Chapter 10 Flashcards
What question did Griffith ask?
How do certain types of bacteria cause pnuemonia
What did Griffith do to test his question?
He isolated two different strains of pneumonia bacteria from mice and grew them in his lab
What observations did Griffith make about his bacteria cultures?
That the disease causing strain’s colony had smooth edges and the harmless strain’s colony had rough edges
What was Griffith’s 4th experiment?
Griffith mixed his heat killed, disease causing bacteria with live, harmless bacteria and injected the mixture into the mice. The mice developed pneumonia and died.
What did Griffith call the process that took place in his 4th experiment?
Transformation
Define transformation
When one strain of bacteria permanently changes into another
What did Griffith hypothesize after he discovered transformation?
That a factor must contain information that could change harmless bacteria into a disease-causing one
What did Avery do and why?
He repeated Griffith’s last experiment to determine which molecule was most important for transformation
What did Avery make an extract from and what did he do with it?
Heat killed bacteria that they treated with enzymes that destroy proteins, lipids, carbs, nucleic acid, and DNA. Transformation still occurred.
What did Avery repeat Griffith’s experiment using and what was their conclusion?
They repeated his experiment using enzymes that would break down DNA. Transformation didn’t occur, so they concluded that DNA was the transforming factor.
What is a virus that infects bacteria known as?
A bacteriophage
Who was Fredrick Griffith?
A British scientist in the 1920s
What did Hershey and Martha Chase study?
Viruses
What is a bacteriophage composed of?
DNA or an RNA core and a protein coat
What did Hershey and Martha Chase grow the viruses with?
They grew the viruses in cultures containing radioactive isotopes of Phosphorus-32 (32P) and Sulfur-35(35S)
Why did Hershey and Martha Chase grow the viruses with 32P and 35S?
Because if 35S was found in the bacteria, it would mean that the viruses’ protein had been injected into the bacteria. If 32P was found in the bacteria, then it was the DNA that had been injected.
Was 35S or 32P found in the bacteria?
Nearly all the radioactivity in the bacteria was from phosphorus (32P)
What did Hershey and Martha Chase conclude from their experiment?
They concluded that the genetic material of the bacteriophage was DNA, not protein
What is DNA made up of?
Nucleotides
What are nucleic acids made up of?
A 5-carbon sugar, a phosphate group, and a nitrogenous base
What is a nucleotide made up of?
A monomer of nucleic acids
What are the 4 kinds of bases in DNA?
Adenine, Thymine, Guanine, and Cytosine
What did Chargaff discover? What is this discovery called?
That the percentages of Guanine and Cytosine are almost equal and the percentages of Adenine and Thymine are almost equal. These are called Chargaff’s rules
What did Rosalind Franklin use to get information about the structure of DNA?
X-ray diffraction
How did Rosalind Franklin use x-ray beams in her research?
She aimed an X-ray beam at concentrated DNA samples and recorded the scattering pattern of the X-rays on film
Who used clues from Franklin’s pictures/ pattern?
Watson and Crick
How did Watson and Crick use Franklin’s research?
They used clues from her pattern to build a model that explained how DNA carried information and could be copied
What did Watson and Crick’s model look like?
A double helix, in which two strands were wound around each other
What did Watson and Crick discover?
That hydrogen bonds can form only between certain base pairs- adenine and thymine, and guanine and cytosine
What is the theory that only A&T and C&G can bond together?
Base pairing
Who discovered base pairing?
Watson and Crick
What does chromatin contain?
DNA tightly coiled around histones
What does DNA and histone form?
Chromatin
Where is chromatin found?
In eukaryotic chromosomes
What makes up a nucleosome?
DNA and histone molecules
What do DNA and histone molecules form?
Nucleosomes
What do tightly packed together nucleosomes form?
A thick fiber
What does each strand of the DNA double helix contain information for?
How to reconstruct the other half by the mechanism of base pairing
In most prokaryote’s chromosomes how does DNA replication work?
It begins at a single point and continues in 2 directions
In most eukaryote’s chromosomes how does DNA replication work?
It occurs at hundreds of places siamotainously. Replication proceeds in both directions until each chromosome is correctly copied
What are the sites where separation and replication occur called?
Replication Forks
What is a replication fork?
The site where separation and replication occurs
What does a cell do before it divides?
It duplicates its DNA in a process called replication
What does replication ensure?
That each resulting cell will have a complete set of DNA
Describe the process of DNA replication
The DNA molecule separates into two strands, then produces tow new complementary strands following the rule of base pairing.
What carries out DNA replication?
Enzymes that unzip the molecule of DNA
What bonds are broken during DNA replication?
Hydrogen bonds between base pairs are broken and the 2 strands of DNA unwind
What is the principle enzyme involved in DNA replication called?
DNA polymerase
What does DNA polymerase do?
It joins individual nucleotides to produce a DNA molecule and then “proofreads” each new DNA strand
What are genes?
Coded instructions that control the production of proteins
What is the production of proteins controlled by?
Genes
How can genetic messages be decoded?
By copying part of the nucleotide sequence from DNA into RNA
What does RNA contain?
Coded information for making proteins
What are the 3 main differences between DNA and RNA?
The sugar in RNA is ribose instead of deoxyribose, RNA is generally single stranded, and RNA contains uracil in place of thymine
What are the 3 types of RNA called?
mRNA, rRNA, and tRNA
What does Messenger RNA (mRNA) do?
It carries copies of instructions for assembling amino acids into proteins
What does Ribosomal RNA (rRNA) do?
Ribosomes are made up of proteins and ribosomal RNA (rRNA)
What does Transfer RNA do (tRNA) do?
During protein construction, tRNA transfers each amino acid to the ribosome
Where does the process of Protein synthesis begin?
At a section of DNA called a promoter
What is an intron?
A part of the DNA that isn’t needed to produce a protein
What is a part of the DNA that isn’t needed to produce a protein called?
An intron
What is an exon?
A DNA sequence that codes for proteins
What is a DNA sequence that codes for proteins called?
An Exon
What is cut out of RNA molecules?
Introns
What are spliced together to form RNA?
The exons
What does a codon consist of?
Three consecutive nucleotides on mRNA that specify a particular amino acid
What is translation?
The decoding of an mRNA message into a polypeptide chain (protein)
What is the process of decoding an mRNA message into a polypeptide chain (protein) called?
Translation
What does the cell use information form mRNA for during translation?
During translation, the cell uses information from mRNA to produce proteins
What binds new tRNA molecules and amino acids together as it moves along the mRNA?
The ribosomes
What do new tRNA molecules bind with during translation?
They bind with ribosomes
What stops the process of translation?
When the ribosome reaches a stop codon
Define a mutation
Changes in genetic material
What are the 2 main kinds of mutations?
Gene mutations and chromosomal mutations
Define a gene mutation
A mutation that produces changes in a single gene
What is a point mutation?
A type of gene mutation that involves a change in only one or a few nucleotides because they occur at a single point in the DNA sequence
What is a chromosomal mutation?
A mutation that produces a change in a whole chromsome
What are some types of point mutations?
Substitutions, insertions, and deletions
What do substitutions (a type of point mutation) usually affect?
Only a single amino acid
What do insertions or deletions usually effect?
Their effect is more dramatic because they cause a shift in the grouping of codons
What are changes that cause a shift in the grouping of codons called?
Frameshift mutations
What happens in an insertion?
An extra base is inserted into a base sequence
What happens in a deletion (gene mutation + point mutation)
The loss of a single base is deleted and the reading frame is shifted
What do chromosomal mutations usually involve?
Changes in the number or structure of chromosomes
What are some types of chromosomal mutations?
Deletions, duplications, inversions, and translocations
What do chromosomal deletions usually involve?
The loss of all or part of the chromosome
