b6 inheritance, variation and evolution

what does meiosis lead to?

the formation of non identical cells

what does mitosis lead to?

the formation of identical cells

what does sexual reproduction involve?

the fusion of male and female gametes

animals: sperm and egg

flowering plants: pollen and egg

what happens in sexual reproduction?

there is a mixing of genetical information which leads to variety in the offspring

what does asexual reproduction involve?

only one parent and no fusion of gametes.

there is no mixing of genetic material.

leading to genetically identical offspring.

only mitosis is involved

what does diploid mean?

two sets of chromosomes?

how are gametes formed?

cells in reproductive organs divide by meiosis 

what happens when a cell divides to form gametes? (3)

copies of the genetic information are made

the cell divides twice to form four gametes, each with a singe set of chromosomes

all gametes are genetically different from each other

how do gametes restore the normal number of chromosomes?

when they join at fertilisation

what are the advantages of sexual reproduction? (3)

produces variation in the offspring

if the environment changes variation gives a survival advantage by natural selection

natural selection can be speeded up by humans in selective breeding to increase food production

what are the advantages of asexual reproduction?

only one parent needed

less time and energy efficient as it does not need to find a mate 

faster than sexual reproduction

many identical offspring can be produced when conditions are favourable

state 3 organisms that can reproduce by both methods.

malarial parasites: reproduce asexually in the human host, but sexually in the mosquito

fungi: reproduce asexually by spores but also reproduce sexually to give variation

many plants: produce seed secually but also reproduce asexually by runners or bulb dicision 

what is genome?

the entire genetic material of an organism

what is DNA ?

a polymer made up of two strands forming a double helix

where is DNA contained in?

structures called chromosomes

what is a gene?

a small section of DNA on a chromosome

what does a gene code for?

a specific sequence of amino acids to make a specific protein

what does a nucleotide consist of?

a common sugar

phosphate group

base

how many bases are there?

4- A,T,C,G

what do long strands of DNA consist of 

alternating sugar and phosphate sections. attached to each sugar is one of the four bases

what is a DNA polymer made up of?

repeating nucleotide units

what is the genome?

the entire genetic material of an organism

what is the importance of understanding the human genome?

can

search for genes linked to different types of disease

understand and treat inherited disorders

use in tracing human migration patterns from the past

what codes for a particular amino acid?

a sequence of three bases

what is transcription?

making a copy of the gene

recall a simple desciption of protein synthesis?

inside the nucleus, the DNA unwinds

a copy of the gene is made in form of mRNA

the mRNA moves from the nucleus to the ribosomes

this is where the proteins are synthesised in the cytoplasm

tRNA brings amino acids to the ribosomes.

the ribosome reads the mRNA code three letters at a time and joins the amino acids together in the correct order.

the chain of amino acids fold to form a protein

how does the structure of the DNA effect the protein made?

as the base sequence of a gene acts as a code that determines the amino acid sequence of a protein

what does coding DNA contain?

the instructions for making proteins

what can a variant in the coding region of the gene cause?

change in the amino acid sequence of a protein. this may change the shape, structure or activity of the protein

could directly change the phenotype

what does the non coding DNA do?

does not code for proteins but it helps control when and how strongly genes are switched on of off

what can a variant in the noncoding region cause?

affect the binding sites for proteins that controls gene expression

make a gene be:

1. switched on too much

2. switched on too little

3. not switched on at all

this changes the amount of proteins produced, which can affect the phenotype even if the protein’s structure is normal

what is a mutation?

a change in the DNA structure

what happens if a mutation occurs in a gene?

it may change the order of the bases in the DNA because the sequence of bases determines the sequence of amino acids

what can a mutation cause?

1.change in the codon on the mRNA

2. This may cause different amino acids to be added during protein synthesis

3. as a result the shape or structure of the protein may be altered

4. if the protein has a different shape, it may not work properly or may work differently

this can change the organism’s phenotype

what happens when the protein shape is complete?

it folds up to form a unique shape to form a unique shaoe. this unique shape enables the proteins to do their jobs as enzyme, hormones or forming structures in the body

what is a gamete?

a sex cell that contains half the number of chromosomes of a normal body cell

what is a chromosome?

structures made of DNA and proteins that package genetic information with the nucleus of a cell

what is a gene?

a segment of DNA that contains instruction for building specific protiens

what is an allele?

a variant of the sequence of nucleotides at a particular location on a dna molecule

what does dominant mean?

a gene variant that is expressed in the phenotype even if only one copy is inherited

what does recessive mean?

a gene variant that is only expressed in the phenotype if.a an individual inherits two copies

what does homozygous mean?

an organism that has two identical allele for a particular gene

what does heterozygous mean?

an organism that has two different allele for a particular game

what is genotype?

an organisms its complete set of genetic material

what is phenotype?

the observable characteristics or traits of an organism

what are characteristics a result of?

multiple genes interacting

what does the genome act as?

a set of instructions for building and running the body

what does the environment affect?

how the instructions are used. conditions around the organism can influence how much they are expressed, and how the organism developes

what is the phenotype come from?

the interaction between gene and environment

where do all variants rise from?

mutations

what can lead to a rapid change in a species?

if the new phenotype is suited to an environmental change

what is evolution?

the change in inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species

what is natural selection?

a process that gives rise to phenotyoes best suited for their environment

what is selective breeding?

the process by which humans breed plants and animals for particular genetic characteristics

what does selective breeding involve?

1.choosing parents withe the desired characteristic from a mixed population.

2. they breed together

3. from the offspring, those with the desired characteristics are bred together

4. this continues over many generations until ALL offspring show desired characteristic

what can selective breeding lead to?

inbreeding where some breeds are particularly prone to disease or inherited defects

what is genetic engineering?

the process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characterisitc

what happens in genetic engineering?

1. enzymes are used to isolate the required gene, this gene is inherited into a vector, usually a bacteria plasmid or a virus

2. the vector is used to insert the gene into required cells

3. genes are transferred to the cells of the animals, plants or microorganism a tan early stage in their development so that they develop with desired characteristics

what is tissue culture?

using small groups of cells from a part of a plant to grow identical new plants

how is tissue culturing important?

for preserving rare plant species

commercially in nurseries

what is cuttings?

am older but simple method used by gardeners to produce many identical new plats from a parent plant

what is embryonic transplant?

splitting apart cells from a developing animal embryo before they become specialised then transplanting the identical rmbryo in to the host mother

what happens in adult cell cloning?

1. the nucleus is removed form the unfertilised egg cells

2. the nucleus of an adult body cell, such as the skin cells, is inserted into the egg cell

3. an electric shock stimulate the egg cell to divide to form an embryo

4. the embryo cells contain. the same genetic information as the adult skin cell

5. when the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development

give an example of natural selection.

antibiotic resitance

what is antibiotic resistance?

bacteria can evolve quickly because they reproduce at a fast rate mutations of bacteria produce new strains. some bacteria might become resistant to certain antibiotics and cannot be destroyed by the antibiotic

what happens during the development of resistance?

1. random mutations occur in the genes of individual bacterial cells

2. some mutations protect the bacteria form the effects of the antibiotic

3. bacteria without the mutation die or cannot reproduce when the biotic is present

4. resistant bacteria can reproduce with less competition fromthe normal bacterial strains

what are fossils?

the ‘remains’ of organisms from millions of years ago which are found in rock

how are fossils formed?

from parts of organisms that have decayed because one or more of the conditions needed for decay are absent

when parts of the organism are replaced by minerals as they decay

as preserved traces of organisms such as footprints, burrows and rootlet traces

why can’t scientists be certain about how life began on earth?

because many early forms of life were soft bodies which means they have left few traces behind. what traces there were, have been mainly destroyed by geological activity

what is extinction?

when there are no remaining individuals of a species still alive

what are human causes of extinction?

1. habitat loss and degradation

2. overexploitation

what are natural factors of extinction?

1. co extinction

2. gradual environmental changes

what is MRSA?

the resistance to antibiotics

what do doctors have to do to reduce the rate of development of antibiotic restraints?

1. doctors should not prescribe antibiotics inappropriately, such as treating non serious or viral infections

2. patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains

why is it unlikely to keep up with the emergence of new resistant strains?

the development of antibiotics is costly and slow

what is archae?

primitive bacteria usually living in extreme environments

what is bacteria?

true bacteria

what is eukaryota?

protists, fungi, plants and animals

what is evolutionary trees?

a method used by scientists to show how they believe organisms are related

what do they use for extinct organisms?

fossil data

what do they use for current organisms?

classification data