Genetic Information and Variation

Question 1

Define a species

Answer 1

a group of organisms which share common traits and are able to reproduce to produce living, fertile offspring.

Question 2

Talk about the Binomial Naming System and how it came about.

Answer 2

At one time. scientists named species depending on their features which resulted in different species coming under the same name.
LINNAEUS- developed the binomial naming system to overcome this featuring:
Generic Name- denotes the genus of the organism
Specific Name- Denotes the species of which the organism comes from and isn’t shared by other organisms in the genus

Question 3

What is Courtship Behaviour?

Answer 3

This is the method so that members of the same species can reconise one another allowing them to mate and produce viable offspring and pass on their genes. They are complex displays that (usually men do) to attract (the females)
During courtship behaviour, animals use signals to communicate with a protenrial mate and members of the same sex. There is a series of actions and responses stimulating further action. This is called a stimulus response chain.

Question 4

Why is Courtship behaviour needed?

Answer 4

1. To recognize members of their own species in order to create fertile offspring
2. Synchronise mating to a time when females are producing eggs.
3. To form a pair bond and ensure mating is successful
4. to identify a mate who is able to breed and is fertile and sexually mature.

Question 5

What is Classification and the two types?

Answer 5

Classification is the grouping of oraganisms into manageable groups.
Artificial- This divides organismes according to differences at the time. These may be things like colour and size.
Phylogenic- is based on evolutionary relationships between organisms and their ancestors using shared features. It arranges them in a hierarchy with no overlap

Question 6

What is Taxonomy and a Taxa?

Answer 6

TAXONOMY- the study of the groups of biological classification and their positions.
TAXA- closely related organisms are grouped together into groups called taxas. Each taxon is arranged into a hierarchy. its divided into smaller more specific taxas at each level. There is no overlap between taxa at the same level.
A domain is the highest Taxa.

Question 7

What are the three domains?

Answer 7

Bacteria- Group of single celled prokaryotes with an absence of membrane bound organelles with smaller ribosomes and murein cell walls

Archaea- group of single celled prokaryotes that were origionally classified as bacteria which they resemble in appearance. They differ from bacteria because their genes and protein synthesis are more similar to eukaryotes and there is no murein in their cell walls,

Eukarya- group of organisms made up of one or more eukaryotic cells. They have got membrane bound organelles like mitochondria and chloroplasts and larger ribosomes. This is divided into:
Protoctista, Fungi Plantae and Animalia.

Question 8

What is the order of classification?

Answer 8

Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 9

Describe Phylogeny.

Answer 9

Phylogeny is the evolutionary relationship of an organism or group of organisms.

it is based on the fact that all organisms share a common ancestor and more closely related organisms will share more recent common ancestors.

Question 10

What does a phylogenic tree show?

Answer 10

A phylogenic tree shows the evolutionary relationship between different species and their most recent common ancestor. Each branch shows a different species and the point at which they join together is the common ancestor of the two species.

Question 11

What is Biodiversity?

Answer 11

general term used to describe variety in the living worlds. It refers to the number and variety of living organisms in a particular area

Question 12

What’s the difference between Species Diversity and Genetic Diversity?

Answer 12

Species Diversity- Number of different species and the number of individuals of each species within one community

Genetic Diversity- variety of genes possessed by the individuals that make up a population of a species.

Question 13

What is species richness?

Answer 13

This is the number of different species in a particular area at a given time.
Two communities may have the same number of species but the proportions of the community made up of each species may differ markedly.

Question 14

How does agriculture effect the biodiversity of an area?

Answer 14

Agricultural ecosystems reduce the biodiversity and the number of species present because humans select for particular characteristics thus reducing the number of alleles and therefore the genetic diversity of the population.

Monoculture Farming-only using a single species of crop on a field. this therefore means that fewer individuals of other species can survive there

Question 15

How do we maintain biodiversity through agriculture?

Answer 15

• Using hedgerows insulted of fences
• Growing different crops in the same area known as intercropping
• reducing the uses of herbicides and pesticides
• preserving wetlands

Question 16

Talk about Hedgerows.

Answer 16

Many Traditional mixed farms require hedgerows to contain livestock and act as a barrier, however, as many farms have been converted to large, monoculture arable farms, fields need to be larger to accomodate a maximum amount of crops and the large machinery.
In Britain, this has led to the loss of thousands of kilometers of hedgerow each year. A threat to them is also neglect and improper management which is resposnible for for almost half the loss. In 1997, legislation was introduced to control the destruction meaning land owners must apply to remove a section of hedgerow over 20 meters.

They are important because:
- support up to 80% of Englands Birds, 50% of mammels and 30% of butterflies
- Ditches and banks associated with hedgerows provide habitat for amphibians and reptiles.
- Provide nesting material and food for birds
- Act as corridors along which animals can safely move
- Barriers for windborne pests
- Reduce wind speed to prevent erosion

Question 17

How and why do we investigate biodiversity?

Answer 17

Comparing genetic diversity within and between species helps scientists to determine the evolutionary relationships between them.

• Comparison of Observable Characteristics
• Comparison of DNA base sequences
• Sequence of Amino Acids

Question 18

Talk about the Comparison of Observable Characteristics

Answer 18

Traditionally, genetic diversity was measured by observing the characteristics of organisms. It is based on the fact that each observable characteristics are determined by a gene or genes.

However, this has many limitations such as :

• the characteristics could be coded for by more than one gene
• The same characteristic could have arisen sepeartly
• The characteristics could be influenced by the environment and the not the genes.

Question 19

Talk about the comparison of DNA base sequences

Answer 19

With the introduction of gene technology, we can now read the base sequences of the DNA of any organism. Using techniques, they can determin the exact order of nucleotides on DNA by dying them with flouresent dye which produces a serous of coulourded bands. Here, we can measyre abd sequence it to produce a pattern of colourded bands. Analysing these pattersn allows us to compare species with each other. This can also be done with mRNA

However, due to mutations, the sequences of nucleotide bases of the new species will change. Overtime, more and more mutations lead to the creation of new species.

Question 20

Talk about the sequence of amino acids

Answer 20

this can be taken back to the mRNA
sequence and thus the DNA sequence. The differences between species are called interspecific
variation. There are also differences between individuals of the same species which is known as
intraspecific variation.

Question 21

Talk about genes.

Answer 21

A gene is a base sequence of DNA that contains the coded information for making functional RNA and polypeptides. The information is in the form of a specific sequence of bases along the DNA molecule.
A gene occupies a fixed position called a locus.
The amino acid sequence of a polypeptide: polypeptides make up proteins, therefore genes determin the proteins of an organism- enzymes are proteins that control chemical reactions therefore genes are responsible for the development of organisms

Question 22

Talk about the genetic code

Answer 22

The genetic information is therefore stored as a three-base sequence called a triplet. The order of these bases is called the genetic code. Each codon represents one of 20 amino acids which is effectively universal, being the same in all living things. It codes for a specific amino acid.
The code is also degenerate meaning more than one codon codes for each amino acid. This also reduces the amount of mutations
The code is also non-overlapping, each base in a gene is only part of one triplet of bases and each base is only read once
The amino acids are then joined by peptide bonds and form a polypeptide chain.

Question 23

Talk about evidence for the three base theory.

Answer 23

The genetic code is the code our body uses to convert the instructions contained in our DNA. It is the order of bases on DNA
Scientists suggested that there must be a minimum of three bases that coded for each amino acid due to the fact that:
- There are only 20 different amino acids
- Each amino acid must have its own code
- Only 4 different bases in DNA
- if each base coded for a different amino acid, there will only be 4
- Using a pair of bases = 4 squared which is 16 which is too little
- by using 3 it would be 64 different codes which is more than enough

Question 24

Talk about non coding and coding regions of DNA

Answer 24

Much of the DNA in eukaryotes doesnt code for polypeptides, between genes there are non-coding sequences made up of multiple repeating base sequences between genes called introns. Even with a gene, only some sequences, exons, code for amino acids.

Question 25

Whats the difference between prokaryotic and Eukaryotic Cell DNA?

Answer 25

Prokaryotic cells: DNA is shorter, form a circle and not assosiated with proteins

Eukaryotic Cells: DNA is longer, form a line (linear) and occur in assosiation with proteins called histones to form structures called chromosomes

Mitochondria and chloroplasts also contain DNA which is like prokaryotic cells

Question 26

Talk about Chromosomes

Answer 26

Chromosmes are linear strands of DNA split into genes. They are only visible as distinct structures during division. They appear as two threads called chromatids joined by a centromere. They are held by histones to keep it in a fixed position.

Humans have 46 chromosomes in every cell in the body that are arranged into homogulous pairs- two chromosomes that carry the same genes. They are non-identical as they can carry different alleles (alternative form of the same gene). They 23rd chromosome determins the sex of the individual with females having two x and males having an x and a y. Every individual inherits two alleles of every gene from their parents.

Question 27

Whats the difference between Geonomes and Pretonomes?

Answer 27

Geonome- Entire genetic material of an organism found in a nucleus
Pretonome- Entire set of proteins that is or can be expressed by a genome

Question 28

What is RNA and the two types?

Answer 28

Ribonucleic acid is a polymer made up of repeating mononucleotide sub-units. There are two important types:

Messenger RNA (mRNA)- long single strand created during transcription in which the base sequence is complementary to DNA. Each set of three bases is called a codon and matches the triplet on DNA

Transfer RNA (tRNA)- Small, single stranded molecule folded into a clover leaf shape. Here is where an amino acid attaches. At the opposite end is an anti-codon which is specific to the amino acid that the tRNA attaches to.

Question 29

What is protein synthesis and the two stages?

Answer 29

During protein synthesis, a section of a DNA strand is transcribed into mRNA which is then transcribed into a polypeptide chain formed of amino acids.

DNA → RNA → PROTEIN

Transcription and Translation.

Question 30

Talk about Transcription.

Answer 30

Transcription- A molecule of mRNA is made in the nucleus
1. The hydrogen bonds between the complementary bases break thus separating the two strans and exposing the organic bases
2. One of the DNA strands is used as a template to make mRNA
3. Free nucleotides line up by complementary base pairing and adjacent nucleotides are joined by phosphodiester bonds thus forming mRNA. This is caalysed by DNA polymerase. When a stop codon is reached it ceases and the DNA rejoins and RNA polymerase moves away
4. In eukaryotic cells, the pre mRNA is then spliced to remove the introns leaving strands of exons. the mRNA moves through a pore and attaches to a ribosome

Question 31

Talk about translation.

Answer 31

1. mRNA attaches to a ribosome and tRNA collects amino acids from the cytoplasm and carries to ribosome.
2. tRNA attaches itsself to the corect codon on the mRNA and drops off the amino acid.
3. The amino acids attached to two tRNA moldecules by a peptide bond and then tRNA detach themselves.
4. This process is repeated leading to the formation og a polypeptide chain until a stop codon is reached.

Question 32

Talk about genetic mutation

Answer 32

Changes in DNA can arise spontaneously during replication and any change in the base sequence or quantity of DNA is called a mutation. A change in the base sequence of a gene can change the sequence of amino acids. Sometimes this can result in a mutation that is harmful, however due to the genetic code being degenerate the amino acid sequence may not always be changed

Question 33

What is Meiosis?

Answer 33

Meiosis is a form of cell division that gives rise to four daughter cells that are all genetically
different and have half the number of chromosomes found in the parent cell. The main role of
meiosis is the production of haploid gametes. a

Question 34

How is genetic variation achieved through meiosis?

Answer 34

• Independent assortment of chromosomes – there are various combinations of
  chromosome arrangement. During meiosis 1 homologous chromosomes line up in pairs,
  the arrangement of these pairs is random, meaning that the division into the daughter
  cells is also random.
• Crossing over of chromatids - When pairs of chromosomes line up they can exchange
  some of their genetic material. Crossing over occurs when one chromosome may swap
  places with the same part of its homologous pair leading to a different combination of
  alleles on the gene

Question 35

What are the two stages of meiosis?

Answer 35

The stages of meiosis can be split into two nuclear divisions, they are summarised below:
Meiosis 1 - homologous chromosomes pair up whereby crossing over at the chiasmata may take
place. The cell then divides whereby each daughter cell contains one chromosome from each
homologous pair.
Meiosis 2 - the chromatids of each chromosome are separated producing 4 haploid daughter
cells.

Question 36

What is Genetic Diversity?

Answer 36

the total number of different alleles in the population
The greater the number of alleles in a population the greater the genetic diversity, and therefore the greater the chance that a population would survive a change in their habitat.

Question 37

What is a population?

Answer 37

a community of animals, plants, or humans among whose members interbreeding occurs:

Question 38

What is a species niche?

Answer 38

The niche of a species is its role within the environment. Species which share the same niche compete with each other. The idea that better adapted species survive is the basis of natural
selection.

Question 39

What is natural selection and Evolution?

Answer 39

Natural selection is the process in which fitter individuals who are betted adapted
to the environment survive and pass on the advantageous genes to future generations.
Evolution is the process by which the frequency of alleles in a gene pool changes over time as a result of natural selection.

Question 40

Define the two types of selection

Answer 40

Directional Selection - directional selection occurs when the environmental conditions
change and the phenotypes best suited to the new conditions are more likely to survive. As a
result these individuals will breed and produce offspring. Overtime the mean of the
population will move in the direction of these individuals.

Stabilising Selection - In stabilising selection the phenotypes with successful characteristics are preserved and those of greater diversity are reduced. This selection doesn’t occur due to changes in the environment. If the environment stays the same then the individuals closest to the mean are favoured because they have the alleles that have given them the survival
advantage.