Bio Chapter 12

What does it mean to say that bacteria exists in strains?

there are different forms of the same bacterial/viral species

What value did Griffith’s experiments add to the study of DNA?

discovered the process he named transformation (one strain of bacteria permanently changed into another), showed a chemical has to pass traits on

What value did Avery add to the study of DNA?

discovered that DNA was the factor that caused transformation

What happens in transformation?

one bacterial/viral strain is permanently changed into another

What value did the Hershey-Chase experiment add to the study of DNA?

concluded that the genetic material of the bacteriophage was DNA, not protein

How is a bacteriophage different from a cold or flue virus?

bacteriophage affect only bacteria, cold/flu viruses affect everything

Describe what happens in the process of DNA replication

* process is carried out by enzymes that “unzip” a molecule of DNA at the Replication forks
* Hydrogen bonds are broken & 2 strands of DNA unwind →enzyme helicase
* main enzyme involved is DNA polymerase, which joins individual nucleotides to produce a DNA molecule & then “proofreads” each new DNA strand
* One direction forms __leading strand__ & grows one base after another, adding new nucleotides
* second direction forms a __lagging stand__ & forms in chunks called Okazaki fragments, growing a few bases at a time & working backwards, then jumping up & growing a few more bases
* Both continue until complete DNA strands are replicated

Describe what happens in the process of Transcription

* process where DNA is copied onto mRNA
* genetic messages decoded by copying part of the nucleotide sequence from DNA into RNA
* Genes are coded DNA instructions to control protein synthesis
* requires RNA polymerase, which binds to DNA & separates the DNA strands, then uses one strand of DNA as a template, assembling the nucleotides into a strand of RNA
* Introns - seq. of nucleotides not ininvolved in coding for proteins
* Exons - coding nucleotides for proteins
* introns & exons both copied from DNA when RNA molecules are formed
* introns cut out of RNA; exons spliced together to form mRNA; cap added to 1 end (modified guanine); Poly-A Tail added to other end (series of repeating A bases}

What makes Transcription a necessary process?

RNA needs info on protein synthesis from DNA bc DNA can’t leave the nucleus to get to the ribosome

How are the nucleotide structures of DNA and RNA different?

DNA has/uses: 2 strands, deoxyribose sugar, thymine

RNA has/uses: 1 strand, ribose sugar, uracil

What value did Chargoff add to the study of DNA?

discovered that percentages of guanine and cytosine bases are almost = in any sample of DNA & the same goes for adenine & thymine

What value did Franklin add to the study of DNA?

used x-ray diffraction to get info about DNA structure; showed the helical/twisted structure

What did Watson & Crick add to the study of DNA?

used Franklin’s pattern & built a model to explain how DNA carried info & could be copied/discovered that hydrogen bonds can only form b/w certain base pairs (A&T, C&G)

How does the genetic set-up of prokaryotes differ from eukaryotes?

Eukaryotes: DNA in nucleus, DNA is bigger, forms chromosomes

Prokaryotes: DNA in cytoplasm, DNA is smaller, does not form chromosomes

Discuss the set up of DNA as it relates to chromosomes and chromatin.

chromosomes contain DNA and uncoil to form chromatin

chromatin consists of DNA tightly coiled around proteins (histones)

Why do the strands in DNA replication not copy in the same direction?

one strand has to start as 5-prime and end as 3-prime & the other has to start as 3-prime and end as 5-prime

What are the different forms of RNA?

mRNA - single linear strand that carries a copy of the DNA code out of the nucleus

tRNA - carries amino acids to the ribosome, used during translation

rRNA - makes up each ribosome, used during translation to bond together amino acids delivered from tRNA

What is the function of tRNA?

carries amino acids to the ribosome during translation

What are 3 similarities between DNA and RNA?

involved w/protein coding, are nucleic acids, have nucleotides C, G, and A

What roles do the cap, intron, tail, and exon play in Transcription?

intron - sequence of nucleotides not involved in coding for proteins in eukaryotic cells

exons - nucleotides that code for proteins and are spliced together to form mRNA

cap - modified type of guanine added to one end

Poly-A Tail - series of repeating A bases added to opposite end of cap

cap & poly-a tail give the ribsome a way of knowing to react with it

Describe what happens in the process of Translation

Overall: decoding of an mRNA message into a polypeptide chain, taking place on ribosomes

* messenger RNA transcribed in the nucleus & enters the cytoplasm, attaching to a ribosome
* ribosome reaches start codon (AUG) & protein synthesis starts
* each codon of mRNA molecule moves through ribosome & the proper amino acid is brought into ribosome by tRNA (has an anticodon that follows base pairing rules to bring proper amino acid)
* First 2 tRNA molecules attach to the mRNA stand carrying their specific amino acid
* ribosome attaches 2 amino acids together, forming a peptide bond
* 1st tRNA then releases from mRNA strand, 3rd tRNA taking its place next to the 2nd, passing the amino acid chain to the 3rd tRNA
* process repeats until entire protein is complete

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What is the difference between a peptide bond and a hydrogen bond?

hydrogen bond: connects nitrogen bases, in DNA, weaker

peptide bond: in proteins, stronger, connects amino acids