Inheritance, Variation And Evolution Flashcards
1
Q
what is DNA
A
- polymer
- made up of 2 strands forming a double helix
- contained in structures called chromosomes
2
Q
What is a gene
A
-small section of DNA on a chromosome
-each gene codes for a particular sequence of amino acids, to make a specific protein
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Q
What is a genome
A
-the entire genetic material of that organism
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Q
Importance of understanding human genome
A
1) It allows scientists to identify genes in the genome that are linked to different types of disease.
2) Knowing which genes are linked to inherited diseases could help us to understand them better and could help us to develop effective treatments for them.
3) Scientists can look at genomes to trace the migration of certain populations of people around the world. All modern humans are descended from a common ancestor who lived in Africa, but humans can now be found all over the planet. The human genome is mostly identical in all individuals, but as different populations of people migrated away from Africa, they gradually developed tiny differences in their genomes. By investigating these differences, scientists can work out when new populations split off in a different direction and what route they took.
5
Q
How many pairs of chromosomes in a human
A
23
6
Q
How many chromosomes control characteristics and how many control gender
A
22 control characteristics
1 controls gender
7
Q
Female chromosomes
A
XX
8
Q
Male chromosomes
A
XY
9
Q
Gamete
A
A reproductive cell of an animal or a plant
10
Q
Chromosome
A
A thin strand of DNA
11
Q
Allele
A
A different version of the same gene
12
Q
What is the dominant
A
The allele which is expressed in the phenotype when only 1 copy is present (the one that decides the phenotype)
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Q
What is the recessive
A
allele that only expresses itself when there are two copies of the allele present in an individual
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Q
Homozygous
A
2 of the same alleles (AA, aa)
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Q
Heterozygous
A
2 different alleles (Aa)
16
Q
Genotype
A
The two alleles for a characteristics (for an organism it’s ALL the DNA for that organism)
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Q
Phenotype
A
The physical characteristics (blonde hair)
18
Q
Polydactyl
A
Having extra fingers or toes, caused by dominant allele
19
Q
Cystic fibrosis
A
Disorder of cell membranes, caused by recessive allele
20
Q
Economic issues with embryo screening
A
- High Costs: Embryo screening can be very expensive, making it inaccessible to many families. This limits its availability mainly to wealthier people.
- Healthcare Spending: Public healthcare systems might need to allocate substantial funds to cover embryo screening, potentially taking resources away from other medical needs.
- Future Cost Savings vs. Immediate Cost: While screening could help prevent costly genetic diseases, the immediate costs are high, making it challenging to justify for public funding.
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Q
Ethical issues with embryo screening
A
- “Designer Babies”: Screening could be used to select traits beyond health, like appearance or intelligence, raising concerns about choosing babies’ characteristics and ethical boundaries.
- Value of Life: Deciding which embryos to keep based on genetics raises questions about whether all lives are valued equally, potentially stigmatizing certain conditions.
- Consent: Embryos can’t consent to screening or selection, leading to ethical debates on making such significant choices on behalf of a future person.
22
Q
Social issues with embryo screening
A
- Increased Inequality: If only wealthier families can afford embryo screening, it could deepen social inequalities and create divides based on genetic “advantages.”
- Discrimination: Emphasizing genetic “normality” may foster discrimination against people with disabilities, suggesting that only certain types of people are desirable.
- Pressure on Parents: Social norms could develop, pressuring parents to screen embryos or risk being judged for not doing everything to ensure a “healthy” child.
23
Q
5 steps of IVF
A
- Stimulating the Ovaries: Medicine is given to help the ovaries produce multiple eggs (usually, only one egg is released each month, but IVF aims to get several).
- Retrieving Eggs and Sperm: Doctors collect the eggs from the ovaries and also get a sperm sample from the partner or a donor.
- Fertilization in the Lab: The eggs and sperm are combined in a lab, where hopefully some eggs become fertilized and turn into embryos.
- Selecting and Transferring Embryos: Once the embryos grow for a few days, a healthy one (or sometimes more) is chosen and placed into the uterus.
- Waiting for Pregnancy: If the embryo attaches to the uterus lining, pregnancy begins, and the process continues like any typical pregnancy.
24
Q
Explain meiosis
A
- before cell starts to divide, it duplicates its genetic information, forming 2 armed chromosomes: one arm of chromosomes is an exact copy of the other arm
- after replication, the chromosomes arrange themselves into pairs
- in the first division in meiosis the chromosome pairs line up in the centre of the cell
- the pairs are ten pulled apart so each new cell only has 1 copy of each chromosome. Some of the father’s chromosomes and some of the mother’s chromosomes go into each new cell
- in the second division, the chromosomes line up again in the centre of the cell
- the arms of the chromosome e pulled apart
- you end up with 4 gametes, each with only a single set of chromosomes in it
- each gamete is genetically different from the others because the chromosomes al get shuffled up during meiosis and each gamete only gets half of them at random
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What happens after meiosis
- two gametes fuse during fertilisation
- the resulting new cell divides by mitosis to make a copy of itself
- mitosis repeated many times to produce lots of new cells in an embryo
- as the embryo develops, these cells then start to differentiate into different types of specialised cell that make up a whole organism
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What is variation
- when organisms of the same species look slightly different
- variation can be genetic: caused by differences in the genotype which affects its phenotype
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What affects variation in phenotype
- genotype
- interactions with environment: plant grown on a nice sunny windowsill could grow luscious an green whereas the same plant grown in darkness would grow tall and spindly and its leaves would turn yellow
- most variation is a mixture of genetic and environmental factors
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What is a mutation
- A rare, random change in an organism’s DNA that can be inherited
- mutations occur continuously
- mutations mean that the gene is altered which produces a genetic variant
- as the gene codes for a sequence of amino acids that make up a protein, gene mutations sometimes lead to changes in the protein that it codes for
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Genetic variant influence on phenotype
- most genetic variants have very little or no effect on the protein the gene codes for
- some will change it to such a small extent that its function is unaffected
- this means that most mutations have no effect on an organisms phenotype
- however sometimes they can have a dramatic effect such as cystic fibrosis
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What is the theory of evolution
All of today’s species have evolved from simple life first started to develop over 3 billion years ago
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Survival of the fittest
Darwin concluded that the organisms its the most suitable characteristics for the environment would be more successful competitors and would be more likely to survive
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What happens after survival of the fittest
- the successful organisms that survive are more likely to reproduce and pas on the genes for the characteristics that made them successful to their offspring
- the organisms that are les well adapted would be less likely to survive and reproduce, so they are less likely to pas on their genes to the next generation
- overtime, beneficial characteristics become more common i the population and the species changes: it evolves
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What is extinction
When no individuals of a species remain
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Reasons for extinction
- the environment changes too quickly
- a new predator kills them all
- a new disease kills them all
- they can’t compete it’s another (new) species for food
- a catastrophic happens that kills them all
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What is speciation
- the development of a new species
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Explain speciation
- over a long period of time, the phenotype of organisms can change so much because of natural selection that a completely new species is formed
- speciation happens when populations of the same species change enough to become reproductively isolated
- this means that they can’t interbreed to produce fertile offspring
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Basic process of selective breeding
- from your existing stock, select the ones which have the characteristics you’re after
- breed them with each other
- select the best of the offspring, and breed them together
- continue this process over several generations, and the desirable trait gets stronger and stronger, eventually all the offspring will have the characteristics
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What is selective breeding
- when humans artificially select the plants or animals that are going to breed so that the genes for the particular characteristics remain in the population
- organisms are selectively bred to develop features that are useful or attractive
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Main problem of selective breeding
- reduces the gene pool (the number of different alleles) in a population
- this is due to inbreeding
- it can cause health problems because theres a higher chance of organisms inheriting harmful genetic defects when the gene pool is limited
- so there is less chance of any resistant allele bing resistant alleles being present in the population,so if one is killed by a new disease, the others are likely to succumb to it
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What are fossils
- remain of organisms from many thousands of years ago which are found in rocks
- they provide the evidence that organisms lived ages ago
- they can tell us a lot about how much or how little organisms have changed over time
- fossils form rocks in 3 ways
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Fossils formed by gradual replacement by minerals
- things like teeth, shells, bones etc., which don’t decay easily, can last a long time when buried
- they’re eventually replaced by minerals as they decay, forming a rock-like substance shaped like the original hard part
- the surrounding sediments also turn to rock, but the fossil stays distinct inside the rock and eventually someone digs it up
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Fossils formed by casts and impressions
- sometimes fossils are formed when an organism is buried in a soft material like clay
- the clay later hardens around it and the organism decays, leaving a cast of itself
- an animal’s burrow or a plant’s roots can be preserved as casts
- things like footprints can also be pressed into these materials when soft, leaving an impression when it hardens
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Fossils formed by preservation in places where no decay happens
- in amber (a clear yellow stone made from fossilised resin) and tar pits theres no oxygen or moisture so decay microbes can’t survive
- in glaciers its too cold for the decay microbes to work
- peat bogs are too acidic for decay microbes
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Hypothesis of where life began
- maybe from primordial swamp or under the sea here on earth
- maybe brought to earth on comets which could then become more complex organic molecules and eventually very simple life forms
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Why are the hypotheses on how life began not supported or disproved
- many early life forms were soft bodied and the soft tissue tends to decay away completely : so the fossil record is incomplete
- fossils that did for millions of years ago may have been destroyed by geological activity
- lack of good valid evidence
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What did Carl Linnaeus create
- the classification system
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Order of classification system
- kingdom
- phylum
- class
- order
- family
- genus
- species
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What is the classification system
- organisms being classified
- depends on which groups living things according to their their characteristics and the structures that make them up
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3 domain system members
- archaea
- bacteria
- eukaryota
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Why has classification changed over time
- knowledge of biochemical processes taking place inside organisms have developed and microscopes have improved
- scientists have been able to put forward new models of classification
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Who proposed the 3 domain system
Carl Woese
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What is the 3 domain system
- using evidence gathered from new chemical analysis techniques such as RNA sequence analysis
- he found that in some case,species thought to be closely related in traditional classification systems are in fact not as closely related as first thought
- organisms are split into the 3 large groups called domains
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Archaea (3 domain system)
- organisms in this domain are primitive bacteria
- often found in extreme places such as hot springs and salt lakes
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Bacteria (3 domain system)
- this domain contains true bacteria like E. Coli and staphylococcus
- although they look similar to archaea, there are lots of biochemical differences between them
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Eukaryota (3 domain system)
- this domain includes a broad range of organisms including fungi, plants, animals and protists
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Binomial system
- every organism has a two part Latin name
- first part is the genus of the organism (use capital letter for this)
- second part is the species (lower case)
- underline the whole thing
-its used worldwide so scientists from different countries or who speak different languages all refer to a particular species by the same name - avoiding potential confusion
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What are evolutionary trees
- they show how scientists think different species are related to each other
- they how common ancestors and relationships between species
- the more recent the common ancestor, the more closely related the two species
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What happens when bacteria develop random mutations in their DNA
- can lead to changes in the bacteria’s characteristics eg. Being less affected by particular antibiotic
- this can strains forming as the gene for antibiotic resistance becomes more common in the population
- bacteria also reproduce very quickly and can evolve quite quickly
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Why is bacteria’s ability to resist antibiotics a big advantage
- they’re better able at surviving, even in a host who’s being treated to get rid of the infection and so it lives for longer and reproduces many more times
- this increases the population size of the antibiotic resistant strain
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Why are antibiotic-resistant strains a problem
- they’re a problem for people ho becomes infected with these bacteria because they aren’t immune to the new strain and there is no effective treatment
- this means hat the infection easily spreads between people
- sometimes drug companies can come up with a new antibiotic thats effective, but superbugs that are resistant to most known antibiotics are becoming more common
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MRSA
- relatively superbug thats really hard to get of
- it often affects people in hospitals and can be fatal if it enters their bloodstream
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Why is the problem of antibiotic resistance getting worse
- due to the overuse and inappropriate use of antibiotics
- eg. Doctors prescribing them for non-serious conditions or infections caused by viruses
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Why do you need to take all the antibiotics that doctors prescribe you
- taking the full course makes sure that all the bacteria are destroyed
- this means there are none left to mutate and develop into antibiotic-resistant strains
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Why is it important that doctors only prescribe antibiotics when they really need to
- its not that antibiotics actually cause resistance
- they create a situation where naturally resistant bacteria have an advantage and so increase in numbers
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What is genetic engineering
- to transfer a gene responsible for a desirable characteristic from one organisms genome into another organism, so that it also has the desired characteristic
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Process of genetic engineering
- a useful gene is isolated (cut) from one organism’s genome using enzyme and is inserted into a vector
- the vector is usually a virus or a bacterial plasmid depending on the type of organism that the gene is being transferred to
- when the vector is introduced to the target organism, the useful gene is inserted into its cell(s)
- scientists use this method to do al sorts of things
- in some cases, the transfer of the gene is carried out when the organism receiving the gene is at an early stage of development. This means that the organism develops with the characteristic coded for by the gene
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Why is genetic engineering a controversial topic
- its an exciting area of science, which has the potential for solving many of our problems
- but there are worries about the long-term effects of genetic engineering - that changing an organism’s genes might accidentally create unplanned problems, which could get passed on to future generations
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Cons of GM crops
- some say it will affect the number of wild flowers that live in and around the crops - reducing farmland biodiversity
- not everyone is convinced that GM crops are safe and some people are concerned that we might not fully understand the effects of eating them on human health
- another concern is that transplanted genes may get out into the natural environment. For example, the herbicide resistance gene may be picked up by weeds, creating a new superweed variety
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Pros of GM crops
- the characteristics chosen for GM crops can increase the yield, making more food
- people living in developing nations often lack nutrients in their diets. GM crops could be engineered to contain the nutrient that’s missing. For example, ‘golden rice’ is a GM rice crop that contains beta-carotene - lack of this substance causes blindness
- GM crops are already being grown in some places, often without any problems
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