what do genes look like?. i. genes – segments of dna that carry hereditary instructions and are...

What do genes look like?

I. Genes – segments of DNA that carry hereditary instructions and are passed from parent to offspring; genes are located on chromosomes

Chromosome Structure of Eukaryotes

Chromosome

Supercoils

Coils

Nucleosome

Histones

DNA

double

helix

Section 12-2

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II. DNA – Hereditary material that controls all the activities of a cell and provides the instructions for making proteinsA. DNA is made of nucleotides

B. Nucleotides have three parts; 5-carbon sugar, phosphate group and a nitrogen base

1. Nucleotides are identical except for the nitrogen base

2. A nucleotide can contain 1 of 4 Nitrogen Bases – • Adenine• Guanine• Cytosine• Thymine

Phosphate Group

Sugar

Nitrogen Base

Can Be:

Adenine

Guanine

Cytosine

Thymine

3. The amount of Adenine = Thymine, Cytosine = Guanine (Chargaff’s Rule)

III. The Double Helix- 1953, 2 American scientists, Watson and Crick, discovered the structure of DNA using the X-rays made by Rosalind Franklin

A. 2 strands wound around each other like a twisted ladder

B. Strands are held together by hydrogen bonds between the nitrogen bases

C. Adenine bonds to Thymine and Cytosine bonds to Guanine

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Structure of DNASection 12-1

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Mealor’s First Love

IV. Replication: Before a cell divides, DNA on every chromosome is copied so that each new cell has an identical set of chromosomes

DNA Replication

IV. Replication: Before a cell divides, DNA on every chromosome is copied so that each new cell has an identical set of chromosomes

AGTCCGATCGTAACTGGGTCACATCGTAAGTGTACACGTA

TCAGGCTAGCATTGACCCAGTGTAGCATTCACATGTGCAT||||||||||||||||||||||||||||||||||||||||AGTCCGATCGTAACTGGG

TCAGGCTAGCATTGACCC||||||||||||||||||

TAAGTGTACACGTA

AGTGTAGC

TCACATCG

ATTCACATGTGCAT

TCACATCGTCACAT

CGTCA

CATCGTAAGTGTACACGTATAAGTGTACACGTATAAGTGTACACGTA

AGTGTAGCAGTGTAGC

ATTCACATGTGCATATTCACATGTGCAT

||||||||||||||||||||||

ATTCACATGTGCAT

TAAGTGTACACGTA

Make a complimentary strand

ATT CGT ACG TTT ACT


ATT CGT ACG TTT ACT

TAA


ATT CGT ACG TTT ACT

TAA GCA


ATT CGT ACG TTT ACT

TAA GCA TGC


ATT CGT ACG TTT ACT

TAA GCA TGC AAA


ATT CGT ACG TTT ACT

TAA GCA TGC AAA TGA

I. How DNA works to create our traits – DNA cannot leave the nucleus. A copy of the DNA code is made in the nucleus into RNA. RNA travels to the ribosome where the code is read and the protein is assembled

A. The nitrogen bases in every gene make a code

B. Every three bases makes one codonC. One codon is the code for one amino

acidD. Long chains of amino acids make

proteinsE. ****Proteins determine an organisms

traits and characteristics

Messenger RNA

Messenger RNA is transcribed in the nucleus.

Transfer RNA

The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon.

mRNA Start codon

Ribosome

Methionine

Phenylalanine tRNALysine

Nucleus

Making a Protein – Translation Section 12-3

mRNA

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The Polypeptide “Assembly Line”The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids.

mRNARibosome

Translation direction

Lysine tRNA

tRNA

Ribosome

Growing polypeptide chain

mRNA

Completing the PolypeptideThe process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.

Making a ProteinSection 12-3

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The Genetic Code

Go to Section:

Making a Protein: Translation

DNA in the Nucleus: ATA GCT CCG TTA

Code is made into RNA: UAU CGA GGC AAU

***In RNA Thymine is replaced by Uracil

Amino Acid Chain is made at the ribosome: Tyrosine: Arginine: Glycine: ___________

The Genetic Code

Go to Section:

Making a Protein:

DNA in the Nucleus: ATA GCT CCG TTA

Code is made into RNA: UAU CGA GGC AAU

***In RNA Thymine is replaced by Uracil

Amino Acid Chain is made at the ribosome: Tyrosine: Arginine: Glycine: Asparagine

http://www.learnerstv.com/animation/biology/Proteinsynthesis.swf

http://www.learnerstv.com/animation/biology/Proteinsynthesis.swf

The Genetic Code

Go to Section:

Making a Protein:

DNA in Nucleus: TTA TTT CCC AAT

RNA:

The Genetic Code

Go to Section:

Making a Protein:


RNA: AAU

The Genetic Code

Go to Section:

Making a Protein:


RNA: AAU AAA

The Genetic Code

Go to Section:

Making a Protein:


RNA: AAU AAA GGG

The Genetic Code

Go to Section:

Making a Protein:


RNA: AAU AAA GGG UUA

Amino Acid Chain (Protein):

The Genetic Code

Go to Section:

Making a Protein:




Asparagine:

The Genetic Code

Go to Section:

Making a Protein:




Asparagine: Lysine

The Genetic Code

Go to Section:

Making a Protein:

DNA in Nucleus: TTA GCG CCC AAT

RNA: AAU CGC GGG UUA


Asparagine: Lysine: Glycine:

The Genetic Code

Go to Section:

Making a Protein:


RNA: AAU CGC GGG UUA


Asparagine: Lysine: Glycine: Leucine

This protein will determine a characteristic or trait

The Genetic Code

Go to Section:

Making a Protein:

DNA in Nucleus: AAA TCT GAC CAT

RNA:

The Genetic Code

Go to Section:

Making a Protein:


RNA: UUU

The Genetic Code

Go to Section:

Making a Protein:


RNA: UUU AGA

The Genetic Code

Go to Section:

Making a Protein:


RNA: UUU AGA CUG

The Genetic Code

Go to Section:

Making a Protein:


RNA: UUU AGA CUG GUA


The Genetic Code

Go to Section:

Making a Protein:



Amino Acids Chain (Protein):

Phenylalanine:

The Genetic Code

Go to Section:

Making a Protein:




Phenylalanine: Arginine:

The Genetic Code

Go to Section:

Making a Protein:




Phenylalanine: Arginine: Leucine:

The Genetic Code

Go to Section:

Making a Protein:




Phenylalanine: Arginine: Leucine: Valine

This protein will now determine a trait or a characteristic

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Structure of DNASection 12-1

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III. Mutations- changes in the DNA sequence that affect genetic information (not all are harmful)

Can affect all types of cells

A. Germ Mutations- affect sex cells – inherited by offspring (ex- Down Syndrome)

B. Somatic Mutations – affect other cells- not inherited (many cancers caused by somatic mutations)

IV. 2 types of mutations

A. Gene Mutations (#1) - changes in a single gene. 2 types of gene mutations-

1. Point mutations- affect only one nucleotide *Can be caused by substitutions

2. Frameshift mutations - type of point mutation where nucleotide is inserted or deleted;affects every amino acid after that point.*Can be caused by deletion or insertion

Effect of Mutations

• Sickle cell disease– single nucleotide change AT

Substitution InsertionDeletion

Gene Mutations:Substitution, Insertion, and Deletion

Go to Section:

B. Chromosomal Mutations (#2) - changes in whole chromosomes. 4 types of chromosomal mutations.

1. Deletion- loss of all or part of chromosome2. Duplication- segment of a chromosome is repeated3. Inversion- chromosome becomes reversed4. Translocation- part of a chromosome breaks off and attaches to a different chromosome

Deletion

Duplication

Inversion

Translocation

Chromosomal MutationsSection 12-4

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V. What are the effects of mutations?

A. Proteins are altered.B. Proteins are unable to perform

“normal” functions.

Sometimes mutations are harmful, sometimes there is no affect, and sometimes mutations can be helpful. (Helpful when mutation produces a trait that aids in survival)

Organisms Can Change!

VI. Genetic Manipulation- when humans change the genes of an organism to achieve a desired result.A. Selective breeding- allowing only the individuals with

desired traits to reproduce. 2 types1. Hybridization-crossbreeding dissimilar individuals:

offspring will have the best of both– Ex: donkey x horse = mule

2. Inbreeding-breeding individuals with similar characteristics: maintain certain characteristics in offspring – Ex: German Shepard x German Shepard = German

Shepard

VII. Genetic Engineering – Desired genes are removed from one organism and added or recombined into another organism. This forms a transgenic organism with recombinant DNA

A. This is used to make proteins not normally made by the cell. Can be used to produce: Drugs like insulin, Vaccines, Plants resistant to Insects, Reduce pollution, Better crops/meat

VIII. Evolution –natural process through which species change over time

A. The environment “selects” the best traits – only those best suited will survive and pass on their traits to offspring.

B. Evolution– occurs because of genetic differences caused by mutations in DNA

Concept MapSection 15-3

includes

Evidence of Evolution

Physical remains of organisms

Common ancestral species

Similar genes Similar genes

which is composed of which indicates which implies which implies

The fossil recordGeographic

distribution of living species

Homologous body structures

Similaritiesin early

development

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