B11 Flashcards
Define inheritance
The transmission of genetic information from generation to generation
Define chromosome
A thread-like structure of DNA carrying genetic information in the form of genes
Long strand of DNA wrapped around proteins
Define gene
A short length of DNA found on a chromosome that codes for a specific protein
Coding the protein plays an important role in determining characteristics
Put the following in order:
Chromosomes
Nucleus
Gene
DNA double helix
Nucleus -> chromosomes -> DNA double helix -> gene
Define allele
A different version of a gene which gives all organisms their characteristics
How does sex differ from other characteristics?
It is determined by a whole chromosome, not one gene
Which parent will be responsible for the sex of the child?
The Father (male) will because they have an XY chromosome
Half the sperm will carry X chromosome
Other half will carry Y chromosome
Show the inheritance of sex in a punnet square
Do it :)
Define diploid nucleus
A nucleus containing two sets of chromosomes Which are arranged in pairs, resulting in 23 pairs in total
Define haploid nucleus
A nucleus contains a single set of unpaired chromosomes (ex: gametes)
Define mitosis
Nuclear division giving rise to genetically identical cells
Explain the process of mitosis
Before mitosis each chromosome copies itself exactly
The nuclear membrane breaks down
The chromosomes line up along the center of the cell
Cell fiber pulls the two identical chromosomes apart
After separation of the chromosomes, the cell divides into two
Results in two identical diploid cells
What is the role of mitosis in humans? (And one non-human?)
Humans:
Growth
Replacement of cells
Repair of damaged tissue
Non-human:
Asexual reproduction
How are all cells in the body produced?
By mitosis of the zygote
Doesn’t apply to gametes
Define meiosis
Reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells
Explain the process of meiosis
Each chromosome creates an identical copy of itself and the nuclear membrane begins to breakdown
Maternal and paternal chromosomes pair up along the center of the cell (NOT LIKE MITOSIS!!!)
Recombination:
Sections of DNA are swapped between maternal and paternal chromosome pairs, creating recombinant chromosomes
Chromosome pair separate, moving to opposite sides of the cell
They are separated by cell fibers
Result in 4 different haploid daughter cells
Why must gametes be produced by meiosis?
Otherwise there would be two times the normal amount of chromosomes after fertilisation
It also increases variation
Define genotype
The genetic make-up of an organism in terms of the alleles present
The combination of alleles that control each characteristic
Define phenotype
The observable features of an organism
Define homozygous
Having two identical alleles of a particular gene
What is pure breeding?
When two identical homozygous individuals breed together
Results in all offspring having the same phenotype and genotype
Define heterozygous
Having two different alleles of a particular gene
Why would it be impossible for a heterozygous individual to pure breed?
Because the offspring would not always have the same phenotype and genotype
Define dominant (in relation to alleles)
An allele that is always expressed if it is present
Usually capital letters
Define recessive (in relation to alleles)
An allele that is only expressed when there is no dominant allele of the gene present
Usually lowercase letters
Define monohybrid inheritance
The inheritance of characteristics controlled by a single gene
Create genetic diagrams for the following in the format of that one question:
TT x tt
Tt x Tt
Tt x tt
Parent phenotype:
Genotype:
Gametes:
Punnet square:
Offspring genotype:
Phenotype:
Ratio/percentage:
Define variation
Difference between individuals of the same species
What is phenotypic variation?
Difference in features between individuals of the same species
What is genetic variation?
Some of the differences in phenotypic variation are caused by differences in genes -> genetic variation
What causes phenotypic variation?
Genetic and environmental factors
What are the two ways phenotypic variation can be classified based on how you are able to group the measurements?
Continuous and discontinuous variation
What is continuous variation?
There is a range (many small degrees of difference) from a particular characteristics between two extremes
When put in order on a scale it usually forms a bell curve
Ex: height, mass, length of a body part
What is discontinuous variation?
Results in a limited number of phenotypes with no intermediates and distinct characteristics
It is usually a result of purely genes
Ex: blood type, eye color, natural hair color
Define mutation
A change in a gene or chromosome which is usually harmless but can result in a new phenotype, survival advantages or harmful changes
What increases the rate of mutation?
Ionizing radiation:
Damages bonds and causes changes in base sequence
Ex: gamma rays and X-rays
(Also certain non-ionising radiation like UV rays)
Chemicals:
Ex: tar and tobacco
What can increased rates of mutation lead to?
It can lead to cancerous cells, hence why many things that can cause mutated cells are also known to increase the risk of certain cancers
Define natural selection
In any environment those with the best adapted feature are more likely to survive/ reproduce, resulting in natural selection
‘Survival of the fittest’
Explain the process of natural selection
Range of variation within a species
When individuals reproduce more offspring are reproduced than the environment can support
Leads to competition for resources
Individuals with characteristics most suited have a higher chance of survival and reproduction
Alleles that result in this advantage are passed to offspring at a higher and higher rate to the next generation as time passes
Explain an example of natural selection (peppered moths)
THERE IS VARIATION WITHIN THE PEPPERED MOTH POPULATION.
LIGHT MOTHS > DARK MOTHS
POLLUTION LEADS TO DARKER BARK ON TREES. THE ENVIRONMENTAL CHANGE IS BENEFICIAL TO THE DARK MOTHS. THEY NOW HAVE THE ABILITY TO CAMOUFLAGE AGAINST THE BARK OF THE TREES.
LIGHT MOTHS ARE NOW MORE LIKELY TO BE EATEN BY BIRDS, AND LESS LIKELY TO REPRODUCE
DARK MOTHS ARE NOW MORE LIKELY TO SURVIVE AND REPRODUCE, PASSING ON THEIR ALLELES FOR A DARK PHENOTYPE TO THEIR OFFSPRING
OVER TIME, THERE IS A GRADUAL INCREASE IN THE PROPORTION OF DARK MOTHS.
DARK MOTHS > LIGHT MOTHS
Define evolution
The change in adaptive feature of a population over time as the result of natural selection
Define the process of adaptation
The process, resulting from natural selection, by which populations become more suited to their environment over many generation
Natural selection -> process of adaptation -> evolution
Explain the development of strains of antibiotic resistant bacteria
random mutations occur in the genes of individual bacterial cells in the gut
some mutations protect the bacterial cell from the effects of the antibiotic making some have antibiotic resistance.
bacteria without the mutation die or cannot reproduce when the antibiotic is introduced. Bacteria causing the illness and healthy gut bacteria is killed, while the resistant bacteria stays.
resistant bacteria can reproduce much more with less competition for resources from normal bacterial strains resulting in a larger population of resistant bacteria that is difficult to control
Describe selective breeding
Selective breeding is when individuals are artificially selected by humans for their desirable feature and then cross-bred with each other to produce the next generation.
This process is repeated over many generation until the characteristic can be reliably shown, creating a new species
What are the differences between natural and artificial selection?
Natural: occurs naturally
Artificial: only occurs with human intervention
Natural: results in the development of features that are adapted to their environment and survival
Artificial: results in the development of a population with feature that are useful to humans (not necessarily for survival)
Natural: usually takes a long time
Artificial: takes less time because only individuals displaying the trait are allowed to breed
How can artificial breeding improve crops?
Crops are selectively bred for beneficial characteristics like: larger fruits, resistance to disease, increased yield, beauty
What is an example of artificial selection with crops?
Wheat -> was bred to be shorter (more resistant to extreme weather) and for higher yield
How can artificial breeding improve animals?
It can increase yield (for meat, milk, etc), larger eggs from chickens, and for desirable traits for example in dogs
Explain the process for selective breeding
Parents chosen with desired traits
Breed them together
Both parents have the gene so the offspring should also have the desired gene
Breed only the offspring that have the desired trait
Continue over generations
What are some positives and negatives of selective breeding?
Positives:
Economic benefits (more yield from less area, more money)
Prevent disease
Negatives:
Selecting for rare diseases (unintentionally selecting dangerous traits)
Reduced genetic variation (less defense against disease, insects, etc)
Ethical issues (bred for negative traits for research, inbreeding, etc)
