B6 - Inheritance, Variation and Evolution Flashcards
What does DNA stand for?
Deoxyribonucleic acid
What is the primary function of DNA?
Contains coded information for building and operating an organism
Where is DNA located in animal and plant cells?
In the nucleus, within chromosomes
What shape does DNA take?
Double helix
What is a gene?
A small section of DNA found on a chromosome
What do genes code for?
Specific sequences of amino acids to make proteins
How many amino acids are commonly used in proteins?
20 amino acids
What determines the type of cell produced?
The proteins produced by the DNA
What is a genome?
The entire set of genetic material in an organism
Why is understanding the human genome important?
Identifies genes linked to diseases and aids in developing treatments
What common ancestor do all modern humans descend from?
An ancestor who lived in Africa
Fill in the blank: DNA is a _______.
Polymer
True or False: Chromosomes normally come in singles.
False
What kind of differences can scientists investigate in genomes?
Tiny differences that developed as populations migrated
What can tracing genetic differences help scientists determine?
When populations split off and their migration routes
What is sexual reproduction?
A process where genetic information from two organisms (a father and a mother) is combined to produce offspring that are genetically different from either parent.
Sexual reproduction involves the fusion of male and female gametes.
How do gametes form in sexual reproduction?
Gametes are produced by meiosis, resulting in egg and sperm cells in animals.
Gametes have 22 chromosomes, which is half the number of chromosomes in a normal cell.
What happens during fertilization?
The egg cell from the mother and the sperm cell from the father fuse together to form a fertilized egg with the full number of chromosomes.
This results in a cell with half the chromosomes from the father and half from the mother.
What is the significance of chromosomes in offspring?
Chromosomes carry the genetic information that determines the features of the offspring, leading to inheritance of traits from both parents.
This genetic mixing produces variation in the offspring.
What is asexual reproduction?
A process where there is only one parent, resulting in offspring that are genetically identical to that parent.
Asexual reproduction does not involve the fusion of gametes, mixing of chromosomes, or genetic variation.
How do new cells form in asexual reproduction?
New cells are formed by mitosis, where an ordinary cell divides into two identical cells.
The new cell is called a clone.
What types of organisms reproduce asexually?
Bacteria, some plants, and some animals reproduce asexually.
This method results in offspring that are clones of the parent.
Fill in the blank: In sexual reproduction, the offspring inherit features from both parents due to the _______ of male and female gametes.
fusion
True or False: Asexual reproduction produces genetically different offspring.
False
What is the result of sexual reproduction in terms of genetic variation?
It produces variation in the offspring due to the mixing of chromosomes from both parents.
Fill in the blank: In asexual reproduction, the offspring are genetically _______ to the parent.
identical
What process produces gametes with half the number of chromosomes?
Meiosis
Meiosis involves two cell divisions and occurs in reproductive organs.
How many copies of each chromosome do gametes have?
One copy
Gametes contain one copy of each chromosome to ensure the correct number after fertilization.
In which organs does meiosis occur in humans?
Ovaries and testes
Meiosis occurs in the reproductive organs of males and females.
What happens to chromosomes before meiosis begins?
They duplicate
Each chromosome forms two identical arms before division.
What is the result of the first division in meiosis?
Pairs of chromosomes are pulled apart
Each new cell receives one copy of each chromosome.
How many gametes are produced at the end of meiosis?
Four gametes
Each gamete contains a single set of chromosomes.
Why are gametes genetically different from each other?
Chromosomes are shuffled during meiosis
Each gamete receives half of the chromosomes at random.
What process occurs after two gametes fuse during fertilization?
Mitosis
The resulting cell divides to produce multiple copies.
What happens to the cells as the embryo develops?
They differentiate
Cells become specialized types that make up the organism.
Fill in the blank: Meiosis involves _______ cell divisions.
two
Each division contributes to the reduction of chromosome number.
True or False: Each gamete contains both maternal and paternal chromosomes.
True
Gametes receive a mix of chromosomes from both parents.
What are the two types of sex chromosomes?
X and Y chromosomes
The 23rd pair of chromosomes that determine sex.
What chromosome combination do males have?
XY
The Y chromosome causes male characteristics.
What chromosome combination do females have?
XX
This combination allows female characteristics to develop.
What is the probability of a sperm cell getting an X or Y chromosome?
50% for each
Each sperm cell has an equal chance of receiving an X or Y chromosome.
What type of genetic diagram is used to show possible genetic outcomes?
Punnett square
It is a model to visualize genetic combinations.
How are the possible gametes arranged in a Punnett square?
One parent’s gametes on the side and the other parent’s gametes on the top
This layout helps to visualize potential offspring combinations.
What can the pairs of letters in the middle of a Punnett square represent?
Possible combinations of gametes
Each square shows the genetic outcome of that combination.
What is the ratio of getting a boy or a girl according to the Punnett square?
50:50
This ratio reflects the probability at each pregnancy.
What is the purpose of the criss-cross lines in the more complicated genetic diagrams?
To show all possible combinations of X and Y chromosomes
These lines connect the gametes from both parents.
Fill in the blank: The original cell that produces eggs has _______ X chromosomes.
two
All eggs have one X chromosome.
True or False: Genetic diagrams can predict the exact sex of an offspring.
False
They show probabilities, not certainties.
What do the middle circles in the more complex genetic diagram represent?
Possible gametes formed
Each circle corresponds to a gamete from one parent.
What are genetic diagrams used for?
To show the possible alleles of offspring
Genetic diagrams help visualize inheritance patterns and probabilities.
What controls the characteristics you develop?
What genes you inherit
For example, mouse fur color and red-green color blindness in humans are controlled by specific genes.
What are alleles?
Different versions of genes
Alleles are represented by letters in genetic diagrams.
What does it mean if an organism is homozygous for a trait?
It has two identical alleles for that trait
Example: AA or aa.
What does it mean if an organism is heterozygous for a trait?
It has two different alleles for that trait
Example: Aa.
What is a dominant allele?
The allele that determines the characteristic present when different alleles are present
Represented by a capital letter (e.g., ‘C’).
What is a recessive allele?
The allele that does not determine the characteristic when paired with a dominant allele
Represented by a lowercase letter (e.g., ‘c’).
What genotype must an organism have to display a recessive characteristic?
Both alleles must be recessive
Example: cc.
What is a genotype?
The combination of alleles an organism has
Determines the organism’s genetic makeup.
What is a phenotype?
The observable characteristics of an organism
Resulting from the interaction of genotype and environment.
In the example of hamsters, what is the dominant allele for normal behavior?
B
The recessive allele for superpowers is represented as ‘b’.
What is the genotype of a superpowered hamster?
bb
This means it has two recessive alleles.
What ratio of offspring will be normal to superpowered when breeding Bb hamsters?
3:1
This means 75% normal and 25% superpowered offspring.
True or False: Genetic diagrams can predict exact outcomes.
False
They only show probabilities, not certainties.
Fill in the blank: If two alleles are different, only one can determine what characteristic is present. The allele that shows is called the _______.
dominant allele
How are genetic crosses often represented?
In a Punnett square
This visual tool shows the possible genotypes of offspring.
What is the definition of homozygous?
An organism with two identical alleles for a trait.
Examples include BB (homozygous dominant) and bb (homozygous recessive).
What is the definition of heterozygous?
An organism with two different alleles for a trait.
An example is Bb.
In a genetic cross between a homozygous dominant hamster (BB) and a homozygous recessive hamster (bb), what is the genotype of all offspring?
All offspring are normal (boring).
This is because BB crossed with bb produces all Bb offspring.
What happens when a homozygous dominant hamster (BB) is crossed with a heterozygous hamster (Bb)?
All offspring are normal (boring).
The offspring will be 50% BB and 50% Bb.
What is the expected offspring ratio when a heterozygous cat (Hh) is crossed with a homozygous recessive cat (hh)?
1:1 ratio of long hair to short hair kittens.
This results in 4 long hair (Hh) and 4 short hair (hh) kittens.
In the context of a family tree, why can it be inferred that cystic fibrosis is not a dominant disorder?
Many family members carry the allele but do not have the disorder.
This indicates that the cystic fibrosis allele is recessive.
What is the probability that a new baby will have cystic fibrosis if both parents are carriers?
25% chance of having the disorder and 50% chance of being a carrier.
Parents who are carriers have genotypes Ff.
Fill in the blank: The allele for long hair in cats is represented by the dominant allele ______.
H
Fill in the blank: The allele for short hair in cats is represented by the recessive allele ______.
h
What is one method to determine the genotype of unknown offspring?
Breed the offspring together and observe the offspring ratios.
If the ratio is 3:1, it likely indicates a BB and bb cross.
True or False: All offspring from a homozygous recessive parent will show the recessive trait.
True
What is an inherited disorder?
A disorder that can be passed from parents to offspring.
What is cystic fibrosis caused by?
A recessive allele.
What is a characteristic of cystic fibrosis?
Thick sticky mucus in the air passages and pancreas.
What is the chance of a child having cystic fibrosis if both parents are carriers?
1 in 4.
What type of allele causes polydactyly?
A dominant allele.
What is polydactyly?
A genetic disorder where a baby is born with extra fingers or toes.
What is the chance of a child having polydactyly if one parent carries the defective allele?
50%.
What is the process of embryo screening during in vitro fertilization (IVF)?
Removing a cell from each embryo to analyze its genes.
What can embryo screening detect?
Many genetic disorders, such as cystic fibrosis.
What are some ethical concerns surrounding embryo screening?
Prejudice against people with genetic problems, potential for ‘designer babies,’ and cost.
True or False: Embryonic screening can lead to the destruction of embryos with ‘bad’ alleles.
True.
What is one argument for embryonic screening?
It helps to stop people suffering.
What is one argument against embryonic screening?
It implies that people with genetic problems are ‘undesirable.’
Fill in the blank: The allele causing cystic fibrosis is represented by the letter _______.
f.
Fill in the blank: The dominant allele for polydactyly is represented by the letter _______.
D.
What does it mean to be a carrier of a genetic disorder?
To have one copy of the recessive allele but not exhibit the disorder.
What happens to embryos that are found to have genetic disorders during screening?
They may be destroyed.
What is a potential financial implication of treating genetic disorders?
It costs the Government and taxpayers a lot of money.
True or False: Parents can currently select the sex of their baby through embryo screening.
False.
What is variation within a species?
Differences among organisms of the same species
Variation can be huge within a population and includes differences in traits like hair color, nose shape, and height.
What is genotype?
All of the genes and alleles that an organism has
Genotype affects an organism’s phenotype.
What is phenotype?
The characteristics that an organism displays
Phenotype is influenced by both genotype and environmental factors.
What is the role of the environment in determining phenotype?
Interactions with the environment can influence phenotype
Example: A plant’s growth differs in sunlight versus darkness.
What is a mutation?
A rare, random change in an organism’s DNA that can be inherited
Mutations occur continuously and can produce genetic variants.
What are alleles?
Genetic variants of a gene
Alleles result from mutations that alter the gene.
How do mutations affect proteins?
They can lead to changes in the protein that the gene codes for
Most mutations have little or no effect on protein function.
What is a genetic disorder caused by a mutation?
Cystic fibrosis
It results from a mutation that affects protein function leading to excess mucus production.
Fill in the blank: Most variation in phenotype is determined by a mixture of _______ and environmental factors.
genetic
True or False: Most mutations have a significant effect on an organism’s phenotype.
False
Most mutations have little or no effect on phenotype.
What determines the maximum height that an organism could grow to?
Its genes
Actual growth also depends on environmental factors like food availability.
What is the theory of evolution?
All of today’s species have evolved from simple life forms that first started to develop over three billion years ago.
This theory suggests a gradual process of change in species over time.
Who formulated the theory of evolution by natural selection?
Charles Darwin.
Darwin’s insights into natural selection were foundational to modern evolutionary biology.
What is phenotype variation?
Organisms in a species show wide variation in their characteristics.
This variation is crucial for natural selection.
What does ‘survival of the fittest’ refer to?
The idea that organisms with the most suitable characteristics for the environment are more likely to survive and reproduce.
This concept emphasizes the role of environmental pressures in shaping species.
How do successful organisms contribute to the next generation?
They are more likely to reproduce and pass on the genes for the characteristics that made them successful.
This process is essential for the evolution of species.
What happens to organisms that are less well adapted?
They are less likely to survive and reproduce, thus less likely to pass on their genes.
This leads to a gradual shift in the traits of a population.
What is speciation?
The development of a new species over a long period due to significant changes in phenotype.
Speciation occurs when populations become reproductively isolated.
What does it mean for populations to be reproductively isolated?
They can’t interbreed to produce fertile offspring.
This reproductive barrier is a key factor in the formation of new species.
What is extinction?
When no individuals of a species remain.
Extinction can result from various environmental and biological pressures.
List some reasons why species become extinct.
- Environment changes too quickly
- New predator kills them
- New disease kills them
- Inability to compete with new species
- Catastrophic events
These factors can drastically affect population viability.
What is the significance of the fossil record in evolution?
It allows observation of how changes in organisms developed slowly over time.
Fossils provide crucial evidence for evolutionary processes.
How has the discovery of genetics supported Darwin’s theory?
It explains how organisms with beneficial characteristics pass them on via their genes.
Genetics provides a mechanism for inheritance that Darwin could not explain.
True or False: The theory of evolution by natural selection is widely accepted today.
True.
It is a foundational concept in biology.
Fill in the blank: The organisms that survive and reproduce are those with the most suitable _______ for the environment.
[characteristics].
This highlights the role of adaptation in survival.
What evidence supports the evolution of bacteria to become resistant to antibiotics?
The relatively recent discovery of bacterial evolution to antibiotic resistance.
This is a modern example of natural selection in action.
What is selective breeding?
Selective breeding is when humans artificially select the plants or animals that are going to breed so that the offspring retain particular characteristics.
What is another term for selective breeding?
Selective breeding is also known as artificial selection.
List some examples of traits that can be developed through selective breeding.
- Animals that produce more meat or milk
- Crops with disease resistance
- Dogs with a good, gentle temperament
- Decorative plants with big or unusual flowers
Outline the basic process involved in selective breeding.
- Select the existing stock with desired characteristics
- Breed them with each other
- Select the best offspring and breed them together
- Continue the process over several generations
What is the main benefit of selective breeding in agriculture?
Selective breeding can be used to improve yields, such as increasing meat yields by breeding cows and bulls with the best characteristics.
How long has selective breeding been practiced?
Selective breeding has been practiced for thousands of years.
What is the main drawback of selective breeding?
The main drawback is a reduction in the gene pool.
What is inbreeding?
Inbreeding occurs when closely related animals or plants are repeatedly bred, leading to a limited gene pool.
What health problems can arise from inbreeding?
Inbreeding can cause health problems due to an increased chance of harmful genetic defects.
Which dog breeds are particularly susceptible to health issues due to inbreeding?
Some dog breeds, such as pugs, are particularly susceptible to health issues like breathing problems.
What is the risk if a disease appears in a population that has been selectively bred?
If a disease appears, it can affect the entire population because they are closely related and may all be susceptible.
What is genetic engineering?
An area of science that involves transferring genes between organisms
What is the first step in genetic engineering?
A useful gene is isolated from one organism
What is typically used as a vector in genetic engineering?
A virus or a bacterial plasmid
What happens when the vector is introduced to the target organism?
The useful gene is inserted into its cells
What is one application of genetic engineering in bacteria?
Producing human insulin for treating diabetes
What modifications are made to genetically modified (GM) crops?
Improving size and quality of fruit or making them resistant to disease, insects, and herbicides
What can sheep be genetically engineered to produce?
Substances, like drugs, in their milk for treating human diseases
What is gene therapy?
Inserting working genes into people with inherited diseases caused by faulty genes
At what stage can gene transfer be carried out in an organism?
At an early stage of development, such as an egg or embryo
What are some potential benefits of genetic engineering?
Treating diseases and more efficient food production
What is a concern regarding the long-term effects of genetic engineering?
Unplanned problems may be created that could be passed on to future generations
How might GM crops affect biodiversity?
They could affect the number of wildflowers and insects, reducing farmland biodiversity
What health concern is associated with GM crops?
Potential development of allergies to GM foods
What risk is posed by transplanted genes in GM crops?
They may get into the natural environment, creating ‘superweeds’
What is ‘golden rice’?
A GM rice crop engineered to contain beta-carotene, which prevents blindness
What is a positive aspect of GM crops for developing nations?
They can be engineered to contain missing nutrients in diets
True or False: GM crops are currently grown in some places without any problems.
True
What are fossils?
Fossils are the remains of organisms from many thousands of years ago, found in rocks.
What do fossils provide evidence of?
Fossils provide evidence that organisms lived ages ago.
How many ways can fossils form?
Fossils can form in three ways:
* From gradual replacement by minerals
* From casts and impressions
* From preservation in places where no decay happens
What is the most common way fossils form?
Most fossils form from gradual replacement by minerals.
What materials can last a long time when buried and eventually become fossils?
Teeth, shells, bones, etc.
How does gradual replacement by minerals occur?
Things that don’t decay easily are replaced by minerals as they decay, forming a rock-like substance.
What happens to the surrounding sediments when fossils form?
The surrounding sediments turn to rock, but the fossil stays distinct inside the rock.
How are casts formed?
Casts are formed when an organism is buried in soft material like clay, which hardens around it.
What types of things can be preserved as casts?
Animal burrows and plant rootlet traces can be preserved as casts.
What are footprints an example of?
Footprints can be pressed into soft materials, leaving an impression when it hardens.
In what environments can organisms be preserved without decay?
In amber, tar pits, glaciers, and peat bogs.
What is amber?
Amber is a clear yellow ‘stone’ made from fossilized resin.
Why can’t decay microbes survive in tar pits and amber?
There is no oxygen or moisture.
What is an example of a fully preserved man found in a bog?
Pete Marsh.
What is known about the origin of life?
No one knows how life began.
What are some hypotheses about how the first life forms came into being?
Hypotheses include:
* Life began in a primordial swamp or under the sea
* Simple organic molecules were brought to Earth on comets
What challenges exist in supporting hypotheses about the origin of life?
There is a lack of good, valid evidence.
Why is the fossil record considered incomplete?
Many early forms of life were soft-bodied, and soft tissue tends to decay completely.
What geological activity might destroy fossils?
The movement of tectonic plates may crush fossils already formed in the rock.
What are antibiotics?
Substances that can treat bacterial infections, such as penicillin
Antibiotics can be effective against bacterial infections but are not a permanent solution.
How do bacteria develop antibiotic resistance?
Through random mutations in their DNA that lead to changes in characteristics
These mutations can make bacteria less affected by specific antibiotics.
What is the impact of rapid reproduction on bacteria and antibiotic resistance?
Bacteria can evolve quickly, increasing the prevalence of antibiotic-resistant strains
Rapid reproduction allows resistant bacteria to survive and reproduce more effectively.
What role does natural selection play in the spread of antibiotic resistance?
It favors bacteria with mutations that confer resistance, increasing their population size
Antibiotic-resistant bacteria survive better in treated hosts.
What is a ‘superbug’?
A strain of bacteria that is resistant to most known antibiotics
MRSA is a common example of a superbug.
Why is antibiotic resistance a growing problem?
Due to the overuse and inappropriate use of antibiotics
Examples include prescribing antibiotics for non-serious conditions or viral infections.
What happens if antibiotics are overused?
The problem of antibiotic resistance becomes larger
Overuse creates an environment where naturally resistant bacteria thrive.
What is the importance of completing an antibiotic course?
It ensures all bacteria are destroyed, preventing the development of resistant strains
Incomplete courses can leave behind bacteria that may mutate.
How does antibiotic use in agriculture contribute to antibiotic resistance?
Antibiotics given to animals can lead to resistant bacteria, which can spread to humans
This can occur during meat preparation and consumption.
What has been done in response to concerns about antibiotic use in agriculture?
Some countries have restricted the use of antibiotics in farming
This aims to reduce the development of antibiotic-resistant bacteria.
What challenges do drug companies face in developing new antibiotics?
The development process is slow and costly, making it hard to keep up with resistance
New resistant strains continue to emerge, increasing the need for effective treatments.
What is the traditional classification system first proposed in the 1700s?
A system that classifies living things based on their characteristics and structures.
What are the primary categories in the Linnaean classification system?
Kingdom, Phylum, Class, Order, Family, Genus, Species.
What significant change in classification was proposed by Carl Woese in 1990?
The three-domain system.
What are the three domains in the three-domain system?
- Archaea
- Bacteria
- Eukaryota
What characterizes organisms in the domain Archaea?
Primitive bacteria often found in extreme environments.
What does the domain Bacteria contain?
True bacteria such as E. coli and Staphylococcus.
What types of organisms are included in the domain Eukaryota?
- Fungi
- Plants
- Animals
- Protists
What system is used to name organisms?
The binomial system.
In the binomial naming system, what does the first part of the name refer to?
The genus.
What does the second part of the binomial name indicate?
The species.
Provide an example of an organism’s binomial name.
Homo sapiens (Homo is the genus, sapiens is the species).
What is the purpose of using the binomial system globally?
To avoid confusion by providing a standardized name for species.
What do evolutionary trees illustrate?
The evolutionary relationships and common ancestors between different species.
How do scientists determine the relationships shown in evolutionary trees?
By analyzing various data types, including DNA analysis and fossil records.
True or False: The more recent the common ancestor, the less likely species are to share characteristics.
False.
Fill in the blank: Organisms that share a recent common ancestor are likely to share _______.
more characteristics.
What type of data is used for extinct species in evolutionary analysis?
Information from the fossil record.
Which two species are closely related due to a recent common ancestor?
Whales and dolphins.
What distinguishes whales and dolphins from sharks in terms of evolutionary relationships?
Whales and dolphins have a more recent common ancestor than sharks.
What is selective breeding?
Selective breeding is when humans artificially select the plants or animals that are going to breed to ensure the genes for particular characteristics remain in the population.
What is another term for selective breeding?
Artificial selection.
What are some examples of organisms selectively bred?
- Animals that produce more meat or milk
- Crops with disease resistance
- Dogs with a good, gentle temperament
- Decorative plants with big or unusual flowers
What is the first step in the process of selective breeding?
Select the existing stock with the desired characteristics.
What is the second step in the process of selective breeding?
Breed the selected organisms with each other.
What happens in the third step of selective breeding?
Select the best of the offspring and breed them together.
What is the purpose of continuing the selective breeding process over several generations?
To strengthen the desirable trait in the population.
What is a major drawback of selective breeding?
It reduces the gene pool, which is the number of different alleles in a population.
What is inbreeding?
Inbreeding is the breeding of closely related organisms, which can occur in selective breeding.
What health problems can arise from inbreeding?
Inbreeding can cause health problems due to the increased chance of inheriting harmful genetic defects.
Which dog breed is mentioned as being particularly susceptible to health issues due to inbreeding?
Pugs.
What risk does a limited gene pool pose when a new disease appears?
There’s a higher chance that all closely related organisms will succumb to the disease.
Fill in the blank: Selective breeding can be used to improve _______ in agriculture.
yields.
True or False: Selective breeding is a new practice.
False.
How long have people been practicing selective breeding?
For thousands of years.
What is the effect of selective breeding on the presence of resistant alleles in a population?
It results in less chance of any resistant alleles being present.
