11 - Inheritance Flashcards
What is inheritance?
The transmission of genetic information from generation to generation.
What is a chromosome?
A thread-like structure of DNA, carrying genetic information in the form of genes.
What is a gene?
A length of DNA that codes for a protein.
What is an allele?
A version of a gene
What is a haploid nucleus?
A nucleus containing a single set of unpaired chromosomes (e.g. in gametes)
What is a diploid nucleus?
A nucleus containing two sets of chromosomes (e.g. in body cells)
How are chromosomes arranged in a diploid and a haploid cell respectively?
In a diploid cell, chromosomes are arranged in pairs. In a haploid cell there are 23 pairs.
What sex chromosomes do people have?
Males have XY and females have XX.
Who is responsible for determining the sex of the child?
A father, as he can pass on a Y chromosome.
What is mitosis?
Nuclear division giving rise to genetically identical cells
When does mitosis occur?
After the exact duplication of chromosomes.
What is meiosis?
Reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells.
What is meiosis involved in?
The production of gametes.
How does mitosis occur in growth?
It produces new cells.
How does mitosis occur in repairing?
It replaces damaged or dead cells
How does mitosis occur in asexual reproduction?
Mitosis produces offspring that are genetically identical to the parent.
What is a genotype?
The genetic make-up of an organism in terms of the alleles present.
What is a phenotype?
The observable features of an organism
What is homozygous?
Having two identical alleles of a particular gene
What classifies as pure-breeding?
Two identical homozygous individuals that breed together are pure breeding, and a heterozygous individual will not be.
What is heterozygous?
Having two different alleles of a particular gene
What is a dominant allele?
An allele that is expressed if it is present
What is a recessive allele?
An allele that is only expressed when there is no dominant allele of the gene present
What is variation?
Differences between individuals of the same species.
What is the difference between phenotypic variation and genetic variation?
Phenotypic variation is the difference in features between individuals of the same species, and genetic variation is when some of these differences are caused by differences in genes.
What does continuous variation result in?
Continuous variation results in a range of phenotypes between two extremes (e.g. height in humans)
What does discontinuous variation result in?
Discontinuous variation results in a limited number of phenotypes with no intermediates (e.g. tongue rolling)
What is phenotypic variation caused by?
Genetic and environmental factors
What is discontinuous variation caused by?
Genes alone (e.g. A, B, AB, and O blood groups in humans)
What is a mutation?
A change in a gene or chromosome.
What increases the rate of mutation?
Ionising radiation and some chemicals.
What results in natural selection?
Individuals in a species show a range of variation, they produce more offspring than the environment can support. This leads to a competition for resources, which results in a ‘struggle for survival’. Higher chance of survival and more chances to reproduce for individuals more suited to the environment. Alleles resulting in these characteristics are passed to their offspring at a higher rate, which will lead to the next generation with a higher number of individuals with better adapted variations.
What is evolution?
The change in adaptive features of a population over time as the result of natural selection.
What is the process of adaptation?
The process resulting from natural selection by which populations become more suited to their environment over many generations.
What is an example of evolution by natural selection?
The development of strains of antibiotic resistant bacteria.
How does selective breeding occur?
Individuals with the desired characteristics are bred together, then their offspring with desired characteristics are bred together, and this is repeated for generations.
What are the differences between natural and artificial selection?
Artificial selection only occurs when humans intervene, results in development of populations with features that are desired by humans and not features that will help them survive, and it takes less time as only individuals with desirable features are allowed to produce. Natural selection occurs naturally, results in development of populations with features that help them survive and adapt, and takes a longer time to occur.
Why is selective breeding carried out?
It is carried out by artificial selection over many generations to improve crop plants and domesticated animals.
