Test2: Lect 10 Susan Olson

Question 1

Degrees of relatedness:

Answer 1

primary = siblings, parents
secondary = grandparents, uncles/aunts
tertiary = cousins
Quaternary = cousins kids

Question 2

Double line on pedigree means:

Answer 2

Inbreeding

Question 3

Autosomal dominant:

Answer 3

Doesn’t skip generations.
Can be male or female inheritance
Can appear even with marriage to someone who doesn’t have the phenotype

Question 4

Autosomal recessive:

Answer 4

Only appears sometimes

Question 5

X-linked recessive:

Answer 5

Females almost never have it, males do, but never pass it on (they do, but only to female carriers)

Question 6

X-linked dominant:

Answer 6

All daughters of affected male will have it
No male to male transmission
50% chance daughter or son of affected female will have it

Question 7

X-linked dominant inheritance male lethality:

Answer 7

Males die before birth when they inherent (when hemizygous)
Only females will have it and transmit it to other females (all of which are heterozygous, 50% chance)
Will have more female offspring than male offspring (1 male : 2 females)

Question 8

How can a female have an x linked recessive trait?

Answer 8

X chromosome inactivation.
Usually 50 : 50 ratio of maternal vs chromosome reaction, but this is a normal distribution.
If majority of maternal or paternal is inactivated, then it is like being hemizygous, and the phenotype will be there

Question 9

EXITS genes:

• Stands for:
• Define:

Answer 9

• Stands for:
  Escapes X-inactivation tumor suppressor gene
• Define:
  Explains increased chance for men to get certain cancers.
  Some tumor suppressors exist on X, if neither is inactivated then they would have to lose both to get cancer
  Males would only have one copy of the tumor suppressor, and so would be vulnerable with a single knockout

Question 10

Mitochondrial inheritance:

Answer 10

Only females pass it on.
May not pass it to all of their offspring (female has some normal and some abnormal mitochondria, so it just depends if the germ cell gets her normal or abnormal one)
Severity can fluctuate with the percentage of
‘bad’ mitochondria passed

Question 11

Factors which may complicate inheritance patterns:

Answer 11

Delayed age of onset
Variable expressivity
Reduced penetrance
Locus heterogeneity
Allelic heterogeneity
Complexity in monogenic diseases
Oligogenic disorders
Pleiotropy
New mutation

Question 12

Penetrance:

• Define:
• Implication:

Answer 12

• Define:
  is all or nothing, they have the disease or they don’t. But reduced penetrance means that they are less likely to get the disease at all.
• Implication:
  A dominant disease may skip a generation

Question 13

Locus heterogeneity:

• Define:
• Example:

Answer 13

• Define:
  The same disease phenotype caused by mutations at two or more different loci
• Example:
  Recessive would require AAbb or aaBB or aabb to cause the disease.
  Could also be x - linked recessive

Question 14

Allelic heterogeneity:

• Define:
• Severity of phenotype?

Answer 14

• Define:
  More than one version of a gene at the same locus can cause the disease (multiple allele types at the loci cause the disease)
• Severity of phenotype?
  Some alleles confer a more severe phenotype than others

Question 15

Complexity in monogenic diseases:

Answer 15

One allele at one loci will always cause the disease.

However, depending on other loci the disease will manifest with different system

Question 16

Oligogenic disorders:

Answer 16

Multiple loci contribute to whether one disease is seen

Question 17

Pleiotropy:

Answer 17

Genes that exert effects on multiple aspects of physiology or anatomy

Question 18

New mutation:

- What is it difficult to distinguish this from?

Answer 18

• What is it difficult to distinguish this from?

A new mutation or incomplete penetrance?

Question 19

Genome Mutation:

- examples:

Answer 19

Aneuploidy (Trisomy, monosomy)

Polyploidy (triploidy)

Question 20

Chromosome Mutation:

- examples:

Answer 20

Translocation

Inversion

Question 21

Gene Mutation:

- examples:

Answer 21

Point mutations
Insertion
Deletion

Question 22

Phenocopy:

Answer 22

Mimic of a phenotype that generally has a genetic cause by the interaction of an environmental factor with a normal genotype.

Question 23

Mosaicism:

- Define:

Answer 23

Somatic mutation occurs, subsequent progeny differ from the rest of your cells, this is called Mosaicism
- Mosaicism can be present in a lot of your cells if the mutation occurred early enough in development

Question 24

Mosaicism:

- Specificity:

Answer 24

• Specificity:
  • Organism
  • Tissue/ Organ
  • Extraembryonic vs. embryonic

Question 25

Gonadal mosaicism:

• Define:
• Testing:

Answer 25

• Define:
  Mutation occurs in germline, children will have chance of getting disorder, parents will not have it if tested
• Testing:
  Test sample of skin or blood shows they don’t have disorder. Hypothesized child was a mutant, then the next child also has it, uh oh, looks like gonadal mosaicism.

Question 26

Mosaicism by somatic reversion:

-

Answer 26

Heterozygous for two autosomal recessive alleles for a locus heterogeneity disease both of which happen to be on the same chromosome. Crossing over occurs, and now one daughter cell is homozygous for both autosomal recessive alleles, and has the disease, and the other daughter cell isn’t even a carrier.
Spoiler alert: cell with the disease causes the problems

Question 27

Anticipation:

• Define:
• What could cause this?

Answer 27

• Define:
  Phenotype presents more severely from one generation to the next.
  E.G.
  Phenotype looks worse each time.
  Phenotype presents sooner each time.
• What could cause this?
  An example could be a sequence which keeps getting increased number of repeats in it from one generation to the next

Question 28

Imprinted genes:

- Define:

Answer 28

• Define:
  You either always receive the maternal or paternal copy of the gene. The other copy is always epigenetically silenced in males or in females.

Question 29

Disorders with imprinted genes:

Answer 29

The same deletion could cover a maternal and paternal imprinted gene.
If you inherent this mutation from your mother you will have one syndrome, if you inherent the same mutation from your father you will have another syndrome.