nucleic acids and protein synthesis Flashcards
what is the shape of DNA?
double helix - spiral staircase or twisted ladder
Who is given credit for understanding the shape of DNA?
James Watson and Francis Crick
What prize did Watson and Crick receive for understanding the structure of DNA? Who shared in the prize?
Nobel Prize - Maurice Wilkins shared in the prize
Why did Rosalind Franklin not share the Nobel Prize with Watson, Crick, and Wilkins?
can not earn the prize posthumously - prize is to further research
Who experimented with mice and pneumococcus bacteria, and what was discovered?
Frederick Griffith discovered bacterial transformation - DNA from one bacterium can enter another bacterium and function - This turned harmless rough bacteria into harmful smooth bacteria
Who extended Griffith’s research to find out what the transforming chemical was, and what did they do?
Avery, Macleod, and McCarty used enzymes to destroy various cellular chemicals. When DNA was destroyed, the transformation didn’t occur, so they determined that DNA was the transforming chemical.
Who discovered base pairing?
Erwin Chargaff
What bases pair together in DNA?
adenine pairs with thymine
guanine pairs with cytosine
What holds DNA base pairs together, and what is significant about this type of bond?
hydrogen bonds - weak bonds - can easily be unzipped for DNA to work
How many hydrogen bonds are found between A-T?
How many hydrogen bonds are found between G-C?
A-T is held together by 2 hydrogen bonds.
G-C is held together by 3 hydrogen bonds.
What monomers are the building blocks of nucleic acids?
nucleotides
What polymer is made of nucleotides?
polynucleotides
Who experimented with bacteriophages and radioactive markers to verify that DNA is the transforming chemical?
Alfred Hershey and Martha Chase
What did the Hershey and Chase mark the bacteriophages with, and why?
radioactive phosphorus marked the DNA
radioactive sulfur marked the proteins
They wanted to know if bacteriophages injected DNA or protein into their host.
What is a bacteriophage?
a virus that infects bacteria
What was the result of the Hershey Chase experiments?
They verified that DNA is the transforming material, the genetic code.
What are the three parts of a nucleotide?
- sugar
- phosphate
- nitrogen base
What sugar is in DNA?
What sugar is in RNA?
DNA - deoxyribose
RNA -ribose
What bases are in DNA?
What bases are in RNA?
DNA - A, T, G, C
RNA - A, U, G, C
What part of DNA is the code portion?
nitrogen base pairs - rungs of DNA ladder
What part of DNA is the supporting backbone?
alternating sugars and phosphates - sides of ladder
What kind of bond holds the sugars and phosphates together?
covalent bond
Who made X-ray images of DNA and saw that it was a helix?
Rosalind Franklin and Maurice Wilkins
Why do we say the DNA strands are antiparallel?
One end starts with a phosphate - 5’
One end starts with a sugar - 3’
What is the significance of the 5’ and 3’ ends of DNA?
It always is copied from 5’ to 3’.
What is the term for DNA making an exact copy of itself?
replication
Why is DNA replication necessary?
It happens before cell division so each daughter cell will have all the information by getting a complete set of DNA
What are the 4 steps in DNA replication?
- DNA unwinds
- DNA unzips
- new bases are brought in
- The new strands are proofread for mutations
What chemicals cause replication?
enzymes
What enzyme unzips DNA?
helicase
What enzyme builds the new DNA strand?
DNA polymerase
Why is proofreading necessary?
to catch and fix mutations so that the new cell has the proper instructions
Why do we call DNA replication semiconservative?
an old strand serves as a template for a new strand. We don’t waste the old strand.
What are the protective caps on the chromosome ends? What is their significance?
telomeres - related to aging as they wear down
What is the difference between prokaryote replication and eukaryote replication?
prokaryotes have circular DNA and replicates from one point outwards in each direction until it meets up - 2 replication forks
eukaryotes have linear DNA and many replication forks to complete the entire strand
Give 5 ways DNA and RNA are different.
- different sugars - ribose in RNA and deoxyribose in DNA
- different bases - T in DNA and U in RNA
- DNA is the code, RNA is the worker that reads the code and builds protein
- DNA has 2 strands while RNA has 1 strand
- DNA stays in the nucleus while RNA leaves
- DNA has 1 type and RNA has 3 forms
- DNA is longer while RNA is in smaller pieces
What are the three types of RNA, and what is the shape and function of each?
- messenger RNA - linear - reads DNA and takes message to ribosomes
- transfer RNA - hairpin or key - brings amino acids to ribosome
- ribosomal RNA - globular - builds ribosomes
What is the name of the process where mRNA reads DNA?
transcription
Why is transcription necessary, and where does it happen?
to take the code to the ribosomes so proteins can be made - happens in nucleus
What enzyme builds the RNA?
RNA polymerase
What is the term for protein synthesis?
translation
Where does translation occur?
ribosomes
What are the building blocks of proteins?
amino acids
How many amino acids are in the human body?
20
Why is the code called a triplet code?
It works 3 bases at a time
What are three bases on DNA or mRNA called?
codons
What are three bases on tRNA called?
anticodon
How many codons are there, and what is the significance of having more codons than amino acids?
64 codons - some codons code for the same amino acids
What amino acid is always the start of a polypeptide chain?
methionine
How does the RNA know when to stop reading the code? How many are there?
stop codons - 3
What is a chain of amino acids?
polypeptide
What do we say is happening when a protein is being made from a gene?
gene expression
What is a mistake in the DNA called?
mutation
What is the general term for factors that cause mutations?
mutagens
Give 3 examples of mutagens.
- radiation
- heat
- cigarette tar
- asbestos
What do we call a mutation that affects 1 or 2 bases?
point mutation
What do we call a deletion or addition mutation that affects the entire code from that point?
frameshift
Which is more dangerous to an organism, a mutation in a body (somatic) cell, or a mutation in a gamete (sex cell)? Why
gametes - every cell forms from a mistake
Are mutations always bad?
no - most have no effect, and some are actually an advantage
What happens when a piece of DNA is missing?
genetic information is lost
What stores information in a cell?
nucleic acids - DNA and RNA
If you have 15% adenine in DNA, what would be the percent thymine in the same DNA?
15%
If you have 15% ademine in DNA, what would be the percent guanine in the same DNA?
35%
Why don’t ademines pair with guanines?
they are both purines - both long, and the rungs would be irregular size
What are purines? What are they like?
A and G - double rings
What are pyrimidines? What are they like?
T and C - single rings
What should the strands of DNA be like after replication?
identical
What is the other half of DNA if one half is ACT GGA
TGA CCT
What is RNA if it reads the following DNA segment: ATT GCA
UAA CGU
Use the genetic code to translate the following mRNA segment: UAC CGU
tyrosine - arginine
What are tyrosine and arginine?
amino acids
genes contain instructions for assembling what?
proteins
What is the central dogma of biology?
DNA - RNA - protein
What do we call the DNA in a cell that is not dividing?
What do we call the DNA in a cell that is dividing?
chromatin - not dividing
chromosomes - dividing
other than the nucleus of eukaryotes, where is some DNA found, and what is unusual about this DNA?
mitochondria - only passed through maternal side
What is the term for the entire set of DNA of an organism?
genome
How many bases are in the entire human genome?
3 billion bases
Where do we get our DNA? What process divides our DNA in half to make gametes (sex cells)
half from mom and half from dad - meiosis
Who originally discovered DNA? When?
Frederich Miecher - 1800s
Why did we not believe DNA could be the code? What did we believe would be the code?
too simple - We thought proteins would be the code.
How are cells specialized?
They express different genes and produce different proteins. RBCs make hemoglobin and pancreas cells produce insulin.
