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.