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 50-50 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 50-50

from both parents.

The 23rd 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

Trait2nd

D2nd

R3rd

D3rd

R4th

D4th

R6th

D6th

R7th

D7th

R

TEAMD

TEAMR

Tongue Rolling 31 13 35 6 28 4 35 8 26 7 155 38

Polydactyl 0 44 2 39 0 32 1 42 0 33 3 190

Eye Wink 40 4 30 11 23 9 38 5 26 7 157 36

Mid-Digital Hair 14 31 9 32 18 14 24 19 7 26 72 122

Dimples 13 31 14 27 15 17 28 15 14 19 84 109

Hairline 17 27 12 29 12 20 18 25 14 19 73 120

Earlobes 35 9 30 11 24 8 31 12 25 8 145 48

Interlocking Finger 33 11 23 18 20 12 32 11 25 8 133 60

Sample Graph

Dominant or Recessive

0

50

100

150

200

TongueRolling

Polydactyly Eye Wink Mid-DigitalHair

Dimples Hairline Earlobes InterlockingFinger

Trait

# of S

tude

nts TEAM-D

TEAM-R