B6 Flashcards
sexual reproduction
the fusion of male and female gametes
asexual reproduction
involves only one parent with no fusion of gametes
meiosis
cell division which produces 4 daughter cells each with half the normal number of chromosomes, forming gametes
mitosis
cell division which produces 2 daughter cells each with the same number of chromosomes, for growth and repair of tissues and for asexual reproduction
DNA
A polymer made up of 2 strands, forming a double-helix, contained in chromosomes carrying the genetic information for an organism
Non coding DNA
Parts of DNA which are not genes but may switch genes on and off and so can still be affected by mutations
Nucleotide
Sugar + phosphate + base- monomer that makes up DNA
Base
4 molecules A/ T/ C/ G which are use to write the DNA code
Protein Synthesis
Process of using the DNA code to order amino acids and build proteins
Triplet Code
Each amino acids is coded for by 3 bases eg CCG or AAT etc
Mutation
A random change in the DNA (could be harmful, harmless or beneficial)
Gene
A small section of DNA on a chromosome which codes for a protein
Chromosome
Long piece of DNA , containing many genes
46
Number of chromosomes (in 23 pairs) in a human body cell
23
Number of chromosomes in a human sex cell
Genome
The entire set of genetic material of an organism
Gametes
Sex cells, such as egg and sperm cells
Allele
Different versions of a gene eg blue eyes/ brown eyes
dominant
A gene that is expressed in the phenotype when at least one allele is present
heterozygous
Alleles present are different
homozygous
Alleles present are the same
genotype
alleles that are present
phenotype
physical characteristics/features produced by the alleles
cystic fibrosis
A disorder of cell membranes where mucus is thick and sticky
polydactyly
Inherited disorder where the individual has extra digits (fingers or toes)
sex chromosome
Female XX Male XY ( in humans)
tissue culture
Method of cloning using small groups of cells from part of a plant to grow identical new plants
cuttings
A simple method used by gardeners to produce many identical new plants from a parent plant
embryo transplant
Method of cloning. Splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers
adult cell cloning
Nucleus is placed into empty egg cell, electric stimulus to start
embryo development then put into the womb of an adult female
variation
Differences in the characteristics of individuals in a population
evolution
A change in the inherited characteristics of a population over time through the process of natural selection
Variation / Advantage/ Natural selection/ Evolution VANE
natural selection
A process which gives rise to phenotypes best suited to their environment because non suited organisms die out
species
A group of animals that can interbreed and produce fertile offspring
speciation
Formation of a new species through natural selection from an isolated population eg by geography on an island
Selective breeding
The process by which humans choose the parents and breed plants and animals for particular genetic characteristics
Darwin
Scientist famous for being the first to publish the theory of evolution
Wallace
Scientist who independently also came up with the idea of evolution
lamarck
Scientist with the idea that life experiences are passed to offspring- this is almost invariably not the case
mendel
German monk known now as the father of genetics whose experiments with pea plants lead others to the idea of the gene
Genetic engineering
A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic eg insulin gene in bacteria
Antibiotic resistance
When a bacteria evolves the ability to survive an antibiotic and then copies itself- this is a growing problem
Bacterial plasmid
A loop of DNA found in bacteria which can be used a vector to carry genes to new organisms
virus
A microbe consisting of a piece of DNA in a protein coat that will inject its DNA into a host cell and therefore can be used a vector
vector
A method of carrying genes into new organisms
extinction
There are no remaining individuals of a species still alive
classification
Arranging all living organisms into similar groups
Keeping Precious Creatures Organised For Grumpy Scientists Kingdom Phylum Class Order Family Genus Species
binomial system
Naming organisms by their genus and species eg Homo sapien
Carl Linnaeus
Scientist from 400 years ago who came up with the firstly widely used classification system.
Carl Woese
Modern scientist who discovered a new group of microbes and reorganised the Linnaeus system into the ‘3 domain system’ of Bacteria/ Archaea/ Eukaryotes
Describe how a protein is made from DNA code
- DNA molecule opens at a gene
- A messenger molecule (mRNA) enters the nucleus and makes a copy of the DNA code at
the open section - The messenger molecule leaves the nucleus and travels to a ribosome
- In the cytoplasm there are carrier molecules bring amino acids in the correct order at
the ribosomes due to the code on the messenger molecule - The protein made from this chain of amino acids will then fold into the correct shape
Describe how a mutation can change the protein made from DNA code
- DNA is copied incorrectly in cell division and there is a change - a mutation- in the code
- A messenger molecule (mRNA) enters the nucleus and makes a copy of the DNA code at
the open section including the mutation - The messenger molecule takes the wrong code to a ribosome
- Amino acids are joined at the ribosome in the wrong order
- The protein made from this chain of amino acids may then fold into the incorrect shape
(this might be bad eg cystic fibrosis or good eg evolving better enzymes)
Describe selective breeding
- Choose parents with the characteristics that you want eg non aggressive nature in dogs/ big flowers in a plant
- Only breed from the parents with the characteristics you want
- Check the offspring for the trait you want and breed using only those offspring
Describe genetic engineering
- Choose an organism with the trait you want
- Remove the gene for that trait using special enzymes
- Insert the gene into a vector eg a bacterial plasmid or a virus
- Vector will carry the gene into the required cell of a different organism (can be the
same species or different species eg insulin gene into yeast or vitamin A gene from
carrots into rice) - Genes are transferred at an early stage in the development eg embryo , so the gene will
be expressed in all the body cells
Describe evolution
- Variation; Sexual reproduction produces variation in offspring
- Advantage; This means some offspring will have an advantage (eg warmer fur)
- Natural Selection; Offspring with this advantage are more likely to survive the
pressures from the natural environment and pass on their genes - Evolution; Over time the species will evolve
Describe evolution of resistance bacteria
- Variation; Mutations produce variation in bacteria population
- Advantage; This means some bacteria will be better at resisting antibiotics
- Natural Selection; Bacteria with this advantage are more likely to survive in an
antibiotic environment and pass on their genes by asexual reproduction - Evolution; Over time the surviving bacteria will all have the resistance and gene and a
resistant population will have evolved
Compare mitosis and meiosis:
How are they the same?
* Both are types of cell division
* Both result in daughter cells
* Both can be used in reproduction (although different types)
How are they different?
* Mitosis is used for growth and repair of tissue and asexual reproduction whereas meiosis is only used for producing gametes
* Mitosis results in 2 daughter cells whereas meiosis results in 4
* Mitosis results in daughter cells with the same number of chromosomes as the parent
cell whereas meiosis results in daughter cells with half the number of chromosomes as
the parent cell
* Mitosis can be used in asexual reproduction whereas meiosis is used in sexual
reproduction
Describe speciation
- Isolation ; A population is isolated from the rest of the species by eg a flood event, or a
volcanic eruption etc - Different environment; the isolated population is exposed to a different environment
eg colder weather/ new predators - Variation; Sexual reproduction produces variation in offspring
- Advantage; This means some offspring will have an advantage (eg warmer fur)
- Natural Selection; Offspring with this advantage are more likely to survive the
pressures from the natural environment and pass on their genes - Evolution; Over time the species will evolve to be so different from the original
population that it can no longer interbreed and is a new species
how does asexual production differ from sexual reproduction
Genetic information comes from only one parent; [1 mark]
Because there is no fusion / mixing of gametes / genetic information; [1 mark]
Asexual reproduction only involves mitosis and not meiosis; as no gametes are involved; [1 mark]
how do The type of cells formed by meiosis and mitosis differ?
Cells formed by mitosis are genetically identical to parent cell; [1 mark]
Cells formed by meiosis have half the chromosome number of the parent cell; [1 mark]
describe mitosis
Mitosis is a type of nuclear division that gives rise to cells that are genetically identical
what is mitosis used for
It is used for growth, repair of damaged tissues, replacement of cells and asexual reproduction
describe meiosis
Meiosis is a type of nuclear division that gives rise to cells that are genetically different
what is meiosis used for
It is used to produce gametes (sex cells)
why is meiosis important
Produces gametes eg. sperm cells and egg cells in animals, pollen grains and ovum cells in plants
Increases genetic variation of offspring
Meiosis produces variation by forming new combinations of maternal and paternal chromosomes every time a gamete is made, meaning that when gametes fuse randomly at fertilisation, each offspring will be different from any others
how do humans use natural selection for our own needs
Natural selection can be speeded up by humans in selective breeding to increase food production
We have controlled sexual reproduction in cows and selectively bred them to produce offspring that produce more milk and more meat than they would have under natural conditions
what are the advantages of sexual reproduction
increases genetic variation
disease is less likely to affect the population due to variation
the species can adapt to new environments due to variation giving them a survival advantage
what are the disadvantages of sexual reproduction
takes time and energy to find mates
difficult for isolated members of the species to reproduce
what are the advantages of asexual reproduction
the population can be increased rapidly when conditions are right
can exploit suitable environments quickly
more time and energy efficient
reproduction is completed much faster then sexual reproduction
list the disadvantages of asexual reproduction
limited genetic variation in the population because offspring are genetically identical to their parents
the population is vulnerable to changes in conditions- only suited for one habitat
disease is likely to affect the whole population as there is no genetic variation
where are chromosomes located
the nucleus of cells
what does a nucleotide consist of
Each nucleotide consists of a common sugar and phosphate group with one of four different bases attached to the sugar
what are the four bases for nucleotides
Adenine (A), Cytosine (C), Thymine (T) and Guanine (G)
how do the bases always pair up
Adenine always pairs with Thymine (A-T)
Cytosine always pairs with Guanine (C-G)
why can Bacteria evolve rapidly
They reproduce / divide rapidly / multiply very quickly in optimum conditions; [1 mark]
Mistakes in DNA replication are more likely to happen; [1 mark]
Leading to mutations / increased genetic variation / more alleles; [1 mark]
explain why Antibiotic-resistant bacteria like MRSA arise
Random mutations lead to variation within bacterial populations / produce new strains; [1 mark]
Some strains / bacteria with mutations may have resistance to antibiotics; [1 mark]
Resistant bacteria are not killed / can survive in presence of antibiotic / non-resistant strains are killed by antibiotic; [1 mark]
Resistant strains survive and reproduce (due to lack of competition); [1 mark]
Passing on alleles / genes for resistance; [1 mark]
why can The emergence of antibiotic resistance in bacteria be used as evidence for Darwin’s theory of evolution
Evolution is the change in phenotype / inherited characteristics (of a population) over time; [1 mark]
Bacteria with resistance have allele(s) / gene(s) that allows them to survive in presence of antibiotic; [1 mark]
Resistant bacteria have a higher chance of survival and chance to reproduce / pass their genes on; [1 mark]
Resulting in a population of cells that are better suited to an environment containing antibiotic; [1 mark]
Proving that offspring (daughter cells) inherit characteristics from their parent(s) (cells); [1 mark]
aside from antibiotic resistance, what other evidence has led to darwin’s theory of evolution becoming more widely accepted
The (subsequent) discovery of more fossils / a greater fossil record showing how species have changed over time; [1 mark]
The development of new antibiotics is costly and slow, explain why
- It is increasingly difficult to develop novel antibiotic / drug development (that target resistant strains)
-There are many stages to antibiotic / drug testing involving cells, animals and humans (volunteers / patients) to check for safety / efficacy / dosage
-Any new potential antibiotic / drug has to be tested
-Many antibiotics / drugs fail testing (don’t work or are unsafe / cause unacceptable side effects) or very few drugs make it to market
mammoth fossils can be preserved in ice
explain how this is possible and name one other situation where this kind of fossilisation can occur
-Decay/decomposition is prevented from occurring
-Microorganisms/decomposers not present / not enough oxygen / incorrect temperature conditions / other correct explanation of
why decomposition is prevented-Another situation that could allow this to happen is in amber / peat
define the term species
Organisms that can breed together / mate;
Successfully / to produce fertile offspring
why does the same gene have to be selected from each species for sequencing when carrying out dna comparisons between species
Allows comparisons Of alleles/versions of the same gene
To show how closely-related the two species are
why is the binomial naming system a useful way of helping scientists classify organisms
-Allows scientists to communicate about species without confusion
-Globally recognised standardised scheme makes it easier for taxonomy (classification)
-Allows for identification and comparison of organisms based on certain characteristics
-It can show the degree that organisms are related to each other (i.e. in the same genus)
explain why It is an advantage for fungi to be able to carry out both sexual and asexual reproduction
they can reproduce very quickly, and they can increase the genetic variation in the populations which means they are more likely to be disease resistant
what is meant by the term variation
Differences in characteristics of individuals in a population Caused by a combination of genes inherited and environmental exposure
Mistakes during DNA replication could impact variation within a species because:
-Mutations occur / there could be a change to base sequence of DNA in a gene
-Mutation could result in a different protein being made/expressed Could lead to a change in -phenotype; increasing genetic variation
how can scientists determine whether two similar animals are the same species or not
Breeding them together to produce offspring,then Breeding the offspring to see if they are fertile, and Comparing the DNA of the two species to identify similarities / DNA analysis
