dna and its functions

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DNA and Its Functions. 3.1 DNA Structure. Double-stranded helical polymer of nucleotides, held together by H-bond between bases A, T, G, C Deoxyribose and phosphate group. Within any DNA molecule, the amount of thymine is always equal to the amount of adenine (same for GC) - PowerPoint PPT Presentation

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Slide 1

DNA and Its Functions

3.1 DNA StructureDouble-stranded helical polymer of nucleotides, held together by H-bond between bases

A, T, G, C

Deoxyribose and phosphate group

Within any DNA molecule, the amount of thymine is always equal to the amount of adenine (same for GC)

These are called complementary pairs

ReplicationProtein SynthesisMutationsRecombinant DNaFunctions of DNA3.2 ReplicationThe replication of DNA is required in order for cells to divide

Replication occurs during Interphase of mitosis

Three stepsThe enzyme, DNA helicase breaks the H-bonds causing it to unzip, exposing the bonding locations of their bases

New DNA nucleotides move into the nucleus where DNA polymerase enzymes ensure they bond onto their exposed complementary bases on the parent strands

The Process continues along the length of the parent strands and results in two separate identical DNA molecules each with an original strand and a new strand.ReviewEqual amount of A and T in DNA is logical because

These molecules bond together

DNA is a double stranded helix

These molecules are not the same size

One is a purine and one is a pyrimidineEqual amount of A and T in DNA is logical because

These molecules bond together

DNA is a double stranded helix

These molecules are not the same size

One is a purine and one is a pyrimidine

DNA molecules from unrelated organisms differ in their

Types of sugar

Number of strands

Sequence of bases

Order of phosphatesDNA molecules from unrelated organisms differ in their

Types of sugar

Number of strands

Sequence of bases

Order of phosphates

Replication MOST accurately refers to the synthesis of

Complementary strands of RNA for mitosis

Complementary strands of DNA for mitosis

Proteins based on the sequence of bases in RNA

Proteins based on the sequence of bases in DNA

Replication MOST accurately refers to the synthesis of

Complementary strands of RNA for mitosis

Complementary strands of DNA for mitosis

Proteins based on the sequence of bases in RNA

Proteins based on the sequence of bases in DNA

A polymer of nucleic acid is found in the cytoplasm of a living animal cell. Which of the following is MOST likely true about this molecule?

HelicalContains riboseDouble strandedContains thymineA polymer of nucleic acid is found in the cytoplasm of a living animal cell. Which of the following is MOST likely true about this molecule?

HelicalContains riboseDouble strandedContains thymine

Which of the following is true for any given strand of DNA?

[A] = [C], [T] = [G]

[A] = [G], [T] = [C]

[A] + [T] = [G] + [C]

[A] + [G] = [T] + [C]

Which of the following is true for any given strand of DNA?

[A] = [C], [T] = [G]

[A] = [G], [T] = [C]

[A] + [T] = [G] + [C]

[A] + [G] = [T] + [C]

3.3 Protein SynthesisAnother function of DNA is the assembly of amino acids into proteins at the ribosomes

The ribosomes can either be

embedded in the walls of the RER, usually following the secretory pathway and are exported via exocytosis

located free In the cytoplasm if it is to be used within the cell

17A gene functions to directly make messenger RNA (mRNA)

To start, the DNA in the region of the gene puffs up by breaking the H-bonds between base pairs

The beginning point for thesynthesis of mRNA is marked by the sequence of nucleotide TAC (bases) on DNA

This process is calledtranscription

Once constructed, mRNA leaves the nucleus and becomes associated with a ribosome where the protein will actually be formed

Each set of 3 nucleotides from an mRNA strand functions as a codon, which gives 64 different combinations

These triplets determine which of the 20 amino acids is to be delivered to the ribosome

Translation is the second phase of protein synthesis and it occurs at the ribosomes

mRNA arrives at ribomose where ribosomal RNA (rRNA) helps align it into the correct position on the ribosome with AUG (methionine) as the start codon for building a protein

Transfer RNA (tRNA) molecules, with anticodons complementary to the mRNA codons, transport specific amino acids into place at the ribosomes

Incoming amino acids are linked by the formation of peptide bonds to the growing polypeptide

Once tRNA is free of its amino acid, it leaves the ribosome to bond onto another amino acid of the correct type in the cytoplasm

The process continues until a terminator codon is reached (tRNA that does not carry an amino acid)

ReviewThe cellular flow of inherited information is from

Protein to RNA to DNA

DNA to RNA to Protein

DNA to Protein to RNA

RNA to DNA to ProteinThe cellular flow of inherited information is from

Protein to RNA to DNA

DNA to RNA to Protein

DNA to Protein to RNA

RNA to DNA to Protein

When using the Genetic Code to determine the aa sequence in a peptide, one must use the

Code sequence from DNA

Codon sequence from mRNA

Anticodon sequence from tRNA

Base sequence from the amino acidsWhen using the Genetic Code to determine the aa sequence in a peptide, one must use the

Code sequence from DNA

Codon sequence from mRNA

Anticodon sequence from tRNA

Base sequence from the amino acids

What is the compliment of a DNA strand with AAGCTT?

UUCGAA

TTCGAA

AACGTT

TTCGUU

What is the compliment of a DNA strand with AAGCTT?

UUCGAA

TTCGAA

AACGTT

TTCGUU

When the genetic message ATC in DNA causes the synthesis of mRNA with UAG, an amino acid will be delivered to a ribosome by a tRNA molecule bearing

TUCAUGAUCATCWhen the genetic message ATC in DNA causes the synthesis of mRNA with UAG, an amino acid will be delivered to a ribosome by a tRNA molecule bearing

TUCAUGAUCATC

Which of the following is NOT true about the Genetic Code?

It contains start and stop codons

It is different in different types of cells

It has 64 different possibilities of base sequences

It is composed of a triplet code of three bases per codon Which of the following is NOT true about the Genetic Code?

It contains start and stop codons

It is different in different types of cells

It has 64 different possibilities of base sequences

It is composed of a triplet code of three bases per codon

3.4 MutationsA gene (point) mutation is an error made during one of the processes that involve base pairing between nucleotides

Chromosome mutations involve segments of chromosomes or entire chromosomes during cell division as in the case of trisomy 21 (down syndrome)Mutations commonly result from a factor from the environment called a mutagen

Radiation and chemicals are the two most common mutagens

Three types of mutations: deletion, addition, substitutionDeletionA single nucleotide gets left out

Gene of daughter strand is one nucleotide short

During transcription, the set of triplets from this point on would be incorrectAdditionNucleotide is inserted along normal DNA strand

Also incorrect from this point on in the daughter strand

Protein produced is often non functional

Cells often die under this mutation, especially if protein was supposed to be essential enzymeSubstitutionEverything is correct, except one nucleotide replaces another

The mRNA strand produced will contain all the right codons except the one that has been substituted

This MAY affect the incorporation of the correct amino acid into the protein

If a substitution does not change the outcome of the protein produced, then it is degenerative

If the substitution did change the protein (different amino acid), it may never function properly

All proteins are intended for some purpose; mutant proteins may reach their appropriate destination, but fail to function properly3.5 Recombinant DNARecombinant DNA technology allows scientists to insert segments of DNA from one organism into the chromosomes of another

E. coli is a relatively common and harmless human bacterium that is easy to maintain in vitro (in the lab) and it will undergo binary fission about every 20 minutes under good conditions.AdvantagesProducing insulin, growth hormones, interferon (cancer treatment), etc

Certain strains that help environment (oil-metabolizing bacteria)

Production of genetic clones to study differential gene expression

Minimize the effects of genetic errors in humans by removing, repairing and reinserting the gene

Production of hybrid species of some food crops that are disease resistant or more tolerant of extreme environmental conditionsReviewIf the normal nucleotide sequence was TACGGCATG, what type of gene mutation is present if the resulting sequence becomes TAGGCATG?

Deletion

Addition

Substitution

chromosomalIf the normal nucleotide sequence was TACGGCATG, what type of gene mutation is present if the resulting sequence becomes TAGGCATG?

Deletion

Addition

Substitution

chromosomal

Which of the following is NOT a result of addition or deletion of the nucleotide sequence CATUAUCCC?

ATUAUCCC

CTUAUCCC

CATUAUCGC

CATTUAUCCCWhich of the following is NOT a result of addition or deletion of the nucleotide sequence CATUAUCCC?

ATUAUCCC

CTUAUCCC

CATUAU