B5 Flashcards
What is a genome?
The entire genetic material of an organism
Where is the genetic material stored in an organism?
The nucleus
How is the genetic material arranged in an organism?
Into chromosomes
What is a chromosome?
A long molecule of DNA which is coiled up
What is a gene?
A short length of a chromosome
What do genes determine?
The production of proteins - this controls the development of different characteristics, and how an organism functions
What is a difference between a species called?
Variation
What is the genotype?
All of the genes and alleles that an organism has.
What does an organism’s genotype affect?
It’s phenotype - the characteristics that it displays
Other than the genotype, what affects an organisms phenotype?
Environmental variations
What is continuous variation?
When individuals in a population vary within a range - there are no distinct categories eg. humans can be any height within a range
What characteristics often show continuous variation?
Characteristics that are affected by more than one gene or that are influenced by genetic and environmental factors
What is discontinuous variation?
When there are two or more distinct categories and each individual falls into only one of these categories. eg. humans can only be one blood group
What characteristics often show discontinuous variation?
Characteristics that are only affected by one gene and that aren’t influenced by the environment
What is a mutation in a gene?
A mutation is a rare, random change in an organism’s DNA that can be inherited
What does a mutation mean (in relation to the sequence of DNA bases)?
The sequence of DNA bases in the gene is changed, which produces a genetic variant (a different form of the gene).
How do genetic mutations affect proteins?
As the sequence of DNA bases codes for the sequence of amino acids that make up a protein, gene mutations can lead to changes in the protein that it codes for.
What is an example of a small influence caused by a genetic mutation?
A slight change in eye colour
What is an example of a dramatic effect caused by a genetic mutation?
Cystic fibrosis can be caused by the removal of just three bases but has a huge effect on an organism’s phenotype.
What are sequences of bases called that don’t code for proteins?
Non-coding DNA
What happens if non-coding DNA is mutated?
It can affect how it is expressed - whether or not the gene is “switched on” - this can stop the transcription of mRNA so that protein coded by that gene is not coded at all.
What is sexual reproduction?
Where genetic information from two organisms (a father and a mother) is combined to produce offspring which is genetically different from the parent
What do the mother and father produce in sexual production?
Gametes - they only contain half the number of chromosomes of normal cells, also known as haploid. Normal cells (with the full number of chromosomes) are known as diploid.
What happens to the fertilised egg after sexual reproduction?
It becomes an embryo and inherits characteristics from both parents as it’s a mixture of chromosomes (and therefore genes).
What is meiosis?
It is a type of cell division which is different to meiosis because it doesn’t produce identical cells.
What happens in the first stage in meiosis?
The cells duplicate their DNA so there’s enough for each new cell - one arm of each X shaped chromosome in an exact copy of the other.
What happens in the second stage in meiosis?
The chromosomes line up in pairs in the centre of the cell. One chromosome in each pair came from the organism’s father and one from the mother.
What happens in the third stage in meiosis?
The pairs are pulled apart, so each new cell only has one copy of each chromosome. Some of the father’s and mother’s chromosomes go into the new cell.
What happens in the fourth stage in meiosis?
Each new cell has a mixture of the mother’s and father’s chromosomes, creating genetic variation in the offspring.
What happens in the fifth stage in meiosis?
A second division happens, and the chromosomes line up again in the centre of the cell. The arms are of the chromosomes are pulled apart.
What happens in the sixth stage in meiosis?
Four haploid gametes are produced - each only has a single set of chromosomes. They are all genetically different.
What is asexual production?
Reproduction with only one parent, so the offspring are genetically identical to the parent - new cells have the exact same genetic information as the parent cell, known as a clone.
Asexual Reproduction Advantages
Can produce lots of offspring very quickly. Only one parent is needed - this means that organisms can reproduce whenever conditions are favourable without having to wait for a mate.
Asexual Reproduction Disadvantages
No genetic variation - so if environmental changes/conditions are unfavourable, the whole population can be affected.
Sexual Reproduction Advantages
Creates genetic variation within a population - if there is unfavourable environmental conditions, some individuals will have characteristics to help them survive. Over time, this leads to evolution.
Sexual Reproduction Disadvantages
Sexual reproduction takes more time and energy, so organisms produce fewer offspring in their lifetime. Two parents are needed for sexual reproduction which can be a problem if individuals are isolated.
What is the characteristic that is presented by something called?
The dominant allele - the other is known as recessive and only appears if both alleles are recessive
What does homozygous mean?
You have two alleles that are the same
What does heterozygous mean?
You have two different alleles
What is the 23rd pair of chromosomes labelled as?
Female - XX
How does the Y chromosome affect gender?
It carries a gene which makes an embryo develop into a male, and as females don’t have it they develop differently.
What did Gregor Mendel do?
He was a monk who lived in the 19th century - he noted how characteristics in plants were passed on from one generation to the next. His work became the foundation of modern genetics.
What is classification?
Organising living organisms into groups
What are the two types of classification?
Artificial and natural
What is artificial classification?
Classifying living organisms using observable features
What is natural classification?
Classifying living organisms using evolutionary relationships
What are living organisms divided into in natural classification?
5 kingdoms (eg. the plant kingdom), which are subdivided into smaller groups (phylum, class, order, family, genus and species)
What new technology exists which leads to improvements in classification?
DNA sequencing - to see how closely related organisms are. It’s a technique that compares the sequence of DNA bases for different species. The more similar they are between species, the more closely related they are.
What do populations of species usually show?
Genetic variation
What do living things have to compete for?
The resources to survive - only some will survive
What do some genetic variants give rise to?
Characteristics which are better suited to a particular environment - organisms with these characteristics have an advantageous phenotype
What happens as a result of organisms with advantageous phenotypes?
They have an increased chance of breeding and passing on their advantageous genes, and therefore a greater proportion of individuals in the next generation will inherit them.
What happens to the best characteristics in a population?
They are naturally selected and the species become more and more adapted to their environment.
What is the definition of evolution?
The change in inherited characteristics of a population over time, through the process of natural selection
What does evolution sometimes mean for a species?
It can sometimes change a species so drastically that it leads to an entire new species being formed.
How is a new species formed through natural selection?
One way that this can happen is because of a physical barrier separating two populations of a species - conditions on each side of the barrier will be slightly different so the phenotypes that are beneficial are different for each population.
What is a fossil and what do they tell us?
A fossil is any trace of an animal or plant that lived long ago. They can tell us a lot about what the organisms look liked like and how long ago they existed.
How are fossils arranged to show evolution?
In chronological order, fossils show the gradual change which occurs due to evolution (how species have developed over many thousands of years)
How do bacteria become antibiotic resistant?
Bacteria can develop random mutations, creating new variants in their population. These can lead to changes in the bacteria’s phenotype - eg. a bacterium can become less affected by a particular antibiotic.
What does it mean if bacteria becomes antibiotic resistant?
It becomes more able to survive and so lives for longer and reproduces more. This means that the resistant genes get passed on as the bacteria which live for longer rapidly reproduce.
What did Darwin do?
He spent 5 years on a voyage around the world studying plants and animals - he noticed that there was variation in members of the same species and that those with characteristics most suited to the environment were more likely to survive.
What was Darwin’s theory?
The theory of evolution and natural selection
What did Alfred Russel Wallace do?
He also came up with the idea of natural selection and worked with Darwin - his observations provided evidence to support the theory of evolution by natural selection (warning colours used by some species, like butterflies, to deter predators).
Why is Darwin generally more known?
Because he published the book “On the Origin of Species”
What did the theory of natural selection affect?
Classification, antibiotic resistance and conservation
What is biodiversity?
The variety of living organisms in an area.
