human genome & disease

Question 1

what are mutations?

Answer 1

mutations are permanent changes to the DNA sequence

Question 2

where can you get mutations from?

Answer 2

mutations can be inherited or acquired

Question 3

what are germline mutations?

Answer 3

germline mutations are things that are inherited

Question 4

how are germline mutations formed?

Answer 4

they are passed on via the gametes (eggs
and sperm)

Question 5

how are mutations acquired if DNA gets damaged or is copied incorrectly

Answer 5

through somatic cells

Question 6

are somatic mutations passed onto the next-gen?

Answer 6

not passed to the next generation

Question 7

what is a driving force for evolution?

Answer 7

Genetic variations/mutations are a driving force for evolution

Question 8

What do mutations do?

Answer 8

• Mutations can have a beneficial effect, no effect, or a
  deleterious (damaging or harmful) effect on the organism.
• The vast majority of mutations have no effect at all

Question 9

what can the outcome of a mutation can also depend on?

Answer 9

• Environmental effects (e.g. diet, exposure to toxins)
• Other genes (‘genetic background’)

Question 10

what are 2 ways to classify mutations?

Answer 10

• Dominant vs Recessive
• Loss of function vs Gain of function

Question 11

are humans and eukaryotes diploid or haploid?

Answer 11

diploid

Question 12

what does diploid mean?

Answer 12

That means they have two copies of each of their genes (one maternal, one paternal).

Question 13

mutations are also known as…

Answer 13

alleles

Question 14

are mutations heterozygous or homozygous?

Answer 14

A mutation (allele) can be either heterozygous (one mutant, one wildtype allele) or homozygous (both alleles mutant)

Question 15

what does the dominant mutation cause?

Answer 15

the dominant mutation is one that causes a phenotype when heterozygous

Question 16

what does the recessive mutation cause?

Answer 16

a recessive mutation is one that causes a phenotype only when homozygous

Question 17

what must happen for a mutation (allele) to have a phenotype?

Answer 17

For a mutation (allele) to have a phenotype, it must affect the function of a gene.

Question 18

what is a ‘Loss of function’ mutation?

Answer 18

A mutation might break a gene to cause it to not work as well as normal, or not work at all

Question 19

why is loss of function mutation often recessive?

Answer 19

because a normal copy of the gene exists on the other chromosome which can replace the lost function

Question 20

what is a ‘Gain of function’ mutation?

Answer 20

Sometimes a mutation can cause a gene to work too well, or to do something unexpected

Question 21

why is a gain of function mutation often dominant?

Answer 21

Gain of function mutations are often dominant, because having an allele that works too well or does something novel, will not be replaced by the normal copy of the gene

Question 22

how to determine if something is dominant or recessive?

Answer 22

• By examining the inheritance pattern of an allele
• it is X-linked, Y-linked, or autosomal

Question 23

what does a line through a pedigree square or circle mean?

Answer 23

they died

Question 24

mutation is a

Answer 24

loss of function

Question 25

what does circles and square mean in a pedigree chart?

Answer 25

circle = female
square = male

Question 26

what are the characteristics of autosomal recessive?

Answer 26

• not seen in every gen of affected family
• passed on by asymptomatic carriers
• both males and females equally likely to inherit

Question 27

what are the characteristics of autosomal dominant?

Answer 27

• commonly in a pedigree
• affected individual – affected parent
• both males and females equally likely to inherit

Question 28

what are the characteristics of autosomal dominant?

Answer 28

• commonly in a pedigree
• affected individual – affected parent
• both males and females equally likely to inherit

Question 29

what are the characteristics of x-linked recessive?

Answer 29

• fathers cannot pass x linked traits to sons
• no male-male transmission
• most often affects males

Question 30

how to determine inheritance patterns?

Answer 30

• examine the pedigree
• look for individuals that break the rules of characteristics
• identify careers that do not have this condition (if none then condition is dominant)
• find an inheritance pattern that explains the disease occurrence in a pedigree

Question 31

what is happening if carriers do not have the condition?

Answer 31

if none of the carriers have the condition then it is dominant

Question 32

what is polygenic disorder?

Answer 32

Polygenic disorders involve several genes acting together or environmental factors interacting with genes.

Question 33

what happens when disorders appear to have a genetic basis but do not follow
straightforward inheritance patterns?

Answer 33

they turn into Polygenic disorders

Question 34

does having a disease-related variation mean
you will get the disease?

Answer 34

no, these diseases come about through a combination of variants and the environment

Question 35

what are most genetic disorders?

Answer 35

probabilistic, not deterministic

Question 36

what is probabilistic?

Answer 36

based on or adapted to a theory of probability; subject to or involving chance variation

Question 37

what does the inheritance of trait in a pedigree tell us?

Answer 37

The inheritance of a trait in a pedigree can tell us a lot about the location and sort of mutation.

Question 38

how are simple diseases caused?

Answer 38

Simple diseases are ultimately caused by loss or alteration of the structure of the protein that is coded for by the gene.

Question 39

examples of single gene disorders:

Answer 39

• Haemophilia A/B - X-linked recessive
• Huntington’s disease - autosomal dominant
• Cystic fibrosis - autosomal recessive