answer 26

When there are 2 faulty copies of the gene to cause disease. 25% chance of parents having an effected child. Slide 2.20+2.21

Question 27

What percentage of the genome are exons?

Answer 27

2-3%. Slide 8

Question 28

Can different mutations in the same gene can cause the same disease?

Answer 28

Yes. Slide 2.17

Question 29

What does CNVs mean?

Answer 29

Copy Number Variations. Slide 2.49

Question 30

What ways does X inactivation come about?

Answer 30

So a gene dosage compensation can be provided.
Some genes on the pseudoautosomal region escape inactivation.
The XIST gene at Xq13 is essential to inactivate X.
Methylation is one mechanism of X inactivation. Slide 2.32

Question 31

If more than half of the female carrier’s cells have the normal chromosome randomly inactivated, what happens to the phenotype of the female?

Answer 31

Her features from the disease will be much more prominent as there are more affected cells working. Slide 2.31

Question 32

What are Mendelian Disorders

Answer 32

A disease that is predominantly cause by a change in a single gene (high penetrance) and segregate in families in the manner predicted by Mendel’s Laws. Slide 2.4

Question 33

If the father was affected in X linked inheritance, why would the male offspring be normal?

Answer 33

There is no male to male transition, mothers provide the x chromosome for males. Slide 2.27