Genetic theory Flashcards
Nucleic acid
polynucleotide macromolecule eg: DNA and RNA
Non-nuclear DNA
- found in mitochondria or chloroplast
- role: allows organelles to reproduce without a nucleus
Heredity
the passing of features from parents to offspring by means of genes
Species
Group of similar organisms capable of interbreeding to produce fertile offspring
Non-coding DNA
DNA which does not code for a protein also known as “Junk DNA”
Codon
- Three bases in a sequence
- Each codon codes for an amino acid
- During protein synthesis
Gene expression
The way in which the genetic code in a gene is decoded and used to make a protein
Gene
- Collection of codons
- Contains the genetic code to form a protein
- Controls a particular characteristic
Genetic screening
Test to establish the presence or absence of a gene
Outline the procedure for Genetic screening
- “DNA probe” is added to a DNA sample with a gene taken from the person being tested.
- DNA probe only attaches to the normal gene.
- DNA that does not attach is the altered gene.
Name the 2 scientists that described the DNA structure
Watson and Crick
What does DNA stand for?
Deoxyribonucleic acid
Where is DNA located
Nucleus
What is the shape of DNA
Double helix
What is the basic building block of DNA
The nucleotide
What does nucleotide consist of
- Phosphate
- Sugar
- Nitrogen base
Name the 4 types of bases
- Adenine
- Guanine
- Thymine
- Cytosine
How are the 2 strands held together?
Hydrogen bonds
What are complementary base pairs?
Each base has a corresponding matching base
How many hydrogen bonds are between adenine and thymine? Guanine and Cytosine?
- 2 hydrogen bonds
2. 3 hydrogen bonds
What are these bases classified as?
- Adenine and Guanine
- Thymine and Cytosine
- Purines
2. Pyrimidines
Function of DNA
- Carries and passes on genetic information from parents to offspring in the form of genes
- Bacteria has one chromosome composed of DNA only
Describe the nature of the genetic code
- A codon is 3 bases in a sequence
- Each gene codes for one amino acid
- Gene consists of a collection of codons that collectively code for one protein
- mRNA copies the genetic code from DNA and brings it to the ribosome in the cytoplasm where protein synthesis occurs
Define DNA replication
DNA makes exact copies of itself which are passed on from one generation to the next
Name the 2 main stages of DNA replication
- Opening of DNA double helix
2. The synthesis of complementary nucleic acid strands alongside the existing strands to form two identical helices
Outline the account for DNA replication
- DNA replication occurs during the interphase of cell division and involves making an exact copy of DNA
- Hydrogen bonds between the base pairs break down
- The two strands separate
- Each DNA acts as a template to form a new complementary strand
- DNA nucleotides from the cytoplasm move into the nucleus and match up with their corresponding nucleotide on the exposed DNA strands
- Two exact copies of DNA are made called helices
- Each new double-strand rewinds to form a double helix
- This process requires energy from ATP and the anabolic enzyme DNA polymerase which is a catalyst to assemble DNA nucleotides
What does RNA stand for
Ribonucleic acid
How are the DNA and RNA similar?
- Both nucleic acids
- Both contain the bases Adenine, Guanine and Cytosine
How do DNA and RNA differ from one another?
DNA - Double Helix - Sugar - Base (Thymine) - Location: Nucleus RNA - Single strand - Ribose - Uracil - Location: nucleus and cytoplasm
Name the 3 types of RNA
- rRNA- ribosomal RNA
- mRNA- messenger RNA
- tRNA- transfer RNA
Describe rRNA
- Forms the ribosomes
2. Holds mRNA in place at the ribosome during protein synthesis
Describe mRNA
- Transcribes the genetic code from DNA
2. mRNA carries this code to the ribosome
Describe tRNA
- Transfers amino acids to mRNA at the ribosome
- It attaches to its complementary mRNA codon placing its amino acid in the correct sequence within the protein
- tRNA has an amino acid attached at one end and anticodon three exposed bases at the other end of the molecule: the anticodon is complementary to mRNA codon
Each mRNA codon specifies one of three possible outcomes during protein synthesis. Name these three possible outcomes
- Start codon
- Codon which assembles an amino acid
- Stop codon
Describe the method to isolate DNA from onion tissue
- Chop onion into small pieces (To disrupt the structure and release cytoplasm when the cell wall is broken down)
- Add chopped onion to salt and washing up liquid (Salt clumps DNA and washing up liquid breaks down cell membranes)
- Warm beaker in a water bath at 60C for 15 minutes (Denatures enzyme)
- Cool beaker by placing beaker in an ice water bath for 5 minutes (allows DNA to break down)
- Blend for 3 seconds (Breaks down cell wall and releases DNA)
- Filter mixture
- Transfer 10cm of the filtrate to a test tube and add 2-3 drops of protease (Breaks down protein around DNA)
- Collect DNA - ice-cold ethanol
- DNA is insoluble in ice-cold ethanol
- Use a glass rod to collect DNA (clear)
- If white mesh DNA has protein
List the steps of how DNA profile is made
- DNA is extracted
- Restriction enzymes are used to cut DNA into fragments
- Separating DNA fragments according to size by electrophoresis
- The band pattern or profile is analysed
Name 2 applications of DNA profiling
- Forensic science (crime scene)
2. Medical (establish biological parents of any child)
Explain what is meant by the term DNA profiling
Making unique pattern of bands from the DNA of a person which can be used to distinguish that DNA from another DNA for comparison purposes
What is meant by genetic screening
Test to establish the presence or absence of genes
Name stage 1 of Protein synthesis and describe
- Initiation
- DNA double helix unwinds
- Enzymes break the hydrogen bonds
- One DNA strand the transcribing DNA strand is used as a template to form a complementary molecule of mRNA
What is meant by Transcription
Copying of a sequence of genetic from a single strand of DNA onto mRNA
Name stage 2 of Protein synthesis and briefly explain
- Transcription
- Occurs in the nucleus
- RNA nucleotide bases bond with one single strand of exposed DNA
- DNA strand acts as a template
- RNA polymerase assembles the RNA nucleotide to form mRNA
- mRNA has a series of bases that are complementary to those on the transcribing DNA strand
- mRNA moves to the cytoplasm and attaches to a ribosome
- Each ribosome is made up of ribosomal RNA and protein
- rRNA holds mRNA in place at the ribosome
What is meant by Translation
Conversion of a sequence of genetic bases on mRNA into a sequence of amino acids
Name the 3rd stage of Protein synthesis and briefly explain
Termination
- Occurs in Ribosome
- tRNA each with an amino acid attached is attracted by their anticodons to mRNA codons
- The first tRNA molecule attaches to mRNA
- Amino acids are aligned in a sequence determined by the codon sequence of the mRNA
- Aligned amino acids bond to form the peptide links of the new protein
- Protein formed folds into its correct shape
Define Genetic engineering
Artificial manipulation or alteration of genes
Genetically modified organisms
Organisms that have genes from other species inserted into them
Define Clone
Genetically identical organisms
Define Recombinant DNA
Two different species combined
Tools required for genetic engineering
- Source of DNA
- Restriction enzymes (Cut human DNA into fragments)
- Cloning vector (Plasmid will accept and carry foreign DNA)
- DNA ligase (Enzymes used to join DNA from 2 different species firmly together)
List the stages involved in Genetic Engineering
- Isolation
- Cutting
- Insertion and ligation
- Transformation
- Cloning
- Expression
In genetic engineering all or some of the following procedures may be involved -Isolation -Cutting -Transformation -Introduction of base sequence changes -Expression Briefly explain each
- Isolation removal of target gene -Cutting Human DNA using restriction enzymes - Transformation Uptake of recombinant DNA by the bacterial host cell - Introduction of base sequence change order of bases in the host DNA - Expression Activation of an inserted gene to produce the product
Give one application of genetic engineering in any two of the following
- An animal
- A plant
- A micro-organism
- An animal
- Sheep produce a protein to treat emphysema (Collapse of the alveoli) - A plant
- production of herbicide-resistant crops - A micro-organism
- Production of insulin
Define what is meant by Variation
The differences in the characteristics of a species are due to differences in the genotype and the effect on the environment
Name 2 types of Variation
- Acquired variation
2. Inherited/Genetic variation
Describe the two types of Variation
- Acquired
- Inherited
- Acquired
- Not genetically controlled
- Not inherited - Inherited/genetic variation
- Genetically controlled by genes
- Passed on to offspring
What is the significance of inherited variation in the evolution of a species?
- Produces new genotypes
- Allows natural selection to occur
Causes of variation
- Sexual reproduction
- Mutations
Define Mutation
Change in the structure or amount of DNA
What is meant by Gene mutation
Change in a single gene
What is meant by a chromosome mutation
Change in the structure or number of chromosomes
Causes of mutations
mutagens
Define spontaneous mutations
Errors during DNA replication so that the DNA doesn’t make the exact copies of itself
What are mutagens
Agents that cause mutations
Name examples of mutagens
- Radiation
- Chemicals
What is meant by somatic cell mutations
Benign tumours
Name an example of a Gene Mutations
Sickle cell anaemia
What is sickle cell anaemia caused by
Change in the base of the haemoglobin
What are the symptoms of sickle cell anaemia
Fatigue
Clumping of red blood cells
Treatment for sickle cell anaemia
Blood transfusion
Name other conditions caused by gene mutations
- Cystic fibrosis
- Haemophilia
- Albinism
Name an example of Chromosome mutation
Down’s syndrome
What does down’s syndrome result from
Extra chromosome 2n=47
What does downs syndrome result in
- Alteration in facial features
- Reduced IQ level
- Reduced resistance to disease
What is meant by evolution?
living things change genetically to produce new forms of life over periods of time
Define natural selection
Organisms have genetically controlled characteristics that allow them to adapt to their environment so they will survive and pass on their genes
Theory of Natural Selection was developed by…
Charles Darwin and Alfred Wallace
Account of the theory of Natural Selection
- Observation 1:
- Overbreeding - Observation 2:
- Population num remains constant - Conclusion 1:
- Struggle for existence - Observation 3:
- Inherited variations - Conclusion 4:
- Natural selection
In the context of natural selection, explain how numbers in a population remain collectively constant despite the production of many offspringing
- Competition
- Best adapted survive
- Death rate equals reproduction rate
Give an account of Theory Selection. Name the scientists who are associated with the theory and refer to one observation that prompted its development
Scientists: Darvin and Wallace Observation: 1. Large number of offspring 2. Low survival so population remains constant 3. Variation in offspring
Evidence of evolution
- Paleontology
- Comparative anatomy
- Comparative embryology
Give one example of evidence for evolution and briefly describe
- Paleontology- a study of fossils
- Fossil is the remains of an ancient organism
Fossil evidence indicates:
- Fossils can be aged
- Modern fossils show increased complexity
- Fossils show changes when compared
- Changes can be linked to environmental change
Evolution of a horse
- Have grown in size
- Have evolved about 60 million years ago
- Horses used to be 0.4 metres tall
- Now they are 1.6m tall
