DNA AND PROTEIN SYNTHESIS TEST REVIEW Flashcards
DNA
Deoxyribonucleic acid, a polymer of nucleotides which are formed by dehydration synthesis. It is the UNITY of life
3 major functions of DNA
Controls cellular activities, DNA replication, and undergoes mutations
Significance of codes in DNA
Genetic information are encoded in the sequence of bases strung together in DNA
XX chromosome
Female
XY chromosome
Male
Two types of nucleic acids
DNA and RNA
Mutations
Mistakes during DNA replication
Significance of mutations
Different combinations of DNA sequences due to mutations and sexual reproduction explain the existence of all the different species that have lived on earth, creating diversity
First form of life on planet
Self-replicating strand of RNA, such as a virus
Who discovered DNA double helix
James Watson and Francis Crick
DNA and RNA are polymers of ___
Nucleotides
What is composed in a nucleotide
- 5 carbon pentose sugar (deoxyribose/ribose)
- Phosphate group
- Nitrogen base
Two types of bases
Purines and pyrimidines
Differences between purines and pyrimidines
Purines have a double carbon ring structure whereas pyrimidines have a single carbon ring structure.
Purines
Adenine and guanine
Pyrimidines
Thymine, cytosine, and uracil (RNA only)
DNA strand explanation
Sequence of nucleotides linked together by synthesis to form double helix. Each strand composed of backbone of alternating phosphate group and deoxyribose molecules with nitrogen base attached to the sugar unit
Anti-parallel
One side of DNA molecule is 5’ to 3’. The other side is upside down running from 3’ to 5’
Bonds holding the strands
Hydrogen bonds. The bases stick out the side of sugar molecules and are linked to bases of other strand
Complementary base pairing
Purine with a pyrimidine. Adenine bonds with thymine (2 hydrogen bonds) and guanine bonds with cytosine (3 hydrogen bonds)
Chargaff’s rule
Number of purine bases are always equal to the number of pyrimidine bases
Significance of sequence of bases
Codes heredity information in genetic code in DNA and RNA
Are DNA strands long
Yes
How long is a DNA strand stretched and how many pairs of bases
About 6 feet long and 3.2 billion pairs of bases
Human genome project
Project from 1990. Wanted to determine the sequence of bases that make up a human’s genetic code and then in 2003, they cracked the code
Genes
Units of inheritance that control characteristics of an organism.
Where are genes located
Chromosomes of the cell nucleus and consist of segments of DNA molecule
Genes consist of how many DNA base-pairs
- About 175,000 genes compose the DNA molecule of a single human chromosome.
What does it mean when a gene occurs in pairs
Half of each person’s genes come from the mother and half from father. Combinations of different genes determine the characteristics of the organism
What do genes control and examples
Cellular chemical reactions by directing the formation of proteins such as insulin or glucagon
Histones
Proteins that keep chromosomes tightly coiled
Before a cell can divide, it must ____
Duplicate
Replication + process
The duplication process. Each strand viewed as a template and can produce a “reverse image” copy. Each new strand of DNA produced has a sequence of bases that are exactly complementary to the template strand
Two strands of DNA
Daughter/leading strand (new copied DNA and lagging strand
Why does the leading strand copy faster
Copies DNA from 5’ to 3’ direction
Why is lagging strand slower
Old DNA molecules needs to continue to unwind and will take longer since it goes the opposite direction
Semi conservative replication
When each new strand of DNA produced contains one “old” strand (the template) and the one new strand
How is accuracy of replication evident
Half the original molecule is conserved in each of the new molecules which ensures that there will be very accurate replication of the parent molecule
Helicase
Enzyme that breaks the hydrogen bonds between DNA strands
DNA Polymerase
Enzyme that proof reads for any errors
Overall process of replication
Helicase enzyme breaks the hydrogen bonds between the two strands of DNA. The double helix unwinds and the two strands of DNA separate. The new nucleotides from nucleoplasm move in to complementary pair up with bases of the template strand at a rate of 50-500 nucleotides per second. Hydrogen bonds form with an enzyme called DNA polymerase, as it gets proof read. Sugar phosphate bonds form between nucleotides of new strand and the new molecule winds up into a double helix
RNA
How DNA communicates its message. Genetic material of some viruses that are necessary in organisms for protein synthesis to occur. Could have been the original nucleic acid when life first arose on earth
Does RNA contain nucleotides
Yes
RNA nucleotides
5 carbon sugar (ribose), phosphate group attached to one end of sugar molecule, and one of several different nitrogen bases linked to opposite end of ribose.
RNA nitrogen bases
Adenine, guanine, cytosine, and uracil instead of thymine to pair with adenine
RNA structure
Single stranded, not a double helix like DNA
3 types of RNA
Ribosomal RNA, messenger RNA, transfer RNA
Ribosomal RNA (rRNA) (4):
- Made by the nucleolus and migrates to cytoplasm through pores of nuclear envelope
- 2 rRNA subunits combine with protein to form ribosomes found on rough ER and throughout cytoplasm
- Aids in protein synthesis by reading mRNA codon
Messenger RNA (mRNA):
- Made by copying sections of DNA
- Template strand (a gene) by a process called transcription (contains codons which are triplet of nitrogen bases)
Transfer RNA (tRNA) (4):
- Able to recognize a very specific amino acid by using anti codon.
- Carries amino acid from cytoplasm to ribosome for protein synthesis
Two major process which occurs in order for protein to be made
DNA copied through transcription into mRNA used in translation to build a protein
Transcription
Process of making an RNA copy of a gene sequence. mRNA leaves nucleus and enters cytoplasm where it directs protein synthesis
Enzyme used in transcription of RNA
RNA polymerase
Steps in translation (6):
- Hydrogen bonds break and specific section of DNA unzips (gene) to expose a set of bases
- On one strand of DNA (sense strand), complementary RNA bases are brought in like uracil pairing with adenine on DNA. The other strand of DNA is not used by mRNA in eukaryotic cells
- Adjacent RNA nucleotides from covalent bonds between sugar-phosphate
- mRNA strand released from DNA (RNA is single stranded)
- DNA molecule rewinds and reforms hydrogen bonds to return to double helix
- mRNA leaves nucleus through nuclear pore and goes into cytoplasm or the Rough ER
Where does transcription occur
Nucleus
Codon
3 letter unit of nucleotides which codes for one amino acid
How many codons
64 in total. 61 codes for specific amino acids and the remaining 3 are the stop codons
Anti-codon
Base sequence that is complementary to the codon and is found on transfer RNA (tRNA)
Translation RNA
mRNA used to build a protein. Translates the codons on mRNA into sequence of amino acids to form a primary polypeptide structure
3 subunits of translation process
initiation, elongation, and termination
Initiation in translation (3):
- Small rRNA subunit attaches to start codon (AUG) on mRNA
- tRNA with an anti-codon UAC complimentary base pair with codon. This tRNA carries specific amino acid called methionine
- Larger rRNA subunit joins with small subunit
If there are 20 different types of amino acids, there are 20 types of tRNA, why?
Each specific type of tRNA codes for specific amino acid
Does tRNA use energy
Yes. It uses ATP to pick up amino acids from cytoplasm
Elongation
More amino acids added and connected together to form polypeptide, as specified by mRNA sequence. An incoming amino-tRNA recognizes the next codon and complementary binds there
Elongation process (7):
- Peptide bond is formed between new amino acid 2 and the first amino acid 1
- Amino acid is removed from tRNA1 so the bond breaks between amino acid 1 and tRNA 1
- tRNA 1 is released and tRNA 2 shifts over to the site previously occupied by tRNA 1
- Ribosomes move over one codon along mRNA in 5’ to 3’ direction
- Movement shifts the tRNA 2 over which is attached to the growing amino acid chain
- tRNA 3 with amino acid 3 can move on and bind with next codon on mRNA
- Process repeats and chain elongates
How many amino acids form a peptide bond every second
10-20
Termination
Repeats special codon called stop codon. Stop codons do not code for amino acids but instead act as signals to stop translation
3 stop codons
UAA, UAG, UGA
Termination process (4):
- Protein called release factor binds directly to stop codon. Release factor causes water molecules to be added to end of polypeptide chain and the chain separates from the last tRNA
- Protein is complete and ready to form a secondary helix structure
- mRNA is broken down with lysosome and ribosome dissociates into large and small subunits
- New protein sent for processing and packaging by rough ER and golgi through secretory vesicles and goes to cell membrane to leave through exocytosis
Polyribosome
When many ribosomes simultaneously transcribe the same mRNA and therefore many copies of the same protein can be made quickly
How many proteins can be synthesized if the materials (nucleotides, amino acids, etc) are available
100,000
RNA polymerase
Enzyme that proof reads the chain because there are always mistakes in 1 in every 30 polypeptide chain
Genetic mutation
a permanent alteration in the nucleotide sequence of one or more genes. If nucleotides are arranged, deleted, added, it could lead to a non-functional protein
Mutation
Change in an organism resulting from chemical change in structure of gene. They are inheritable
American geneticist
Herman Muller. In 1927, he developed experiment to study how mutations occur
Mutagens and examples
Factors that can cause mutations, ex. UV light, cigarette smoke, x-ray, etc
3 types of mutagens and examples:
- Chemical mutagens: food preservatives, cigarette smoke, acetone
- Radiation: UV lights, x-ray, gamma rays
- Viral mutagens: cervical cancer patients, zika, HPV
Carcinogen
Mutagens that cause cancer. They cause cells to undergo mitosis uncontrollably resulting in tumors
Somatic mutations and example
Occur in body cells after birth, ex. Cancer
Germinal mutations and example
Mutations of gametes (egg/sperm) of early in development of embryo, ex. Dwarfism, diabetes
2 main categories of mutations:
- Gene mutations: affects only one gene; small scale effects
- Chromosomal mutations: affects multiple genes because they affect entire chromosome or part of chromosomes; huge effects
Types of gene mutations (3)
- Substitution: One gene (nucleotide) are substituted for another nucleotide
- Addition: Nucleotide is added
- Deletion: Nucleotide is deleted
Sickle cell impact on body
Sickle cell block the veins and arteries. As fewer and fewer normal red blood cells can pass through congested blood vessels, the tissue and cells become starved for oxygen and other nutrients
How can substitution mutations be functional
Although it can be useless in the human body, sometimes the mutation will create a functional protein because some codon will still code for the same amino acid
Chromosomal mutations
Occur after chromosomes are broken due to exposure in drugs, radiations, etc and reform abnormally. Pieces of chromosomes can be lost, added, or whole chromosomes can be lost or added
Types of chromosomal mutations (4):
- Inversion: Changes spatial relationships between element controlling genes
- Translocation: Impairs genetic control of cell and could lead to cancer
- Duplication: Often beneficial. Frees up extra of certain genes to mutate and increase evolutionary complexity. However, it can lead to cancer by producing too much protein
- Deletion: Cells loses ability to produce needed proteins such as enzymes needed for metabolism of proteins, carbohydrates, or lipids
Recombining DNA
DNA from one specie (Green coding for protein insulin) is inserted into DNA of a second specie (ex. Bacteria). The specie can then go on to produce proteins of the first specie and when it reproduces, it will copy the other species DNA and pass it onto offspring. The gene is cloned by allowing bacteria to multiply
Effects of recombining DNA on earth
Allowed production of rare proteins in large quantities. Human gene therapy helps control and cure genetic disorders by isolating, modifying, and reinserting DNA sequences
Cloning genes
viruses and bacteria can be used to make copies of gene of another species. Huge amounts of any piece of DNA can now be made using technique called the Polymerase Chain Reaction
Biotechnology products
Whole organisms can now be clone biotechnology products. Genetically engineered prokaryotic and eukaryotic cells can be used to mass-produce once rare medical proteins, hormones, and vaccines to prevent disease
Pro of recombinant DNA and examples
Allows us to produce large number of resources that are usually only present in small quantities. Ex. Human growth hormone, insulin, tpa
Insulin (Recombinant DNA)
Used to only come from pancreatic glands of cows and pigs but now can be cloned in human DNA
TPA (Recombinant DNA)
Tissue plasminogen activator. A protein that activates an enzyme that dissolves blood clots used to dissolve coronary blood clots of heart attack victims
What other things can biotechnology products treat (4):
- Cancer
- Anemia
- Respiratory distress syndrome
- High blood pressure
Vector and example
Something that can get the DNA from one species into the other species DNA. Ex. Plasmid, a circular piece of DNA found in some bacteria
Process of recombinant DNA
Human gene is inserted into plasmid and is taken up by bacteria. The bacteria reproduce the plasmid along with its own DNA when it reproduces, and translates the human gene, producing human protein
What biochemicals are contained in chromosomes
Nucleic acids, proteins
Compare and contrast gene and chromosomes
Genes are in chromosomes. Each gene contains its own specific DNA
What holds two strands of DNA together
Hydrogen bonds
What is meant by complementary base pairing
When purine binds with a pyrimidine (A with T, G with C)
3 functions of DNA:
- Stores information that controls development
- Stores information that controls metabolic activity of cell
- Stores information to build proteins or lipids
Why is it necessary to replicate DNA in cell
Each daughter cell has exact copy of DNA which can be transmitted in gametes from 1 generation to the next
What is a template strand
Mold or blueprint used to produce a shape opposite to itself
5 major steps of DNA replication:
- Helicase breaks hydrogen bonds causing DNA to unwind
- DNA polymerase brings DNA nucleotides to parent DNA to undergo complementary base pairing
- DNA polymerase proofreads new DNA strand
- New DNA strand links sugar-phosphate backbone by synthesis
- DNA molecule zips back up having 2 identical DNA molecules
Semi-conservative process
New DNA molecule has 50% old (parent strand DNA) + 50% new (new strand DNA
Gene and enzyme relationship
Genes contain a specific DNA segment that contain blue prints to create a specific type of enzyme
mRNA function
Copies the instructional blueprints from DNA for instructions to build protein
How does mRNA take message from DNA to cytoplasm
Using ATP energy mRNA is transported to cytoplasm
mRNA and ribosome relationship
Ribosomes attach to a start codon to begin process of building a protein
How much of the DNA molecule does the mRNA copy
Copies a specific section on DNA segment that has instructions to build a protein
Stop codons
UAA, UAG, UGA
Start codon
AUG
What are ribosomes composed of
2 subunits of protein + rRNA
How is rRNA made
DNA has a specific instructional blueprint in gene for instruction to make rRNA in nucleolus
Function of rRNA
Uses anticodon to pick up and transport amino acids to mRNA
Why is ATP needed for mRNA
To pick up and transport amino acids to mRNA
Function of anticodon
Reads the mRNA codon to allow tRNA to bind to a specific codon site on mRNA
How many tRNAs fit on a ribosome at once
2
How do polysomes work
Several ribosomes can move along 1 mRNA at once. Multiple copies of proteins are done at one time
Summary of protein synthesis steps
- DNA contains series of bases that serve as triplet code
- During transcription, one strand of DNA serves as template for formation of mRNA
- mRNA goes into cytoplasm and becomes associated with ribosomes
- tRNA molecules have anti codons that pair complementary mRNA codons
- As ribosomes move along mRNA, newly arrived tRNA/amino acids receive growing polypeptide chain from tRNA.
Cause of down syndrome
Translocation mutation. Occurs before birth where you get an exchange of parts of chromosomes
If a single nucleotide base is changed in a DNA sequence, what might the result be
Possibly a functional protein but more likely a protein created which is non-functional
What hosts are generally used in recombinant DNA
Bacteria, viruses, human genes
Examples of recombinant DNA (4):
- Cloning genes
- Producing biotechnology products (Insulin, TPA)
- Making transgenic organisms
- Gene therapy
