Biology Unit 4

Chromosomes that are derived from each parent

All chromosomes except those that determine gender (44 in humans, 22 pairs)

Determine gender. There are usually two: XX = Female and XY = Male

Programmed cell death for the benefit of the whole organism

When the cell has outlived its usefulness for example plasma cells after an infection has passed

Saves energy and resources and does not cause inflammation, provides growth and development - replaces damaged cells

• 1. Death signal recieved
• 2. Caspases activated in early stages
• 3. Cytoplasm begins to shrink, cell develops blebs. Apoptotic bodies form
• 4. Apoptotic bodies engulfed and broken down by phagocytes

Cell division for reproduction and for growth in bacteria.

•  - Type of asexual reproduction
•  - Not mitosis because: no nucleus involved, no centromeres, chromosomes attached to cell membrane
•  - Similarities to mitosis: DNA replication, 2 cells are produced from 1 parent cell

•  - For growth and development
•  - To replace dead and damaged cells

Cell division for growth and repair

Division of cytoplasm that follows mitosis

Advantage - if environment stays constant, then the species will remain well suited -  therefore survive and there is no need for a mate

Disadvantages - if environment changes then the whole species is at risk of extinction because all individuals are genetically the same

• 1. Formation of fingers and toes (removal of webbing)
• 2. Cell has outlived its usefulness (plasma cells after an infection has passed)
• 3. The cell was damaged and requires too much energy to be repaired
• 4. Too old/ not efficient
• 5. Does not pass the check points in mitosis

Necrosis occurs if a cell is seriously damaged by mechanical or chemical trauma and it causes damage to the cell membrane. The membrane can no longer control what enters and leaves the cell. Cells may die by bursting and leaking their contents into the cell environment

This type of reproduction requires cell division called meiosis and it only occurs in diploid germline cells found in gonads (ovaries and testes)

A segment og DNA that codes for a protein

Alternate forms of a gene e.g. fur colour (gene) could be black or white (alleles)

The biochemical, physiological and physical expression of the genotype which can be affected by the environment

Refers to the alleles of the genes that make up an individual e.g. Alibinism (phenotype) aa (genotype)

The individual has two different alleles

Individuals has two identical alleles e.g. AA or aa

If a trait is dominant, it is expressed in the heterozygote. Only one copy of the allele is required. E.g. Aa or AA

Only expressed in the homozygous form, two copies of the allele are require to express the recessive trait e.g. only aa will express the trait

A gene that is carried on the autosomes, not the sex chromosomes

A gene that is carried on the sex chromosomes

The genetic code. Contains all genes. Codes for specific proteins found in the nucleus of eukaryotes. It is inherited instructions for an organism

Is when a pair of chromosomes fails to disjoin or segregate so that 2 copies of chromosome are present in the gamete

Two gametes with an extra copy of chromosome 21 and two gametes missing chromosomes 21

One gamete with an extra copy of chromosome 21, one gamete missing a copy of chromosome 21 and two normal gametes, each with one copy of chromosome 21

Trisomy: Union of a gamete with 2 copies of one chromosome, with a normal gamete leads to 3 copies of the chromosome

Monosomy: Union of a gamete without one chromosome with a normal gamete leads to only 1 copy of the chromosome

Chromosome breaks in 2 places and a section is removed, the chromosome then rejoins

A section of the chromosome has replicated so that a set of its genes repeat

• The chromosome breaks in 2 places and the middle piece rotates 180^o

Part of one chromosome breaks off and inserts into another

Part of one chromosome breaks off one chromosome and attaches to another

Genes are located close together on a chromosome and tend to be inherited together (however allele combinations can be altered by crossing over if the parent is heterozygous)

The genes are located on separate chromosomes and therefore the genes assort independently from one another

Refers to how bases are read (transcribed) into RNA and then translated into proteins

•  - Universal = some genetic code is used to translate proteins in all living things
•  - Read in triplets 
•  - Is non-overlapping (the codons do not overlap)
•  - Degenerate or redundant (more that one codon can code for the same amino acid or stop)

The study of whole sets of genes possessed by an organism

•  - Learn more about important agricultural plants
•  - To study animals that have diseases that can cross into humans
•  - To improve diagnosis of human inherited disorders
•  - To help identify people of risk of disease
•  - For comparative genomics to study evolutionary relationships

•  - Cost - money could be spent elsewhere - little benefit for whole community
•  - Poluting of human genes
•  - Exploitation of isolated populations and disadvantaged people in search of certain genes

All the information found in one set of an organisms chromosomes

Polymerase Chain Reaction

Making many copies of segments of DNA from many very small shapes

Because there is a need to use an enzyme to build/join nucleotides that does not denature in high temperatures. Taq Polymerase is derived from bacteriathat lives in hot springs

To separate DNA using an eletric current as DNA is negatively charged. Smaller mass or size of DNA travel further than DNA with larger mass

A group of DNA fragments of known lengths that can be used to work out unknown lengths of DNA run on the same gel

To add colour to the sampleto make loading of the gel easier and to know how long to apply the electric current

Binds to DNA to make it visible under UV light

The genes of an organism has been altered/changed

Gene from a different source has been added from another organism

To recognise a specific base sequence and cut the DNA at his point

When restriction enzymes cut the DNA molecule at bases directly opposite each other

When restriction enzymes cut the DNA unevenly - when the cutting sites are not directly opposite each other

• 1. Fragments are placed in wells on the gel
• 2. The gel is then placed in a bath and covered with a pH controlled solution
• 3. A power source is attached to the bath and it is switched on. As DNA is negatively charged it moves through the gel towards the positive terminal
• 4. The fragments are separated according to their size/mass
• 5. To view the separated DNA fragments, ethidium bromide is added that attaches to the DNA. This dye is visible under ultraviolet light
• 6. Samples of known length and weight (called: strandards) can be run on the gel for comparison

• 1. A segment of DNA, which acts as a template to make millions of copies
• 2. A source of the four DNA nucleotides
• 3. A DNA polymerase which is a heat resistant enzyme found in prokaryote Thermus Aquaticus
• 4.  Single stranded DNA primers, which are synthetic, short pieces of single stranded DNA that are complementary to sequences of bases that flank the DNA region to be amplified. Specify the starting and finsihing points for DNA replication

•  - To work out the specific base sequence for a gene
•  - To produce a probe
•  - To identify base differences in a gene suspected to be the cause of a genetic disorder
•  - To make a DNA sequence from a known amino acid sequence or mRNA strand

The modification or alteration in DNA of an organism and can involve the insertion of a gene froma  different species

• Specific examples include:
•  - human insulin gene into bacteria
•  - insect resistance gene into bacteria and then into a plant

A carrier that allows the gene to be transferred from one organism into another 

A small circular ring of DNA which can self replicate

When a recombinant plasmid is inserted into prokaryotes i.e. bacteria

When foreign DNA is placed into eukaryotic cells

Involves the insertion of a normal, functioning allele into human cells (viruses are the vectors of choice for inserting genes into animals/humans)

This refers to evolutionary theory that includes the concept of natural selection AND incorporates genetic drift, gene flow and polyploidy

• Deduced based on stratigraphy
•  - Lowest rock is the oldest

Not always accurateif layers have been altered by folding, buckling, reburyign or eroding

Can be deduced if there are indicator or index fossils

Can be worked out etiher by using radiometric methods or by non-isotopic methods

Radioactive isotopes decay into different forms at a constant rate for a particular element. It is possible to calculate the amount of decay based on the isotopes half life to work out the age of the fossil or rock

The time taken for half the atoms in a radioactive sample to decay

Can be used to date fossils of living organisms (wood, shells, peat, bone, animal tissue - that is, they are made up of carbon) up to 50, 000 years old because after this time there is too little radioactive carbon remaining.

•  - Electron-spin resonance
•  - Thermoluminescence
•  - Tree rings

Where closely related species (sharing a recent common ancestor) become less similar over time due to different selection pressures.

 - Formation of homologous structures e.g. the forearm in bats, humans, and whales

Rapid divergent evolution - a very recent common ancestor evolves/diverges into a cluster of related species e.g. the finches

The development of similar features in unrelated organisms due to similar selection pressures.

 - Formation of analogous structures e.g. streamlining of dolphins and sharks

Organisms that can interbreed to produce viable and fertile offspring

• 1. Population is separated into smaller groups so that the small group becomes geographically isolated and there is no gene flow.
• 2. Over many generations, the isolated population is subjected to different selection pressures because of different environmental conditions (= natural selection) and/or to other change factors such as genetic drift
• 3. The isolated population changes over time such that, even if the two populations were to come together again, their members are unable to produce viable and fertile offspring.

They are now two distinct gene pools and two different species i.e. they are reproductively isolated

Discrete, non-overlapping classes of phenotypes - usually due to monogenic inheritance

Many intermediate forms of the phenotype which show a normal distribution - usually due to polygenic inheritance

Where humans control the breeding of organisms so that individuals with desriable traits are mated to increase the likelihood that offspring will also display these traits

Movement of alleles due to reproduction between 2 different populations (same species) i.e. migration and breeding with other populations

A change in allele frequencies due to chance, rather than natural selection. Some causes - fire, earthquake

Occurs when there is a severe reduction in the size of a population so very few individuals remain - very little genetic diversity in surviving population - more susceptable to extinction especially if there is environmental changes

When a small number of pioneers (founders) begin a new population and so there is little genetic diversity

All of the alleles in a population

Enzyme which breaks hydrogen bonds between 2 DNA strands so replication can occur

Enzyme that allows complementary DNA nucleotides to bind (via H bonds)

To seal the deoxyribose-phosphate  backbone (between the okasaki fragments to the lagging strand in DNA replication)