inheritance, variation and response Flashcards
mitosis vs meiosis
produces and uses
- mitosis produces genetically identical cells
- mitosis is used for growth and repair of damaged tissues, replacement of cells and asexual reproduction
- meiosis produces genetically different cells
- meiosis is used to produce gametes
what is sexual reproduction
process involving fusion of the male and female gametes
ie. pollen and egg cells- plants
sperm and egg cells- animals
what is fertillisation
the fusion of gamete nuclei
what is asexual reproduction?
process resulting in genetically identical offspring from one parent
involves mitosis
why must no. chromosomes be halved when gametes are formed?
so the no. chromosomes after they join in fertilisation in the zygote, wouldnt be doubled- 98 when there should only be 46
identify stages of meiosis
- cell dupliactes chromosomes
- chromosomes line up along cell and pulled apart into 2 cells- 1st division
- chromosomes line up alon cell and pulled apart into anotehr 2 cells each- 2nd division
- produced 4 genetically different haploid daughter cells
proocess of fertilisation
- gametes fuse to restore normal no. chromosomes becoming a zygote with half male, half female chromosomes
- zygote divides by mitosis and keeps on dividing- forming an embryo
- cell division continues and many cells become specialised
advantages of sexual reproduction
- produces variation in offspring
- species can adapt to new environments by natural selection
- natural selection can be speeded up by humans in selective breeding to increase food production (cows- more milk etc)
disadvantages of sexual reproduction
- takes time and energy to find mates
- difficult for isolated members of species to reproduce
advantages of asexual reproduction
- only one parent needed
- more time and energy efficient as dont need to find mate
- faster than sexual
- many identical offspring can be produced when conditions are favourable
disadvantages of asexual reproduction
- limited genetic varation in population
- population vulnerable to changes in conditions- may only be suited to one habitat
- whole population more susceptible to be affected by disease
what organisms reproduce both asexually and sexually?
- malarial parasites- asexually in human host but sexually in mosquito
- fungi- asexually by spores but sexually to produce variation
- plants- produce seeds sexually, reproduce asexually by:
- ‘runners’ in strawberry plants - stems that grows away fromm parent plants
- bulb division’ in daffodils - new bulb form from main bulb undergound
what is the genome?
the entire genetic material of the organism
the entire human genome has now been discovered and studied
what does DNA stand for?
deoxyribonucleic acid
describe the structure of DNA
a polymer made up of two strands forming a double helix
where is dna found
in chromosomes
what is a gene
small section of DNA on a chromosome that code for a particular sequence of amino acids to form a specific protein
what is the importance of understanding the human genome
- help improve our understanding of the genes linked with different types of dieases and inherited disorders as well as helping find treatments
- helped in tracing human migration patterns from past
what is a nucelotide and what is it made from?
also what do they look like on a diagram
- an individal sub unit of DNA (its a polymer made up of repeating nucleotide units)
- made from a deoxyribose sugar, phosphate and one of 4 different bases
- sugar- pentagon
- phosphate- circle
- base- rectangle with triangle
sugar attched to BOTH base and phosphate
name the 4 different bases
- Adenine
- Cytosine
- Thymine
- Guanine
base pairings
Adenine & Thymine
Cytosine & Guanine
complementary base pairings
what is the code for a particular amino acid?
3 bases on a strand NOT parings
how is protein synthesised? 2 main stages
-
transcription
- base sequence is transcribed from one strand onto an mRNA
- mRNA travels out of nucleus into cytoplasm (DNA strand too big)
2/. translation
- mRNA attaches to ribosomes
- animo acids are brought to ribosomes by carrier molecules called tRNA
- ribomes read the triplets of bases on mRNA and order the amino acids into specifc protein chain
- the protein chain folds into it’s unique shape
mRNA- meesenger RNA | tRNA- transfer RNA
3 examples of proteins
- enzymes
- hormones
- structural proteins like collagen
what are mutations?
random changes that occur in the sequence of DNA bases
3 ways mutation in DNA base sequence occur:
- insertion- random base insterted into sequence- changes groups of bases further on
- deletions- base randomly deleted- changes groups of bases further on
- substitutions- base randomly swapped for different base- only changes amino acid
effects of mutation
most mutatiosn do not alter protein at all or alot
some do- and affects ability of protein to function
e.g active site changes on enzyme- substrate no longer fit in
what are the non-coding parts of DNA
can switch DNA on and off- controls whether a gene can be expressed
what is an allele
different versions of particular gene
what is a zygote
fertilised egg
homozygous vs heterozygous
homozygous- two same alleles
heterozygous- two different alleles
genotype vs phenotype
genotype- combination of alleles
phenotype- physical characteristics observed in individual
dominant vs recessive alleles
dominant- only one needs to be present- CAPITAL
recessive- two copis needed- lowercase
can a dingle g ene control a characteristic?
yes
multiple genes that conrol characteristics- polygenic
monohybrid inheritance
inheritance of characteristics controlled by a single gene
- determinded using a Punnett Square
family trees
- show inheritance of different characteristics through generations of a family
polydactyl
extra finger or toes
caused by dominant allele
cystic fibrosis
genetic disorder of the membrane - large amount of mucus produced in air passges
caused by recessive allele
can be carriers
xx
female
xy
male
what is variation?
differnces in individuals of same species’s phenotypes
what is
genotype?
phenotype?
genotype- organism’s genetic information
phenotype- observable physical characteristics
what is embryo screening?
where a cell is taken from an embryo before being implanted or in womb and its genes are analysed to detect any genetic disorders.
for embryo screening vs against
for:
- avoid suffering
- treatment for disorders are expensive
- laws in place to stop abuse- coosing desired characteristis
against:
- imply that those iwth genetic disorders aere undesirable
- very expensive
- can still be sued to choose desirable characteristics
what is gene therapy?
what is the issue with it?
normal alleles inserted in chromosomes of individual carrying defected alleles
- still developing
- not always successful
what can influence variation?
genes- eg, blood group, eye colour, gender
environement- eg, climate, diet, culture, lifestyle
combinataion- eg, weight, height
how do variants arise
mutations
to which they occur continously
effect of mutations on phenotype
very rarely can lead to new phenotype
some can influence phenotype
most have no effect
what is evolution
change in the inherited characteristics of a population over time through of a process of natural selection which can resut in formation of a new species
how can a new species form?
when 2 populations of 1 species becoome so different in phenotype that they can no longer interbreed to produce fertille offpsring
what does the thoery of evolution by natural selection state
all species of living things have evolved from simple life forms that first developed more than 3 billion years ago
what is selective breeding used to produce?
- domestic dogs to have a gentle nature
- food crops to be resistant to disease
- animals to produce more meat/milk
- plants to produce large/unusual flowers
process of selective breeding
- parents with desired characteristics are chosen
- bred together
- offspring with desirable characteristics are chosen
- bred together
- continues over many generations until all offspring have desired characteristics
problems with selective breeding
inbreeding->
- prone to disease
- inherited disorders
what is genetic engineering?
genome modified by introducing gene from other organism t give desired characteristic
how are bacteria genetically modified
to produce human insulin to treat type 1 diabetes
how are GM crops modified?
- to be resistant to disease/insect attack
- produce bigger/better fruits
- resitant to herbicides
- produce a greater yield^
what is the issue with GM crops?
- concerned about effect onn population of wild flowers and insects
- effets of eating GM crops on human health not explored
process of genetic modificaton/engineering
- identify desired gene
- use enzymes to isolate gene
- transfer gene to plasmid or virus- vector
- desired gene transferred into cell of desired organism At early stage of organism’s so that they develop desired characteristics
what is being explored with genetic modificatoion?
th possiblity to help overcome some inherited disorder
process of tissue cuttings
issue
- take cuttings off plants
- dip into rooting powder containing hormones that will encourage roote developement
- produce genetically identically plant
produces few clones
process of tissue culture
and what is it good for
- divide desired plant into many small pieces
- incubate with plant hormones which stimulate plant growth and
development to fully grown clones
commercial plant nuseries
preserving rare species
process of embryo transplants
issue
- sperm & egg cell from animals with desired characteristics undergo fertilisation
- fertilised egg divides until ealry stage of embryo- no specialised cells
- embryo is split and transplanted into host mothers to produce identical offspring
sexual reproduction- sperm & egg- cannot be certain they will give desired characteristic
process of adult cell cloning
and why is it preferrable
- remove nucelus from an unfertilised egg cell of same species
- replace the nucelus with one ofrom a cell from the animal with desired characteristic
- electric shock the egg cell to divide and form embryo
- embryo developed into ball of cells and inserted into womb of adult female to continue developement
clonig an adult- know dthe characteristics it will clone
what does evolution conclude
- individuals in a species show a wide range of variation caused by differences in genes
- those with characteristics most suited to the environment have a higher chance of survival and more chances to reproduce
- those characteristics are passed onto the next generation
what book did Charles Darwin write?
On the Origin of Species
why wasnt Darwin’s theory widely accepted?
- it challenged belief that God made all animals & plants that live on Earth
- scientists believe there was insufficient evidence to back his theory
- mechanism of genetics and inheritance wasnt understood until 50 yeasr later
what was Lamark’s theory?
and why wasnt it correct?
characteristics regularily used by organism were strengthened and then passed on to offspring
bc changes that occur to an organism during its life cannot be passed on to offspring
what theory did Wallace come up with?
speciation
and he also independently developed his own theory of evolution to which he worked with Darwin
process of speciation
- population of species become isolated due to a physical barrier
- environment is different on either side of barrier
- different alleles more advantageous to surviving in environment therefore are passed on to offsprings
- over many gens- populations will become so distinct that they can no longer interbreed and produce fertile offspring
what did Mendel investigate
how characteristics were passed on between generations of plants- pea plants
what were Mendel’s observations
- characteristics determined by inherited units that do notttytyttt change- genes
- they can be masked OMG and then nherited and show up in later generations- rescessive allele
why was Mendel’s discovery not recognised until after death
chromosomes and genes not discovered until later
evidence for evolution
- shown that characteristics are passed on to offspring in genes
- fossil records
- antibiotic resistance bacteria
what are fossils?
the remains of organisms from millions of years ago which are found in rocks
how are fossils made
- parts of organism not decayed due to absent conditions for decay
- decayed organisms replaced by minerals during decay process
- preserved traces of organisms like footprints
why cant scientists be certain how life on Earth began
- many were soft-bodied organism
- fossil records destroyed by changes to rocks if Earth’s crust
causes of extinction
- catastrophic event
- environment changes
- new disease
- new predator
- more successful species evolved and competing for resources
what causes genetic variation
mutations!!!!!
how bacteria become resistant to antibiotics
- reproduce at a fast rate
- mutations occur during reproduction creaying new genes- resistant genes
- exposure to antibiotics make those mutated bacteria survive
- they reproduce, passing on gene to offspring
- those bacteria spread rapidly as people are not immune
how to reduce antibiotic resistnat bacteria
- not prescribe bacteria inappropiately liek to viral infections
- complete ful course- so alll are killedso none surviev to mutate
- resist use of antibiotis for farming
Carl Linneus
classification of organisms i two kingdoms- animals, plants
classification system
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Kaeya Please Come Over For Great S
binomial system
genus species
Carl Woese
3 domain system
3 domain system
Archae- primitive bacteria that live in extreme environment
Bacteria- true bacteria
Eukaryota- plant, fnugi, animals, protists
