Chapter 8 Mendel and hereditySection 1: The Origins of
GeneticsI. Mendels Studies of Traits- _______________________ - the
passing of traits from parents to offspring. Ex. of traits
-______________________________________
A. Mendels Breeding Experiments
1. Gregor Mendel An Austrian monk, considered to be the father
of genetics. Mendel used ________________ _________________ in his
experiment. _______________________- is the branch of biology that
focuses on heredity.
B. Useful Features in Peas
a. Mendel used these plants because:
-The traits exist in _______________________________________(see
table one) Ex. ____________________________________________
b. The male and female _____________________________ are
enclosed within the same flower. You can control mating by allowing
a flower to fertilize itself
(_________________________________________), or you can transfer
the pollen to another flower on a different plant
(_______________________
______________________). Explain cross pollination:
___________________________
__________________________________________________________________________________
c. Garden peas are ____________________,
_______________________, ______________________ and
___________________________________
II. Traits Expressed as Simple Ratios
1. ______________________________________ is a cross that
involves one pair of contrasting traits. Ex.
___________________________________________
2. Three steps of Mendels Experiment:
a. He allowed each variety of peas to
_____________________________ for several generations. Each variety
was ___________________________ for a particular trait. That is all
the offspring would display only ______________
________________________________________. These plants were the
________________
____________________ or P generation.
b. He then _______________________________2 P generation plants
that had contrasting forms of a _________________, such as
______________________
and ______________________. Mendel called the offspring of the P
generation the first ____________________________ or the
______________________________________
c. Mendel allowed the F1 generation to
________________________________
d. He called the offspring the _______________________________
or the
___________________________________.
C. Mendels Results
a. Mendels F1 plants showed ___________________________________,
When the F1 generation was allowed to
_____________________________________, the missing trait
_______________________ in some of the plants in the F2 generation.
ex. When Mendel crossed purple and white flowers all the offspring
in the F1 generation were _________________________. When the F1
generation was allowed to self pollinate the F2 generation showed a
_______________________________ ratio of traits.
Section 2 Mendels Theory
I. Theory of Heredity
A. Mendels Hypothesis
1. For each __________________ __________________, an individual
has ____________ copies of a __________________- One from each
parent.
2. There are _______________________________________. ex.
_________________________
Different versions of a gene are called
_______________________________. An individual receives one
_________________________ from each parent.
3. When two different alleles occur together, one of them may be
_____________________________________________, while the other may
have no _________________________________ on the organisms
appearance.
____________________________- is the expressed form of the
trait.
____________________________- is the trait that is not expressed
when the dominant form of the trait was present.
4. When gametes are formed, the alleles for each gene in an
individual separate ______________________________. Thus gametes
carry _________________
_________________________________________________________________________________.
When gametes unite during ____________________________, each
gamete contributes one allele. Draw figure 4.
B. Mendels Findings in Modern Terms
1. __________________________ are used to represent alleles.
2. ___________________________ alleles are indicated by writing
the first letter of the character as a capital. Ex
______________
3. ___________ alleles are indicated by writing the first letter
of the dominant trait but the letter is lower case. Ex.
_____________________
4. __________________________= is when the two alleles of a
particular gene are the same. Ex.
__________________________________
5. ___________________________= when the two alleles of a
particular gene are different.
_________________________________________
6. In heterozygous individuals only the ______________ alleles
is expressed. The ____________ allele is present but not expressed.
Ex. ______________________________
7. ________________________ - is the set of alleles an
individual has for a character. Ex.
_______________________________
8. ____________________________- the physical appearance of a
character . ex. ______________________________________.
C. The Laws of Heredity
Laws of Heredity ________________________________
I. Law of Segregation describes the behavior of chromosomes
during meiosis. ________________ ____________ and then
________________________________. The law of segregation states
that the
____________________________________________________________.
II. The Law of Independent Assortment
a. Dihybrid cross- is a cross that considers
____________________________ of contrasting traits. ex.
___________________________________________________________________
b. Law of Independent Assortment that the
__________________________________________ of one another during
gamete formation. For example, the alleles for the
______________________ of a plant separate independently of the
alleles for its ________________________.
-This law applies only to genes that
are________________________________
___________________________________________________________________________________-The
units of heredity are portions of DNA called
__________________.
The inheritance of one character did not influence the
inheritance of any other character.
Section 3 Studying Heredity
A. Punnett Squares
1. Animal and plant breeders try to produce organisms with
______________ _________________________.
2. Punnett Square a diagram that
__________________________________________
___________________________________________________________________________________
3. Punnett squares consist of 4 or more boxes. The possible
gametes that one parent can produce are
______________________________________________
4. The possible gametes that the other parent can produce are
written
______________________________________________________________
5. Each box inside the square is filled in with 2 letters
obtained by
____________________________________________________________________________________________________________.
The letters in the boxes indicate
___________________________________________
______________________________________________________
Draw figure 8Ratio of phenotypes_______
Ratio of genotypes________
I. One Pair of Contrasting Traits
a. Punnett squares can be used to predict the outcome of
__________________________________________________________________________________.
b. Monohybrid cross -
__________________________________________________________
give 3 examples
________________________________________________________________
c. Homozygous for yellow seed color = _________________
d. Homozygous for green seed color = __________________
e. A cross between these 2 organisms would produce offspring
that are all ________________________________________________.
Punnett square Practice Problems
1. In a certain species of animal, Black fur (B) is dominant
over brown fur (b). Using the following punnett square, predict the
genotypes and phenotypes of the offspring whose parents are both Bb
or have heterozygous black fur.
Genotypes: ____________%homozygous black (BB)
___________%heterozygous black (Bb)
___________% homozygous brown(bb)
Phenotypes:____________% black
____________% brown
2. Now do the same when one parent is homozygous black and the
other is homozygous brown
Genotypes: ____________%homozygous black (BB)
___________%heterozygous black (Bb)
___________% homozygous brown(bb)
Phenotypes:____________% black
____________% brown
3. Repeat this process again when one parent is heterozygous
black and the other is homozygous brown.
Genotypes: ____________%homozygous black (BB)
___________%heterozygous black (Bb)
___________% homozygous brown(bb)
Phenotypes:____________% black
____________% brown
Human Traits practice problems
1. Mom is heterozygous for dimples, dad is homozygous, no
dimples. Dimples are a dominant trait.
2. Dad is homozygous dominant for freckles, mom is homozygous
recessive.
3. Mom is heterozygous for widows peak, dad is homozygous
recessive
-widows peak is dominant
Exploring Further (page 171)
a. _____________________________________ - is a cross that
involves 2 pairs of contrasting traits. Ex.
_____________________________________
b. Determine possible gametes
1. If both parents are heterozygous for pea color and shape
(RrYy) what type of gametes can they produce. The gametes they can
produce are _____________________________________________
Draw figure A
Complete Figure B
II. Determining Unknown Genotypes
a. Animal breeders need to know whether an organism with a
dominant phenotype is _________________________________ or
______________________________.
__________________________________- an individual whose
phenotype is dominant , but whose genotype is not known, is crossed
with _________________________________________ individual.
A. Inheritance of Traits
1. ____________________________- a family history that shows how
a trait is inherited over several generations.
_________________________ are individuals who are heterozygous for
an ________________________________ but do not show symptoms of the
disorder.
2. Albinism the body is unable to produce an
__________________________ necessary for the production of
_________________________.
3. If a trait is autosomal it will appear in both sexes
________________________
*Recall autosomes are
_______________________________________________________
4. If a trait is sex-linked it usually occurs only in
________________________.
5. ___________________________________ - is a trait whose allele
is located on the __________________________________ and are
recessive.
a. Males have only one __________ chromosome, a male who carries
a ________________________ allele on the X chromosome will exhibit
the sex-linked condition. In order for a female to demonstrate a
sex-linked recessive disorder she must have
______________________________ alleles.
8.4 Complex Patterns of Inheritance
I. Complex Control of Characters
A. Characters Influenced by Several Genes
1) Polygenic
inheritance-______________________________________________
__________________________________________________________________
2) The genes for a polygenic __________________________ may be
scattered along the same ____________________________ or located on
___________________ chromosomes.
3) Due to ____________________ ___________________ and
crossing-over during _________________, many different combinations
appear in offspring.
4) Examples of polygenic characters in humans include
_____________, ____________, ______________ and ______________. All
the characters have degrees of intermediate conditions between one
extreme and the other.
B. Intermediate Characters
1) In Mendels pea-plant crosses, one _______________ was
completely ______________ over another.
2) Incomplete
dominance-_______________________________________
____________________________________________________________
Ex.
_________________________________________________________
3) In Caucasians, the child of a ______________________ parent
and a _______________________ parent will have _________________
hair. Wavy hair is a ____________________ and is intermediate
between straight and curly hair.
C. Characters Controlled by Genes with 3 or More Alleles
1) Multiple
alleles-_____________________________________________
_____________________________________________________________
2) Blood type is determined by three alleles ___, ____, and
____.
3) The letters A and B refer to two __________________________
on the surface red blood cells.
4) In the i allele, ____________ carbohydrate is present.
5) The IA and IB alleles are both ____________________ over i.
But neither IA or IB is dominant over the other.
6) When IA and IB are both present they are
________________________.
7) The combinations of the three different alleles produce four
different blood types, ____, ____, _____, and ____ blood.
D. Characters with Two Forms Displayed at the Same Time
1)
Codominance-____________________________________________________
__________________________________________________________________
2) Codominance is different from _________________
_____________________ because both traits are displayed.
3) The situation of human ABO blood groups is an example of
___________________.
4) The genotype of a person who has blood type AB is
___________, and neither allele is ________________ over the other.
Type AB blood cells carry both A- and B- types of carbohydrate
molecules on their surfaces.
E. Characters Influenced by the Environment
1) An individuals phenotype often depends on conditions in the
environment. Hydrangea plants in acidic soil bloom ______________
flowers, while those in ____________ to _______________ soil will
bloom pink flowers.
2) The color of the arctic fox is affected by
______________________. During summer, the fox produces
__________________ thats make ____________________. These pigments
darken the foxs coat to a reddish brown, enabling the fox to blend
in with the summer landscape. During the winter, the
pigment-producing ___________ of the arctic fox do not
________________ because of the cold temperature. As a result, the
coat of the fox is ____________, and the animals _____________ in
with the snowy background.
3) Fur color in Siamese cats is also influenced by temperature.
In a Siamese cat, the fur on its ________, _____________,
___________ and _________ is darker than on the rest of its
body.
4) In humans many traits, such as ______________, are influenced
by the environment. For example, height is influenced by
_________________, an ______________________ environmental
condition.
5) Exposure to the sun, an _______________________ environmental
condition, alters the _______________ of the skin.
6) Many aspects of human __________________________, such as
aggressive behavior, are strongly influenced by the
_____________________, although genes appear to play an important
role.
7) Because identical twins have _______________ ____________,
they are often used to study environmental influences. Because
identical twins are genetically identical, any
________________________ between them are attributed to
environmental influences.
II. Genetic Disorders
1)
Mutations-_________________________________________________
____________________________________________________________
2) Genetic
disorders-___________________________________________
____________________________________________________________
3) Mutations are ______ because cells have efficient
__________________ for correcting errors.
4) Many mutations are carried by ________________ ______________
in heterozygous individuals. This means that two
___________________ normal people who are _______________ carriers
of a recessive ______________ can produce children who are
__________________ for the recessive allele.
A. Sickle Cell Anemia
1) Sickle cell anemia, a condition caused by a ________________
allele that produces a ___________ form of the protein
__________________.
2)
Hemoglobin-___________________________________________________
________________________________________________________________
3) The sickle-shaped cells rupture __________________, resulting
in __________ oxygen being carried by the __________________.
Sickle-shaped cells also tend to get stuck in
_____________________; this can cut off blood supply to an
organ.
4) The recessive ________________ that causes sickle-shaped red
blood cells also helps protect the cells of _____________________
individuals from the effects of malaria.
5)
Malaria-_________________________________________________________
__________________________________________________________________
6) The sickled red blood cells of __________________ individuals
cause the death of the parasite. But the individuals ______________
red blood cells can still transport enough _________________.
7) Therefore, these people are _______________________ from the
effects of malaria that threaten individuals who are
__________________ _________________ for the hemoglobin gene.
B. Cystic Fibrosis
1) Cystic fibrosis is the most common __________,
______________, _________________ disorder among Caucasians.
2) 1 in 25 Caucasian individuals has at least one copy of a
_______________ gene that makes a ________________ necessary to
move into and out of cells.
3) About 1 in ______________ Caucasian infants in the United
States is homozygous for the cf allele.
4) The airways of the lungs become clogged with
____________________, and the ducts of the _______________ and
________________ become blocked.
C. Hemophilia
1) Hemophilia-
_____________________________________________________
__________________________________________________________________
2) Hemophilia is a __________________________ trait.
3) More than a dozen ______________ code for the proteins
involved in ___________ clotting.
4) Hemophilia
A-____________________________________________________
__________________________________________________________________
5) If the mutation appears on the X chromosome, which a male
receives from his ______________, he does not have a _____________
____________ on the Y chromosome to compensate. Therefore, he will
develop _____________________.
D. Huntingtons Disease (HD)
1) Huntingtons disease is caused by a _____________________
allele.
2) In time, HD causes loss of ______________________________,
uncontrollable _____________ spasms, etc.
3) Many people who have HD do not know that they have the
disease until ___________ they have had _________________. Thus,
the disease is _________________ passed on from one
________________________ to the next.
III. Treating Genetic Disorders
1) Genetic
counseling-________________________________________________
__________________________________________________________________
2) Phenylketonuria
(PKU)-_____________________________________________
__________________________________________________________________
Gene Therapy
1) Gene therapy-
____________________________________________________
__________________________________________________________________2)
The cold virus-carrying the normal ________________________-easily
infects _______________ cells.