Sex Linked Traits Lecture

Genetics Unit Solving Genetics Problems Upon the completion of this unit the learner will be able to:

1. Apply genetic terminology while solving five types of genetic problems.

2. Predict the genotypes of organisms within a pedigree.

Vocabulary Genetics

Chromosome

Dominant

Recessive

Homozygous

Heterozygous

Hybrid

Purebred

Homozygous Dominant

Homozygous Recessive

Pedigree

Genotype

Phenotype

Punnett Square

Monohybrid

Dihybrid

Parental Generation

F1 Generation

F2 Generation

1 Genetics Vocabulary Lecture Heredity.

Allele –

Gene –

Dominant trait –

Recessive trait –

Homozygous – (Purebred)

Heterozygous – (Hybrid)

Genotype – the DNA for a trait, i.e. R or r.

Phenotype – the appearance of a trait determined by a genotype, i.e. round or wrinkled peas. Seven Steps: Cross a hybrid white flower with a homozygous purple flower.

2 Sex Linked Traits Lecture The study of inheritance of genes located on sex chromosomes was pioneered by T. H. Morgan and his students at the beginning of the 20th century. Although Morgan studied fruit flies, the same genetic principles apply to humans. Since males and females differ in their sex chromosomes, inheritance patterns for X-chromosome linked genes vary between the sexes What are sex chromosomes?

What are sex-linked traits?

Which sex chromosome is home of the most sex-linked traits

What are examples of traits that are sex-linked?

1) Color blindness – (red-green)

2) Hemophilia –

3) Muscular Dystrophy –

What letters should we use to designate these normal and mutant traits? B = ______b = ______H = ______h = ______M = ______m = ______

How should we write these genotypes to help us remember they are sex-linked?

Color Vision Color Vision Genotypes Phenotypes XBXb

Complete this chart: Genotypes Phenotypes XHXh Man with hemophilia Normal Vision Girl XMY Woman carrier of muscular dystrophy

3 Try This: Cross a colorblind male with a carrier female with healthy vision

5. & 6.

7. Chance of Normal ______Chance of Carrier ______Chance of colorblind ______Incomplete Dominance Lecture

Sometimes genes that are present to not completely dominate their other allele. In these cases the end result is a blend of the two phenotypes. All genes in the problems today are Incompletely Dominant.

Example: Some species of flowers when you cross a red petal and a white petal produce a pink petal. We change the nomenclature to show the user what is happening in these problems. 1. Dominant = Red, Recessive = White, Incomplete = Pink 2. Red = R, White =W, Pink = RW 3. Crossing a red and a white = RR x WW 4. Sperm = R or R Egg = W or W 5. & 6.

7. What are the chances for: Red ______Pink ______White ______

4 Blood Type Lecture Multiple Alleles

So far we have been working with traits that are usually either/or situations. Tall or short, green or yellow. Sometimes there are more then two choices. Human eye color is one example of this. Human blood type is another example.

There are many different ways that we type blood. Today, we’ll look at two systems, ABO and the Rh- factor.

ABO Typing: Each red blood cell has proteins on its surface that let the body identify it as belonging to yourself.

Blood Type Antigen Antigen Antibody Antibody  G A B Anti-B anti-A A yes no no yes e ne B no yes yes no O no no yes yes s “A” and “B” are SB yes yes no no ______genes.

 Gene “o” is the ______gene.

Sample Problem: Mom is hybrid type B blood, Dad is hybrid type A blood. 1.

5. & 6.

7. Chance of Each Blood Type:

5 Rh Factor Blood Type

Rh+ means that

Rh- means that

The dominant gene is ______

The recessive gene is ______

Let’s assign letters for each genotype:

Phenotype Genotype Rh+ Rh-

Try This: Dad is heterozygous Rh+ factor and mom is homozygous for Rh- factor blood.

5. & 6.

7. Chance of each blood type ______

Does this type of problem remind you of a type you’ve already done?

Note: There is a danger if a mom with Rh- blood has a Rh+ fetus in her body her antibodies may attack the fetus and cause her to be sick or die.

6 Pedigree Lecture Pedigree –

A sample pedigree

Symbol Description

Unaffected male

Unaffected female

Label the following on your pedigree: P generation, F1 generation, Affected male F2 generation.

Affected female

Deceased male Example #2:

Deceased female

Possibly affected male

Possibly affected female

Carrier male

Carrier female

7 Dihybrid Lecture

1. Definition –

Try This: Given B = brown hair, b = blond hair AND T = Tall while t = short.

BbTt = ______phenotype Bbtt = ______phenotype bbTT = ______phenotype bbtt = ______phenotype

2. When drawing your sperm and egg for the 7 steps in this type of problem each: a. Sperm contains ______genes? b. Egg contains ______genes? 3. Predict the sperm or eggs possible for a critter of BbTt.

4. Arrow Rule:

5. What sex cells could be obtained from the genotypes below?

a. Bbtt: ______, ______, ______, ______b. bbtt: ______, ______, ______, ______c. BBTT: ______, ______, ______, ______d. BbTt: ______, ______, ______, ______e. Hint repeated sperm or eggs can be crossed out. 6. Cross a totally heterozygous brown eyed tall girl with a heterozygous brown eyed homozygous tall guy.

8 Multiple Genes Lecture

For many traits there are two or more genes the produce variations of one trait. For example, 6 pairs of genes, determine one’s skin color. This results in 4,096 different genotypes of skin color.

Example: The redness of some wheat kernels seems to be determined by two pairs of genes acting in an additive way. 1. Four dominant genes produce very, dark red kernels. 2. Three dominant genes produce dark red kernels. 3. Two dominant genes produce a medium red kernel. 4. One dominant gene produces a light red kernel. 5. A lack of any dominant genes produces a white kernel.

If R and S are genes related to the redness of wheat kernels (r and s represent the lack of redness) what will the phenotypes of each of the following genotypes be?

RrSs RrSs RRss Rrss RrSS RRSS

Give the different genotype combinations that could be present in each of the above genotypes: (Hint: The arrow rule)

Cross medium red wheat (RrSs) with dark red wheat (RrSS).