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.