Modes Of Inheritance (17)

Question 1

What does it mean if someone is homozygous?

Answer 1

they have 2 identical copies of an allele for that gene

Question 2

What does it mean if someone is heterozygous?

Answer 2

they have 2 different alleles for a particular gene

Question 3

What are characteristics of dominant autosomal disorders?

Answer 3

• dominant= manifests in a heterozygote
• single gene/allele disease/trait
• affects males and females equally
• vertical pedigree pattern
• passed down to offspring w/ multiple generations affected
• each affected person normally has 1 affected parent
• each child of an affected person has 50% chance of being affected

Question 4

What are potential areas for DNA expansions?

Answer 4

long stretches of repetitive DNA

–> more copies–> more severe disease, earlier onset

Question 5

What are the mechanisms of dominant autosomal disorders?

Answer 5

• gain of function: mutated gene now makes a protein w/ new function
• dominant negative effect: altered gene product acts antagonistically to the wild-type allele
• insufficient: mutant in 1 gene can result in half the amount of a protein that is not enough for normal function

Question 6

What are characteristics of recessive autosomal disorders?

Answer 6

• carriers: have no phenotypic problems as they have only 1 copy of mutated gene
• 2 copies of mutated gene must be present for the disease/trait to develop
• parents and children of an affected person are normally unaffected
• horizontal pedigree pattern
• 25% chance if parents are carriers
• males and females equally affected
• commonly loss of function mutation

Question 7

What are loss of function mutations?

Answer 7

result in reduced or loss of protein function

Question 8

What are characteristics of X-linked disorders?

Answer 8

• mainly affects males (as an alteration of a gene on X chromosome has more of an effect if there is only 1 X)
• females can be carriers, have to have 2 copies to get disease
• parents and children of affected person are usually unaffected

Question 9

What are Y-linked disorders?

Answer 9

• affect only males
• all sons of an affected father get disease
• vertical pedigree pattern

Question 10

What is the inheritance pattern of X-linked recessive diseases?

Answer 10

• more common in males
• females often carriers
• all daughters are carriers if father has disorder, whilst sons are not
• females have disorder if they have 2 X w/ mutated allele

Question 11

What is the inheritance pattern of X-linked dominant diseases?

Answer 11

dominant inheritance but all daughters and no sons have disorder if father is affected

Question 12

What are mitochondrial disorders?

Answer 12

• are all maternally inherited bc all mitochondria come from maternal line
• mutations in mitochondrial DNA can affect function
• children of affected men are never affected
• all children of an affected woman affected, but variably
• vertical pedigree pattern
• can present as unrelated multi-system symptoms
• motor and nerve function common

Question 13

Why are mitochondrial conditions variable even within a family?

Answer 13

• different cells have different numbers of mitochondria
• random allotment of mutant mitochondria into each cell (random segregation)–> severity of symptoms vary w/ amount of wild type to mutated mtDNA and the severity of the mutation