Protein Synthesis Flashcards
1
Q
What are the 3 major functions of DNA?
A
- controls cellular activities, including reproduction; genetic information is encoded on chromosomes in bases, which are used to build proteins
- replicates; in order for every cell to have genetic information DNA must replicate itself
- mutates; mutations and recombination in the structure and number of DNA molecules are the source of life’s diversity
- DNA is the source of unity of life
2
Q
Describe nucleic acid structure
A
- DNA & RNA are polymers of nucleotides; each nucleotide is composed of a pentose (5 carbon) sugar, a phosphate group, and a nitrogenous base
- components of the nucleotides are linked together by strong covalent bonds
- each nucleotide links together by a covalent bond attached to the carbon 3 of the sugar
3
Q
Describe the double helix structure
A
- -a long, twisted ladder
- DNA strand that consists of a sequence of nucleotides linked together
- each strand or one side of the ladder is composed of alternating molecules of deoxyribose and phosphate with a nitrogenous base attached to each deoxyribose unit
- pairs of joined bases form the rungs of the ladder by linking to the bases of the other strand by hydrogen bonds in a very strict pattern
- sugar-phosphate run in opposite directions; this is called anti-parallel
4
Q
What is complimentary base pairing?
A
-the bases can be in any order, but have specific pairings:
A bonds with T with a DOUBLE hydrogen bond
G bonds with C with a TRIPLE hydrgogen bond
-it’s the sequence of bases that codes heredity information in the genetic code in DNA and RNA
5
Q
Nucleosomes
A
- in long strands of DNA, there are “fillers” of information, called introns and there are exons that seperate the genes, which will be transcribed when making proteins
- because DNA is so long, it supercoils around 8 histone proteins to form a nucleosome; this helps regulate transcription as they can serve as markers
6
Q
What are genes?
A
- units of inheritance that control particular characteristic or capabilities of an organism
- located on the chromosomes of the cell nucleus and consist of segments of DNA molecules
- genes act in pairs that dictate traits(half of the genes are from the mother and half from the father)
- most ordering characteristics like height and eye colour are determined by combinations of several different genes
7
Q
What are the steps for DNA replication?
A
- helicase unwinds(or unzips) the DNA, breaking the hydrogen bonds between the bases
- RNA primase(primer)is added to indicate replication
- DNA polymerase III adds nucleotides to 3’ end(hooks up bases and the sugar phosphate backbone)
- DNA primase I removes RNA primer and replaces with DNA
- ligase seals gaps and joins the pieces together. DNA replication is now complete
8
Q
What is DNA replication?
A
- DNA making identical copies of itself in order for the cell to divide
- occurs in a 5’ - 3’ direction; 5’ end of the free DNA nucleotides is added to the 3’ end of the strand of DNA that is already synthesized
- each strand of DNA can be viewed as a template; it produces a “reverse image” copy of itself
- each new strand of DNA produced contains one “old” strand and one new strand, aka “semi-conservative”; this ensures that there will be very accurate replication of the parent molecule
- the product of replication by one DNA molecule is 2 complete double-stranded DNA molecules
- replication occurs at many forks along the DNA strand in both directions in order to speed up the process
9
Q
What is RNA composed of?
A
- 5 carbon-sugar called ribose
- a phosphate group that is attached to bend of the sugar molecule
- one of several different nitrogenous bases linked to the opposite end of the ribose
10
Q
What is the difference between DNA and RNA?
A
- in RNA, the base uracil is used instead of thymine
- RNA is single stranded & not double helix; DNA is double stranded
- RNA is produced by a process called transcription; DNA is copied by a process called replication
- RNA polymerase is used instead of helicase
11
Q
What are the steps of transcription
A
- RNA polymerase binds to a specific section of the DNA that is needed and unwinds that section
- along one strand of DNA(the “antisense” strand), complementary RNA bases are brought in (uracil binds with adenine, cytosine binds to guanine), and the other strand(“sense” strand) isn’t read
- adjacent RNA nucleotides form sugar phosphate bonds
- RNA polymerase reaches the terminator region and the polymerase breaks free and the RNA strand is release from DNA
- RNA polymerase rewinds the DNA molecule, and returns to its normal double helix form
- mRNA strand is processed
- RNA leaves the nucleus and go into the cytoplasm
12
Q
What is rRNA?
A
- becomes a structural part of ribosomes and serves as a genetic link between mRNA and tRNA
- rRNA varies in size and is the most plentiful RNA
- forms ribosomes; 1 binding site for mRNA and 3 sites for tRNA
- small subunit is where the mRNA lands and the tRNA binding site are found on the large subunit
- site A holds the tRNA carrying the next amino acid; site P holds the tRNA carrying the growing polypeptide chain and site E is the discharge sit
13
Q
What is tRNA?
A
- deliver amino acids from the cytoplasm to the ribosome
- a different tRNA for each amino acid; each type of tRNA is to bring its specific amino acid to a ribosome, using ATP and an enzyme to attach to ribosome
- tRNA molecules consist of about 80 nucleotides and are structured in a cloverleaf pattern
14
Q
mRNA
A
- carries the genetic code contained in the sequence of bases in the cell’s DNA from the nucleus to the ribosme
- acts as a “go-between” for DNA in the nucleus and the ribosmes in the cytoplasm
15
Q
What is translation?
A
- the process that changes the RNA message into the actual protein and occurs at the surface of the ribosome
- occurs when mRNA leaves the nucleus and enters the cytoplasm
