Bio 12 Semester 2 Flashcards
Define DNA
DNA is the common genetic material for all organisms
and carries the information coded in genes
Account for the different location of DNA including; nuclear, plasmid, mitochondrial and
chloroplast
Nucleic Acids in prokaryotes (no nucleus, floating DNa )
DNA is found as a circular molecule in the cytoplasm as:
- Chromosomal DNA
– Plasmid DNA
Nucleic Acids in eukaryotes
Deoxyribonucleic acid (DNA) consists of two chains wrapped around each other in a spiral to form a double helix.
DNA is found in:
– Chromosomes in the nucleus of eukaryotes and cytoplasm of prokaryotes
– As circular DNA in mitochondria and chloroplasts
Describe the structure of DNA.
What is it made up of?
Elements: C, H, O, N P
Subunit: Nucleotides
Polymer (molecular building blocks):
-Nucleic acid
-DNA (deoxyribonucleic acid)
-RNA (ribonucleic acid)
Nucleic acids are involved with the
transmission of inherited information
Define DNA replication
Describe the process of DNA replication.
Where does it occur
Is it semi conservative (what does that mean)
-the process by which the genome’s DNA is copied in cells.
-occurs in the nucleus
-semi conservative
which means each new dna molecule contains one of the parent strands
Nucleotides
What is a nucleotide?
How many components do they have and what are they called?
What way does it grow in?
-the basic unit of a nucleic acid
-a nucleotide has three components
-Phosphate group
-5 carbon sugar (ribose in RNA and Deoxyribose in DNA)
-Nitrogen base (5 possible types )
Nucleotide bases are
(adenine and guanine)=purines
(thymine and cytosine)=pyrimidines
u=uracil
-carbons of sugar are linked from 1’ to 5’
-nitrogen base attached to 1’ and phosphate attached to 5’
-nucleotides are linked 5’ to 3’ and DNA strands grow 5’ (phosphate) to 3’ (hydroxyl)
-read from 5’ to 3’
DNA structure
-Each strand of DNA (2) is connected by hydrogen bonds
-Guanine bases always pair with
cytosine – via 3 hydrogen bonds
- Thymine bases always pair with
adenine – via 2 hydrogen bonds
* The two strands of DNA are
antiparallel
Nucleic Acids:
What is Ribonucleic acid (RNA)
What is its role
What are the three types
- consists of a single chain.
It plays a role in converting the genetic code of DNA into proteins.
– Transfer RNA (tRNA)
– Messenger RNA (mRNA)
– Ribosomal RNA (rRNA)
Account for the different location of DNA including; nuclear, plasmid, mitochondrial and
chloroplast.
DNA is found as a circular molecule in the
Enzymes involved in DNA replication
Explain what each does including:
1)Helicase
2)RNA Polymerase (primase)
3)DNA polymerase
4) DNA ligase
1)Helicase
-catalyses the unwinding of the parent DNA molecule, which results in both of the strands exposed to be used as the template
2)RNA Polymerase (primase)
-builds a short RNA primer sequence
3)DNA polymerase
-after primer
-extends primer by adding nucleotides to the growing 5’ to 3’ sequence
-leading strand is built normally
-lagging strand is built backwards in shorter okazaki fragments
-okazaki fragments are joined together with DNA LIGASE
Define biotechnology
What is and give examples of BIOtechnology
exploitation of biological processes for industrial and other purposes, especially the genetic manipulation of microorganisms for the production of antibiotics, hormones, etc.
The use of enzymes including endonucleases (restriction enzymes), ligases and
polymerases
* Amplification of DNA using the polymerase chain reaction
* The use of gel electrophoresis in sorting DNA fragments, including interpretation of gel
runs
* The use of recombinant plasmids as vectors to transform bacterial cells
Describe the processes of PCR, restriction enzyme digests and gel electrophoresis.
Describe the benefits and limits of PCR, restriction enzyme digests and gel electrophoresis.
Describe the processes of PCR, restriction enzyme digests and gel electrophoresis.
Describe the benefits and limits of PCR, restriction enzyme digests and gel electrophoresis.
Where does DNA replication occur
What does it produce?
-nucleus
-copy of a chromosome before a cell divides
What way does DNA polymerase build new DNA strands
Why?
What strand is built continuosuly
5’ to 3’
(sugar phosphate backbone, one is upside down compared to the other )
(5’ to 3’= phospoate connected to the molecules 5th carbon and ending at the 3rd carbon which is connected to base)
(5’ has phosphate at start of chain)
(phosphate to hydroxyl end)
only the leading strand is built continuously
How is rna different to dna
-rna is single stranded
-rna has a different sugar ribose
-base is uracile (what binds to adenine)
The Lagging Strand
-dna can only copy dna in a 5’ to 3’ direction, and the lagging strand is built 3’ to 5’
What is the cell cycle?
-derivation of all cells from pre existing cells through the completion of the cell cycle
-every cell coming from sperm and egg cell
The rapid procession of prokaryotic cells through their cell cycle by binary fission
The key events in the phases (G1, S, G2, M and C) of the eukaryotic cell cycle, including the characteristics of the sub- phases of mitosis (prophase, metaphase, anaphase and telophase) and cytokinesis in plant and animal cells
Chromosomes
What are they?
What are the three types of chromosomes?
DNA strands coil and twist into compact chromosomes
More chromosomes in a speciies does not mean more complexity
Reason for more chromosomes date back to evolution
1) Sex Chromosomes
-x and y chromosomes
-determine biological gender
-XX=female
-XY=male
-females can live without an x chromosomes and because only relevant to male reproductive traits
-Y chromosomes getting smaller, less usage
2)Autosomes
-not a sex chromosome
-same for all members of a species
-come in pairs that are called:
3) Homologous Chromosomes
-chromosome pairs contain the same genes but may have different versions of the gene
What is a Somatic Cell
What is a Sex Cell (Gametes )
Somatic Cells:
-Body cells
-All body parts have different ways of reading genetic code but have the same DNA
-Chromosome pairs
Gametes:
-sperm and egg cells create a new child
-has 50 % of required DNA
Describe the Process of Mitosis
What are the stages of Mitosis
Interphase (not a part of mitosis or meoisis)
-prophase
-metaphase
-anaphase
-telophase
-cytokenesis
Meosis: Crossing over and recombination
During Prophase I in meiosis,
chromosomes undergo a process called
crossing over and recombination
* This involves homologous chromosome
pairs sitting side by side, and one or more
arms of the chromosomes will twist
together.
At the chiasma, the arms of the
chromosomes will break and re-join on the
other homologous chromosome.
* This creates variation without disrupting
the genes that are present on that
chromosome.
Meosis
What is a haploid?
Sexual Reproduction in Eukaryotes
Egg (n) +Sperm (n) =zygote (2n)
Haploid=pne of each chromosome
What are the sources of variation in meosis (sexual reproduction)
1) Random Independent Assortment during metaphase 1. The combination of homogolous pairs moving to seperate poles of the cell may vary
2)Crossing over a recombination between the chromatids of homogolous chromosomes. The chromatids corssing over may contain different versions of the same genes, therefore recombination creates new combinations (what pairs cross over)
3) Fertilisation: Which gamete is fertilised (which sperm/egg cell was used)
4)Mutation
Meiosis errors
-individuals can have more or less chromosomes as a result of non disjunction of chromosomes in one of their parents
-non dijunction occurs when the chromosomes do not seperate properly in anaphase 1 or 2
-Triploid organisms are generally unable to undergo meiosis due to problems with chromosome pairing.
The results of meoisis
-in males, one cycle of meiosis results in 4 haploid gametes (sperm)
-in females it results in 1 haploid gamete and (ovum/egg) and 3 haploid polar bodies
Define the term gene
A gene is a segment of DNA that
codes for a protein
DNA is read as three-letter codes
called?
triplets
What do genes code for?
What are genes transcribed into? which is translated into what?
-proteins
-transcribed into RNA, which is then translated into the amino acid sequences that make up proteins
Explain Mendel’s principals of inheritance, Law of segregation and independent assortment.
What was the law of segregation?
-combined pure breead green and yellow pea plant, and got only yellow seeds, therefore yellow was deamed dominant
-yellow seeded hybrid plants breeded, but green was still produced, meaning the trait was hidden and recessive
Genotype
YY=homozygous
Yy=heterozygous
Phenotype=result of genotype
Law of segregation: During the formation of gamete, each gene separates from each other so that each gamete carries only one allele for each gene
Independent assortment:
the alleles of two (or more) different genes get sorted into gametes independently of one another.
Alleles
What are they?
-represent different versions of a gene
-different version of a gene
-People inherit one allele for each autosomal gene from each parent, and we tend to lump the alleles into categories.
Define heterozygous.
Define homozygous.
-homo= type copies of the same allele from each parents
AA or aa
-heterozygous
two different alleles for a trait
Aa
Define genotype:
Define phenotype:
Genotype
-the genetic makeup of an organism, describes the genes
-combination of alleles present in an organism
-eg AA
Phenotype
-physical appearance
-observable traits; the expression of genotype
-eg; blue eyes, right or left handed
-genotype determines the phenotype of an individual
What are the two genetic cross types ?
What are test crosses used for?
How to do a monohybird cross
-monohybird
-dihybrid
used for:
-used in plants and insects and determine inheritance
a monohybird cross
-assign genotype
-punnet square
-genotype and phenotype percentages
Types of Inheritance:
Sex Linked:
Autosomal:
-Sex linked traits
-on the X chromosome
-male is XY and female is XX, meaning female has back up X chromosome
-example; gene for colour blinness is on x chromosome
Sex Linked= X^A X ^a
Autosomal:
-2 or more genes being on the same autosomes (not sex chromosomes)
A,a
Complete dominance:
-heterozygote shows the dominant trait
Codominance/co recessive if only recessive allele
-Both traits shown because both alleles are dominant A^B A^
-hetorozygote shows both traits
Example= F^R F^R x F^B F^B = F^R x F^B
Red and Blue Plant is created
Incomplete Dominance
-Heterozygote shows a mix of both traits (can be more or one)
A^B x A^M = purple plant
Lethal Alleles:
-lethal if individual is homozygous
-allele can be dominant or recessive
Difference between coding and non coding DNA
Noncoding DNA does not provide instructions for making proteins
Coding=encodes for a protein
What are polygenetic traits
-a trait whose phenotype is influenced by more than one gene
-a characteristic, such as height or skin color, that is influenced by two or more genes
Transcription
-making a copy
-DNA replication= copy of whole DNA, transcription is using the proteins
-transcription=make a copy of gene so that it can be taken out of the nucleus
-only template strand is used
-built 5’ to 3’
Post Transcription Modification
What are introns?
In eukaryotes, transcription produces pre-mRNA molecules. These molecules are then modified to form (mature) mRNA via:
Splicing (removal of introns)
Addition of 5’ cap
Addition of 3’ poly-A tail
Prokaryotes do not undergo post-transcriptional modification.
Introns sequences of DNA that have no protein-coding function.
Introns are removed and exons rejoined by RNA splicing before the mRNA leaves the nucleus
What are ribosomes?
What are tRNA molecules
-ribosomes
-Made of subunits of protein and ribosomal RNA (rRNA).
-rRNA makes ribosomes
-large and small subunits
Trna molecules
There is a specific complimentary tRNA molecule and anticodon for each type of codon.
The anticodon is the site of the 3-base sequence that ‘recognizes’ and matches up with the codon on the mRNA molecule.
-amino acid attachment site
-anti codon
-ribosome attachment point
Translation
-occurs in rybosome in cells cytoplasm
-the process of building a protein from amino acids, guided by the sequence of codons om the mRNA
Structures involved in translation
messenger Rna molecules
-carries code from the DNA so that it can be translated into an amino acid sequence
Amino Acids
-constructs hte polypeptides (proteins)
Ribosomes
-provide the environment for tRNA attachment and amino acid linkage
The Genetic Code
-DNA codes for the assembly of amino acids and polypeptides
The code is read in a sequence of bases called:
-triplets on DNA
-codons on mRna
Each codon codes for an amino acid
More than one codon can code for the same amino acid, making it degenerate
Some codons construct the tart and stop sequences for the polypeptide chain formation
Name the 3 nucleic acids
-transfer tRNA
-messenger mRNA
-ribosomal rRNA
Define genetic variation
Genetic variation is the difference in DNA among individuals or the differences between populations among the same species.
Define mutation
-permanent changes in the DNA nucleotide base sequence of an organism which may result in the formation of new alleles.
-The effects of mutations vary depending on their location both within chromosomes and the body of the organism.
Identify the factors that cause mutation
Is it random or spontaneuos?
Examples of mutagens
-may occur randomly or spontaneously
-arise from errors in replication
-may be induced by environmental factors (mutagens)
Including:
radiation (e.g. UV rays)
viruses
microorganisms
environmental poisons and irritants
alcohol and diet
Types of mutations
What are points mutations- substitution mutations
Point mutations: Substitution mutations:
The change of a nucleotide
Silent Mutations:
-occurs when the substitution results in a new codon that still codes for the same amino acid
Nonsense mutations:
-occurs when substitution results in a premature stop being introduced and shortening polypeptide chain
Frame shift mutations
(insertions or deletions )
Single or multiple bases are inserted or deleted.
Causes a ‘frame shift’ - results in new amino acids in the polypeptide chain from the point of insertion/deletion onwards.
Resulting protein is significantly different from original (most likely non-functional).
What are chromosomal mutations
the mutation of the chromosomal segments of the DNA strands
changes in the number or structure of chromosomes.
Fitness of mutation
What does this refer to?
A mutation can be…
- its value to the survival and reproductive success of the organism.
-Lethal: Embryos are non-viable.
Harmful: e.g. Down syndrome, sickle cell disease. Lower an individual’s fitness.
Silent (neutral): No noticeable effect on the phenotype.
Beneficial: Occasionally mutations may be useful, particularly in a new environment, e.g. insecticide resistance in insects, antibiotic resistance in bacteria.
Mutations to variation
What cells can mutation be in?
All new alleles arise through mutation
New alleles introduce genetic variation
Natural selection and evolution act on variation
Most mutations occur in somatic cells and are not inherited.
Only mutations in gametes can be inherited.
Why is diversity important?
-more likely for species to survival
-inbred species are less likely to survive if the environment changes
What is a species?
What is a population?
species
-grouping of organisms that can interbreed and produce viable and fertile offspring in the natural environment
What is a population?
comprises the total number of one species in a particular area.
What is a gene pool?
-the complete set of alleles carried in a population
-individuals in the population will have some but not all of the available alleles
-large gene pool indicates more diversity
The range of variation possible in a population is restricted by the alleles available in the gene pool
What is a fixed allele?
-Genes with only one allele in the gene pool are said to be fixed.
Environmental selection pressures
-Phenotypes may be selected for and give the organism a ‘selective advantage’. Such organisms have a higher ‘fitness value’.
Phenotypes may be selected against. Such organisms have a lower ‘fitness value’.
Selection factors can be natural or artificial.
Steps involved in natural selection:
Reciple for natural selection
-variation of phenotypes exist in populations
-factors in the environment act as cselection pressures on phenotypes
Differential reproduction occur:
-phenotypes are selected for and against, these individuals survive and reproduce in larger numbers, their allele frequency becomes higher
-phenotypes selected against, do this in lower numbers, reducing frequency of alleles
Selection Pressures
Give examples
Competition between species for food or territory
Predator-prey relationships
Competition within species for food or water
Competition within species for territory/space
Sexual selection
Climatic conditions
Natural selection
-is a mechanism for evolution
Natural selection increases the frequency of ‘favorable alleles’ in the gene pool, but it does not produce the “perfect organism”.
Natural selection does not create new alleles or new phenotypes, it can only work on existing phenotypes.
Natural selection reduces variation in populations.
Natural selection depends on the environment, changes in the environment can alter selective pressures.
Artificial selection
Humans have controlled the breeding of domesticated animals and plants for centuries.
Artificial selection or selective breeding, involves breeding (selecting) individuals with the most desirable phenotypes. It can result in an astounding range of phenotypic variation over relatively short time periods.
Selection imposed by humans is often more rapid and intense than that occurring in nature.
Steps to artifical breeding
Determine the desired trait
Interbreed parents who show the desired trait
Select the offspring with the best form of the trait and interbreed these offspring
Continue this process until the population reliably reproduces the desired trait
Issues with artifical breeding
-reduces resistance to change
-reduces biodiversity
-generates genetic abnormalities
Allele frequencies
-How common particular alleles of a gene are in the population.
Evolving populations
What are factors resulting in changes in gene frequencies
-mutation
-gene flow: migration of individuals and their genes between populations
-(immigration and emigration).
-makes different populations gene pools similar
-genetic drift: changes in allle frequencies due to random large scale events
Greatest effect is when allelic frequency is very low or the population is very small
can be seen in random mating, fertilisation chance, the bottleneck effect and the founder effect.
-environmental selection pressures: natural selection working against particular phenotypes
-non random mating: individuals seek our specific phenotypes with which to mate
Population size and genetic diversity
-smaller populations have fewer alleles to begin with, change of alleles is faster
-small populations have a greater risk of inbreeding
-populations with low diversity are of risk of dangers from environmental pressures
-endangered species and captive breeding populations are at risk of this
Genetic Drift: Population Bottlenecks
Events, such as fires, floods, disease, etc…, may severely reduce the size of a population.
By chance, the small sample that survives will often not be representative of the original, larger gene pool.
Allele frequencies will change by chance and the genetic diversity may decrease.
Genetic Drift: The founder Effect
-small number of individuals migrate away from their population
-This founder population will have a small and probably non-representative sample of alleles from the original gene pool.
The founder population may evolve in a different direction than the parent population.
Speciation
What is it?
What is Allopatric speciation:
What are the steps
-the process by which new species are formed
Allopatric speciation:
-populations become isolated and differences accumulate overtime
1)moving into new environments
-this population still has a common gene pool
2)geographical isolation
-physical barriers isolate the 2
-gene flow is prevented
3)formation of a subspecies
-environmental pressures from each environemtn occur, selection pressures, species form different traits
4) reproductive isolation
Subspecies become reproductively
isolated and attain species status.
Even if geographical barriers
are removed interbreeding will not occur.
Isolationg mechanisms
-Geographical isolation
Occupation in different niches within the same ecosystem
Temporal (time) isolation
Behavioural isolation
Structural or morphological isolation
Hybrid inviability
