GENETICSGENETICSPart 3Part 3

Contents:

Review, DNA Song, A-T & C-G,

RNA: transcription, translation, codons, amino acids

Video: 29 min.

Codon Wst

Website: How Does DNA Work?

REVIEW:

REVIEW:

Most human cell have a

nucleus that contains 23

pairs of chromosomes

which are made of DNA.

p. 194

Nucleic acids – DNA (deoxyribonucleic acid) and RNA (ribonucleic

acid)

Nucleotides – 3 parts: a sugar (deoxyribose), a phosphate group and a

nitrogen base.

In DNA these form a series of units called

genes = encoded information about how the organism will grow

and develop.

 DNA SONG: (sung to Row, Row, Row Your Boat)

We love DNA made of

nucleotides, sugar, phosphate, and a

nitrogen base bonded down each

side.

Oh! Deoxyribonucleic

acid, RNA is ribonucleic acid

DNA – double helix that encodes the sequences of all the cell’s proteins, as well as information that determines when each protein is to be made.

Bundles of protein – DNA are called chromosomes. Made up of 4 bases: (p.195)

Purines – adenine and guanine (2 larger bases)

Pyrimidines – cytosine and thymine (2 smaller bases)

  Adenine + Thymine (A = T)

Cytosine + Guanine (C = G)

 DNA SONG: (sung to Row, Row, Row Your Boat)

We love DNA made of nucleotides, sugar, phosphate, and a nitrogen base bonded down

each side.

Oh! Deoxyribonucleic acid, RNA is ribonucleic acid

Adenine and Thymine make a lovely pair, Cytosine without Guanine would feel very bare.

Printout from a DNA sequencer showing the peaks and valleys of a portion of a sequenced gene that correspond to the color-coded bases adenine A,

thymine T, guanine G and cytosine C. In this particular section of 34 bases, there are 434 = 2.951479 X 1020 or about 295 quintillion different

possible sequences. In the San Diego trial of David Westerfield, the probability of a blood sample in his motor home matching the murder

victim's DNA was 25 quadrillion to one.

Replication – process of copying DNA before the cell can divide. The DNA will “unzip” to separate the bases, and then the exposed base will find its complimentary partner. p. 198

A - T

T - A

T -

G - C

C -

A -

T -

A - T

T - A

T - A

G - C

C - G

A - T

T - A

The difference between deoxyribose (DNA) and ribose (RNA)?

Deoxyribose (DNA) Ribose (RNA)

In RNA uracil (U) replaces thymine as a base.

RNA – (ribonucleic acid) makes the protein. p. 208

Made of 4 bases: adenine, guanine, cytosine, and uracil (U).

A – U

C – G

T – A

G -

A –

A –

T -

A – U

C – G

T – A

G - C

A – U

A – U

T - A

For a cell to make protein, the information from a gene is copied, base by base, from DNA into new strands of messenger RNA (mRNA). Then mRNA travels out of

the nucleus into the cytoplasm, to cell organelles called ribosomes. There, mRNA directs the assembly of amino

acids that fold into completed protein molecule.

Gene expression – use of genetic information in DNA to make proteins – 2 stages -

1. transcription – a RNA copy of the gene is made. Information encoded in DNA is transferred to mRNA (messenger RNA – p. 212) molecule.

* It must be copied because the DNA cannot leave the nucleus.

2. translation – three different kinds of RNA work together to assemble amino acids into a protein molecule.

Every 3 nucleotides in mRNA specify a particular amino acid = codon. The order of bases in the codon determines which amino acids will be added to a growing protein chain. The order of amino acids will determine the structure and function of a protein.

EX. UUU = amino acid phenylalanine.

Codons (groups of 3 nucleotides) make amino acids (p. 211)

The final protein molecule may

consist of several hundred amino

acids linked together according to the

instructions encoded in the mRNA.

For example, the mutation toward sickle cell anemia is based upon the production of one different amino acid, which in turn

affects the polypeptide strands produced, etc.

Mutations are usually non-beneficial to an organism, however, they are almost always recessive and unless two mutations are coupled together

the mutation will not be expressed.

Protein or DNA? It was not until 1944 that scientist proved DNA was the genetic material in our cells.

Many scientist found it hard to believe the DNA was the hereditary material instead of protein.

Protein has 20 different amino acids that can be combined in a variety of ways. DNA consists of basically 4 nucleotide bases.

Scientist reasoned that the complex processes involved in heredity would be controlled by something complex.

Proteins help determine the structure of cells and increase the rates of chemical reactions, such as those that occur during metabolism and photosynthesis.

There are 20 amino acids that

combine to make all

the protein in your body.

 DNA SONG: (sung to Row, Row, Row Your Boat)

We love DNA made of nucleotides, sugar, phosphate, and a nitrogen base bonded down each

side.

Oh! Deoxyribonucleic acid, RNA is ribonucleic acid

Adenine and Thymine make a lovely pair, Cytosine without Guanine would feel very bare.

Video: DNA / RNA / Protein Synthesis 29 min.

Worksheet: Central Dogma and Codons

Worksheet: How Does DNA Work?

http://www2.edc.org/weblabs/WebLabDirectory1.html