dna and protein synthesis notes Flashcards
what are the 3 major functions of DNA?
controls cellular activities, DNA replication, and DNA mutations
DNA carries a ____
code
DNA controls ____
cellular activities
what are encoded wishing the DNA?
genetic instructions (the code)
what is DNA replication?
when DNA makes exact copies of itself, made to be passed onto other cells
explain how DNA mutation has changed species that live on earth?
different combinations of DNA sequences due to mutations and sexual reproduction explain the existence of all different species on earth
DNA is the source _____
of the unity of life
what did life most likely begin as?
a nucleic acid
what are the two types of nucleic acids?
DNA and RNA
the first form of life on earth is thought to be a self-replicating strand of what?
RNA
who discovered the first x-ray data for the DNA structure?
franklin in 1951
who discovered that DNA has a double helix?
james watson and francis crick (bad people)
1953
DNA and RNA are polymers of what?
nucleotides
what is a nucleotide composed of?
- a pentose (5 carbon) sugar (deoxyribose/ribose)
- a phosphate group
- a nitrogenous base
what are the two types of bases?
purines and pyrimidines
which base has a double nitrogen ring structure?
purines
which base has a single nitrogen ring structure?
pyrimidines
what are the two nucleotide bases of purines?
adenine and guanine
what are the three nucleotide bases of pyrimidines?
thymine, cytosine, uracil (RNA ONLY)
DNA is a _____ helix
double
what is linked together to form the double helix of DNA?
a sequence of nucleotides linked together
what are the strands of DNA composed of?
alternating molecules of deoxyribose and phosphate
what is attached to each deoxyribose unit in DNA?
a nitrogenous base
what can the double helix be described as?
a twisted ladder
what connects the two nucleotides to form the helix of DNA?
hydrogen bonds
what are the bases in DNA attached to?
the sugar molecules ( P and S )
what are the 4 bases in DNA?
adenine (A), thymine (T), guanine (G), cytosine (C)
what pyrimidine (letter) connects to the purine adenine (A)?
thymine (T)
what pyrimidine (letter) connects to the purine guanine (G)?
cytosine (C)
how many hydrogen bonds do adenine and thymine have in DNA?
2 H-bonds
how many hydrogen bonds do guanine and cytosine have in DNA?
3 H-bonds
what is chargaffs rule?
the number of purine bases equals the number of pyrimidine bases
T or F: the bases can be paired with any of the other bases in DNA
FALSE:
the bases may only be paired as A-T or T-A, G-C or C-G
T or F: the bases have to be in a certain order every time within the DNA
FALSE:
order does not matter, as long as they are paired correctly.
roughly how many pairs of bases are in the human body?
3 billion; about one meter in every human
where are the genes located in the cell?
on the chromosomes within the nucleus
roughly how many base-pairs are in a gene?
about 1000 DNA base-pairs
genes always occur in ____
pairs
how are a persons genes determined?
half come from the mother and half from the father
how do genes control cellular chemical reactions?
by directing the formation of enzymes
what do genes occur in?
pairs
how many DNA base-pairs do genes consist of?
about 1000
where are genes located?
on the chromosomes of the cell nucleus, and in segments of DNA molecules
what do chromosomes contain?
genes
what are the chromosomes held together by?
the protein histones
what must happen to the DNA before a cell can be divided?
the DNA must be duplicated
what is the duplication process of DNA called?
replication
how many DNA molecules are produced after replication?
two
DNA can be viewed as a _____ which can produce a _______ copy of itself
template, reverse image
what does the replicated strand have in common with the “template” strand?
it has a sequence of bases exactly complementary to the template strand
what two things does each new strand of DNA that is produced contain?
one “old” strand and one new strand
when a new strand of DNA has one old strand, and one new strand, what is that called?
semi-conserving replication
what must occur prior to cells dividing and why?
semi-conservative replication; to ensure that the daughter cells receive the same genetic material as the parent cell
what are the 4 steps to DNA replication
- unzipping 2. pairing 3. h-bonds form 4. sugar-phosphate bonds form between adjacent nucleotides
what happens in the unzipping process of DNA replication?
enzyme helicase help break h-bonds between 2 strands, double helix unwinds and separate
what happens in the pairing stage of DNA replication?
new nucleotides move in to complementary pair up with bases of each template strand
what helps form h-bonds between two new strands of DNA?
the enzyme polymerase
what happens in the last step of DNA replication?
sugar-phosphate bonds form between adjacent nucleotides, then winds into a double helix
what is RNA necessary for?
protein synthesis
RNA the genetic material of some ____
viruses
what do all RNA and DNA molecules consist of?
nucleotides
DNA and RNA have similar what?
chemical organization
how many subunits does RNA consist of?
3
what are the 3 sub-units of RNA
- 5-carbon sugar called ribose
- a phosphate group
- one of several different nitrogenous based
which base is different in RNA than DNA?
U instead of T (uracil instead of thymine)
is RNA single stranded or double stranded?
single
what are the 3 types of RNA?
- ribosomal RNA (rRNA)
- messenger RNA (mRNA)
- transfer RNA (tRNA)
what is the most numerous type of RNA
rRNA, 85-90%
what is rRNA made by and where?
by the nucleolus in the nucleus; migrated to cytoplasm through the pores of the nuclear envelope
what protein does 2 rRNA subunits form?
ribosomes
what is the function of rRNA?
aids in protein synthesis by ready the mRNA codon
what percent does mRNA constitute in the cell?
5%-10%
roughly how many nucleotides long are mRNA?
900-1500
how is mRNA made? what is the process called?
made by copying sections of the DNA template strand by a process called transcription
what % does tRNA make up in a cell?
about 5%
how many nucleotides long is tRNA?
about 80 nucleotides long
what is tRNA able to recognize using it’s what?
able to recognize a very specific amino acid using its anti-codon
what is tRNA’s function?
carries the amino acid from the cytoplasm to a ribosome for protein synthesis
what are the 2 major processes that occur for proteins to be made?
transcription and translation
what are the 5 steps for proteins to be made?
DNA-transcription-mRna-translation-protein
what is the first step in transcription?
the hydrogen bonds break in the DNA, and double helix unzips; to expose the bases
in RNA, what does adenine bind to?
Uracil (U)
what is brought in on the one side of DNA during transcription
complementary RNA bases are brought in
what forms between sugar-phosphate in the transcription process
adjacent RNA nucleotides for covalent bonds
what is released from the DNA during the transcription process?
the RNA strand
what happens after the RNA is released from DNA during the transcription process?
the DNA molecule rewinds and returns to normal double helix form
what is the enzyme involved in transcription known as?
RNA polymerase
where does transcription occur in the cell?
the nucleus; the nucleoli to be exact
what is the summery of translation?
translating the codons on mRNA into a sequence of amino acids to for a primary polypeptide structure
what is the 3 letter “unit” of mRNA
a codon
how many codons are there in total?
64 in total, 61 codes for specific amino acids
what are the three letters of a codon used for?
for one amino acid
what is an anticodon?
base sequence that is complementary to the codon
where is anticodon found?
on tRNA
