Mendelian Inheritance III

Question 1

Phenotype

Answer 1

overall genotype and unique environmental history
Ex: hydrangeas are pink in basic soil and blue in acidic soil

Question 2

Norm of reaction

Answer 2

the way in which the environmental distribution is transformed into the phenotypic distribution for a given phenotype

Question 3

Is it possible to predict the phenotypes of different genotypes in new environments?

Answer 3

No because norm of reaction curves of different genotypes in new environments

Question 4

Pedigree

Answer 4

a family tree that describes the interrelationships of parents and children across generations

Question 5

Rare autosomal dominants

Answer 5

-Every affected person has an affected parent
-About 1/2 of offspring of an affected parent are also affected
-Usually occurs in both sexes

Question 6

Rare autosomal recessives

Answer 6

-Affected people usually have two parents who are not affected
-In affected families, about 1/4 of children of unaffected parents are affected
-Usually occurs in both sexes

Question 7

Dominantly Inherited Disorders

Answer 7

-homozygous or heterzygous
-Ex: achondroplasia, Huntington’s Disease

Question 8

Achondroplasia

Answer 8

-dominantly inherited disorder
-a form of dwarfism
-homozygosity is lethal

Question 9

Recessively Inherited Disorders

Answer 9

-ONLY homozygous
-Ex: albinism, CF, hemochromatosis, phenylketonuria, spinal muscular atrophy

Question 10

Sickle Cell Disease

Answer 10

-caused by a substitution of a single amino acid in the hemoglobin protein in RBCs
-affects 1/400 African Americans
-reduction against malaria symptoms

Question 11

Symptoms of Sickle Cell Disease

Answer 11

physical weakness, pain, organ damage, and even paralysis

Question 12

Sickle Cell Disease alleles

Answer 12

-2 sickle-cell alleles: ONLY sickled RBCs
-1 sickle-cell and 1 normal allele: Sickled and normal RBCs (carrier)

Question 13

Carrier

Answer 13

heterozygous individuals who carry the recessive allele for a disorder but are phenotypically normal

Question 14

Why are recessively inherited disorders more common than dominantly inherited?

Answer 14

Because carriers of recessively inherited disorders are phenotypically normal

Question 15

Why do inherited disorders show variable frequency in different human populations?

Answer 15

Because historical geographic isolation of different human populations

Question 16

Theodor Boveri (1885)

Answer 16

First to propose that chromosomes are the physical basis of inheritance

Question 17

Chromosomal Theory of Heredity

Answer 17

Mendel’s hereditary factors (genes) have specific loci (positions) on chromosomes, and it is chromosomes that undergo segregation and independent assortment

Question 18

Thomas Hunt Morgan’s Chromosome Experiment

Answer 18

-First solid evidence associating a specific gene w/ a specific chromosome
-Used fruit flies to provide evidence that chromosomes are the location of Mendel’s heritable factors

Question 19

Why did Thomas Hunt Morgan use fruit flies for his experiment?

Answer 19

1. They breed at a high rate (a generation can be bred every 2 weeks)
2. They only have 4 pairs of chromosomes

Question 20

Wild type phenotype

Answer 20

normal phenotypes that are common in populations

Question 21

Mutant phenotype

Answer 21

traits alternative to the wild type

Question 22

Results of Thomas Hunt Morgan’s experiment

Answer 22

-Mated male flies w/ white eyes (mutant) w/ female flies w/ red eyes (wild type)
-F1 generation: ALL red eyes
-F2 generation: 3:1 red:white eye ratio, but ONLY MALES had white eyes
-White-eye mutant allele must be located on X chromosome

Question 23

sex-linked gene

Answer 23

a gene located on either sex chromosome, follow specific patterns of inheritance

Question 24

Recessive X-linked

Answer 24

1. Female needs 2 copies of allele (homozygous)
2. Male needs only one copy of allele (hemizygous)
   -More common in males (only one X chromosome)
   -Ex: color blindness, Duchenne muscular dystrophy, hemophilia

Question 25

Diversity of Sex Determination Systems

Answer 25

Z-W system: 76 + ZW/SS
X-0 system: 22 + XX/X
Haplo-diploid system: 32 and 16