Introduction to Genetics

Fact or Fiction?

Man is the highest of the animals; therefore, he has the most chromosomes. FALSE

No one really knows what determines the number of chromosomes in an organism, though related species tend to have similar chromosome numbers. This is because chromosomes may split or combine during evolution and speciation. While humans have 46, other great apes have 48. It is important to remember that the chromosome number has nothing to do with how "advanced" a species is. Horses, dogs, and several species of ferns have more than we do.

An injury suffered in an accident will be passed on to one’s children. FALSE

You get 23 chromosomes from each parent. 1 of the 23 chromosomes determines whether you are male or female. The other 22 chromosomes (Autosomal DNA) pretty much determine your genetic profile. You get Autosomal DNA from both parents. The two germ cells, male sperm and female egg, have chromosomes with DNA in them. When the germ cells get fused they form a zygote and this process is responsible for transferring the character from parent to offspring.

If your parents both have brown eyes, you will definitely have brown eyes. FALSE

Genetics is all about PROBABILITY. There is a very high percentage that you will because brown eyes is a dominant trait. But then again you should also look at your grandparents, aunts and uncles, because anyone in your gene pool has had an affect on what color eyes you will have. But in most cases, yes, you will most likely have brown eyes.

You have inherited traits, which are not apparent. TRUE

All the traits you are going to have in your lifetime you have at the time of conception and is outlined in your genetic map (DNA). However, not all traits are visible at birth. Most traits are “time released” meaning that they present themselves at various stages of growth and development.

In many organisms, the female determines the sex of the offspring. FALSE

The sex chromosomes carry genes that determine whether a person is male or female. The sex chromosomes are the only chromosome pair that do not always match. Since both of a female’s sex chromosomes are X chromosomes, all eggs carry one X chromosome. Males, however, have two different sex chromosomes. Therefore, half of a male’s sperm cells carry an X chromosome, while half carry a Y chromosome.

Each person inherits exactly half of his genetic makeup from each parent. TRUE

When the male sperm and female egg get fused during fertilization the phenomena of CROSSING OVER takes place which mix all the characters of the parents and the child gets a combination of both of them.

You inherit more from your mother if you are a girl. FALSE

You get 23 chromosomes from each parent. The 22 chromosome pairs with the Autosomal DNA pretty much determine your genetic profile. Your Autosomal DNA is from both parents. The 23 rd chromosome pair, one from each parent, determines your sex and are made up of Y & Mitochondrial DNA. Y goes from father to son only. Mitochondrial goes from mother to both sons and daughters but only the daughters pass it on to their children.

A parent may give a trait to his child without ever having the trait himself. TRUE

A person can carry an allele (code) for a particular gene (trait) that is not visibly present in them. But, because it is part of their DNA they can pass it on to their offspring and it may become visible in their offspring or even future generations of offspring within their family.

If you resemble one parent more than the other, you probably inherited more from that parent. FALSE

Because children inherit alleles (codes) for genes (traits) from their mother and father, children often look like both of their parents. If a child resembles one parent over another it is because one parent may have a stronger (dominant) gene pool.

You have all the hereditary traits you are ever going to have at birth. TRUE

All the traits you are going to have in your lifetime you have at the time of conception and is outlined in your genetic map (DNA). Most traits are “time released” and will present themselves at various stages of growth and development.

Human Genetics Lab

Background Knowledge Gregor Mendel developed the basic principles of genetics that are still used today in our current study of heredity. Using pea plants, observing multiple generations and thousands of offspring, Mendel determined that most traits are controlled by genes with two alleles. –Dominant –Recessive

Lab Objective How frequently do certain dominant and recessive phenotypes occur in humans? PHENOTYPE – AN ORGANISM’S PHYSICAL APPEARANCE, OR VISIBLE TRAITS.

Question / Hypothesis Does the dominant form of a trait always occur more often within a population than the recessive form?

Tongue Rolling

Polydactyly

Eye Wink

Mid-Digital Hair

Dimples

Hairline

Earlobes

Interlocking Fingers

General Procedure Read all instructions for this activity before you begin your work. Collect and Analyze Data. –Record your phenotype for each trait in the data table. –Report your data. –Record the “class” data for each trait in the table.

Data Table Trait 2 nd D 2 nd R 3 rd D 3 rd R 4 th D 4 th R 6 th D 6 th R 7 th D 7 th R TEAM D TEAM R Tongue Rolling Polydactyl Eye Wink Mid-Digital Hair Dimples Hairline Earlobes Interlocking Finger

Sample Graph