Genetic information,variation and relationship between organisms

What is a karyotype

A karyotype is a visual representation of chromosomes in a cell, organized by size and structure.

What is a somatic cell

A somatic cell is any cell in the body that is not a sperm or egg cell, typically making up the majority of an organism's tissues and organs.

Important feature of a somatic cell

It is a dipolid (it has 2 copies of each chromosomes, maternal and paternal)

What a re homologous chromosomes

Homologous chromosomes are pairs of chromosomes in a diploid organism that have the same structure and gene sequence, one inherited from each parent.

What is a gene

A gene is a section of DNA that is a code for building a protein or polpeptide chain

Why are genes important for mRNA

it acts a s a template to make m RNA (Transcription)

The genetic code (image)

What is the start codon

AUG (methionine) is the start codon

How many differnet amino acids exist

20

How many bases are required to code for a single amino acid

3

What is a codon

3 bases that correspond to an amino acid

How many possible combination of bases exist to code for amino acid.

64

What is degenerative code

There are multiple codons that code for the same amino acid

What is does RNA being universal code mean?

It is read the same way by any ribosomes

What does RNA being non overlapping mean?

It is read as a triplet everytime

What are introns and exons

Exons are a sequence of DNA bases that code for the amino acid sequence

Introns are a sequence of DNA bases that do not code for the amino acid sequence

What does it mean when introns do not code for the amino acid sequence

Non coding base sequences are used for gene expression. This tells the cell when to turn genes on and off in order to tell the tibosomes to make or stop making amino aicds. They are positioned between genes

How does splicing work?

Splicing is a crucial step in RNA processing where introns (non-coding sequences) are removed from the pre-mRNA, and exons (coding sequences) are joined together to form mature mRNA. This process is carried out by a complex molecular machine called the spliceosome, which recognizes specific sequences at the intron-exon boundaries. The spliceosome cuts the pre-mRNA at these sites, removes the introns, creating a continuous coding sequence that can be translated into a protein.

What is alternative splicing

Alternative splicing is a regulated process during gene expression that results in a single gene coding for multiple proteins. After transcription, pre-mRNA undergoes splicing, where introns are removed and exons are joined. In alternative splicing, certain exons may also be excluded or included, or introns may be retained, leading to different mRNA transcripts. Alternative splicing increases the diversity of proteins that can be produced from a single gene,

RNA leaving the nucleus (image)

How does transcription work?

An enzyme (DNA helicase) acts on aspecific region of the DNA causing the 2 strands to separate and expose the nucelotide bases in that region. The nucleotide bases on the template stran pair with their complimentary nuecleptodes from the gene pool. The enzyme RNA polymerase then moves along the strand and joins the nucleotides together making phosphodiester bonds. C joins to G and A to U. When the RNA polymerase reaches a specific sequence which it recognises as a stop codon and then stops the process.

What is the role of T RNA in transcription/ start of translation

tRNa has a specific anticodon that is complimentary and attatches to the amino acid.

Translation of proteins

The ribosomes moves along the mRNA bringing together 2 tRNA molecules at one time, each pairing up with the corresponding first 2 codons on the mRNA. the 2 amino acids (methionine and threonine) on the tRNA are joined by a bond using an eznyme and energy. The ribosomes moves on the 3rd codon in the sequnce and therefore linking amino acids on the 2nd and 3rd tRNA molecules. As this happens the tRNA is released from its amino acids and is free to collect another amino acid. This process continued making the polypeptide chain until a. stop codon is reached

Assembling a protein

Often a number of polypeptide are linked together to give a functional protein. First the polypeptide is coiled or folded, producing its secondary structure. The secondary structure is folded, producing the tertiary structure, different polypeptide chains along with non-protein groups are linked to form the quaternary structure

What are the different gene mutations

Deletion mutation, insertion mutation and substitution mutation

Image of the different gene mutations

What is a frame shift and what is it caused by?

Basically where all the bases shift to the right or to the left by an insertion or mutation mutation

What is a silent mutation

No change to amino acid coded for (due to degenerative nature of genetic code

What is a missense mutation

Change to amino acid coded for (change to primary structure may cause change to tertiary structure)

What is a nonsense mutation

Change to a stop codon (polypeptide chain is shorter than required)

Steps to how a mutation occurs

1) Randomly,during cell division a single base is substituted for another

2) This chnages the base sequence of the DNA

3) the DNA is transcribed in the nucleus to produce pre m RNA

4) Then the introns are removed and the exons are spliced together in the process of splicing

5) the mature mRNA produced has an altered codon

6) The mature mRNA moves via the nuclear pores to the ribosomes and attaches to one

7)The process of translation begins and a different specific tRNA is able to complementary base pair with this new codon

8)So a different amino acid is brought into the polypeptide than normal

9) This gives a differen primary structure to the polypeptide

10) Which causes a difference in the bonding pattern of the secondary and tertiary structure of the protein

11) The active site is a different shape and an enzyme substrate complex cannot form so the enzyme does not carry out its function.

Differences between mitosis and meiosis

Mitosis has 1 division phase whilst meisosis has 2 division stages

Meiosis produces 4 genetically different cells whilst mitosis produces 2 genetically identical cells

Mitosis produces diploid cells whilst meiosis produces haploid cells

Prophase 1

The chromosomes which up until this point are thin unpacked threads invisible under a light microscope, begin to pack into dense visible masses. Homologous pairs then attach fo form bivalent/tetrads and exchange DNA (cross over)

Prophase 2

The nuclear envelope breaks down and the spindle apparatus forms. The chromosomes start moving towards the equatorial plane. The chromosomes still have the chromatifs attached by the centromere.

Metaphase 1

The celluar machinery attatches itself to the tetrads and moves them to the equator of the cell (“Metaphase plate”)

Metaphase 2

Single chromosmes align on the metaphase plate, much as chromosomes do in mitosis. This is in contrast to metaphase 1 , in which homologous pairs of chromosomes align on the metaphase plate

Anaphase 1

The hmologous chromosomes separate during this stage, the chromosomes migrate to the opposite poles of the cell. The sister chromatids remain together at this stage

Anaphase 2

The centromere separate, and the 2 chromatids of each chromosome move to opposite poles on the spindle. The separated chromatids are now called chromosomes in their own right

Telopahse 1

One chromosome from each homologous pair reaches each pole and the cell separates into 2 daughter cells

Telophase 2

A nuclear envelope forms around each set of chromosomes and cytokinesis occurs, producing 4 daughter cells each with a haploid set of chromosomes.

In what phase does crossing over occur?

Metaphase 1

How are chromosomes in a homologus pair different?

they are different because different alleles but the same genes at the same location

What is independent assortment?

The production of differne combinations of alleles in daughter cells due to the random alignment of homologous pairs along the equator of the spindle during metaphase 1.

What does VASPA stand for?

Variatiom (random mutation)

Advantage (In a particular selection some individuals have an advantageous phenotype/allele)

Survive + reproduce

Pass on advantageous allele

Allele frequency in the population changes

What tends to show discontinuous variation

variation that is caused by different alleles of a single gene

What tends to show continuous varaqiation

Variation that is caused by many different genes and/or is affected by the environment

What are examples of discontinuous and continuous data

Discontinuous data ( height)

Continuous data (eye colour)

What shape is normal distribution

bell shaped

What is standard deviation

A measure of “spread outness” around the mean. It takes into account all the values not just the largest and smallest. A measure of where the bulk of the data is.

What is directional selection

Phenotypes at one extreme of the range survive a selection pressure better than those at the other extreme.

Bacteria example of directional selection

An example of this is when bacteria become resistant to antibiotics. A single bacteria will have had a mutation that meant it was not kill by penicillin as it could produce the enzyme penicilase. This allowed it to grow and the frequency of the allele that enabled penicilase production increased in the population.

What is stablising selection?

Phenotypes at either extreme of the range are disadvantageous. Selection pressure does not favour any extreme therefore the middle of the range is selected for.

What is disruptive selection?

Phenotypes at either extreme of the range are advantageous. The middle phenotypes can not the survive selection pressure. Disruptive selection causes polymorphism: the continued existence of 2 or more distinct phenotypes in a species.

What is evolution

A change in allele frequency

What is behavorial adapatation

A behavioral adaptation is an inherited characteristic behavior that helps an organism survive and reproduce in its environment by allowing them to respond to certain stimuli. These behaviors can be instinctive or learned and often involve complex coordination of sensory, neural, and motor systems.

Examples of behavorial adapatations

Migration patterns, foraging behavior and mating rituals

What are anatomical adapatations

Anatomical adaptations are physical structures or features that enhance an organism's survival and reproduction in its specific environment. These adaptations are often the result of natural selection acting over many generations, favoring traits that provide a selective advantage. These can vary greatly, depending on the organism and its environment.

Examples of anatomical adaptations

The thick fur of animals living in cold climates, cactus’ spines detract prey from eating them

What is physiological adaptation

Physiological adaptations are internal systematic responses to external stimuli that help organisms survive and reproduce in their environment. These adaptations involve changes or adjustments in the internal biological processes of an organism. They are crucial for maintaining homeostasis and optimal function in varying environmental conditions.

Examples of physiological adaptations

Temperature regulation, osmoregulation and chemical balances. Camels coverting their fat into water.

What is Artificial classification

Divides organisms according to differences that are useful at the the time. Such features may include, colour,size, number of legs, leaf shape etc. These are described as analogous characteristics where they have the same function but do not have the same evolutionary origins.

What is Natural classification

It is based upon the evolutionary relationships between organisms and their ancestors, classifies species into groups using shared features derived from their ancestors. Arranges the groups into a hierarchy in which the groups are contained within larger composite groups with no overlap. Relationships are based upon homologous characteristics

What is the Binomial system

The way in which an organism is named

What is the scientific name for humans

Homo sapien

What is the Hierarchy of the taxonomic ranks

Ki - Kingdom

P - Phylum

C - Class

O - order

Fa - Family

G - Genus

S - Species

What is the definition of genetic diveristy

The total number of different alleles in the population.

What is a population

A group of individuals of the same species that live in the same place.

What is a species

A group of organisms that are able to interbreed with one another to produce fertile offspring

What is a niche

The role of a species inside of its habitat

What are recombinant chromatids

Some genetic material merged with other genetic material

What are extremophiles (with examples)

Organisms that can live in extreme environments, such as bacterial that are found at the bottom of the ocean near deep sea vents. (Can withstand high heat and pressure)

What are the 3 domains

Archaea, bacteria and Eukarya

Cell structure, Type of DNA and if they contain Membrane bound organelles of the 3 domains

bacteria, archaea and eukarya respectively

Cell structure → Prokaryotic, prokarotic, eukaryotic

Type of DNA → circular, circular, linear

Membrane bound organelles → no (70s ribosomes), no (70s ribosomes), yes (80s ribosomes)

Do they contain introns?, How many proteins does RNA polymerase work on and can they grow at 100 degrees for the 3 domains

bacteria, archaea and eukarya respectively

Do they contain introns? → No, Some, yes

How many proteins? → 5, 8-10, 12

Can they grow at 100 degrees? → no, some can, no

Do they contain a cell wall of peptidoglycan?, Do they have a cytoskeleton?, are they poisoned by diphtheria toxin? (bacterial toxin), are they sensitive to streptomycin (antibiotic)?

bacteria, archaea and eukarya respectively

Cell wall of peptidoglycan → yes, no, no

Cytoskeleton → no,no yes

Poisoned by diptheria toxin → no, yes, yes

Sensitive to steptomycin → yes, no, no

Explain the process of evolution via natural selection

• There is a variety of different phenotypes within a population

• An environmental change occurs and as a result of that selection pressure changes

• Some individuals. Possess advantages alleles, which give them a selective advantage and allow them to survive and reproduce

• The advantages alleles are passed on to their offspring

• Over time, the frequency of alleles in a population changes and this leads to evolution

What is DNA Hybridisation

A method of analysing how similar DNA from different species are to each other

• DNA from 2 species is extracted and purified and cut into small species

• DNA is heated to about 90 degrees to break the H bonds (seperate the strands)

• On cooling, the strands combine (anneal) with others that have a complimentary base sequence. The more similar, the more H bonds.

• The hybrid molecules are then heated, the higher the temperature needed to break the strands apart = more Hydrogen bonds so the more closely related the species.

What is cytochrome C

It is a small haemoprotein found loosely associated with the inner membrane of the mitochondria.

What are the 3 types of diversity

Species diversity, habitat diversity, Genetic diversity

What is Habitat diversity

The range of different habitats or number of ecological niches per unit area in an ecosystem, community or biome.

What is species diversity

The variety of species per unit area. This includes both the number of species present and their relative abundance

What is Genetic diversity

The total number of different alleles in a population

What is species richness

Number of species in a community

What is species eveness

How spread out species are in a community

What is a diversity index

This a quantitative measure (numerical value) that reflects how many different types of a factor (such as species) there are in a dataset (A community)