Chapter 13 - DNA; The Code For Life Flashcards
Explain the Structure of DNA
- histones, chromatin, chromosomes, genes, genetic code
DNA = deoxyribose nucleic acid
- is a molecule found in the NUCLEUS in the cells of all organisms
- contains genetic information which determines the structure and function of the cell
- DNA molecule are in the form of LONG STRANDS
- 2-3 meters long
- 2millionth of a mm
- has 46 DNA molecules in nuclei
HISTONES are round proteins which DNA strands are bound to.
- DNA strand is coiled around the histories, so these long molecules can fit into small spaces.
- beads structures and the thread is DNA
- nucleosome = 8 part his tone structure
CHROMATIN - is coiled DNA that forms a tangled network in a non dividing cell.
CHROMOSOMES - ‘super - coiled’ structures large enough to be seen with a light microscope when cell is about to divide.
- for durability and stability
GENES - sequence of bases in the DNA molecule
GENETIC CODE - stored information that determines the structure and activities of a cell found in the genes.
- Every cell has identical DNA except - RBCs which loses nuclei
DNA, Gene, Chromosomes
What is a Karyotype ?
A photograph of chromosomes arranged in HOMOLOGOUS (1-23 prs) of order and size
What is a Double Helix?
The two chains of alternating sugars and phosphates, joined by the base nitrogen pairs, are twisted into a spiral shape.
What is a nucleotide? The nitrogen bases? And base pairing rule.
A phosphate group, sugar molecule (deoxyribose) with a nitrogenous base is a nucleotide. Healed together by strong hydrogen bonds.(stabiles it)
*units that make up DNA
Adenine (A) - Thymine (T)
Guanine (G) - Cytosine (C)
G and A = purine (larger phosphate)
T (U) and C = pyrimidines
Draw a DNA model
Learn five prime and 3 prime
Template and complementary
What is DNA replication?
What are the stages of it? (5)
DNA Replication is when the DNA molecules in the cell from exact replicas of themselves for cell division in the phase of interphase.
Stages of this include
- The enzyme HELICASE unwinds and unzips the double stranded DNA to make it into 2 SEPARATE CHAINS- each chain has half of the information
* this is possible because the base pair bonds are weak and easily broken - PRIMASE is required to START replication - it helps the DNA polymerase know where to begin copying
- DNA polymerase binds to a single strand and helps create a COMPLEMENTARY strand.
* by using free nucleotides in nucleus
* from 5 prime to 3 - LIGASE GLUES and seals the DNA fragments together
- DNA molecule is FORMED - has one strand of the ORIGINAL parent DNA and one new strand
What are proteins and their uses?
Proteins are chemical substances that are essential for cell structure.
Eg Enzymes, Hormones, antibodies and structural materials of cells
Examples
- haemoglobin
- fibrin for blood clotting
- Actin and myosin
- albumin; egg and plasma
- insulin ; hormone regulating blood sugar levels
- amylase; starch breakdown
- collagen; bones, teeth, cartilage, ligaments and tendons
- immunoglobulin; in blood to act as antibodies
What is protein synthesis? And why proteins?
Synthesis is the combining of smaller molecules to make bigger ones; requires energy ( to form chemical bonds that hold them) and matter (small molecules to be joined)
Protein synthesis - the process by which amino acids are linearly arranged into proteins through the involvement of ribosomal RNA, transfer RNA, messenger RNA, and various enzymes.
- Proteins make STRUCTURAL MATERIALS IN CELL
- CHEMICAL REACTIONS ARE CONTROLLED BY PROTEINS
- Genetic - GENES CAN DETERMINE WHAT PROTEINS CELLS MAKE
What is the genetic code? What is a triplet ? How are Proteins made in cells?
The types of proteins a cell can make is determined by GENEs which forms parts of DNA molecules.
Body Cells have identical DNA (not sex cells; sperm and egg) but different genes are activated in different cells to determine their function and protein production.
The order in which the 4 nitrogenous bases occur makes up the GENETIC CODE.
A TRIPLET = a sequence of 3 base is the code for a particular AMINO ACID.
What are the different Types of RNA?
RNA (ribonucleic acid) - single strand of ribose sugar, phosphates and bases.
* has URACIL bass (U) than THYMINE (T)
Messenger RNA (mRNA) - messenger RNA communicates with cytoplasm
Transfer RNA (tRNA) - transfers AMINO ACIDS to ribosomes (has anticodon)
Ribosomal RNA (rRNA) - make up of ribosomes
What is Transcription?
Transcription is the process by which the mRNA is formed using the code in DNA molecule.
* 1st stage of Protein synthesis
- Takes place in the nucleus
Explain the Process of TRANSCRIPTION (8)
- Triggered by a hormone that enters the nucleus and binds to specific gene on DNA - TRIPLET
- RNA POLYMERASE attaches to begin the process
- HELICASE makes a double stranded DNA molecule unzip (17bp @ a time) to allow DNA strands to be decoded = TEMPLATE STRAND
- mRNA nucleotides which are found floating in the nucleus find their COMPLEMENT on the DNA strand and BONDS together (base pair rule)
- Once DNA strand has been COPIED by mRNA bases (3 letters = CODON), the mRNA strand separates from DNA.
* mRNA contains complementary bases to O.G strand - INTRONS; excess junk DNA is removed via RNA modification
- mRNA leaves the nucleus via pore and ENTERS CYTOPLASM and attaches onto Ribosome for PROTEIN SYNTHESIS
- DNA ZIPS UP again to create the O.G helix
* 300 000 rna copies are made
What is Translation
Translation is the 2nd stage of protein synthesis where production of a protein using info that is coded mRNA.
* occurs @ RIBOSOME
- for each bond formed between 2 amino acids the energy is from the break down of one ATP molecule.
EXPLAIN the Process of TRANSLATION.
- mRNA is read 3 CODONs @ a time and Starts with AUG codon.
- First Codon Attaches to RIBOSOME (made up of ribosomal rna - small and large subunits.)
- TRANSFER RNA molecules deliver AMINO ACIDS to ribosomes
*each tRNA carries a specific AA ( 20 types of AA)
*the tRNA ANTICODON will pair with complementary mRNA CODON
Eg CGC - GCG - RIBOSOME works it’s way down the strand of mRNA’s, Reading off the code. The rRNA joins AA’s by forming a PEPTIDE BOND (ATP NEEDED)
* tRNA is recycled bringing in more AA’s.
* detached from ribosome and then picks up another amino acid from cytosol - As Process continues, POLYPEPTIDE CHAIN is formed until STOP CONDON.
- Multiple COPIES of PROTEINS are made as other ribosomes (10-20) follow the 1st RIBOSOME.
- mRNA is recycled- broken down into nucleotides and reused.
- PROTEINS ARE MODIFIED by folding and shortening in a unique way.
- PROTEINS are then TRANSPORTED to other areas of the body that need them.
What is gene expression?
The process of copying information from DNA onto mRNA and then translating the message into a series of Amino acids is GENE expression
How does this relate to ANTIBIOTICS ?
Many antibiotics work by blocking translation during the process of Protein synthesis.
Because bacteria are unable to reproduce if they cannot make new proteins
Eg. Tetracycline, streptomycin and erythropoietin
What is a CODON, ANTICODON?
What are the STOP and START CODONs
ANTICODON = a sequence of three nucleotides forming a unit of genetic code in a transfer RNA molecule, corresponding to a complementary codon in messenger RNA.
* determines the type of AA carried by tRNA
CODON = a sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule.
Start CODON = AUG Methionine
Stop codon = UAA, UAG, UGA
What is Lipid and Carbohydrate Synthesis?
- there are NO GENES to carry instructions to make lipids and Carbohydrates
- ENZYMES are needed to make these
- so indirectly the genes make/ control synthesis of lipids and carbohydrates.
- smooth E.R = lipid synthesis and carbon metabolism
Explain Mitochondrial DNA
- Cellular respiration and ATP production occur in Mitochondria
- inner membranes of it provides attachments sites for ENZYME activity
- 10-20 mitochondria per cell
MITOCHONDRIAL DNA encodes for different PROTEINS specific for the Mitochondrion.
- these are to make enzymes and other proteins needed in pathways to produce energy.
- mDNA is the form of small circular molecules that are not bound to proteins
- 5-10 of these molecule in each mitochondrion
- has 37 genes; 24 genes contain code for transfer RNA molecules involved in protein synthesis, 13 for making enzymes required for protein synthesis.
Inheritance of Mitochondrial DNA and uses
- Inherited via mother side
Because mitochondria in sperm are destroyed in fertilisation
Uses
- trace back the ancestry of people
- gives us information about ancestors migration path
- forensic science
- evolution and variation
Mitochondrial disease and disorders
- any defects/mutations in any mitochondrial bases - could result in rare disease.. Inability to produce suffice not energy in things like nervous system, muscles and kidney
Symptoms; muscle weakness, cognitive defects, brain degeneration
Frequency; 1;5000-10000 births USA
What is EPIGENETICs?
EPIGENTIC - study of genetics
Changes in gene activity that DO NOT involve changes to gene code or DNA
EPIGENETICs - study of mechanisms that SWITCH GENES ON OR OFF
* refers to changes in the gene expression that result from mechanisms other than changes in the gene - that is in DNA
Explain GENOME, EPIGENOME, CHEMICAL TAGS.
Genome - complete set of genetic information encoded in their DNA.
EPIGENOME - (2nd set of instructions; sum of all factors that interact with DNA that ACTIVATE OR SUPPRESS the expression of genes.
* 200 types of cells, it’s the genome that tells nerve cells to behave like nerve cells.ect
Chemical tags = get attached to genome
What is Chromatin Remodelling?
Chromatin = histone + DNA
*DNA molecules coiled around Histones
Chromatin remodelling is one way which genes are regulated epigentically
There are 2 ways ;
ACETYLATION AND METHYLATION
- histones can change how TIGHTLY or LOOSELY DNA winds itself around them
Explain ACETYLATION
- histone modification
- adding acetyl group (CH3CO) to Histone protein causes DNA to unwind
- enhance gene expression/ gene SWITCHED ON
Explain METHYLATION
- addition to methyl group (CH3) to DNA
- causes genes SILENCING/ Gene switched OFF
- occurs at CYTOSINE - phosphorus- GUANINE site
- DNA TIGHTLY COILS
- inhibit gene expression
What can be a factor that changes a person’s EPIGENOME
Exposure to eviromengal stimuli
- Severe stress,
- NUTRITIONAL factors (diet)
- toxins (poisons)
- chemicals
- drugs (meds or substances)
- smoking
- aging
- lifestyle
- does not change DNA but interferes with transcription and translation processes involved with protein production
- EPIGENETIC factors can influence any step in gene expression
- any step in the pathway from gene to protein
What stabilises double helix structure?
What 2 factors prevent a mismatch from occurring?
- DNA double helix structure is stabilised by the Hydrogen bonds between the bases
- the number of H bond attractions
Eg. Not enough space for 2 adenines to fit within the helix- the size/length of base (C and T short) (A and G long)
Eg. too much space for 2 thymine to get close enough to each other to from hydrogen bonds
- the size/length of base (C and T short) (A and G long)
- the number of H bond attractions
New - 4 stages of transcription
- INITIATION - DNA double helix ‘unwinds’ near the gene being transcribed. RNA polymerase attaches and HELICASE unwinds.
- ELONGATION - process by which nucleotides are added via RNA polymerase growing the mRNA chain
- TERMINATION - process of ending transcription
- PROCESSING - pre mRNA - mature mRNA by modifying chain (get rid of INTRONS and keep exons.
New - 3 stages of Translation
- INITIATION - mRNA gets attached to ribosome and tRNA comes in so translation may begin
- ELONGATION - tRNA with anticodon brings Amino Acid from cytoplasm and begins to make a polypeptide chain
- TERMINATION - finished polypeptide chain is released
- Processing - ribosome makes sure to modify protein through shortening and folding movements
