Test #1B- Mendelian Genetics, Genetic Engineering and the Human Genome (Chapters 11, 13 & 14)

Test #5- Mendelian Genetics and Human Heredity(Chapters 11& 14)

I. Heredity Vocabulary

• Heredity –______

• Parental Generation (P1 ) – ______

• Filial Generation (F1 ) – ______

• Pure – ______

______

• Hybrid - offspring of crosses between pure parents with different traits

II. Mendel’s Experiments and Results

• Mendel crossed two pure traits and saw that only one of the traits appeared in the F1 generation, only to reappear in the F2.

• Mendel concluded that something inside the plant controlled which of the two traits appeared, he called it a factor. What Mendel called a factor, we call a ______.

• Mendel concluded that since there were two forms of every trait/characteristic he studied (height, color, seed texture, etc.) that there were two factors/genes controlling each trait.

• Gene – ______

• Allele – Alternate forms of a trait (tall vs. short, round pea vs. wrinkled pea, etc.)

Mendel’s Principles (based on observational evidence without the help of microscopes, chemical evidence, etc...)

Why is Gregor Mendel called the “Father of Genetics” – ______

______

1.Principle of Dominance & Recessiveness – When 2 different factors for the same trait appear in a organism, 1 factor (or “gene”) will dominate or be expressed, while the other factor/ gene will not appear or be expressed.

*Ex. tall pea plant X short pea plant = tall pea plant

1. Principle of Segregation – Since all organisms have 2 factors/genes for each trait, then

during the making of sex cells (meiosis) there must be a

separation of factors, one to each new sex cell (during

anaphase).

1. Principle of Independent Assortment – Factors for different traits are not connected,

they are sent to sex cells independent of each

other (just because the plant was tall it need not have round seeds).

What could cause the Principle of Independent Assortment to be incorrect? -

* How far apart different genes are on a

chromosome is indicated by how often

the genes are found together. Linked

genes do not assort independently, they

tend to get sent to sex cells together

because they are so close to each other

on the chromosome. This information

has helped scientists build chromosome

maps.

Many organisms are used today to study heredity. Zebrafish and Fruit Flies are just a couple of examples.

Why are these good organisms to study –

**

**

**

IV. Genetic Crosses

Dominant alleles will be symbolized with a capital letter (T), Recessive alleles with a lower case letter of the dominant allele (t).

Genotype – The actual genes an organism possesses (TT, Tt, tt) - one from each parent

Phenotype – The outward appearance of the organism, which is determined by its genotype

(TT = Tall, Tt = Tall, tt= short)

Homozygous – ______

Heterozygous – ______

Probability – The likelihood that a specific event will occur. It can be expressed as a decimal, percentage, fraction, or a ratio.

Ex. Flipping a coin. What is the chance of getting 1 heads?

What is the chance of getting 3 heads in a row?

Punnett Square – A tool used to predict the genotypes and phenotypes of genetic crosses.

How to set up a punnett square:

1)Identify and abbreviate all known alleles (T = tall, t = short)

2)Write the genotype of the parents to be crossed (Tt x tt)

3)Draw a punnett square and put one parent across the top and the other down the side.

4)Complete the punnett square. Place the parental alleles in the empty boxes of their corresponding row/column.

5)List all genotypes and phenotypes in probability form.

Offspring Genotypes: Tt = 50%Offspring Phenotypes:Tall = 50%

tt = 50%Short = 50%

1. Simple Dominance and Recessiveness

Tall is dominant to short. Cross two parents who are both heterozygous for height.

Alleles =

Parental Genotypes:

Offspring Genotypes:

Offspring Phenotypes:

1. Codominance – When both forms of a trait are dominant. The resulting phenotype for a heterozygous offspring is a combination of the two traits. Ex: White x Red = red + white speckles (Roan)

Both Red ( R ) and White ( W ) are dominant. RW would be both red and white and look roan. Cross a red horse with a white horse.

Alleles =

Parental Genotype =

Offspring Genotype =

Offspring Phenotype =

1. Incomplete Dominance – When neither form of a trait is dominant. The resulting phenotype for a heterozygous offspring is usually a mix. Ex: White x Red = Pink

Neither red nor white is dominant. In incomplete dominance, heterozygotes would look pink. Cross two pink flowers.

Alleles =

Parental Genotypes:

Offspring Genotypes:

Offspring Phenotypes:

1. Multiple Alleles- When more than two alleles (forms of a trait) determine the phenotype

Alleles = A, B, O (A and B are both dominant, while O is recessive)

Blood Types: AA (homo) or AO (hetero) = Type A BB (homo) or BO (hetero) = Type B

AB = Type AB OO = Type O

Heterozygous Type A x Homozygous Type B

Alleles:

Parental Genotypes:

Offspring Genotypes:

Offspring Phenotypes:

1. Genetic Problems involving Two Traits:

Alleles: T = Tall, t = short, R = Round, r = wrinkled

Homozygous dominant for Height & Homozygous recessive for Seed Texture x Heterozygous for both traits

Parental Genotypes:

Offspring Genotypes:

Offspring Phenotypes:

F.Sex-linked TraitsSperm (male)Eggs (female)

1. Sex Determination

a)Sex Chromosomes – Chromosomes that determine the gender of an organism (XX = female, XY = male).

b)Autosomes – ______

(22 pair in human body cells).

Human cells -2 sex chromosomes

Males - ______

Females- ______

+44 autosomes = _____ chromosomes per cell

1. Sex linked punnett squares

Sex-linked traits are those carried on the X chromosome, such as colorblindness or male pattern baldness:

N = Normal Visionn = colorblind

Possible female genotypes: XN XN = ______X N Xn = ______X n Xn = ______

Possible male genotypes: XN Y = Normal Xn Y = Colorblind male

What does “carrier” mean? Why can’t males be carriers for sex-linked traits? ______

Cross a normal visioned male with a carrier female

Parental Genotypes:

Offspring Genotypes:

Offspring Phenotypes:

V. Genetic Disorders: Some diseases can be inherited from our parents through alleles that they pass down.

A. Chromosomal abnormalities

1.Down Syndrome: Caused by a trisomy (3) of chromosome 21; produces mild

to severe mental retardation. Most common cause is

non-disjunction- ______

______

2.Turner’s Syndrome: Caused by a missing X chromosome (genotype XO). Most women with Turner’s

syndrome are sterile because their sex organs do not develop during puberty.

3. Klinefelter’s Syndrome: Caused by an extra sex chromosome (genotype XXY). Men with this disorder

have underdeveloped sex organs, abnormally long legs and arms, and large hands.

B. Dominant Allele

1. Achondroplasia: The most common form of dwarfism.

2. Huntington's disease: Symptoms develop in the 30's when the nervous system begins breakingdown.

C. Codominant Allele

1. Sickle cell disease: Sickle-shaped blood cells develop that can cause blockage in blood vessels.

1. Recessive Allele

1. Tay-Sachs disease: Results in nervous system breakdown and death in the early years.

2. Cystic Fibrosis: Excess mucus is present in the lungs, the digestive tract, and the liver. People with CF

are more susceptible to infections, respiratory and digestive problems

E. Sex-linked Recessive Disorders

1. Hemophilia: Missing a protein necessary for blood clotting. People with this disease can die from a minor cut.

2.Color blindness: Symptoms can vary from difficulty distinguishing similar colors to complete absence of color vision.

VI. Human Heredity

Pedigree – A family record that shows how a trait is inherited over several generations. It is useful in helping determine the risk of having a child with a family disease

Pedigree Key:

In humans, Albinism is a recessive trait. The disorder causes a lack of pigment in the skin and hair making an albino appear very pale with white hair. Fill in the genotypes of all individuals.

What phenotypes would these genotypes have: NN=normal Nn = ______nn = ______

How many generations are depicted in this pedigree?

How many children does the initial couple have?

What are the sexes of those children?

How many great grandchildren does the initial couple have?

How many individuals in this pedigree are carriers of albinism?

Test #5 Format: Genetics Test Date: ______

Multiple Choice from the notes:

• Gene: ______

• Allele: ______

• Principle of Dominance and Recessiveness: ______

• Principle of Segregation: ______

• Principle of Independent Assortment:______

• Phenotype: ______

• Genotype: ______

• Homozygous: ______

• Heterozygous: ______

• Probability: ______

• Multiple alleles: ______

• Codominance: ______

• Incomplete Dominance: ______

• Down Syndrome: ______

• Turner’s Syndrome: ______
• Klienfelter’s Syndrome: ______

• Achondroplasia: ______

• Huntington’s Disease: ______

• Sickle Cell: ______

• Tay Sach’s: ______

• Cystic Fibrosis: ______

• Hemophilia: ______

Written Questions –

• Be able to work through a pedigree problem (determine which individuals would be heterozygous, identify what the symbols on the pedigree mean, be able to write out the genotypes of individuals on the pedigree)

• Be able to work through four (4) punnett squares (could include dominant/recessive, blood typing, sex-linked, codominance, and incomplete dominance).

1