Lecture 2

Question 1

incomplete dominance

Answer 1

heterozygote shows a mixture of two alleles–phenotype varies in proportion to the amount of protein

Question 2

codominance

Answer 2

traits of both alleles show up in the phenotype for heterozygotes– neither phenotype is recessive

Question 3

non-mendelian inheritance

Answer 3

when the inheritance of phenotype is not as clear cut as Mendel observed in his experiments for inheritance of alleles

Question 4

penetrance

Answer 4

the percentage of INDIVIDUALS with a specific genotype that exhibit the expected phenotype (it’s a population thing)

Question 5

expressivity

Answer 5

the degree that a given genotype is expressed phenotypically in ONE INDIVIDUAL

Question 6

cytoplasmic inheritance

Answer 6

inheritance due to NON-chromosomal mutations via female gametes (can be from mitochondria or chloroplasts)– literally only the female’s genotype matters

Question 7

endosymbiosis

Answer 7

evolutionary theory that eukaryotic cells arose from prokaryotes (mitochondria have their own circular DNA, they have similar sized ribosomes 70S, double membrane, same size as bacteria, and can be produced by division of pre-existing mitochondria and chloroplasts)

Question 8

heteroplasmy

Answer 8

the presence of more than one type of organelle genome (occurs when mitochondrial DNA from sperm leaks into egg cytoplasm at time of fertilization–very rare)

Question 9

proband

Answer 9

Person being studied

Question 10

propositus

Answer 10

male

Question 11

proposita

Answer 11

female

Question 12

Assumptions with disease-causing mutations:

Answer 12

• Affected individuals for a dominantly inherited trait are usually heterozygous - For recessively inherited diseases, most unrelated individuals will not be carriers

Question 13

TRAITS OF A PEDIGREE– autosomal recessive

Answer 13

• -unaffected parents with affected progeny
• -m/f equally affected
• -rare phenotype in general population
• if affected individuals do not appear in every generation, it is recessive

Question 14

TRAITS OF A PEDIGREE– autosomal dominance

Answer 14

• phenotype occurs in every generation
• affected parents transmit phenotype to both sons and daughters
• roughly half of children of affected individuals will show phenotype

Question 15

TRAITS OF A PEDIGREE– X-linked dominant

Answer 15

• affected female transmits to male and female equally
• affected male transmits to 100% daughters, 0% sons

For both x-linked traits, fathers can never pass sex-linked traits to sons

Question 16

TRAITS OF A PEDIGREE– X-linked recessive

Answer 16

• only females are carriers
• carrier female will transmit to 50% sons (affected) and 50% daughters (carriers)
• affected male cannot transmit to sons but 100% of daughters are carriers

For both x-linked traits, fathers can never pass sex-linked traits to sons

Question 17

TRAITS OF A PEDIGREE– Y-linked inheritance

Answer 17

• only from father to sons
• no daughters affected

Since most Y-linked genes involved in spermatogenesis, mutations can cause sterility and are unlikely to be passed down

Question 18

TRAITS OF A PEDIGREE– mitochondrial DNA inheritance

Answer 18

• moms pass to everyone
• affected males do not transmit mtDNA or the disease phenotype

Question 19

Baye’s Theorem

Answer 19

helps to determine carrier status of an individual in a pedigree

Question 20

If a diploid organism is heterozygous at six different gene loci, e.g. Aa;Bb;Dd;Ee;Gg;Hh, how many different gametes would they make?

Answer 20

2^6 gametes

Use equation 2^n, with n being the number of heterozygous genes

Question 21

null mutation (amorph)

Answer 21

a mutation that gives no function, even if the protein gets made

Question 22

silent mutation

Answer 22

mutation that occurs either in a noncoding region, or does not change the amino acid coding for it

Question 23

leaky mutation (hypomorph)

Answer 23

partial loss of function– gene sits on the border of an active site of chromosome

Question 24

Why are x-rays so damaging to DNA?

Answer 24

Because they break both strands of DNA, really hard to repair

Question 25

How might one distinguish a hypomorph from an amorph?

Answer 25

Take a deletion-removing segment of DNA, cross the deletion with the either hypomorph or amorph so that the only functional copy is the mutation. If it looks worse, you’ve got a hypomorph, if it looks the same, you’ve got an amorph (loss of function)

Question 26

hypermorph

Answer 26

more than usual function–activity of the gene is increased either by increasing the amount of the protein or the protein’s efficiency

Question 27

neomorph

Answer 27

uncommon– mutation that results in a new function of the mutant gene, often (but not always) with loss of the normal function

Question 28

antiomorph

Answer 28

uncommon– gain of function mutation that acts in opposition to the normal gene’s function, usually dominant or incomplete dominant (stronger than null)

Question 29

haplosufficiency

Answer 29

one copy is enough for it to function normally–wild-type is dominant to mutant

Question 30

haploinsufficiency

Answer 30

mutant allele is dominant to wild-type because individuals heterozygous or homozygous for the mutant allele are both mutant in phenotype

Question 31

pleiotropic allele

Answer 31

a single chromosomal mutation that affects several different characteristics (multiple phenogypes)

Agouti is a recessive lethal pleiotropic allele for huge mice–since recessive lethal ones are dead, viable ones can only be heterozygous