Unit 9: Ch. 11 DNA and Genes

CHS

                                                                                          

Key Terms to watch for:

DNA RNA Enzymes Nucleotides Cytosine Watson and Crick Adenine Guanine Thymine Nucleotide Replication Protein Nucleic Acid Amino acids Transcription Translation Ribosomes Codon Mutations Mitosis Meosis Nondisjunction

Unit Objectives

Describe the structure of DNA Compare and contrast DNA and RNA Understand the processes of

transcription, translation and replication Identify types of mutations and causes

of mutations

The riddle of life-DNA

DNA: Deoxyribose Nucleic Acid

that is the blueprint for building life

Nucleotides:

DNA subunits that include a sugar, a phosphate and one of four nucleic acids

Double Helix: a twisted ladder structure

RNA:

Ribonucleic acid, three types, messenger, transfer and ribosomal

Replication:

the process by which DNA copies itself

Mutation:

a change in DNA that results in an altered trait

Transcription and Translation (4 min)

Transcription:

the process by which DNA is converted into RNA

Translation:

the process by which information in RNA is converted to protein

Watson and Crick (9 min)

What is DNA?

All living things contain proteins called enzymes which are needed for the functions of life.

Within the structure of DNA is the information for life- the complete instructions for manufacturing all the proteins for an organism.

The Structure of DNA I DNA is a polymer

made of repeating subunits called nucleotides.

Nucleotides have 3 parts: a simple sugar, a phosphate group, and a nitrogen base.

The Structure of DNA II The simple sugar in

DNA is called deoxyribose.

The Structure of DNA II

The phosphate group is composed of one atom of phosphorous and four atoms of oxygen.

The Structure of DNA II A nitrogen base is a carbon ring structure

that contains one or more atoms of nitrogen.

There are four possible nitrogen bases: adenine (A), guanine (G), cytosine (C), and thymine (T).

DNA is made of two chains of nucleotides joined together by the nitrogen bases (determined by Watson and Crick).

The two strands twisted together make a shape called a double helix.

The bases on one strand determine the bases on the other strand. They can be held together in this way because they are complimentary to each other.

The Structure of DNA III

Adenine bonds with thymine and guanine bonds with cytosine.

The amount of adenine is always equal to the amount of thymine while the amount of guanine is always equal to the amount of cytosine.

These bonded bases are called complementary bases.

Nucleotide Sequences Differences in The closer the relationship

between two organisms, the greater the similarity in their order of DNA nucleotides.

Scientists use nucleotide sequences to determine evolutionary relationships among organisms, as well as criminal evidence.

Nucleotide Sequences The closer the

relationship between two organisms, the greater the similarity in their order of DNA nucleotides.

Scientists use nucleotide sequences to determine evolutionary relationships among organisms, as well as criminal evidence.

DNA Replication Copying of DNA in

chromosomes Without DNA

replication, new cells would have only half the DNA of their parents

Species could not survive, reproduce, or grow

Mapping the Human Genome

How DNA Replicates See pg 292, Copying DNA Inside Story After fertilization of egg, replication

begins During replication, each strand serves

as a pattern to make a new DNA molecule

How DNA Replicates Enzyme breaks the hydrogen bonds

between nitrogen bases that hold the two strands together; unzips DNA

Free floating nucleotides attach by base pairing to the individual single strands of DNA

Another enzyme bonds the nucleotide to the strand

Continues until entire strand replicates Each new strand is a compliment of one

of the original parent strand Result is the formation of two DNA

molecules, identical to the original strand

DNA Replication Illustration

From DNA to Proteins

The sequence of nucleotides in DNA contains information for the production of proteins. – These proteins become everything from

muscle tissue to walls of blood vessels and enzymes to assist in reactions of body (digestion, respiration)

Genes and DNA

RNA, like DNA is a nucleic acid

RNA differs from DNA in 3 ways– RNA only has 1 strand, DNA has 2– RNA has Ribose sugar, DNA has

deoxyribose– RNA and DNA both contain Adenine,

Cytosine, and Guanine. RNA has Uracil instead of Thymine

RNA receives instructions from DNA on how to assemble specific amino acids which go together to make proteins Three types of RNA

– Messenger RNA (mRNA) Brings info. From the DNA in the nucleus to the cytoplasm of the cell

– Ribosomal RNA (rRNA) contacts the mRNA and uses this info. To place amino acids in the correct order

– Transfer RNA (tRNA) transports amino acids to the ribosome to be built into proteins

Transcription

The making of RNA from a DNA molecule– See Fig. 11.6– The nucleotide sequence is the blueprint to build

proteins.– There are 20 different amino acids, and every 3

nitrogen bases (ex. AGU = Serine) codes for a different one. This is called a CODON

– There are 64 possible codons in the genetic code• Some code for “stop” or “start”, others for amino acids

Translation

Turns mRNA into a sequence of amino acids which makes up a protein

Takes place in the ribosomes mRNA and tRNA meet

– Each tRNA carries anticodons, complimentary to codons on mRNA and picks up the correct amino acid and takes it to bond with the previous one. It releases one and goes to get the anticodon for another amino acid.

– When a “stop” codon is reached, translation ends and the entire protein is released from the ribosome

Mutations: Mistakes in DNA

Nuclear gamma radiation, etc. can alter the molecule if it comes in contact

Mutations: Mistakes in DNA

A change in DNA sequence is called a mutation– Affect reproductive cells of an organism

• Can result in a new trait (+, but rare), a protein that does not correctly function, or an embryo that cannot survive

Types of Mutations

UV radiation can change skin cells, which then grow and divide too rapidly causing skin cancer

Types of Mutations

A POINT mutation is a change in a single base pair in DNA, which can change an entire protein.

Types of Mutations

A FRAMESHIFT mutation adds or deletes a base and causes the entire code to shift up or down one

Chromosomal Mutations

Most common in plants Parts of chromosomes can be lost

during mitosis or meiosis

Albino redwood Two headed kitten

Chromosomal Mutations Affect the distribution of genes to

gametes, causing nondisjunction to occur (Down Syndrome trisomy)

Few of these mutatations are passed on to next generation because people with these cannot mate

Chromosomal Mutations Most important types are: deletions,

insertions, inversions, translocations– See figure 11.11

Causes of Mutations

Just happen (spontaneous) Environmental factors

– Caused by mutagens like UV, Nuclear and X-Ray radiation, chemicals, asbestos, cyanide, formaldehyde

Review Unit Objectives

Describe the structure of DNA Compare and contrast DNA and RNA Understand the processes of

transcription, translation and replication Identify types of mutations and causes

of mutations

Practice Questions

Answer : B

Gene Therapy 4:45min