chapter fourteen part two

Question 1

types of dominance variations

Answer 1

1. complete dominance
2. codominance
3. incomplete dominance

Question 2

complete dominance

Answer 2

one allele is completely dominant over another in a heterozygous pair

Question 3

codominance

Answer 3

both alleles equally affect phenotype in the heterozygote
- AB/MN bloodtypes

Question 4

incomplete dominance

Answer 4

phenotype of the heterozygote appears intermediate
- coloring (redxwhite=pink)
- cross of F1 yields 1 red: 2 pink: 1 white

Question 5

ABO blood group example

Answer 5

• multiple (3) alleles
• each allele codes for enzyme that may add specific carbohydrates to red blood cells

Question 6

pleiotropy

Answer 6

1 gene has several phenotypic effects
- responsible for multiple symtpoms

Question 7

epistasis

Answer 7

alleles of 1 gene mask allele expression of a totally separate gene
- ex. labs - mutant E would disallow expression of gene B by not dipositing brown pigment in hair

Question 8

polygenic inheritence

Answer 8

one character, 2+ genes affect and control it
- height, intelligence, skin color, hair color

Question 9

nature vs. nurture impact on phenotype

Answer 9

• nutrition affects heigh, sun tanning affects skin color
• norm of reaction - phenotypic range depends on environment
• ex. soil pH and hydrangea flowers color, fanwort leaves

Question 10

family pedigree

Answer 10

a diagram showing occurrence of heritable characters over generations
- studies inheritance patterns of human triats

Question 11

genetic counseling

Answer 11

helps parents-to-be to understand likelihood of traits showing up in their children

Question 12

ex. of recessively inherited traits

Answer 12

• albinism
• color-blindness (red-green, x-linked)
• cystic fibrosis
• Duchene muscular dystrophy (x-linked)
• hemophilia (x-linked)
• Tay-Sachs

Question 13

cystic fibrosis

Answer 13

chloride ion channels that transport ions between cells/ECF defective
- causes uptake of water
- thicker/stickier mucus

Question 14

Tay-Sachs disease

Answer 14

brain cells can’t metabolize certain lipids because certain enzymes don’t work properly

Question 15

carriers

Answer 15

heterozygotes who are phenotypically normal but who can transmit a recessive allele to their offspring

Question 16

ex. of dominantly inherited disorders

Answer 16

• achondroplastic dwarfism
• Huntington’s disease

Question 17

achondroplasia dwarfism

Answer 17

Aa - dwarf, rare
AA - extremely rare, often fatal
aa - normal

Question 18

Huntington’s disease

Answer 18

Hh - Huntington’s rare, fatal
HH - extremely rare, fatal
hh - normal

Question 19

recessive disorders with codominance

Answer 19

sickle cell anemia
- ss - sickle-cell anemia
- Ss - sickle-cell treat
- SS normal

Question 20

types of fetal testing

Answer 20

1. amniocentesis
2. chorionic villus sampling
3. ultrasound

Question 21

amniocentesis

Answer 21

• karyotype
• done as early as 14-16th weeks of gestation (2nd trimester)
• needle inserted into uterus to collect amniotic fluid sample

Question 22

chorionic villus sampling

Answer 22

• tube inserted into cervix and sample of placenta taken
• results in 1 day
• can be done as early as 8-10th weeks of gestation (1st trimester)

Question 23

ultrasound/fetoscopy

Answer 23

noninvasive way to check fetus

Question 24

newborn screening

Answer 24

biochemical tests on blood from a baby’s heel
- PKU and others

Question 25

PKU (phenylketonuria)

Answer 25

causes amino acid phenylalanine to build up
- tested few days after birth

Question 26

how many disease-causing genes have tests available as of a few years ago?

Answer 26

2000