Genetics and Heredity

DNAD.N.A. - Deoxyribonucleic Acid Molecule made of:

1. Deoxy Sugar2. Combination of four nitrogen bases

Either: a. Guanineb. Cytosinec. Thymined. Adenine

COOL FACT!: The sum total of combinations that these four bases are capable of creating are greater than all the stars visible in the night time sky!!

DNA• Nitrogen bases pair up

– Cytosine & Guanine– Thymine & Adenine

• Pairing creates a ladder shape• Angle of bonds creates a twist

Ladder and Twist produces the famous“Double Helix”

DNA

• DNA resides in all cells– Inside the nucleus

• Each strand forms a chromosome

CellNucleus

DNA

DNADNA is found in all living cells

– It controls all functions inside a cell

– It stores all the genetic information for an entire living organism

– Single cell like an amoeba– Multi cell like a human

Why do we study DNA?We study DNA for

many reasons:• its central

importance to all life on Earth

• medical benefits such as cures for diseases

• better food crops.

Chromosomes and DNA

• Chromosomes are made up of genes.

• Genes are made up of a chemical called DNA.

One Strand of DNA

• The backbone of the molecule is alternating phosphate and deoxyribose, a sugar, parts.

• The teeth are nitrogenous bases.

phosphate

deoxyribose

bases

Nucleotides

C C

C

OPhosphate

O

C

C

O -P O

O

O

O -P O

O

O

O -P O

O

O One deoxyribose together with its phosphate and base make a

nucleotide.

Nitrogenous base

Deoxyribose

Do Now!

• Where is DNA located?

• What does it look like?

• What are its bases?• Why do you think

DNA is located there?

DNA by the numbers• Each cell has

about 2 m of DNA.• The average

human has 75 trillion cells.

• The average human has enough DNA to go from the earth to the sun more than 400 times.

• DNA has a diameter of only 0.000000002 m.

The earth is 150 billion mor 93 million miles from the sun.

What’s the main difference between DNA and RNA

RNA

• In RNA Thymine is replaced by Uracil

• A-U (RNA)• not• A-T (DNA)

• IF the DNA strand is GTACCAGATTAGC• What would the RNA strand be?

Transcription

• When a secretary transcribes a speech, the language remains the same. However, the form of the message changes from spoken to written

Transcription

• Transcription- RNA is made from a DNA template in the nucleus.

• This type of RNA is called messenger RNA or mRNA

Transcription

• DNA is protected inside the nucleus.

• mRNA carries the message of DNA into the cytoplasm to the ribosome's

Translation

• To translate English into Chinese requires an interpreter.

• Some person must recognize the worlds of one language and covert them into the other.

tRNA Transfer RNA

• The cells interpreter

• tRNA translated the three-letter codons of mRNA to the amino acids that make up protein.

Codon

• The flow of information from gene to protein is based on codons.

• A codon is a three-base word that codes for one amino acid

Information Flow: DNA to RNA to Protein

Genetics The study of heredity, how traits are passed from

parent to offspring

x =or

or

What is it?!• Genetics is the study of genes.

• Inheritance is how traits, or characteristics, are passed on from generation to generation.

• Chromosomes are made up of genes, which are made up of DNA.

• Genetic material (genes, chromosomes, DNA) is found inside the nucleus of a cell.

• Gregor Mendel is considered “The Father of Genetics"

GeneticsSmall sections of DNA are responsible for a

“trait”. These small sections are called “Genes”.– Gene - A segment of DNA that codes for a specific

trait– Trait - A characteristic an organism can

pass on to it’s offspring through DNA

Gene

Genetics

Hair color is a perfect example of a trait

Prince Charming is blond Snow White has dark hair

What color hair should their children have?

Genetics

There are three basic kinds of genes:– Dominant - A gene that is always expressed and

hides others– Recessive - A gene that is only expressed when a

dominant gene isn’t present– Codominant - Genes that work together to

produce a third trait

GeneticsDominant and Recessive Genes• A dominant gene will always

mask a recessive gene.

• A “widows peak” is dominant, not having a widows peak is recessive.

• If one parent contributes a gene for a widows peak, and the other parent doesn’t, the off- spring will have a widows peak.

Widows Peak

TERMS TO KNOW

ALLELES DIFFERENT FORMS OF A TRAIT THAT A GENE MAY HAVE T,t

HOMOZYGOUS AN ORGANISM WITH TWO ALLELES THAT ARE THE SAME TT, tt

HETEROZYGOUS AN ORGANISM WITH TWO DIFFERENT ALLELES FOR A TRAIT Tt, Gg

TERMS TO KNOWHYBRID SAME AS

HETEROZYGOUS Tt, GgDOMINANT A TRAIT THAT

DOMINATES OR COVERS UP THE OTHER FORM OF THE TRAIT

REPRESENTED BY AN UPPERCASE LETTER

T OR GRECESSIVE THE TRAIT BEING

DOMINATED OR COVERED UP BY THE DOMINATE TRAIT

REPRESENTED BY A LOWER CASE LETTER

t or g

TERMS TO KNOW

PHENOTYPE THE PHYSICAL APPEARANCE OF AN ORGANISM(WHAT IT LOOKS LIKE)

TALL, SHORT, GREEN, WRINKLED

GENOTYPE THE GENE ORDER OF AN ORGANISM(WHAT ITS GENES LOOK LIKE)

TT, GG, Tt, ggGg, tt

RATIO THE RELATIONSHIP IN NUMBERS BETWEEN TWO OR MORE THINGS

3:1, 2:2, 1:2:1

Gregor Mendel

• Austrian Monk.• Experimented with “pea plants”.• Used pea plants because:

– They were available– They reproduced quickly– They showed obvious differences in the traits

Understood that there was something that carried traits from one generation to the next.

Mendel’s Pea PlantsMendel based his laws on his studies of garden pea plants. Mendel was able to observe differences in multiple traits over many generations because pea plants reproduce rapidly, and have many visible traits such as:

Plant Height

Tall Short

Pod color

Seed Shape

Pod Shape

Seed Color

Green Yellow

Green Yellow

RoundWrinkled

Smooth Pinched

To test the hypothesis, Mendel crossed true-breeding plants that had two distinct and contrasting traits—for example, purple or white flowers.

What is meant by “true breeding?”

Mendel cross-fertilized his plants by hand. Why is it important to control which plants would serve as the parents?

Mendel’s ExperimentsMendel noticed that some plants always produced offspring that had a form of a trait exactly like the parent plant. He called these plants “purebred” plants.

EXAMPLE: -purebred short plants always produced short offspring purebred tall plants always produced tall offspring.

X

Purebred Short Parents

Purebred Tall Parents

X

Short Offspring

Tall Offspring

Mendel’s First ExperimentMendel crossed purebred plants with opposite forms of a trait. He called these plants the parental generation , or P generation. For instance, purebred tall plants were crossed with purebred short plants.

Parent TallP generation

Parent ShortP generation

X

Offspring TallF1 generation

Mendel observed that all of the offspring grew to be tall plants. None resembled the short short parent. He called this generation of offspring the first filial , or F1 generation, (The word filial means “son” in Latin.)

Mendel’s Second ExperimentMendel then crossed two of the offspring tall plants produced from his first experiment.

TallF1 generation

X

3⁄4 Tall & 1⁄4 ShortF2 generation

Mendel called this second generation of plants the second filial, F2, generation. To his surprise, Mendel observed that this generation had a mix of tall and short plants. This occurred even though none of the F1 parents were short.

Parent Plants Offspring

Mendel studies seven characteristics in the garden pea

How is it possible to maintain such genetic continuity?

Martin SheenCharlie Sheen

Emilio Estevez Kirk Douglas Michael

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