Chapter 13

Question 1

incomplete dominance

Answer 1

each allele makes some contribution to the expression of a trait
heterozygous people have different traits than homozygous people
genotype ratio is the same as the phenotype ratio

Question 2

multiple alleles

Answer 2

more than two for a gene are present in a population but an individual can only have 2 alleles

Question 3

ABO blood groups in humans

Answer 3

3 alleles: code for production of carbohydrate on the surface of red blood cells
IA: codes for type A carbohydrate
IB: codes for type B carbohydrate
i: codes for no carbohydrate
IA and IB are codominant: both together are expressed when found together
i is recessive

Question 4

geno and pheno blood type

Answer 4

ii: type o
IAIA or IAi: type A
IBIB or IBi: type B
IAIB: type AB

Question 5

how can the carbohydrate be detected

Answer 5

by reactions with different antibodies

Question 6

blood transfusions

Answer 6

antibodies are produced against carbohydrate types a person does not produces
Ex) a person with type A blood will produce atinbodies against the B carbohydrate
type AB: universal recipient
type O: universal donor

Question 7

multiple genes

Answer 7

different genes code for proteins that contribute to the same character OR
there are multiple copies of the same gene in different locations on the chromosmes

Question 8

skin color

Answer 8

caused by the production of melanin
2 alleles-dominant and recessive
3 copies of the gene
each copy of a dominant allele results in the production of more melanin

Question 9

hair color

Answer 9

result of two pigements :
1. eumelanin-brown to black
2 alleles-dominant and recessive 
there are 4 copies of the gene on different chromosomes 
2. promelanin 
2 alleles-dominant and recessive
1 copy of the gene 
eumelanin masks the presence of promelanin

Question 10

human disorders based on dominant/recessive alleles

Answer 10

most genetic disorders are recessive for the following reasons:
1. recessive alleles generally produce non fuctional proteins
many mutations can produce non functional versions of the same protien
2. dominant alleles mask the effect of the recessive alleles:
therefor: recessive alleles can be caried by indivduals and have no effect on their phenotype
they are difficult to eliminate from a population

Question 11

examples of recessive allele disorders: cystic fibrosis

Answer 11

cystic fibrosis: excess mucus production
many mutations can cause the disease
1 in 30 people have a recessive allele
1 in 3600 people are homozygous recessive

Question 12

examples of recessive allele disorders: tay-sachs disease

Answer 12

tay-sachs disease
liquid accumaltion in brain cells
common in some ethnic groups (up to 1 in 20 people carry recessive allele)

Question 13

examples of recessive allele disorders: PKU

Answer 13

phenylketonuria (PKU): accumulation of phenylanaine (type of amino acid)
1 in 50 people carry the recessive allele

Question 14

in dieases with incomplete dominance

Answer 14

the non- functional allele is usually rarer than dieseases of thr recessive alleles

Question 15

disorders associated with dominant alleles

Answer 15

every affected person should have a parent with the disorder
dominant alleles are usually very rare in a population
usually associated with conditions that occur late in life

Question 16

examples of dominant allele disorders: alzheimer’s disease

Answer 16

mental deterioration, especially memory

Question 17

examples of dominant allele disorders: huntington disease

Answer 17

mental deterioration, muscle control

1 in every 20,000 people have the allele for the diease

Question 18

frequency of alleles causing diease early in life

Answer 18

common to very rare
dominant/recessive
imcomplete dominance
dominant/recessive

Question 19

independent assortment of alleles

Answer 19

pairs of alleles for gene separate independently of other alleles for other genes during gamete formation.
ex) YyRr produces
YR Yr yR yr
only occurs when the genes are on different choromsomes

Question 20

linked genes

Answer 20

genes found on the same chromosome

Question 21

crossing over seperate linked genes

Answer 21

the rate which gene are seperated depends on how far apart they are from one another

Question 22

if genes are on the same chrosmosome (linked) then:

Answer 22

the phenotype conination on the parents will be the most commom combinantion in the offspring
- the ratio of phenotypes in across will be different from the ratio of unlinked genes

Question 23

how do we find the location of genes

Answer 23

some chromosomeal mutations are associated with phenotypes and can be used to map genes onto chromosomes

Question 24

2 ways sex can be determined genetically

Answer 24

1. presence of sex chromosome

2. difference in the number of chromosomes

Question 25

sex chromosomes XY system

Answer 25

males: one X abd one Y chromosome
females: two X chromosome
eggs cells all have an X chromosome, sperm will either have a X or Y

Question 26

chromosome XY

Answer 26

Y chromosome is smaller than the X chromosome
Y chromsosome has gene which causes the dveelopment of testes (instead of overaies)
found in humans and many other animals

Question 27

XO system

Answer 27

males: one X chromosome
females: two X chromsome
sperm have either X or no X chromosome
eggs cells all have X chromosome
found in some insects

Question 28

ZW system

Answer 28

males: two Z chromosomes
females: one Z and one W chromosome
sperm cells all have a Z chromosome
eggs cells have a Z or a W chromosome
the W chromosome is smaller than the Z
found in birds, fish, and some insects

Question 29

sex determineation by chromosome number

hapoid/diploid system

Answer 29

haploid/diploid system
males: haploid
females: diploid 
males develop from unfertilized eggs
found in ants, bees, and termites

Question 30

enviornmental induced sex determinartion

Answer 30

males and females are not genetically different

examples: temp affects sex determination in turtles

Question 31

heraphrodites

Answer 31

males and females sex organs present in ech individual
common in plants, fungi, and simple animals
common organisms with limited access to mating partners

Question 32

sex linked genes

Answer 32

found on sex chromosomes and not involved in determing the sex of an indivdual
ratios of phenotypes differ between males and females

Question 33

XY system

Answer 33

X linked geens are more common than Y linked genes

males show higher occurance of recessive traits

Question 34

ex) eye color is fruit flies

Answer 34

XR- dominant or red eye color
Xr recessive allele for white eye color
Y- non allele for eye color

Question 35

general rules for X-linked

Answer 35

1. males pass alleles to duaghters, not sons
2. daughter of males with dominant trait will also have the dominant trait
3. sons of females with recessive trait will also have the recessive trait

Question 36

sex linked genes in humans

Answer 36

x- linked recessive traits - red/green color blindness
hemophilia -lack of blood clotting factor
occurs in 1 of every 10,000 males
1/3 of caes are due to spontaneous muations