Genetics Flashcards
What does sexual reproduction involve!?
Sexual reproduction involves the joining of two sex cells, or gametes during fertilisation
What is sexual reproduction!?
The formation of a new organism by combining the genetic material of two organisms.
What is fertilisation!?
The joining of a male and female gamete.
What is a gamete!?
Sex cell (sperm in males and ova/eggs in females).
Describe organisms produced by sexual reproduction……
They have two parents and are genetically similar to both but not identical to either.
What does asexual production involve!?
Asexual reproduction only involves one parent so there is no joining of sex cells during fertilisation
Describe the organisms produced by asexual reproduction…..
Organisms produced by asexual reproduction are genetically identical to each other and their parent. They are clones.
What does the process of mitosis produce!?
Mitosis produces identical diploid body cells for growth and repair.
What does the process of meiosis produce!?
Meiosis produces haploid non-identical sex cells, or gametes. These fuse to form a diploid fertilised egg cell during fertilisation.
What is diploid!?
A cell that contains two sets of chromosomes.
What is haploid!?
A sex cell (gamete) that contains one set of chromosomes.
What does meiosis produce in animals!?
Egg and sperm
What does meiosis produce in plants!?
Pollen and egg cells
What is pollen!?
Male sex cell (gamete) from flowering plants.
What happens in the process meiosis!?
A diploid cell splits into 4 NON identical haploid cells
What happens in the first step of meiosis!?
Each chromosome makes a copy of itself
What is step 2 of meiosis!?
The pairs of chromosomes line up
What is step 3 of meiosis!?
The cell divides to create 2 cells
What happens in step 4 of meiosis!?
Those 2 cells immediately split again to create 4 cells each with a single set of chromosomes
What is unique about each of these 4 new cells in meiosis!?
Each one has a different combination of genetic material from the father and the mother
What does this variety in combination mean!?
None of the sex cells a person produces are ever the same
When a sperm fertilises an egg what happens to the chromosomes!?
The unique new combination of chromosomes are made,creating a new diploid cell
What then happens to this new diploid cell!?
It divides many times to create a person meaning no one looks exactly the same!
What is a polymer!?
A large molecule formed from many identical smaller molecules known as monomers.
What is DNA in terms of molecules!?
A polymer, made from many smaller units called nucleotides
What is a nucleotide made from!?
A nucleotide is made of a sugar and a phosphate group,
What is a nucleotide made from!?
A nucleotide is made of a sugar and a phosphate group,
As well as a sugar and phosphate group, what else is a a nucleotide made from!?
One of the four bases
What are the four bases!?
adenine (A)
cytosine (C)
guanine (G)
thymine (T)
When nucleotides join together what do they form!?
2 strands
What do these 2 nucleotide strands make!?
A double helix
What is a double helix!?
The shape of the DNA molecule, with two strands twisted together in a spiral.
What is a double helix held together by!?
The double helix is held together by weak hydrogen bonding between complementary base pairs
What are the complementary base pairs!?
A and T (Adenine and Thymine)
C and G (cytosine and Guanine)
What does a double helix carry!?
It carries the genetic code, which determines the characteristics of a living organism.
What is the genetic code!?
The code formed by the order of the bases in DNA that determines an organism’s characteristics.
What are chromosomes and where are they found!?
The cell’s nucleus contains chromosomes. These are long threads of DNA, which are made up of many genes.
What is a gene!?
The basic unit of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell’s chemistry - particularly protein production.
Where is the gene found!?
A gene is a small section of DNA in a chromosome
What is the job of the gene!?
Each gene codes for a particular sequence of amino acids in order to make a specific protein
What is heredity!?
Genetic information that determines an organism’s characteristics, passed on from one generation to another. To do with passing genes to an offspring from its parent or parents.
What is a gene the unit of!?
Heredity
And what could happen to a gene!?
may be copied and passed on to the next generation.
What is a genome!?
The complete set of DNA found in an organism.
Describe the genome in humans…
humans this is all the DNA that makes up the 23 pairs of chromosomes found in all diploid body cells. That is all the cells except sex cells or gametes, which only have half of a person’s genome.
What were the aims of the human genome project!?
1.to work out the order or sequence of all the three billion base pairs in the human genome
2.to identify all the genes
3.to develop faster methods for sequencing DNA
When was the human genome project started!?
At the end of the last century
When was the sequencing project finished!?
The sequencing project was finished in 2001, and work continues to identify all the genes in the human genome
What did scientists do in the human genome project!?
The HGP used the DNA of several people to get a sort of average sequence, but each person has a unique sequence (unless they have an identical twin).
What positive impact can mapping a humans genome have!?
Mapping of a person’s genome can help in predicting how likely they are to develop certain conditions.
How does the human genome project benefit doctors!?
Scientists and doctors are also now beginning to use the information they have discovered in the HGP to help make more effective medicines as the effectiveness of medicines can be affected by variations in alleles.
What can variation within genes lead to!?
Variation within genes leads to different genotypes
What is a genotype!?
The alleles that an organism has for a particular characteristic, usually written as letters.
How can different genotypes be seen!?
they can be seen by a different phenotype
What is a phenotype!?
The visible characteristics of an organism which occur as a result of its genes.
What causes different phenotypes!?
Genetic variation and environmental variation can both cause these different phenotypes.
Where does a variation arise from!?
All variation arises from mutations and most have no effect on the phenotype.
What is a mutation!?
A random and spontaneous change in the structure of a gene, chromosome or number of chromosomes.
Where do mutations arise from!?
Mutations arise spontaneously and happen continually.
What happens to the phenotype when a mutation occurs!?
A mutation rarely creates a new phenotype, but if the phenotype is changed as a result of a mutation and the new phenotype is suited to a particular environment,
What can happen if a phenotype is mutated to suit a particular environment!?
it can lead to a change in a species over time.
Give an example of a mutation leading to a change in phenotype….
as feather colouring in birds, this change may allow those individuals to reproduce more frequently, due to them being more attractive and seen as a more desirable mate. This would result in the mutated gene being passed on more frequently than the original gene and would result in an increase in the proportion of birds with the new feather colour compared to the original feather colour. This is the basis of natural selection.
What does natural selection describe!?
Natural selection describes how organisms that are better adapted to an environment are more likely to survive long enough to reproduce and pass on their genes.
What is “survival of the fittest”!?
It is the process when organisms that are better adapted to an environment are more likely to survive long enough to reproduce and pass on their genes.
process where
Natural selection and “survival of the fittest” are fundamental to what process!?
Evolution
What is evolution!?
The process of change in the inherited traits of a population of organisms from one generation to the next.
Who came up with the theory of evolution!?
The English naturalist Charles Darwin
What is a famous example of natural selection!?
A famous example of natural selection is the peppered moth.
Why were light coloured oaths no longer camouflaged in the 1800s!?
airborne pollution in industrial areas blackened the birch tree bark with soot
What happen to light coloured moths!?
Light moths were no longer camouflaged and got eaten by birds
What happened to the dark moths when the air became polluted!?
The dark moths were better camouflaged.
Why did pollution not cause this change!?
Note that this change was not due to pollution making the moths darker. The dark variety had always existed, but had an advantage when the environment changed.
What was the result for the dark moths!?
dark moths had a greater chance of surviving long enough to reproduce and pass on their genes, including those genes that caused their dark colour
What happened to the proportion of light to dark moths and what did this lead to!?
The proportions of the two types of moth changed over time. This led to a gradual increase in the proportion of dark moths, and light moths became very rare in industrial areas.
What can mutations a,so be a cause of!?
1.ionising radiation
2.chemical mutagens, such as tar from cigarette smoke
What is ionising radiation!?
Radiation that is able to remove electrons from atoms or molecules to produce positively charged particles called ions.
What is a mutagen!?
A physical or chemical agent that can induce or increase the frequency of mutation in an organism.
What does iodising radiation include!?
Ionising radiation includes gamma rays, X-rays and ultraviolet rays.
What happens as a result of the greater dose of radiation!?
The greater the dose of radiation a cell gets, the greater the chance of a mutation.
What is radiation!?
Energy carried by particles from a radioactive substance, or spreading out from a source.
What could mutations potentially cause!? And what is the result of it!?
Mutations could cause different genes to be switched on or off, and this could create a different or faulty protein to be synthesised.
Give an example of radiation causing a faulty protein…..
For example, if the protein is an important enzyme, the specific substrate might not fit into the substrate binding site. If it is a structural protein such as collagen, it might lose its strength.
What do most DNA mutations not significantly do!?
most DNA mutations do not significantly alter a protein, they only alter it slightly, or not at all, so its appearance or function is not changed.
How can mutations be positive!?
It gives an organism an advantage
How can mutations be negative!?
It can give a disadvantage to the organism
What are chances that a mutation will have a significant effect!?
They are very rare
What do most mutations not change!?
They do not change to the organism’s phenotype.
What may result in a change in a phenotype!?
These mutations may change the activity of a protein if they occur within a gene. This might result in a change in phenotype
If the phenotype is changed what might also happen!?
The phenotype might appear hidden and be unnoticed
If the phenotype is not hidden what might happen!?
might result in a serious consequence, such as genetic disease like as cystic fibrosis.
What is the normal order of the bases for one of the strands in a DNA molecule!?
CGAACTCGA
What is only one of the DNA stands involved!?
Protein synthesis
A change from the normal order of bases leads to different types of gene mutation. List some examples……
CGA
ACC
CGA
What is a triple code!?
the bases are read in threes
What might happen to synthesis when a triple code is present!?
this may result in a different amino acid being synthesised, and therefore possibly a different protein eg CCA / ACC / CGA
How might mutations change the activity of a protein!?
if they occur within a gene. This might result in a change in phenotype or it might appear hidden, and be unnoticed. Alternatively, they might result in a serious consequence, such as genetic disease like as cystic fibrosis.
What are alleles!?
The different forms of a gene for a particular characteristic
How are alleles represented!?
As letters
Give an example of alleles in cats!?
H - short hair
h - long hair
How many alleles does each gene inherit!?
Every organism inherits 2 alleles for each gene.
Where do the 2 alleles come from!?
One from each parent
What is the genotype!?
The combination of alleles for a particular gene in an individual
What is a Phenotype!?
The way the genes are expressed, the appearance of an individual
Some characteristics are!?
Are dominant
What determines the phenotype!?
Just one dominant allele in the genotype determines the phenotype.
What is recessive!?
Describes the variant of a gene for a particular characteristic which is masked or suppressed in the presence of the dominant variant. A recessive gene will remain dormant unless it is paired with another recessive gene.
What is homozygous!?
This describes a genotype in which the two alleles for the characteristic are identical.
What is heterozygous!?
This describes a genotype in which the two alleles for a particular characteristic are different.
What do the alleles look like in a heterozygous organisms!?
It contains one dominant and one recessive allele
How do you know if a individual will be heterozygous or homozygous!?
You don’t! It’s all up to chance
What do you use to work out the probability that a particular genotype or phenotype is arising!?
A punnet square
Draw a punnet square!
Check BBC
Give some examples of characteristics controlled by a single gene
Fur in animals
red-Green blindness in humans
What are alleles!?
Different forms of the same gene.
What makes an allele dominant!?
An allele that always expresses itself whether it is partnered by a recessive allele or by another like itself.
What is a always expressed!?
A dominant allele is always expressed, even if one copy is present
What are dominant alleles represented by!?
A capital letter
If the allele for brown eyes is B (dominant) how many of B do you need to inherit brown eyes!?
You only need one copy of this allele to have brown eyes. Two copies will still give you brown eyes.
When is a recessive allele only expressed!?
A recessive allele is only expressed if the individual has two copies and does not have the dominant allele of that gene.
What are recessive alleles represented by!?
Recessive alleles are represented by a lower case letter, for example, b
If the allele for blue eyes, b, is recessive. How many of b would you need for blue eyes!?
You need two copies of this allele to have blue eyes.
Give an example of a homozyous allele…
BB
or
bb
Give an example of a heterogeneous allele….
Bb (Note:dominant always comes first!)
What are most characteristics a result of!?
Most characteristics are a result of multiple genes interacting, rather than a single gene.
What is monohybrid inheritance!?
Monohybrid inheritance is the inheritance of characteristics controlled by a single gene (mono = one)
How is monohybrid inheritance shown!?
On a punnet square
What does a punnet square show!?
These show the possible offspring combinations that could be produced, and the probability of these combinations can be calculated.
What is probability!?
The extent to which something is likely to be the case.
What is the first step to constructing a punnet square!?
Determine the parental genotypes. You can use any letter you like but select one that has a clearly different lower case, for example: Aa, Bb, Dd.
What is the second step to constructing a punnet square!?
Split the alleles for each parent and add them into your Punnett square around the edges.
What is the third step to constructing a punnet square!?
Work out the new possible genetic combinations inside the Punnett square.
What is a Pedigree analysis chart!?
A family tree diagram which show the inheritance of a genetic condition in a family, eg cystic fibrosis.
How can a pedigree analysis chart help to see how likely someone in the family will inherit a condition!?
They can use this to work out the probability
When is pedigree analysis usually undertaken!?
A pedigree analysis is usually undertaken if families are referred to a genetic counsellor following the birth of an affected child.
What does the pedigree analysis chart show !?
The pedigree analysis chart is used to show the relationship within an extended family.
How are males shown on the pedigree analysis chart!?
Males are square shapes
How are females shown on the pedigree analysis chart!?
Females are represented as circles
What colour is an infected individual represented as!?
They are red
And what colour are unaffected individuals represented as!?
They are represented as Blue
How do we know by looking on the PA chart that a male and a female have produced children together!?
A horizontal line is present between them
How to you express the outcome of a genetic cross!?
Using probability, direct proportion or ratios
Why is nothing guaranteed when finding the probability of a genetic cross!?
during the process of fertilisation, the allele combinations created are a random process, and that is why probability is used, as nothing is guaranteed. Each of the four possible offspring combinations is as likely to happen during every fertilisation event.
What is diabetes!?
A serious disease in which the body is unable to regulate blood sugar.
What does diabetes do to a body’s blood sugar!?
body’s blood glucose levels remain too high because glucose is not effectively removed from the blood
How can diabetes be treated!?
By injecting insulin
What is insulin!?
A hormone that regulates the level of sugar in the blood and can be produced by genetically modified bacteria.
What does insulin do!?
It acts just as natural insulin and causes glucose to be taken up by the liver and other tissues, which results in cells receiving the glucose they need, and blood glucose levels stay normal.
What has been genetically modified to produce human insulin!?
Bacterial cells
What are some of the reasons that some crops are genetically modified!?
So they become resistant to insect attack or are
Herbicide resistant
What do these genetically modified features increase!?
Crop yield
What is a yield!?
The mass of a crop produced
What do herbicide crops allow!?
Herbicide resistant crops allow them to tolerate herbicide, but the weeds are killed by it, therefore less herbicide is needed.
What do some wild rice now produce due to scientists adding a gene to it!?
beta carotene
What is beta carotene!?
A red-orange pigment important in the diet for maintaining health.
What did beta-carotene do to the rice!?
It changes the colour of the wild rice to a golden colour
What do humans need beta-carotene for!?
Beta carotene is needed by humans in order to make vitamin A which is essential for good vision.
List the advantages of golden Rice…..
can be used in areas where vitamin A deficiency is common, so it can help prevent blindness.
Why is golden rice not being grown commercially in many countries!?
In many countries golden rice is not being grown commercially over fears associated with genetically modified crops.
What are the ethical concerns about genetic modification!?
1.about the possible health risks of genetically modified food.
2.Others think it is ethically wrong to create new life forms or to move genes between species
Why might people be concerned about genetically modified food!?
a genetically modified food might contain a substance that causes an allergic reaction in some people, or higher levels of a toxin naturally found in the food.
What are the future uses of genetic modification!?
researchers are hoping to use genetic engineering to be able to overcome some inherited disorders, such as cystic fibrosis and Huntington’s disease amongst others.
What is the first main step of genetic engineering!?
1.Restriction enzymes are used to isolate the required gene leaving it with sticky ends. Sticky ends are a short section of unpaired bases
What is the second main step of genetic engineering!?
A vector, which is usually a bacterial plasmid or a virus, is cut by the same restriction enzyme leaving it with corresponding sticky ends.
What is the third step of genetic engineering !?
The vector and the isolated gene are joined together by ligase enzyme.
What is the fourth main step to genetic engineering!?
The vector inserts the gene into required cells.
What is the fifth main step to genetic engineering!?
The genes are transferred to animal, plant or microorganism cells, during early development, which allows them to develop with the desired characteristics.
What is genetic engineering!?
Describes a cell or organism that has had its genetic code altered by adding a gene from another organism.
When did the human genome project start!?
It began in 1990
When was the human genome project completed!?
2003
What were the hundreds of scientists trying to determine!?
Hundreds of scientists from different universities all over the world collaborated together to determine the sequence of base pairs that made up the genome of a random man and woman
How many base pairs that made up the genome between a man and woman were discovered!?
More than 3 billion!!!!
What does having a full understanding of the human genome enable us to do!?
1.search for genes linked to different types of disease
2.understand inherited disorders and their treatment
3.trace human migration patterns from the past
What are scientists now searching for to do with the human genome!?
They are searching for disease associated with genes
Name an example that these genes are contributing to disease!?
these are genes that can contribute to breast
cancer , which are known as BRCA1 and BRCA2.
What % of breast cancer cases are inherited through genes!?
10%
How did scientists detect BRCA1 and BRCA2 genes!?
studying families where breast cancer was known to have been inherited between individuals
What were scientists able to create after studying these families where breast cancer was known to be inherited between individuals!?
They were able to create a pedigree analysis, which is similar to a family tree diagram that showed the close relationship of those affected and unaffected within the family.
What does the pedigree analysis illustrate!?
The pedigree analysis illustrates the inheritance pattern of the disease to be determined
What does the pedigree analysis illustration enable!?
This enabled scientists to test
DNA
from the affected and unaffected individuals to identify differences.
How is now possible to detect the cancer gene due to the help of the human genome project!?
It is now possible to detect the presence of the genes by having a simple blood test.
What is selective breeding (also know as artificial selection)!?
An artificial process in which organisms with desired characteristics are chosen as parents for the next generation.
What 6 plants have been selectively bred from wild mustard!?
Kale
Kohlrabi
Broccoli
Brussels sprouts
Cabbage
Cauliflower
What part of the wild mustard plant was cauliflower bred from!?
The flower buds
What part of the wild mustard plant was cabbage bred from!?
Terminal leaf buds
What part of the wild mustard plant was Brussel sprouts bred from!?
Lateral leaf buds
What part of the wild mustard plant was broccoli bred from!?
The flower buds and the stem
What part of the wild mustard plant was kale bred from!?
The leaves
What part of the wild mustard plant was kohlrabi bred from!?
The stem
What is the first main step of selective breeding!?
Decide which characteristics are important enough to select
What is the second main step of selective breeding!?
Choose parents that show these characteristics from a mixed population. They are bred together.
What is the third main step of selective breeding!?
Choose the best offspring with the desired characteristics to produce the next generation.
What is the fourth main step of selective breeding!?
Repeat the process continuously over many generations, until all offspring show the desired characteristics.
How long does selective breeding take!?
Selective breeding takes place over many generations
Why do farmers selectively breed different types of cows with highly desirable characteristics!?
To produce the best meat and dairy as well as increasing meat and dairy yield
What are the 3 desired characteristics in plants!?
1.disease resistance in food crops
2.wheat plants that produce lots of grain- increase crop yield
3.large or unusual flowers
What are the 3 main desirable characteristics in animals!?
1.animals that produce lots of milk or meat- increased meat and dairy yield
2.chickens that lay large eggs
3.domestic dogs that have a gentle nature
Why might the new varieties of cow be economically important!?
they may provide more or better quality food, or allow farmers to feed more people.
What are highland cows bred for!?
Highland cows have been bred for their meat
What are Friesian cows bred for!?
Fresian cows have been bred to produce large volumes of milk
What have Aberdeen Angus been bred for!?
Aberdeen Angus cows have also been bred for their meat
What is one of the main problems of selective breeding!?
future generations of selectively bred plants and animals will all share very similar genes which will reduce variation
What is a gene pool!?
Genes and their different alleles within a population are known as its gene pool
What are the affects of inbreeding!?
1.Inbreeding can lead to a reduced gene pool, making it more difficult to produce new varieties in the future.
2.This also makes organisms prone to certain diseases or inherited defects.
What are the benefits to selective breeding!?
1.new varieties may be economically important, by producing more or better quality food
2.animals can be selected that cannot cause harm, for example cattle without horns
What are the risks to selective breeding!?
1.reduced genetic variation can lead to attack by specific insects or disease, which could be extremely destructive
2.rare disease genes can be unknowingly selected as part of a positive trait, leading to problems with specific organisms
3.creation of physical problems in specific organisms,
Give an example of when a rare disease gene has been unknowingly bred!?
eg a high percentage of Dalmatian dogs are deaf
Give an example of when a physical problem in an organism has been unknowingly bred!?
eg large dogs can have faulty hips due to not being formed correctly
What does a herbicide resistance crop allow!?
It allows them to tolerate herbicide, but the weeds are killed by it, therefore less herbicide is needed.
