Chapter 6: DNA Flashcards
DNA
Deoxyribonucleic acid
What is a nucleic acid?
Molecules that store information
DNA
What is the connection between DNA and chromosomes?
DNA exists as long fibers called chromosomes, which contain genes.
Polymer
A large molecule made by repeating a smaller unit
What are the polymers in DNA called?
Nucleotides
How many chromosomes do humans have?
46; 23 pairs
DNA helicase breaks which type of bond in the DNA molecule?
Hydrogen bonds
The overall structure of DNA is a…
Double helix
What does a nucleotide contain?
A central five-carbon sugar (deoxyribose in DNA), a negatively charged phosphate, and a base made from one or two rings of nitrogen and carbon.
T/F: The sugar and phosphate are identical among all DNA nucleotides
True
Polynucleotide
A polymer made up of many nucleotides covalently bonded together. Contained in one molecule of DNA.
T/F: A polynucleotide can contain any combination of the four bases along its length
True
An A-T base pair is held together by how many hydrogen bonds?
2
A C-G base pair is held together by how many hydrogen bonds?
3
DNA Replication
The process by which a DNA molecule is copied
DNA replication is said to be semi-conservative because…
Each new molecule conserves half of the original molecule
Describe the first step in DNA replication
The double helix is peeled apart by the enzyme helicase. This forms a “replication bubble” where the bases in each separate DNA strand are exposed.
Describe the second step in DNA replication
DNA polymerase binds the two separate DNA strands together. Using the original strand as a template, DNA polymerase matches the correct bases together.
Describe the third step in DNA replication
DNA ligase fuses the two individual fragments into a final DNA molecule
What are the two types of nucleic acids found in all living cells?
DNA and RNA
What does RNA stand for?
Ribonucleic acid
What are the similarities between DNA and RNA?
- Both are polymers of nucleotides
- Each consists a sugar
- Both have phosphates
- Both have bases
What are the three structural differences between DNA and RNA?
- DNA is double stranded; RNA is single stranded
- The sugar is DNA is deoxyribose; the sugar in RNA is ribose
- DNA has Thymine base; RNA has Uracil base
How does DNA direct the production of proteins?
DNA first produces RNA, which manufactures the production of proteins
T/F: DNA produces your appearance
False; DNA produces proteins that are responsible for physical traits
How does genetic information flow from DNA to RNA to protein?
Flow of information starts in the DNA in the nucleus; information encodes into RNA that leaves the nucleus; RNA is used to produce proteins using ribosomes in the cytoplasm.
Transcription
The synthesis of RNA on a DNA template
How does RNA leave the nucleus?
Through an opening in the nuclear envelope called the nuclear pore.
Translation
The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule
Messenger RNA (mRNA)
A ribonucleic acid that encodes genetic information from DNA and encodes it to ribosomes
Codon
A three-nucleotide sequence in mRNA that specifies a particular termination signal; the basic unit of the genetic code
In eukaryotic cells, transcription takes place in the…
nucleus
Describe the first step on transcription
An enzyme called RNA polymerase binds to a promoter, which is a “start here” signal for the beginning of a gene
Describe the second step in transcription
RNA polymerase synthesizes a molecule of RNA; A matches with T, U matches with A, C matches with G, G matches with C
Describe the third step in transcription
Introns are removed, eons are joined together (RNA splicing)
What is the fourth step of transcription?
mRNA leaves the nucleus
Translation takes place in what part of the cell?
Ribosomes within the cytoplasm
Ribosomal RNA (rRNA)
The type of nucleic acid that makes ribosomes along with proteins. It is the most abundant type of RNA
Transfer RNA (tRNA)
An interpreter in translation. The specific anticodons pick up an amino acid and and conveys the appropriate codon.
Anticodon
On a tRNA molecule, a sequence of three nucleotides that is complementary to a codon
Triplet code
The correspondence between an mRNA codon and its amino acid
What is the specific start codon?
AUG
What are the three stop codons?
UAA, UAG, UGA
Where are the binding sites for mRNA and tRNA?
In ribosomes
Initiation
The first step of translation. An mRNA molecule binds to a small ribosomal subunit. tRNA then binds to the “start” codon
Elongation
The second step of translation. The polypeptide grows longer due to the newly made amino acids from tRNA and mRNA. That tRNA molecule then leaves the cell, making room for the next one.
Termination
The final step in translation. The ribosome disassembles once it reaches a “stop” codon on an mRNA.
What is the first step of gene expression?
Transcription
What is NOT a modification to the mRNA?
Promoter binding
RNA polymerase is transcribing a segment of DNA that contains the sequence shown below, using the upper strand as template. What will the sequence of this segment of RNA be?
5’GATCTACGTA3’
3’CTAGATGCAT5’
UACGUAGAUC
Name the process of PCR in order
- Start with a sample of double-stranded DNA
- Heat sample to two DNA strands
- DNA polymerase duplicates DNA strands
- Cool sample to allow DNA helices to form
Which of the following is FALSE regarding X-Chromosome inactivation?
Inactivated X chromosome happens in the Zygote
Which part of a nucleotide molecule in DNA encodes genetic information?
The base
Which nucleic acid acts like an enzyme, stabilizing and orienting different molecules to facilitate the formation of bonds between them?
rRNA
How is translation initiated?
Two ribosomal subunits bind to the mRNA transcript.
PCR is used to copy just a relatively small region of DNA, not the entire genome. How do researchers specifically target the region of interest?
They use two primers, each about 15 to 20 nucleotides long, that flank the region of interest.
T/F: Both genetically modified plants and animals make up a significant part of our food supply.
False
When is cell-to-cell communication particularly important in regulating gene expression?
During embryonic development
Puberty is caused by the release of follicle stimulating hormone and luteinizing hormone from the pituitary gland. These hormones are delivered to the ovary in girls and initiate the monthly release of mature egg cells. This is an example of what mechanism of regulation of gene expression?
A typical signal transduction pathway
The small circular molecules of DNA commonly found in bacteria are called…
Plasmids
Gel electrophoresis separates DNA fragments according to their…
Length
T/F: Standard STR analysis of a DNA sample from a crime scene and DNA from a suspect shows matches at four sites. The suspect is guilty.
False
Where does the bond form that binds one strand of DNA to its other strand?
Between the bases
Do all cells of the body express the same genes?
No, since they don’t all need to make the same proteins
T/F: During transcription of a specific gene, only one DNA strand serves as a template for the formation of RNA.
True
Which enzyme is responsible for adding complementary DNA bases to an exposed DNA strand?
DNA polymerase
After DNA replication…
Each of the two daughter DNA molecules contains one strand from the original DNA molecule and one newly synthesized strand
What is the role of primers in the PCR techniques?
To target specific areas of DNA
Gene cloning is used to…
Produce large quantities of human proteins
Finding a male calico cat is…
Not impossible, but rare. X-chromosome inactivation can sometimes happen in males, but mostly females
What is the monomer of the DNA molecule?
Nucleotide
Gene regulation
The turning on and off of specific genes within a living organism
Gene expression
The process whereby genetic information flows from genes to proteins; the flow of genetic information from the genotype to the phenotype: DNA → RNA → protein.
What happens if a chromosome is condensed?
The many genes that it contains are inaccessible and won’t be able to produce proteins
X-chromosome inactivation
In female mammals, the inactivation of one X-chromosome in a somatic cell. All descendants have the same copy of X-chromosome inactivation
Barr body
A dense body formed from a deactivated X chromosome found in the nuclei of female mammalian cells.
Transcription factors
A series of proteins that must bind to DNA before transcription can begin
Intron
Noncoding regions that are spliced out
Exon
Coding regions that are pasted together, forming multiple mRNAs
What ways can the RNA transcribed from a gene be altered?
- A cap and a tail are added
- Introns are spliced out and eons are pasted together. Several mRNAs can be produced from a single gene
- microRNAs bind to RNA molecules and prevent them from producing protein
Signal transduction pathway
A series of molecular changes that converts a signal received on a target cell’s surface to a specific response inside the cell.
What is the usual result of a signal transduction pathway?
Turning off one or more genes. A new protein is made from the signal
Development
The growth and specialization of cells and tissues that occur as the cells of a zygote multiply and differentiate to form a multicellular organism. An important example of cell-to-cell signaling
Induction
Occurs when one group of cells influences the development of the adjacent group of cells
Homeotic genes
Master control genes; helps with the development of an overall structure in an organism
Mutation
Any change in the nucleotide sequence of DNA
Mutagen
A chemical or physical agent that interacts with DNA and causes a mutation.
Carcinogen
Cancer-causing agents
Point mutation
A change in a single nucleotide pair of a gene.
Silent mutation
Does not change the amino acid produced
Missense mutation
Substituting one amino acid for another
Nonsense mutation
Changes an amino acid codon into a stop codon, resulting in a shorter defective protein
T/F: A codon is three consecutive nucleotides
True
Insertion
Mutations that add nucleotides
Deletions
Mutations that remove nucleotides
Frameshift mutation
When an insertion or deletion throws off a reading frame
Sickle-cell disease is caused by…
The replacement of an A with a T at the 17th nucleotide of one of the genes for hemoglobin
Tumor
An abnormal mass of cells that forms within otherwise normal tissue.
Cancer
A malignant growth or tumor caused by abnormal and uncontrolled cell division.
Cell cycle control system
A cyclically operating set of proteins that triggers and coordinates events in the eukaryotic cell cycle.
Cell cycle control system
A cyclically operating set of proteins that triggers and coordinates events in the eukaryotic cell cycle.
Oncogene
A gene that leads to uncontrolled cell growth
Growth factor
A protein secreted by certain body cells that stimulates other cells to divide.
Tumor supressor gene
A gene whose product inhibits cell growth
Cancer is defined as…
Abnormal growth of the body’s own cells
Cancer begins within…
A single cell when multiple photo-oncogenes into oncogenes
Metastasis
The spread of cancer cells from their site of origin to sites distant in the body
Proto-oncogenes
Normal, necessary genes that help regulate cell growth
A typical genetic engineering challenge is…
To produce large quantities of a desired human protein
Gene cloning
The production of multiple copies of a gene
Restriction enzyme
DNA cutting enzymes that only target specific nucleotide sequences
Examples of humans manipulating nature
- Biotechnology
- DNA technology
- Genetic engineering
Restriction site
A specific DNA sequence recognized by a particular restriction enzyme
Sticky ends
The result of restriction enzymes, fragments with single-stranded regions which can join to other pieces of DNA
Recombinant DNA
A DNA molecule containing nucleotides from more than one source
Genome
An organism’s entire set of DNA
Genomic library
A collection of cloned DNA fragments that include the organism’s entire genome
What role does DNA ligase play in the manipulation of DNA?
DNA ligase pastes DNA fragments onto plasmids
Nucleic acid probe
A complementary molecule that helps visualize the target DNA
Reverse transcriptase
An enzyme that can synthesize DNA molecules from the collection of mRNAs within a cell
Complementary DNA (cDNA)
The result of reverse transcriptase; represents just the genes that were producing proteins in the cell at that time. Results in a gene with only exons
Genetically modified organisms (GMOs)
Ones that have acquired one or more genes by artificial means
Transgenic organism
An organism that contains genes from another organism, typically another species
What is the relationship between producing a GMO and plasmids?
Plasmids act as a temporary DNA carrier, allowing genes to be inserted into another
Polymerase chain reaction (PCR)
A laboratory technique by which a specific segment of DNA can be targeted and copied quickly and precisely
What is the key to PCR?
DNA polymerase, because it synthesizes the new strands of DNA
DNA polymerase
An enzyme that synthesizes a new strand of DNA that is complementary to the original
Primers
Artificially created, single-stranded DNA that bind to a target sequence
DNA profiling
Allows an investigator to determine with certainty whether two samples of DNA came from the same individual
Short tandem repeats (STRs)
Sites where a short nucleotide sequence is repeated many times in a row
STR analysis
A comparison of the length of STRs
Gel electrophoresis
Allows visualization of DNA samples based on length
How identical are the genomes of two humans?
99.5%
How much of human DNA codes for proteins?
1.5%
24% of human DNA…
Consists of sequences that control genes but are not genes themselves
59% of human DNA…
Is repetitive
