Lecture 24

Question 1

Mutations

Answer 1

• mutations can be inherited or acquired
• mutations are permanent changes to the DNA sequence
• mutations that are inherited are called germline mutations and are passed on via the gametes (eggs and sperm)
• mutations can also be acquired by somatic cells if DNA gets damage or is copied incorrectly - somatic mutations are not passed to the next generation
• the molecular bias of a mutation often is not consistent

Can be dominant / reccessive or loss of function/gain of function

Question 2

What do mutations do?

Answer 2

• genetic variations/mutations are a driving force for evolution
• 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
• the outcome of a mutation can also depend on
  
  • environmental effects
  • other genes

Question 3

Alleles

Answer 3

• mutations in a single gene can have different effects
• recessive and dominant
• two copies of each gene in human, diploid
• a mutation (allele) can thus can be either heterozygous (one mutant, one wild type)
• or homozygous (both alleles mutant)
• a dominant mutation is one that causes a phenotype when heterozygous
• a recessive mutation is one that causes a phenotype only when homozygous

Question 4

Loss of function mutation vs gain of function

Answer 4

• for a mutation (allele) to have a phenotype, it must affect the function of a gene
• a mutation might break a gene to cause it to not work as well as normal or not work at all
• somethings a mutation can cause a gene to work too well, or to do something unexpected

Question 5

Loss of function

Answer 5

Loss of function mutations are often recessive, because a normal copy of the gene exists on the other chromosome which can replace the lost of function

Question 6

Gain of function

Answer 6

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 7

Table

Answer 7

Question 8

Finding potential disease genes

Answer 8

Question 9

Polygenic disorders

Answer 9

• most dissorders appear the have genetic bias but do not follow straightforward inheritance patterns
• polygenic disorders involve several genes acting together or environmental factors interacting with genes
• Examples include: obesity, diabetes, athritis, gout, bipolar disorder
• identifying genes associated with polygenic disorders is very hard

Question 10

Answer 10

Question 11

Genetic determinism

Answer 11

• for most diseases, having a disease-related variation does not mean you will get the desease
• such diseases come about through a combination of variants and the environment
• different sufferers may have different disease mechanisms
• most genetic disorders are probabilistic, not geterministic
• this is also true of most traits with a genetic component, your genes do not direct your destiny

Question 12

Different ways mutations can be classified

Answer 12

• dominant vs recesssive
• loss vs gain of function

Question 13

What does the inheritance of a trait in a pedigree tell us

Answer 13

• location and sort of mutation

Question 14

What are simple diseases ultimately caused by

Answer 14

Loss or alteration of the structure of the protein that is coded for by the gene

Question 15

Examples of single gene disorders

Answer 15

• Haemophilia A/B - recessive
• Huntington disease - autosomal dominant
• cystic fibrosis - autosomal recessive
• most disorders are influenced by multiple genes and the environment
• genetics is probabilistic not deterministic

Question 16

Characgerstics of autosomal recessive and examples

Answer 16

• typically not seen in every generation of an affected family
• passed on by two asymptomatic carriers
• males and females equally likely to inherit

E.G: inability to taste PTC, cystic fibrosis

Question 17

Characteristics of autosomal dominant and examples

Answer 17

• occurs commonly in a pedigree
• affected individuals have an effected parent
• males and females equally likely to inherit

E.G: widows peak, huntingtons disease

Question 18

Characteristics of X-linked recessive and examples

Answer 18

• fathers cannot pass X-linked traits to their sons
• no male-to-male transmission
• most often effects males