Molecular Biology and Cell Division Flashcards
Nucleotide:
The simplest subunit in DNA.
What is a nucleotide composed of?
A five-carbon sugar, a phosphate, and one of four nitrogen bases.
What are the four DNA nitrogen bases?
Adenine, thymine, cytosine and guanine.
In a strand of DNA, the backbone of the molecule alternates between _________ and ___________.
phosphate, deoxyribose
What is the shape of DNA?
A double helix.
What forms the rungs of the DNA ladder?
Nitrogenous bases.
How do nitrogenous bases from one spine of the ladder join to the nitrogenous base on the other spine of the ladder?
Hydrogen bonds.
Adenine will bond with _______.
Thymine
Thymine will bond with _______.
Adenine
Guanine will bond with ________.
Cytosine
Cytosine will bond with _______.
Guanine
What is Chargoff’s rule?
Nitrogen bases bond with their complimentary pair making up a total of 100% of the rungs.
How many hydrogen bonds are in A-T?
Two.
How many hydrogen bonds are in G-C?
Three.
Which occurs first, DNA replication or cell division?
DNA replication.
Why must DNA be able to duplicate itself?
Growth, repairing of damaged cells, and maintaining cells.
Replication:
A single strand of nucleotides acts as a template for forming a complementary strand.
What does DNA replication require?
Enzymes, nucleotides, and a DNA template.
What are the steps to DNA replication?
- Starts at the replication origin
- Helicase unzips the hydrogen bonds
- The bases attract free-floating bases, which attach through DNA polymerase
Semi-conservative strands:
The daughter strands are made up of one-half old strands and one-half new strands.
What direction does DNA polymerase move in on the new strand?
From 5’ to 3’.
What synthesizes new DNA strands together?
DNA polymerase.
RNA primer:
Attaches to templates and guides DNA polymerase enzyme to starting point.
Leading Strand:
Continuous DNA part.
DNA ligase:
Glues together sugar-phosphate backbone and DNA fragments together.
Protein synthesis:
The flow of genetic information.
Proteins are made up of a long chain of specific sequences of _____ _____.
amino acids
Transcription:
Splitting DNA and making a copy of mRNA. Occurs in the nucleus.
Translation:
Proteins are made by tRNA bringing amino acids as described by the mRNA. Occurs in the cytoplasm with ribosomes.
Which occurs first, transcription or translation?
Transcription.
How is RNA different from DNA
RNa can leave the nucleus, its backbone is made of ribose instead of deoxyribose, it uses Uracil instead of Thymine, it’s single-stranded, and it can exist in multiple different forms.
DNA:
Codes for the sequence of bases in mRNA.
mRNA:
Carries messages from DNA in the nucleus to ribosomes in the cytoplasm. The message is a blueprint for the synthesis of a protein.
Ribosomes:
Attach to a strand of mRNA and synthesizes to a protein.
tRNA:
Carries amino acids to the ribosomes.
Amino Acids:
The units that are bonded together to form a protein.
Polypeptide Chain:
A chain of many amino acids. May form a complete protein or only part of a protein molecule.
Explain the full process of transcription:
- DNA unwinds in the nucleus by RNA polymerase
- One strand of the DNA will be transcribed
- RNA polymerase adds the appropriate mRNA nucleotide to create a strand of mRNA in the direction of 5’ to 3’ on the mRNA strand
- A stop signal is reached, and transcription ends
- mRNA moves to ribosome out in the cytoplasm
Codon:
Three bases that code for one amino acid on mRNA.
Redundancy:
Several codons for each amino acid.
How many amino acids are there?
20
What are the four special codes?
AUG (start codon), UAA, UAG, UGA (stop codons).
Continuous:
No punctuation/spaces in code.
What would an insertion or deletion in the code do?
Frame shift. Leads to mutation.
Explain the universal aspect of amino acids and proteins:
They are the same codes for all organisms. This supports a common origin of life theory.
Explain the process of translation:
- mRNA arrives at the ribosome
- Ribosomes form from two subunits and attach to mRNA
- Start codon (AUG) will start the translation process
- tRNA will bring the correct amino acid to the mRNA codon
- Amino acids get put together like a chain using ATP with peptide bonds
- A terminating codon will turn translation off
What are the two types of mutations?
Somatic and germ line.
Somatic mutation:
Body cell mutation.
Germline mutation:
Sex cell mutation.
Beneficial mutations:
Give organisms a selective advantage, tends to become more common over time, leads to evolutionary change.
Harmful mutations:
Reduces an individual’s fitness, tends to be selected against, occurs at low rates.
Neutral mutations:
No benefit or cost, not acted on by natural selection.
Insertion:
An extra nucleotide is inserted into the DNA, which causes a frame shift.
Deletion:
A nucleotide is deleted from the DNA, which causes a frameshift.
Substitution:
One nucleotide is substituted for another, which causes a point mutation.
Hemophilia:
An inherited bleeding disorder in which the blood does not clot properly.
Cystic fibrosis:
A disorder that damages your lungs, digestive tract and other organs. It’s an inherited disease caused by a defective gene that can be passed from generation to generation.
Genome:
Makes up all the DNA in the cell
Genes:
A finite or discrete unit of heredity that is coded by a sequence of DNA bases. It produces a polypeptide (protein) made of many amino acids.
Genetic Engineering - Recombinant DNA:
To recombine DNA. A technique to determine gene expression. Gene segments from different sources are recombined in vitro and transferred into cells (usually E. coli) to see what happens.
What was the first successful genetic engineering recombinant DNA project?
The first successful GE experiment with human DNA took place in 1980. The human gene, which codes for the protein interferon, was successfully introduced into a bacteria cell. The bacteria produced human protein. Interferon combats viral infections and may help in fighting cancer.
Explain the process of recombinant DNA:
- The desired gene is isolated and cut out of the DNA with a restriction enzyme.
- Bacterial DNA, called a plasmid, is opened using a restriction enzyme.
- The isolated desired gene is inserted into a bacterial plasmid using a ligase. The new DNA is now called recombinant DNA.
- The plasmid is absorbed by a bacterium which reproduces asexually to produce many clones containing the recombinant DNA.
- Bacterial cells produce the protein coded by the foreign gene. Desired protein can be isolated and purified from the culture.