LABORATORY 4 Name: Name: Genetic LEARNING OBJECTIVES Know how to use the

LABORATORY 4

Name: Name:

Genetic

LEARNING OBJECTIVES

Know how to use the template stand of DNA and make the coding strand.

Be able to translate the coding stand of DNA in m-RNA.

Be able to translate m-RNA into amino acid polypeptide (protein).

Introduction: From DNA to Protein

DNA is a double helix compose of a template strand and coding strand. The two strands are link by their nitrogenous bases, which are pairs together in the following way: Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C). The DNA coding strand is transcribed in messenger RNA (m-RNA), where all the Thymine (T) is change to Uracil (U). The m-RNA exit the nucleus and join the ribosome, which will translate the m-RNA into a polypeptide of amino acids (create a protein). The translation between the nucleic acids code of m-RNA to the amino acids code of protein is done using the table below.

Activity 1. From DNA to Protein

Using the following template strand of DNA, please write the complementary coding strand of the DNA molecule, transcribe the coding strand DNA in m-RNA and finally into amino acids using the table.

Introduction: The genotype and phenotype of offspring

The fertilisation of an egg by the sperm brings together the 23 chromosomes from the male with 23 chromosomes from the female to create a baby with 46 chromosomes. Each pair of the 23 chromosomes, called homologous chromosomes, have the same gene for a specific trait (eye colour, hair colour, etc.). However, this pair of chromosomes may differ in the specific information, for example both chromosomes will have a gene for the colour of the eyes, but each chromosome may code for a specific colour (blue, brown, etc.). This variation in information for a same gene is called an allele. If the person has the same allele, given by both parents (blue eyes allele from the mother and father side) it will be called homozygous alleles (b, b). If the allele differs, it will be called heterozygous alleles (B, b). If one allele is always express when heterozygous, it is called a dominant allele, if it’s not express when heterozygous it’s a recessive allele. If both alleles are expressed at the same time, it is called codominance. The physical expression of a trait is called its phenotype and the allele version of the gene is called the genotype (ex.: blue eye phenotype have a b, b allele genotype.

Activity 2. Find the phenotype and genotype using a Punnet squares

One parent is homozygous for brown hairs (B, B) while the other is homozygous for blond hairs (b, b). Knowing that the brown allele is dominant, determine the proportion of phenotype and genotype of their babies using a Punnet square (Each square must have the genotype allele and phenotype).

Both parents are heterozygous for brown hairs (B, b). Knowing that the brown allele is dominant, determine the proportion of phenotype and genotype of their babies using a Punnet square (Each square must have the genotype allele and phenotype).

Blood types have codominant A and B alleles, while the O allele is recessive. Tell all the possible blood type of their children’s. Remember that blood type may have hidden recessive alleles (Blood type A phenotype, may have the genotype A, A or A, O).

Female: A

Male: A

All possible blood type of the children’s

Genotype

Phenotype

Female: AB

Male: O

All possible blood type of the children’s

Genotype

Phenotype

The Charlie Chaplin case. In 1941, Charlie Chaplin became romantically involved with a young actress named Joan Barry. In 1943, twenty months after the relationship ended, she had a child and claimed Charlie Chaplin as the father. A paternity suit ensued. Chaplin had type O blood. Barry had type A blood. The baby had type B blood. Was the baby Chaplin’s? What’s your evidence?

A father with type B blood and a mother with type O blood have a baby with type O blood. What is the father’s genotype?

Introduction: Sex-link inheritance

Some traits can be transmitted to the offspring on the sex chromosomes (X or Y). Since, male (XY) and female (XX) have different pair of sex chromosomes, the phenotypic effect of those alleles, especially the recessive one, will affect male and female differently. Male will be more susceptible to sex-link inherited genetic disease, since they only have one of each sex chromosomes (Y or a X), thus they will express the mutated recessive alleles 100% of the time. Female on the other hand, have two sex chromosomes (XX) and are twice less likely to receive 2 mutated alleles from their parents and thus will have less genetic sex link disease compared to male.

Activity 3. Sex-link inheritance

Hemophilia is a genetic disorder located on an allele on the X chromosome. Using the following pedigree of a royal family, tell me

What are the phenotypes and genotypes of the male and female grandparents (P generation)?

What are the phenotypes and genotypes of the parents of the two boys (F1 generation)?

What are the phenotypes and genotypes of the two boys in the F2 generation?

In this pedigree there is not female with hemophilia. Tell me all the combination of parents (phenotype and genotype) that would be needed to have a female offspring with a hemophilia phenotype.