Lecture 17 - Mendelian Genetics

Question 1

Answer 1

Autosomal recessive

Question 2

Answer 2

Autosomal recessive (or X-linked)

Question 3

Answer 3

Autosomal dominant

Question 4

Answer 4

Mitochondrial

Question 5

Locus heterogeneity

Answer 5

Same phenotype (disease) caused by mutations in different genes

Question 6

Allelic heterogeneity

Answer 6

Different mutations (alleles) in the same gene causing the same disease

Question 7

Clinical (phenotypic) heterogeneity

Answer 7

Different mutations in the same gene that lead to different diseases

Question 8

Do diseases work in an all-or-nothing fashion?

Answer 8

No! Many diseases work on contiuums (ex. cystic fibrosis)

Question 9

Dominance and recessiveness are properties of __________, not _______

Answer 9

Characters, not genes

Question 10

If the product from a heterozygote is not enough to cross threshold, the mutation is…..

Answer 10

Dominant!

If the reverse is true, it’s recessive!

Question 11

Autosomal dominant Inheritance Criteria

Answer 11

• Most affected individuals will be heterozygous
• expressed every generation
• Recurrence risk of 50%
• Affected individuals usually have affected parents
  *

Question 12

Autosomal recessive inheritance

Answer 12

• Both parents of affected individuals to be carriers and asymptomatic
• May appear as sporadic
• Recurrence risk is 1 in 4
  *

Question 13

Compound heterozygote?

Answer 13

An organism is a compound heterozygote if it has two recessive alleles for the same gene, but with those two alleles being different from each other (for example, both alleles might be mutated but at different locations). Compound heterozygosity reflects the diversity of the mutation base for many autosomal recessive genetic disorders; mutations in most disease-causing genes have arisen many times.

ex. cystic fibrosis

Question 14

After birth and not affected by autosomal recessive disease, what is the chance a brother or sister of an affected individual have of being a carrier?

Answer 14

2/3

Question 15

Describe the chances of parents, grandparents, uncles, and cousins being carriers…

Answer 15

Question 16

X-linked recessive inheritance

Answer 16

• Usually males affected (unless an affected male marries a carrier female, or extreme X-inactivation)
• All daughters of affected males are carriers
• Half the sons of carrier females are affected
• No male to male transmission
  *

Question 17

Haldane’s Law

Answer 17

???? look up!

Question 18

X-linked dominant

Answer 18

• RARE
• Affected males have normal sons and affected daughters
• Twice as many affected females as males
• Most affected females will be heterozygous, so offspring will be affected
• Usually more sever/lethal in males

Question 19

Y linked

Answer 19

No/few known Y linked diseases

Only males would be affected

Question 20

Mitochondrial inheritance

Answer 20

Trait appears to be inherited exclusively through females

All offspring of affected females will probably be affected

Highly mutatable compared to nuclear DNA

Question 21

New Mutation

Answer 21

Disease will appear sporadic but will be familial in descendents of affected individuals but not in earlier generations

Mitochondria have high mutation rate

Estimate of 100-200 new bp changes in each person

Question 22

Mosaic

Answer 22

Germline or somatic

Tissue has two or more cell lines of different genotype (derived from single zygote)

ex. lymphoma or leukemia

Question 23

Chimeras

Answer 23

Individuals derived from cells of two different zygotes

Ex. recipient would be bone marrow transplant from donor

Or absordbing twin in utero