Inheritance Variation Evolution Flashcards
What are Chromosomes?
Really long molecules of DNA
Describe the structure of DNA (2)
DNA is a polymer , it’s made up of two strands coiled together in the shape of a double helix
What is DNA (1)
It’s the chemical that all genetic material in a cell is made up from
Where is DNA found ? (1)
DNA is found in the nucleus of animal and plant cells in really long structure called chromosomes
How many Chromosomes do humans have
23 pairs
What is a Gene? (1)
small section of DNA found on a chromosome
What is the role of a gene ?(1)
Each gene codes for a particular sequence of amino acids which are put together to make a specific protein
What do genes tell cells ?
Genes simply tells cells to in what order to put amino acids together
What is a Genome ?
Genome is the entire genetic material of an organism
What does a nucleotide consist of ?
One sugar molecule, one phosphate molecule and one base
Name the four different bases and what they link to
Thymine links to Adenine
Cytosine links to Guanine
What decides the order of amino acids in a protein
The order of bases in a gene
What are enzymes ?
Act as a biological catalyst to speed up chemical reactions in the body
What do hormones do ?
They are used to carry messages around the body
What are mutations ?
Changes in the DNA base sequence
How is the chance of a mutation increased ?
By exposure to certain substances or some types of radiation
What happens to the DNA during mutation
Mutations change the sequence of DNA bases in a gene which produces genetic variant
What does sexual reproduction produce ?
Genetically different cells
What is the process of sexual reproduction (2)
Sexual Reproduction is where genetic information from two organisms is combined to produce offspring which are genetically different to each parent
In sexual reproduction, the mother and father produce gametes, what are gametes ?
Sex cell
What are the gametes called in sexual reproduction?
Egg and sperm
What happens between the egg and the sperm cell
The egg cell and the sperm cell fuse together to form a cell with a full number of chromosomes
Why do offsprings inherit features from both parents ?
Because they receive a mixture of chromosomes from both parents
What does Asexual reproduction produce. ?
Genetically Identical cells
What type of cells division is involved in asexual reproduction
Meiosis
What type of cell division is involved in Sexual reproduction
Mitosis
Name factors of Asexual reproduction
• only one parent
• no fusion of gametes
• no genetic variation between parent and offsprings
• they are clones
• no mixture of chromosomes
Examples of things that reproduce asexually ?
Bacteria , some plants and animals
Suggest why there is variation in the offspring of sexual reproduction (2)
Because there are two parents the offspring contains a mixture of their parents genes(1) The mixture of genetic information is called variation(1)
How many copies of chromosomes do gametes have ?
one copy (23)
How many cel divisions does Meiosis have
two
Explain the steps of meiosis (6)
• Before the cell starts to divide it duplicates it’s genetic information forming two armed chromosomes, the chromosomes then arrange themselves into pairs
• In the first division the chromosomes pairs line up in the centre of the cell
• The pairs are then pulled apart so each new cel only has one copy of each chromosome
• In the second division the chromosomes line up again in the centre of the cell , the arms of the chromosomes are then pulled apart
• You get four gametes each with only a single set of chromosomes in it , each of the gametes are genetically different from one another
After two gametes fuse what happens ?
The resulting new cell divides by mitosis to make a copy of itself
Mitosis repeats many times to produce lots of new cells in an embryo , as the embryo develops these cells then start to differentiate into the different types of specialised cell that makes up a whole organism
Give one advantages of sexual reproduction over asexual reproduction
• The offspring has a higher survival advantage due to the genetic variation
What is Natural Selection ?
The process where organisms better adapted to the environment tend to survive and produce more offspring
Give three advantages of asexual reproduction over sexual reproduction
• There only needs to be one parent (less energy organisms don’t need to find a mate)
• Asexual reproduction faster
• Many identical offspring can be produced in favourable offspring
Explain how an organism that reproduces using both methods
For example , Maria is caused by a parasite that’s spread by mosquitoes (1)
When a mosquito carrying the parasite bites. a human the parasite can be transferred into the human (2) The parasite reproduces sexually when in the mosquito but asexually when in the human (3)
What letter chromosomes do males have ?
X AND Y
What letter chromosomes do females have
X AND X
What does homozygous mean ?
When two alleles are the same
What does heterozygous mean ?
Two different alleles
How are dominant alleles shown
Capital letters
What is a genotype?
Combination of alleles you have
What is your phenotype
The characteristics you have
What is Cystic Fibrosis?
A genetic disorder of the cell membranes, it results in the body producing a lot of thick sticky mucus in the air passages and pancreas
What Allele is Cystic Fibrosis caused by
Recessive allele (f)
What is polydactyly ?
Genetic disorder where a baby’s born with extra fingers or toes
What allele is polydactyly caused by ?
Dominant allele (D)
Name 3 reasons against Embryonic Screening
It implies that people with genetic problems are “undesirable” which could lead to prejudice
There may come a point where everyone wants to screen their embryos so they can pick the most desirable one
Screening is expensive
Name 3 advantages of Embryonic screening
It will help to stop
There are laws to stop it going too far at the moment parents cannot even select the sex of their baby
Why won’t someone heterozygous for the cystic fibrosis allele have the disorder
The allele which causes the disorder is recessive meaning you need to have two recessive alleles to have the disorder Heterozygous have one dominant and one recessive allele meaning they will not have the disorder
What were Mendels observations
Mendel noticed how characteristics in plants were passed on from one generation to the next
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What is Variation
Differences between organisms in a population
What are the two types of variation
Genetic and Environmental
What is Genetic Variation
Combination of genes from two parents
Name 3 characteristics that are only determined by genes
• Eye colour
• Inherited disorders
• Blood Group
What is Environmental variation
The environment including the conditions that organisms live and grown in also causes differences between members of the same species
One example of environmental variation
A plant grown in sunlight will be luscious and green whereas the same plant grown in darkness will be spindly and have yellow leaves
3 Examples of characteristics that are due to genetic and environmental variation
• Body weight
• height
• skin colour
What was Darwin’s conclusion of Evolution?
Darwin concluded that organisms with the most suitable characteristics for the environment would be more successful competitors and would be more likely to survive.
“survive of the fittest”
What would happen with the successful organisms that survive
The successful organisms are more likely to reproduce and pass on the genes for the characteristics that made them successful for their offspring
What would happen to the organisms that were less well adapted
The organisms would less like survive and reproduce so are less likely to pass on their genes
What is Extinction ?
When no individuals of a species remain
Give three factors that lead to a species becoming extinct
1( A new predator (kills them all)
2) A new disease (kills them all)
3) A catastrophic event (kills them all)
Explain why Darwin’s theory was considered controversial when it was first proposed
It contradicted the common religious beliefs of the time that all life on Earth was created by God (1) Darwin lacked the evidence that he needed to convince many other scientists (1) He didn’t have any explanation for why new beneficial characteristics appeared on how they were passed on to offspring (1)
What is selective Breeding?
When humans artificially select the plants or animals that are going to breed so that the genes for particular characteristics remain in the population
What is Selective Breeding also known as
“Artificial selection”
Outline the basic process of selective breeding
- From your existing stock select the ones which have the characteristics you’re after
- Breed them with eachother
- Select the best of the offspring and breed them together
- Continue this process over several generations and the desirable trait gets stronger and stronger
Explain a disadvantage of selective breeding
It reduces the gene pool, (the number of different alleles forms of a gene in a population) This is because the farmer keeps breeding from the “best” animals or plants which are closely related. This is known as inbreeding
What can inbreeding cause
Health Problems
Give one reason why it is important for scientists to have na important understanding of a human genome
It allows scientists to identify the links genes have to specific diseases, knowing this they will be able to identify the most effective treatment to cure the disease
Suggest one possible effect of a mutation that changes the shape of a structural protein
A mutation can result in the protein becoming weak meaning that it may no long be able to carry out its job for providing structure and support
Suggest one possible effect of a mutation in a gene that codes for a particular enzyme
The shape of the enzymes active site could change meaning it’s substrate could no longer bind to it , so the enzyme would no longer be able to catalyse the reaction
Give four ways in which asexual reproduction is different from sexual
• Asexual reproduction produces two genetically daughter cells rather than 4
• asexual reproduction does not involve gametes
• asexual reproduction only uses one parent
• asexual reproduction uses the cell division of mitosis not meiosis
Explain why sexual reproduction increases the chance of the population surviving (4)
Sexual reproduction results in genetic variation (1) Variation means offspring may have genes that allows them to be more adapted to the environment and better chances of survival (1). Individuals with this gene have better chances of survival and breeding successfully (1) They can then pass the gene of to future generations which will allow them to survive in the environment (1)
What is Genetic Engineering
The deliberate modification of the characteristics of an organism, by transferring a gene responsible for a desirable characteristic from one organisms genome into another
What is the method of genetic engineering?
A useful gene is cut from one organisms genome using enzymes and is inserted into a vector .
The vector is usually a a virus or a bacterial plasmid
When the vector is introduced to the target organism the useful gene is inserted into its cells
One advantage and disadvantage of GM crops
GM crops can be engineered to contain certain nutrients which some people may lack from their diets
Some people are not convinced GM crops are safe and are concerned that we might not fully understand the effects of eating them on human health
Define two ways plants can be cloned
By tissue culture
Cuttings
Describe how animals can be cloned by adult cell cloning (5)
The nucleus is removed from an unfertilised egg(1) and a complete set of chromosomes from an adult body is et into the egg(1) The egg cell is them stimulated to divide, by an electric shock to form an embryo (1) The embryo is then implanted into the female (1) where it develops into a clone of the original adult body (1)
What are fossils ?
remains of plants and animals
Name three ways fossil forms in rocks
Gradual replacement of minerals
Casts and impressions
Preservation in places where no decay happens
Suggest what makes low-oxygen environments suitable for formation of fossils
The microbes that cause decay cannot survive in low oxygen environments so the dead organisms are preserved
How can speciation occurs ?
When a populations of the same species becomes so different they can no longer successfully interbreed to produce fertile offspring
Why might natural selection work differently on two isolated populations of species (3)
The two populations may be in different environments (1) and so different characteristics will be beneficial (1) Natural selection will work differently in each population so that individuals with beneficial characteristics are more likely to survive
What is a disadvantage of an anti biotic resistant bacteria
We aren’t immune to the new strain and there is no effective treatment
Explain why it is important that people take the full course of anti biopics prescribed
Taking the complete course makes sure all bacteria are destroyed (1) This means that there are none left to mutate and develop into antibiotic resistant strains (1£
What is Evolution ?
a change in the inherited of a population over time through a process of natural selection
What cell undergoes mitosis ?
Somatic cell
What cell undergoes meiosis
reproductive cell
What are the main uses of proteins ?
• enzymes
• hormones (send messages around the body)
• structure proteins (strength to cell and tissues)
The sequence of bases in DNA determines ..
the sequence of amino acids in the chain
Different sequences of amino acids leads to..
Proteins with different shapes allowing proteins to carry out different functions
What does DNA stand for
Deoxyribonucleic acid
Define Transcription
copying of a single gene of DNA to mRNA
Why does a gene have to be copied
As it is too large to leave the nucleus
Define translation
When the combination of amino acids produce a protein from mRNA
How is mRNA different from DNA
• it is shorter
• single stranded
after the mRNA leaves the nucleus where does it go ?
The cyptoplasm then the ribosome
Function of ribosome
assemble proteins from amino acids
What are the chain of amino acids called
Polypeptide
What increases the risk of mutations ?(2)
• Harmful chemicals (carcinogens)
• Radiation
Where does mutations normally occur ?
non-coding DNA
3 types of mutations
Insertions
Substitutions
Deletions
Define insertion
extra base is added into sequence
Define substitutions (least effective)
one of the bases is changed for another base
Define deletions
A base being deleted
Describe how a change of one of the bases in a a gene for an enzyme could effect they function of an enzyme (4£
Changes in the base changes the codon which changes the amino acid it codes for (1)
The different sequence of amino acids will result in the polypeptide fold into a differently shaped protein(1)
Proteins will have a different active site and will not bind to the substrate(1)
This means there will be no enzyme-substrate complex and cannot catalyse the reaction (1)
Define natural selection
Fittest individuals are selected to survive
Who created the evolution theory ?
DARWIN
Define evolution (2)
The inheritance of certain characteristics in a population over multiple generations that can lead to change in the whole species
Name two evidence for the theory of evolution
• Spread of anti biotic resistance
• The fact that variation is due to genes and the environment
Describe a series of events that might result in zebras evolving to run more quickly (4)
There is a variation among the zebra population where some can run faster then others(1)
A mutation arises allowing some zebras to run faster (1)
Therefore more likely to reproduce and pass on advantageous alleles (1)
This repeats over multiple generations and advantageous allele is spread throughout population until species are evolved (1)
Does selective breeding increase or decrease variation
Decrease variation
Name two factors determining body mass
Genetic
Environmental
Name 3 disadvantage of inbreeding
•Reduced size of gene pool
• rare inherited disease more likely to appear
• Population will be more risk of disease as a whole
Describe the process of selective breeding uses to increase milk production in cows (3)
Cows that produce most milk are selected and bred together
process repeated with offspring of those cows and repeated for multiple generations
Define DNA
a double stranded polymer of molecules nucleotides
What are the force bases
A T C G
How many amino acids are there in humans
20
What determines the shape of the protein
the specific order of amino acids
What does the shape of the protein determine
it’s function
What determines the order of the protein
the sequence of bases in the gene for that protein
What is the first stage of protein synthesis
The first stage takes place in the nucleus
this is called transcription
• the base sequence of the gene i copied into a complementary template molecule (mRNA)
• the mRNA now passes out of the nucleus and into the cytoplasm
What is the second stage of protein synthesis
This is called translation and happens in the cytoplasm
• the mRNA molecules attaches to a ribosome
• Amino acids are then brought to the ribosome on carrier molecules
• the ribosome now reads the triplets of bases on the mRNA and uses this to join together the correct amino acids in the correct order
• It now folds into its unique shape
what is the template messenger called
Rna or mRNA
define alleles
different versions of the same gene
What is speciation
the formation of a new species
when two populations become so varied that they cannot interbreed to produce offspring
state two kinds of evidence to show evolution
fossils
antibiotic resistant bacteria
why are there few traces of early life-forms left behind
mostly soft-bodied
what enables bacteria to evolve quickly
the faster rate of their reproduction
one resistant strain of bacteria
MRSA
what can be done to reduce the rate of development of antibiotic resistant bacteria
• reduce inappropriately prescribing antibiotics
• patients should complete the prescribed course of antibiotics
why is it difficult to keep up with emerging resistance strains
developing antibiotics have a high cost and take a long time to develop
What’s the order of the Classification system (King Philip Came Over For Good Soup)
Kingdom
Phylum
Class
Order
Family
Genus
Species
How is very organism named from
Genus and species
bionomial name
genus and species
who developed three domain system
Woese carl
two ways biomass is lost
• urea from excretion
• carbon dioxide from respiration
Why were new classification models proposed
• developments in microscopy allowed better examination of internal structures
• Improvement in understanding of biochemical processes
two benefits of understanding the human genome
• diagnosis of inherited disorders
• treatment of inherited disorders
why would children look different from eachother
• different egg
• different combination of alleles
