dna, rna and proteins

DNA, RNA and Proteins

Ms. Hughes

Mendel showed that traits are passed from parent to offspring.

Instructions for how genes are inherited. Genes are made up of segments of DNA:

Deoxyribonucleic acid. DNA is the primary material that causes

recognizable, inheritable characteristics in related groups of organisms.

DNA Genetic Material

DNA is composed of four nucleotide subunits:

◦ Each nucleotide has the same five carbon sugar molecule and phosphate group but different nitrogenous bases: Adenine Guanine Cytosine Thymine

Genetic Material

Winding stair case – 1 Parts of the nucleotide subunits – 2

1’s find another 1 and compare notes! 2’s find another 2 and compare notes!

Shape of DNA

If you are a 1 find a 2 If you are a 2 find a 1

Share your information but DO NOT COPY!!! You must explain it to your partner!!!

Pyrimidines: Thymine and Cytosine Purines: Adenine and Guanine

DNA is in the shape of a spiral stair case/ double helix of two complementary strands of nucleotides.

Information in DNA

A always binds with T G always binds with C

So A=T and G=C

Purine always binds to pyrimidine Watson, Franklin and Crick discovered 3D

model .

Base Pairing Rule

A = T G = C

Base pair rule

Chargaff’s observation

Read and summarize watson and cricks model of DNA.

K,W,L ◦ Knew◦ Would like to learn more about◦ Learned

Activity

Draw, label and explain a strand of DNA including the nucleotide subunits, base pairing and complimentarity of the strands.

Activity/homework

DNA replication: the process of making a copy of DNA.

In DNA replication, the DNA molecule unwinds, and the two sides split. Then new nucleotides are added to each side until two identical sequences result. DNA replication occurs before a cell divides so that each cell has a complete copy of DNA. The basic steps of DNA are:

DNA Replication

DNA replication McGraw Hill

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120076/micro04.swf::DNA%20Replication%20Fork

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The double helix unwinds. Complementary strands of DNA separate

from each other and form Y shapes areas are called replication forks.

Unwinding and Separating DNA Strands

At the replication fork, new nucleotides are added to each side and new base pairs are formed according to the base pairing rules.

The original two strands serve as a template for two new strands.

Adding Complementary Bases

DNA replication produces two identical DNA molecules

Formation of Two Identical DNA Molecules

During the replication of DNA, many proteins form a machinelike complex of moving parts.

Replication Proteins

DNA helicases unwind the DNA double helix during DNA replication.

This process causes the helix to unwind and forms a replication fork.

DNA Helicase

Proteins called DNA polymerases catalyze the formation of the DNA molecule.

The polymerases add nucleotides that pair with each base to form two new double helixes.

DNA polymerases also have a “proofreading” function. During DNA replication, errors sometimes occur, and the wrong nucleotide is added to the new strand. DNA polymerase cannot add another nucleotide unless the previous nucleotide is correctly paired.

DNA Polymerase

In prokaryotic cells, replication starts at a single site. In eukaryotic cells, replication starts at many sites along the chromosome.

Prokaryotic and Eukaryotic

Prokaryotic cells usually have a single DNA molecule, or chromosomes. Prokaryotic chromosomes are a closed loop, may contain protein, and are attached to the inner cell membrane.

Prokaryotic DNA Replication

While prokaryotes have a single chromosome/loop, eukaryotic cells often have several chromosomes.

By starting DNA replication at many sites along the chromosome they can replicate their DNA faster than prokaryotes, two distinct replication forks form at each start site, and replication occurs in opposite directions.

Eukaryotic DNA Replication

Eukaryotic vs. Prokaryotic

Activity: DNA replication

Create a comic strip explaining DNA replication of a eukaryotic organism using all proteins and correct terminology.

Activity

Proteins perform most of the functions of cells. DNA provides the original “recipe”.

RNA: ribonucleic acid allows genetic information to be taken from DNA and proteins be made.

Gene expression: the manifestation of genes into specific traits.

RNA and Gene Replication

The first stage of gene expression. RNA is making proteins from the information

found in DNA.

Transcription: DNA to RNA

Second stage of gene expression. Information form RNA is used to make

specific proteins.

Translation: RNA to Proteins

In cells three types of RNA complement DNA and translate the genetic code into proteins.

RNA vs. DNA◦ Both have four bases and carry genetic

information.◦ RNA is composed of one strand of nucleotides and

DNA is composed of two strands of nucleotides.◦ RNA substitutes Uracil for Thymine.

RNA: Major Player

1 – messenger RNA 2 – transfer RNA 3 – ribosomal RNA

1 share with other 1’s Then 1, 2, 3

1, 2, 3

Messenger RNA: carries instructions for a gene to the site of translation.

Transfer RNA: reads the messenger mRNA sequence.

Ribosomal RNA: found in ribosomes, transports proteins from the ER as they are produced.

Types of RNA

During transcription , the information in a specific region of DNA is transcribed, or copied into RNA.

Step 1: RNA polymerase binds to the promoter ( a specific DNA sequence/start location).

Step 2: RNA polymerase unwinds the dbl helix to expose both paired nucleotide bases.

Step 3: RNA polymerase links and binds complementary base units to each strand of DNA.

The result once the stop codon is reached is one strand of mRNA is produced.

Transcription: Reading the Gene

Both use DNA as a template. Transcription – mRNA is made, using

portions of each strand of DNA Translation – DNA is made, using both entire

strands of DNA.

Transcription vs. Replication

Transcribe and then translate this sequence:

A T C G G C G G G A T T T A T T C C C G


ATCGGCGGGATTTATTCCCG

Create a comic strip for the steps of transcription and translation of a eukaryotic organism.

Homework

Each 3 nucleotide sequence is called a codon.

Each codon unit codes for a specific amino acid.

Turn to page 307 and look at the amino acids that are possible there are 20.

Genetic Code: 3 letter “words”

Translation occurs in a sequence of steps, involves three kinds of RNA and results in a complete polypeptide.

Translation: RNA to proteins

The relationship of gene expression is complex.

Despite the neatness of the genetic code, every gene cannot be simply linked to a single outcome.

Complexities of Gene Expression


ATC GGC GGG ATT TAT TCC CG

Now use the codon chart to determine which amino acids this codes for.

dna, rna and proteins

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