heredity pt 2 Flashcards
Continuity of life requires the replication of genetic material and it transfer t the next generation through process such as;
binary fission, mitiosis, meiosis and fertilisation.
describe the structure of DNA
- deoxyribosenucleic acid
- double heliex molecule
compesed of subunits - nucleotide which unclude sugar phosphate and nitrigenous bases - adenine, thymine, guanine, cytosine
AT CG
what is a histone
a special protein that DNA is wrapped around
whats a nucleosome?
a combination of DNA and protein
a chromotin are
lots of nucleosomes together
what are genes
genes are specific sections which code for specific proteins
allels are?
they refer to different versions of genes and can be distinguished by small differences in dna
difference between DNA in prokaryotes and eukaryotes?
pro- DNA exist in a circular loop floating in the cytoplasm
- do not have histones
- some contain plasmid DNA that often contain survival related genes.
eukaryotes- DNA exists in the nucleus and some mitochondria and do have histones that wrap up the DNA
describe the process of DNA replication
- the helicase enzyme assists in unwinding the DNA molecules
- primers binds to the leading strand and acts as a starting point
- DNA Polymerase collects spare nucleotides and them with complimantary nucleotides on the parent strand only in 5’ to 3’ direction
the leading strand is replicating in the direction of the unwinding and takes place shortly after it has been unwound
the lagging strand is replicated in smaller sections with primers binding at various points polymerase enzyme constantly detaching and reattaching. moving in opposite direction.
these individual fragments are called okazaki fragments
DNA ligase then seals the nucleotide together to make a long continuous strand.
and DNA starnd then recoiled around the histones.
what are the phases of mitosis
I- interphase
- cell growth and production of organelles
- dna replication
produces proteins necessary for mitosis
p- prophase
- chromosomes condense and become visible
- each chromosome is comprised of chromotids
-spindle fibers begin to form
- nuclear membrane begins to break down
M-metaphase
- chromosomes begin to line up in the middle (equator)
A- anaphase
- spindle fibers atttach to centromeres
- sf pull chromotids to opposite poles of cell
T- telophase
- chromotids group together
- 2 nucleo membranes form
chromosomes unravel
cytokenesis
- the division of the cyto plasm to form 2 new cells
replicatioon of somatic cells is
mitosis
the differnce in the cyto kenesis process of aniamls vs plant is what?
plant create new cell wall and cell membrane between cells and then they break apart.
animal cell membrane moves inwards pinching 2 daughter cells apart (cleavage)
i dentify the process of cell repliaction in prokaryotes?
binary fission
what is binary fission
DNA replication each copy attatches to a part of the cell membrane
2 sides of the cell begin to pull part and divide into two separate cells
what process is faster mitosis or binary fission?
binary fission as it occurs in prokaryotes which are usually in larger numbers
why is mRNA used
because DNA is so long and important that is doesnt leave the nucleus
differences of RNA and DNA
RNA
- made up of sugar ribose
- single stranded
- uracil replaces thymine
- usually a lot shorter
DNA
- deoxyribose sugar
double stranded
long
describe the process of transcription
Transcription is the process in which a gene’s DNA sequence is copied (transcribed) to make an RNA molecule.
RNA polymerase is the main transcription enzyme.
Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins).
RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule.
Transcription ends in a process called termination. Termination depends on sequences in the RNA, which signal that the transcript is finished. a methylated cap and poly-a tail is connected to the mRNA strand as well.
what is a promoter sequence?
a particular sequence at the begining of a gene in transcription
how is mRNA packaged and why?
the methalated cap joins acting like a signaling molecule that can be recognised by ribosomes
poly A-tail
sequence of lots of ADENINE nucleoties added to the 3’ end to stabilise and protect the mRNA molecule.
splicing the process of removing introns and joining extrons together
describe the process of translation
During translation, proteins are made using the information in the mRNA sequence.
The mRNA binds to the small subunit of the ribosome via the methelyated cap and is threaded along.
- the 3 nucleotides are called codons and are read by tRNA molecules. Each tRNA has an anticodon, a set of three nucleotides that binds to a matching mRNA codon through base pairing. The other end of the tRNA carries the amino acid that’s specified by the codon.
- As each tRNA bind to the codon the amino acid that matches the mrna sequence joins with the previous amino acids to form a polypeptide chain.
- Once all of the amino acids have coded for the mRNA strand the completed protein is released from the ribosome to be folded.
describe the differneces of meiosis and mitosis
meiosis
- the parent cells divide twice
- 4 daughter cells are rpoduced
- chromosome number is halved haploid 23
- daughter cells are not genetically identical
- occurs in gametes
- purpose for reproduction
mitosic
- parent cell divide once
2 daughter cells are produced
- chromosome number is 46 diploid
- occurs in body cells
- purpose is to repair replace and for growth
- theres no variation in daughter cells
list examples of where the environment has affected the phenotype of an organism
hydrangeas- acidic soil flowers appear purple
alkaline soil flowers appear pink
what is a mutation and what are the different types of mutagens
is any change to the DNA sequence
there is spontaneous mutation, physical mutagens, chemical mutagens, biological mutagen
what are the types of mutation and the levels at which they could occur (small or large)
neutral mutation- has no effect on the coded product
deleterious mutations- which either stop or alter the productions of proteins
beneficial mutation- leading to advantageous variation that allows species to evolve
what happens to a baby if somatic or gamete cells mutate
somatic= baby will re,ain normal
gamete- baby will carry mutation
what are the different scales at which mutation can occur at
point mutation- which is small scale and refers to only one nucleotide is altered
chromosomal variation is when mutations occour on a larger sclae with chanhes happening to chromosomes
why is variation important?
important in survival and adaptability of a species environment changes, slight variation enables individuals with differnces to survive and maintain a breeding population.
list an example of a physical mutagen
x-rays which are capable of breaking and severing DNA strands which effect replication and protein synthesis.
list an example of chemical mutagens
cigarette smoke- has upto 60 different carcinogeneic chemicals which tag DNA preventing or encouraging transcription this is can be bad and be responsible for cell division
whats an example of a biological mutagen
this is caused by invasive pathogens such as bacteria and virus’
HIV- uses a enzyme called reverse transcri[tase to incorporate the viral DNA into the host DNA
whats the difference from transgenic organisms vs GMO’s
transgenic organsims
- organisms that have had the DNA of a different species inserted into their genome
GMO’s
organisms that have their DNA modified
- this may be transgenic
- or may have genes turned off/on
like green apples getting the gene that turns them brown off
what are restriction enzymes
enzymes taken for bacteria they cut DNA to recognition site. the two types of cuts from the restrcition enzymes are stick ends or blunt ends
what are blunt and sticky ends
sticky ends have overhanging ends and ensures dna is inserted in the correct way.
blunt ends are cut straight off with no over hang this meaning they could be inserted the wrong way around or worng position
list the prosess in which transgenic organisms are made
detergent breaks down cell ad nuclear membrane to relese DNA.
2. isolate the gene of interest via restriction enzymes
3. intert gene into plasmid of bacteria through DNA ligase
4. insert plasmid into bacteria through calcium chloride and electroporation to make bacteria membrane more permiable
describe the process of making a GMO
a gene will be inserted into a bacteria (agrobacterium) which can then be inserted into a plant or animal in hope the gene will incorporated into the host DNA and then expressed in the host.
describe the use of transgenic organisms
alternative of pestisides, control feral animals, processing oils and toxic waste, disease resistant crops and vaccines
describe the process of dna profiling
extract DNA from sample
STRs (short tandem repeats) cut into sections using restriction enzymes
amplified by PCR to make enough DNA to make a profile and specific primers are used in pcr that attatch a fluoresent tage to the copied STR
determind the size of STRs using gel electrophoresis.
the number of times a nucleotide sequence is repeated in each str can be calculated from the size of the STR. which scientists can use to determinf if a body fluid comes from a particular person
uses of dna profiling
genetic figerprinting, dna identification, paternity tests, monitoring biodiversity in wild or breeding programmes
describe the process of gel electrophoresis
- DNA is cut up using restriction enzymes and florescent dye is added to samples
- samples are added to the wells in the gels at the neg electrode end
- electricty runs through gel and neg charged dna is attraced to the pos electrode (smallest fragments moving the furthest)
- dna is viewed under a uv light causing it to flouresce
- now qw can compare the dna samples to the dna ladder as we know the dna ladder has dna fragments of varrring lengthes
now scientists can estimate the size of the fragments by comparing them to the samples of the known sized one.
describe the main processes of DNA sequencing (sanger method)
- heated to 96deg and denatures template dna
- primers are added lower to 50 allowing primers to anneal to the single strand dna
- 60deg to allow dna polymerase to synthesise complimentary strand from the primers until terminator base.
steps 1-3 are repeated 25 cycles producinf quadrillions of strands
6. separated through gel electrophorsiss where the laser illuminates each fragment allowing the dye to be detected and scientists can now identify the length of each and identify the the sequence of nucleotide based in the dna
describe when do we use pcr
pcr is to amplify dna for example: crime scenes, preserved extinct animals, detected viruses early
why have trangeneic organisms or GMO’s been engineered?
- resistance
round up ready crops
-faster growth rate
aquaadvantage reaching market size in 18months instead of 3yrs
- greater product quality and yeild
goldern rice - tolerance to adverse environment conditions
salt tolerant crops
where is dna found?
is found as unbound circular DNA in the cytosol of prokaryotes and in the nucleaus mitochondria dna chloroplast in eukaryotes
what is the main role of dna
to provide a bluprint for proteins
what two processes produce an enzyme
transcription and translation
what is meiosis
a process where a single cell divides twice to produce 4 cellls containing half the original amount of genetic information(gametes)
describe the process of meiosis
prophase 1
- homologous pairs pair up
- diploid 46
metaphase 1
- homologous chromosomes lineup along equator
anaphase 1- pulled to separate side of a cell chromosome and copy go to one side
telophase 1
- 2 haploid cells form 23 chromosomes
p2- spindle fibers form perpendicular to first set
m2- line up along equator perpendicular to first
a2- chromosomes split at centromeres, sister chromotids separate to opposite poles haploid 23
t2- 4 daughter cells form
describe the process of pcr
- denaturing- heat to 95 to separate into 2 complimentary strands
- annealing- primers are added and the solution is cooled to 50-60 which causes primers to bind to single strand of DNA
- synthesis - dna polymerase added as well as free nucleotides and are heated to 72, the polymerase binds free nucleotides together to make new sections of DNA
- steps 1-3 are repeated till millions of copies are made.
whats the difference between dna profiling and dna sequencing
DNA profiling (Fingerprinting) - DNA fragments created by restriction enzymes is unique for an individual organism. These fragments can be visualized by gel electrophoresis.
DNA sequencing- Determining the exact sequence of nucleotides in a fragment of DNA.
determine the phenotypes and geno types of a male with the skin colour AaBb + AABb using a punnet square
genotype
2 Aabb
4AAbb
4AABb
2AaBb
2AaBB
Phenotype 1 dominant alleles = light
2 = intermediate
3 = dark
what are the the results of having multi coloured cats if the mum is Xb Xr and the dad is Xb Y
b= black
r= red
variation in the genotype of offspring arise as a result of the processes of..
meiosis including crossing over and random assortment of chromosomes and fertilisation as well as mutations
define what STRs are when theyre used
STRs are non-coding, short sequences of DNA, repeated over and over, and scattered throughout the genome.
different people can vary in the numbers of repeating units.
The identification of these variations between people (or animals) can be used for forensic studies.
The likelihood of people (or animals) sharing the same microsatellites is about one in a billion.
Comparing these repeated DNA areas between people can establish the level of genetic relatedness. (1 mark)
describe how bioloigest could determine whether the allele that gave resistance was dominant or recessive to the allele that caused susceptibility
- use a breeding a experiment
- cross resistance flies with eachother
- determine if offspring are resistant or susceptible
- if some are susceptable then parent must be heterozygous
- susceptablilty being recessive
- resisace being domiant
- can test if serceptable by spraying offspring
the genetic composition of the groups of individulas in the different esturaies are the same. provide a plausible explanation for why this is so
- gene flow
- individuals migratebetween estuaries
- this preventing permamant differences evolving in the different estuaries
in making conservation plans to maintain viable gene pools, why do biogeogrpahy, reproductive behavior and population dynamics need to be considered?
biogeography
- nature conservation area needs to large enough and have suitable conditions to maintain viable populations of species
- small population loose genetic diversity and may not be viable
- because the individuals may be from differnt environments
- could cause outbreeding depression and decrease fitness
reproductive behavior
-this is the behaviors associated with mating
- reproducing bahviors may change in captivity due to human contact
- there would be highlevels of inbreeding resulting in loss of fitness
population dynamics
- about how and why populations change size
- smaller populations pose more of a threat to extinction due to lack of genetic diversity
- consrvation planning should be based around smallest population size.
Mateing between red cattle and roan cattle produces red calves about half of the time and roan calves the other half. Why?
Red cattles can only contribute a red allele to the offspring
Road cattle have 50% chance of contibuting a red allele resulting in a red offspring
Roan have a 50% chance of contributing a white allele which will result in a roan offspring
decribe the process of DNA hybridisation
DNA from two species is extracted and cut into short, complementary fragments using primers
DNA from each species is then mixed together
The fragments are incubated at 86oC to dissociate the bonds between the double strands
The mixture is cooled to allow DNA fragments to re-bond (re-anneal) and form hybrid DNA strands
Hybrid strands that are more alike will bind more firmly/make more bonds between base pairs
Mixture is reheated. Level of dissociation of hybrid fragments indicates the level of species relatedness
outline how crossinf over creates genotypic variation
- crossing over exchanges alleles between homologous chromosomes
- occurs in prophase 1
- chromosomes therefore have unique combination of alleles compared to their parents thus creating new genotypes
outline how independent assortment creates genotypic variation
- homologous chromosomes separate independently of one another into gametes
- this occurs in meiosis 1 when homologous pairs line up in random orientations at the middle of the cell as they prepare to separate
- forming random combinations of chromosomes in cell creating different genotypes. this providing unique combinations and increases genetic variation in a population
describe the effect that uv light as on dna structure
physical mutagen and can damage dna
- interferes with base pairing
- breaks hydrogen bonds between bases
- causing errors in dna replication and transcription
explain why mutation is the ulimate source of genetic variation
- mutations are changed in dna sequence
- this creating dna variation
- only process that creates new alleles
- new alleles then creating new combinations of genotypes
describe the functions of dna and messenger rna
dna
- stores genetic information
- this information is required for the development of organisms
- self replicating through mitosis
- information is passed on to next generaation
- genes code for essential proteins
- maintain chromosome structure and function
-
mRNA
- rna reads the genetic code
- copies sequence of dna
- time this information to the cytoplasm
- interact with rivosome in transcription
- ennsures amino acids are assembled to form a protein
describe what bacterial plasmids are and why theyre used in recominant dna
plasmids are small circular parts of bacterial dna and are used as vectors to store and carry genetic material. the are also autonomous replicates so will replicate a re-combinate dna quickly
how is sex inherited
The X and Y chromosomes, also known as the sex chromosomes, determine the biological sex of an individual: females inherit an X chromosome from the father for a XX genotype, while males inherit a Y chromosome from the father for a XY genotype (mothers only pass on X chromosomes). men determine the sex depending on if ther sperm is carrying an X or Y chromosome.
