Chapter 12 Biology Test
Terms in this set (80)
What did most scientists believe during the 1900s?
that proteins had to be the molecules that made up genes
How many sub-units does DNA have?
What was Fredrick Griffith's experiment?
(1928) he looked at a pneumonia bacteria to try and figure out why it made people die
- rough strain-mice lived
- smooth strain-mice died
- if he heated the lethal strain, mice lived
- if he mixed the heated strain with the rough strain-mice died
What did Griffith call his findings?
transformation-because one strain of bacteria transformed into another
What was Oswald Avery's experiment?
(1944) Avery wanted to find the molecule that caused this transformation
- after heating the lethal bacteria, he treated them with digestive enzymes
- these enzymes destroyed all kinds of molecules
What was destroyed when transformation still occurred?
proteins, polysacchrides, lipids, or RNAs
What happened when Avery's team treated the lethal bacteria with enzymes that destroyed DNA?
no transformation occurred (DNA was the molecule)
What did Griffith's experiment show?
that genetic material could be passed between bacteria and cause a change
What did Avery's experiment show?
that the genetic material was DNA
(1952) Alfred Hersey and Martha Chase did what?
experimented with viruses that infect bacteria-bacteriophages
- knew bacteriophages were made of proteins and DNA
What was the conclusion of the Hersey-Chase experiment?
showed only DNA and not protein entering cell during infection
concluded that the genetic material in a virus was DNA and not a protein
What lead to the discovery of the DNA structure in 1953?
X-ray experiments by Rosalind Franklin, James Watson, and Francis Crick
What are nucleic acids built from?
subunits called nucleotides
(sugar in DNA is deoxyribose)
What are the nitrogen bases in DNA
adenine, guanine, thymine, cytosine
What is the structure of the helix?
double-stranded-backbone is made of phosphates and sugars
Which two bases are purines?
adenine and guanine
Which two bases are pyrimidines?
cytosine and thymine
What are Chargaff's rules?
that adenine can only bond with thymine, and guanine can only bond with cytosine
What holds the base pairs together?
What are some characteristics of the DNA molecule in bacteria?
single, circular, and found in the cytoplasm
What are the characteristics of DNA in a eukaryotic cell?
it is in multiple chromosome bundles, found in the nucleus
Chromosome structure of eukaryotes?
they are made of DNA and proteins called histones
-together DNA and histone proteins form a bead-like structure called a nucleosome
-nucleosomes pack together to form thick coiled fibers
- when the cell is not dividing, these fibers spread out in the nucleus (chromatin)
- when the cell is ready to divide they pack tightly together into chromosomes
How is DNA copied?
- each strand has all the information needed to construct the matching other half
- if strands are separated, base-pairing rules allow you to fill in the complementary bases
What are the sites called where separation and replication occur?
What are the replication steps?
1) enzymes unzip the molecule by breaking hydrogen bonds
2) DNA polymerase joins nucleotides using original strands as a template and spell checks for errors
3) copying happens in opposite directions along the two strands and in multiple places at once
What is a virus?
an infectious agent consisting of a nucleic acid in a protein coat
What are purines?
(adenine and guanine) they have a double nitrogen ring with four nitrogen atoms
What are pyrimidines?
(cytosine, thymine, and uracil) they have a single nitrogen ring with four nitrogen atoms
What is a nucleosome?
a structure of eukaryotes, consisting of a length of DNA coiled around a histone
What is DNA polymerase?
the enzyme that is responsible for forming new sets of DNA
Characteristics of RNA?
-sugar is ribose
-contains uracil instead of thymine
-made of nucleotides
Characteristics of DNA?
-sugar is deoxyribose
-contains thymine not uracil
-made of nucleotides
What does ribosomal RNA do?
(rRNA) combines with proteins to form ribosomes
What does transfer RNA do?
(tRNA) matches mRNA codon to add correct amino acids during protein synthesis
What does messenger RNA do?
(mRNA) carries code from DNA to ribosomes
What does RNA polymerase do?
separates the strands, then uses one strand as a template to assemble an RNA copy
How does the enzyme know where the gene starts and stops?
it binds to places with specific DNA sequences called promoters-these promoters tell the enzyme where to start
What does RNA require before use?
What are the steps of transcription?
-RNA polymerase binds to DNA and separates the DNA strands
-RNA polymerase then uses 1 strand of DNA as a template from which nucleotides are assembled into a strand of RNA
Where does transcription (DNA to RNA) take place?
in the nucleus of the cell
What is translation?
the decoding of an mRNA message into a polypeptide chain
What is the translation process?
during translation, the cell uses information from mRNA (codons) to produce proteins
Where does translation take place?
on ribosomes in the cytoplasm
What is a codon?
a message read in groups of three-represents different amino acids
How many possible codons are there?
What is the start codon?
How many stop codons are there?
How many amino acids do each tRNA carry?
What are the anticodons?
amino acids carried by the tRNA that match up with a codon on the mRNA
What is edited out of the RNA molecules?
What is left after the exons are edited out of the RNA?
What occurs during translation (repeat)
the cell uses information from mRNA to produce proteins
What are amino acids?
protein monomers that are crucial to carrying out many biological procedures?
What is another term for the mRNA instructions?
the genetic code
Which direction does translation follow?
left to right
What is the process of protein synthesis?
-the ribosome forms a polypeptide bond between the first and second amino acids
-at the same time, the ribosome breaks the bond that had held the first tRNA molecule/and releases the tRNA
-the ribosome then moves to the next codon, where the tRNA brings it the specified amino acid
-the polypeptide chain continues to grow until the ribosome reaches the stop codon on the mRNA molecule
-it then releases the chain and the mRNA molecule
What are mutations?
changes in the genetic material
What are mutations caused by?
-when cells make mistake in copying their DNA
What are gene mutations?
mutations that produce changes in a single gene
What is point mutation?
mutations involving one or a few nucleotides because they occur at a single point in the DNA sequence
What are the three types of point mutations?
substitutions, deletions, and insertions
What does substitution do?
changes one base for another (sickle cell anemia)
What does deletion do?
piece of DNA code for one gene is lost (DMD)
What does insertion do?
piece of DNA is copied too many times
What do subsitutions affect?
usually no more than a single amino acid
What are the insertion and deletion effects?
they have a more dramatic affect
What do frame shift mutations do?
change multiple bases in the code
What do frame shift mutations change?
every amino acid and protein following the shift, they make it so that the protein is unable to function
What are chromosomal mutations?
mutations involving changes in the number or structure of whole chromomsomes
What are the types of chromosomal mutations?
deletions, duplications, inversions, translocations
What does inversion do?
a segement of the chromosome flips
What does translocation do?
a segment breaks off and joins a different non-homologous chromosome
What causes Huntington's
addition of extra CAG (repeated)
What are a majority of mutations?
neutral, meaning they have little or no effect on gene function
Mutations that cause defective proteins are usually what?
What can harmful mutations cause
disorders and cancer
Mutations can also be what?
helpful, they provide variation for natural selection to act upon
What is polyploidy?
condition in which an organism has extra sets of chromosomes
Is polyplodiy lethal in humans?
yes, but helps some plants