Inheritance, Variation and Evolution Flashcards
How does meiosis work?
Parent cell
Chromosomes duplicate to make identical copies of themselves
Similar chromosomes pair up and line up along the equator
Sections of DNA are swapped
Cell wall and cytoplasm divides
Chromosomes divide into gametes
What are the factors of sexual reproduction?
Two parents
Fusion of gametes
Mixture of genetic information
Offspring are genetically different
What are the factors of asexual reproduction?
One parent
No fusion of gametes
No mixture of DNA
Offspring are genetically identical
What are the advantages of sexual reproduction?
Offspring are genetically different
If environment changes more organisms are likely to survive
What are the disadvantages of sexual reproduction?
Needs two parents
Time and energy used to find a mate
Offspring harder to form
What are the advantages of asexual reproduction?
Many offspring produced
One parent needed
No time and energy needed for a mate
What are the disadvantages of asexual reproduction?
Less variation
If environment changes more organisms will likely die
When does asexual reproduction occur in plants?
When they grow new stems called runners
When does sexual reproduction occur in plants?
When male gamete (pollen) join to female ovules
How does malaria reproduce?
Reproduces asexually inside of a human
Reproduces sexually inside pf a mosquito
How does fungi reproduce asexually?
Spores land elsewhere and grow
How does fungi reproduce sexually?
Extensions from one fungi to another and share DNA
What is DNA?
The genetic material inside a nucleus of a cell
What does DNA carry?
The genetic instructions used in the growth, development, functioning and reproduction of all living organisms
What are DNA strands?
Polymers made up of lots of repeating units called nucleotides
What does an individual nucleotide made up of?
Phosphate
Base
Deoxyribose sugar
What do the bases do?
They join to a base on the opposite strand of the helix
What are the four bases?
A
T
C
G
What does A join to?
T
What does C join to?
G
What does the order of bases in a gene decide?
The order of amino acids in a protein
How many bases does one amino acid code for?
3
What do amino acids form and why is this important?
Form proteins which determine your physical characteristics
What can the genome be used for?
Identify and find genes linked to diseases
Understand how to treat inherited diseases
Trace human migration patterns
What is the genome?
The entire genetic material of that organism
Where are proteins made?
In the cell cytoplasm on ribosomes
How do ribosomes make protein?
They use code from the DNA
How does the ribosome get DNA from the nucleus?
They use a molecule called mRNA as it is small enough to leave the nucleus
How are proteins made using mRNA?
DNA unzips to expose bases mRNA makes template of the DNA Moves out of nucleus tRNA (found in cytoplasm) attaches to amino acids to bring them to them ribosome tRNA attaches to mRNA Order they join are dictated by the DNA Forms protein Protein detaches and folds into specific shape
What are three amino acids called?
Codon
What is a chain of amino acids called?
Polypeptide chain
What happens if the base sequence changes?
Change in order of bases
Changes amino acid coded for
Changes the proteins made
Protein may not fold correctly
How does a mutation affect an enzyme?
Change in amino acids Changes the way the protein folds Active site changes No longer complementary Enzyme will become denatured
What is deletion?
When a base is taken away
What is insertion?
When a base is inserted
What is substitution?
When a base is replaced by another
What does non-coding DNA do and what are they called?
Switch genes on and off and are called stop codons
How does changes in stop codons affect genes?
How genes are expressed
What can alleles be?
Dominant or recessive
What do you need to express a dominant trait?
Only need to receive one dominant allele
What do you need to express a recessive trait?
You need two recessive alleles
What would happen if you had one of each?
The dominant one would be expressed
What is heterozygous?
2 alleles present are different
What is homozygous?
2 alleles present are the same
What is genotype?
The alleles you have
What is phenotype?
What you look like (visible characteristics)
What are genetic crosses used for?
To show the potential offspring that might result from 2 known parents
How do you get the F2 generation?
Taken from the first offspring
What are the male chromosomes?
XY
What are the female chromosomes?
XX
What is variation?
The differences in the characteristics of individuals in a population
What causes variation?
Genes inherited
Environmental influence
Combination of both
What influences the development of the phenotype of an organism?
Genome
Its interaction with the environment
What is Darwin’s theory?
Individuals with characteristics that make them better suited/adapted to their environment are more likely to survive and reproduce
What did Darwin notice?
Variation in species means individuals have different characteristics
What did Darwin say about those best adapted?
They are more likely to reproduce and pass on favourable characteristics
What did Darwin say about those that cannot adapt quick enough?
Would eventually become extinct
What did Darwin call this process?
Natural selection or survival of the fittest
What did Darwin define evolution as?
A population would gradually change over many generations
Why does evolution occur?
Due to a random genetic mutation
Why was Darwin’s idea not accepted?
Challenged idea of God as creator
Insufficient evidence to support his theory
Mechanisms of inheritance (genes) were only discovered 50 years later
What did Lamarck think?
Organisms changed over time and these changes were caused by the environment
What did Lamarck propose?
The ay an organism behaved affected the features of their body
What did Lamarck think if an animal used a feature a lot?
This feature would grow and develop and would be passed to its offspring
What is isolation?
Where a population of a species are separated
Why does isolation happen?
Due to a physical barrier, floods or earthquakes can geographically isolate some individuals from the main population
What will the conditions be like on either side of the barrier?
Different eg. climate
What happens if the environment is different?
Different characteristics will become more common in each population due to natural selection operating differently
What will eventually happen to each population?
Individuals from different populations will have changed so much they cannot breed with each other to pass on fertile offspring
Who was Wallace?
Early scientist to work on the idea of speciation
Contributed to how we understand speciation today
Came up with natural selection and published with Darwin
What is cystic fibrosis?
A genetic disorder of the cell membranes
What does cystic fibrosis cause?
Body produces thick sticky mucus in the air passages and in the pancreas
What is the allele that causes cystic fibrosis?
A recessive allele
What does it mean because the allele is recessive?
People with only one copy of the allele won’t have the disorder but they will be a carrier
What must have happen for a child to have cystic fibrosis?
Both parents must be carrier or have the disorder
What is polydactyly?
A genetic disorder where a baby is born with extra fingers or toes
What is polydactyly caused by?
A dominant allele so it can be inherited if only one parent carries it
What does it mean if the parents has polydactyly?
They will also have it as it is a dominant allele
Why do organisms become extinct?
Environment changes too quickly New predator New disease Can't compete with another species for food Catastrophic event (volcanic eruption)
What is selective breeding?
When humans artificially select plants or animals to breed so that the genes are particular for characteristics
Why are organisms selectively bred?
To develop features that are useful or attractive
What is the process for selective breeding?
Select the organisms with the characteristics your after
Breed them with each other
Select best offspring and breed them
Continue process over several generations till desirable trait gets stronger
What is the main problem with selective breeding?
Reduces the gene pool because the farmer keeps breeding from the best animals which are closely related
What can inbreeding cause and why?
Health problems because there’s more a chance of the organisms inheriting harmful genetic defects when the gene pool is limited
What can also happen with selective breeding if a new disease appears?
There’s not much variation so if one of them gets killed by the disease the rest of them likely will as well
What is the process of genetic engineering?
Useful gene is isolated from an organism’s genome using enzymes
Inserted into a vector
Vector is introduced to the target organism
Useful genes inserted into its cells
What is the vector usually?
Virus or a bacterial plasmid
What has bacteria been genetically modified to produce?
Human insulin to treat diabetes
What happens if the gene is transferred when the organism is at an early stage of development?
Organism develops with the characteristic coded by its gene
What do some people worry about genetic engineering?
Long term effects- will it create unplanned problems for future generations
What are the pros of GM crops?
Increase the yield
Engineered with more nutrients for developing countries
Grown without problems
Longer shelf life
What are the cons of GM crops?
Affect number of wild flowers so reduce biodiversity
People may develop allergies
Transplanted genes ay spread to other plants, eg. herbicide to weeds
What is the process of cuttings for cloning plants?
Find a suitable shoot on the parent cell and cut it off
Dip in rooting powder
Push into a pot of compost and keep moist
What are the advantages of cuttings for cloning plants?
Low cost
Greater crop yield at faster rate
Clone plants that have a resistant gene to a disease
Desirable characteristics
What is the process of tissue culture for cloning plants?
Small group of cells taken from a plant to grow identical plants
Preserve rare species
Nurseries are able to grow many identical plants
What is the process of embryo transplant?
Sperm is taken from bull that has a high dairy yield
Cow is artificially inseminated
Zygotes develop into embryo
Removed from cow’s uterus
Embryos split into smaller embryos before cells differentiate
Identical embryos are inserted into surrogates
What are the advantages of embryo transplant?
Produce bigger yield eg. milk Desirable features Multiple births (high yield)
What are the disadvantages of embryo transplant?
All will carry genetic defects
Small gene pool
What is the process of adult cell cloning?
Body cell taken from sheep Egg cell taken from another sheep DNA extracted from body cell Nucleus removed from egg cell Fused together Electric shock starts egg to divide Cells become an embryo Lamb is a clone of sheep 1
What are the advantages of cloning?
Large number of identical offspring Desirable features Quick Cheap Saves animals from extinction
What are the disadvantages of cloning?
All may die to new disease/changes in environment
Small gene pool
Any genetic defects will be passed on to all offspring
Ethical objections
How do fossils form via gradual replacement by minerals?
Bones are replaced by minerals as they decay
Form a rock like substance like the original shape
Surrounding sediment turns to rock
Fossil stays distinct
How do fossils form casts and impressions?
Buried in a soft material like clay
Clay hardens and the organism decays
Leaves a cast
Why do animals not decay in certain places?
In amber and tar no oxygen so no decay microbes
Glaciers too cold for decay microbes
Peat bogs too acidic for decay microbes
How is antibiotic bacteria caused?
Random mutations lead to changes in bacteria characteristics
Leads to antibiotic resistant strains forming as the gene is more common
What does bacteria have if it is antibiotic resistant?
Big advantage as it is able to survive so it reproduces longer, increasing population size of strain
Why is antibiotic resistant strains a problem?
Because they can’t be treated so it easily spreads between people
What is MRSA?
Relatively common superbug
Why is antibiotic resistant getting worse?
Due to overuse and inappropriate use of antibiotics for non-serious conditions
What causes the resistance?
Not the antibiotic but they create a situation where naturally resistant bacteria have an advantage so increase in numbers
What does taking the full curse of antibiotics makes sure?
All bacteria is destroyed so none is left to mutate
How can antibiotic resistance spread?
Used in farming to prevent animals from becoming ill and to make them grow faster which can lead to resistance and humans can ingest them
What are the five groups?
Mammals Bird Reptiles Fish Amphibians
What must an animal have to be a mammal?
Fur/hair
Produce milk
What must an animal have to be a bird?
Feathers
Beaks
What must an animal have to be a reptile?
Dry scales
What must an animal have to be a fish?
Wet scales
Gills
What must an animal have to be an amphibian?
Moist skin
Gils and lungs
