Biology Module 5

Asexual reproduction is the production of genetically identical organisms from a single parent without fertilisation/fusion of gametes. The offspring have exactly the same genes as the parent - so there's no genetic variation.

Sexual reproduction usually involves two parents producing an offspring that have a combination of the genes of each parent, resulting in offspring that are different to each other and to the parents. Involves the fusion of gametes

parthenogenesis is a natural form of asexual reproduction in which an egg developes into an embryo without fertilization and within a single parent

Diploid cells contain two complete sets (2n) of chromosomes.
- Embryo, fetus, somatic cells
Haploid cells have half the number of chromosomes (n) as diploid
- Gametes

- Genetic variation
- Survival of the species

- energy and time costly (mating, courtship, production of gametes)
- usually sacrifices the fitness of one sex to the other eg: the mother (one species is left vulnerable)

External fertilization is a type of reproduction in which the sperm of a male creature fertilizes the egg of a female organism outside the female's body. Eg; amphibians and fish

- Wide dispersal of young, which reduces competition for food and other resources with their parents

- Less energy used to reproduce and in parental care, so the parent has more energy for their own survival (e.g. finding food or escaping predators).

Internal fertilization occurs when the sperm fertilizes the egg inside the female; there are three methods: oviparity, viviparity, and viviparity. (Dont need this)

- Increased chance of successful fertilisation
- Fewer eggs needed
- Offspring can be retained internally for protection and/or development
- Higher offspring survival rate

Internal: Terrestrial (land) Environments
- Provides direct protection from desication (drying out on land) , immediate predation and more efficient fertilisation

External: Aquatic Environments
- the moist environment prevents dessication, the water provides a medium for the sperm to travel through to reach the widely dispersed ova

- Runners
- Suckers

asexual reproduction in plants using vegetative parts of the plant rather than through specialised reproductive structures

EG: bulbs, tubers, rhizomes and suckers

Are long, thin, modified stems that grow along the surface of the soil. The runners connect newly established plants to the parent plant, break off and form their own plant. eg; Grasses

Modified roots that extend out from the plant, in which the outer roots may grow obliquely upwards forming its own shoot. eg; Pineapple

Sexual reproduction in plants also relies on the fusion of male and female gametes. This can prove challenging as plants cannot move! Therefore, they rely on other agents to carry the male gametes to another parent plant.

Male Gamates = Pollen Grains from anthers

Female Gamates = Ovules from the ovary

Pollinating agents include wind and animals. Plants also rely on wind, water and animals to disperse their seeds away from the parent plant to reduce competition

Once seeds have formed they must be dispersed, preferably over a large distance to prevent over crowding and reduce competition for resources.
Widespread distribution is also an advantage to increase the chance of continuity of the species in the face of a changing environment or natural disaster. Many plants have adaptations that increase the chance of seed dispersal:

- Fleshy fruits that are eaten by animals and the seeds are dispersed when the animal defecates

- Seeds are adherent so stick to animals fur, feathers, etc.

- Dry fruits, possibly with "explosive" mechanisms to allow air dispersal.

- May have light or other structures that enable them to catch the air so they can stay adrift longer.

The flowers have adaptations to attract the animals which are in search of a reward such as nectar. As they search for the nectar, pollem rubs onto their bodies and is then deposited on to the next flower they visit.

Male Parts (Stamen)
- Anther - Produces pollen
- Filament - Supports Anther

Female Parts (Pistil)
- Stigma - Sticky bulb that catches pollen
- Style - Passage way for pollen grains to Ovary
- Ovary - Holds/produces eggs awaiting fertilisation

When conditions are favourable Fungi reproduce asexually as this requires less energy and fewer nutrients.

However when conditions are not suitable, fungi can induce a sexual phase in the reproductive cycle

Budding involves the production of a small bud from an adult organism that can then separate from the parent and grow into a new individual.

Spores are small, unicellular reproductive cells that are produced in great numbers by the fungi from structures called sporangia. These spores are light and can easily be dispersed by agents such as wind, enabling the fungus to move into new environments. Note that this differs from pollination and seed dispersal as the spores do not need to fuse with gametes from another organism.

- The parent first replicates its genetic material
- The nucleus then divides and one copy moves into the bud while the other remains in the parent.
- When it grows to a size where it can survive on its own, it will break away from the parent.
- This can continue as long as there are sufficient nutrients in the environment.

Bacteria reproduce by binary fission - this means splitting in two.
Once the bacteria cell reaches full adult size it replicates its DNA then splits into two with both cells having identical genetic material.

A form of asexual reproduction in which the parent divides into two approximately equal parts with genetically identical material.

Most Protists reproduce through binary fission which involves mitosis.

Mammals reproduce sexually, using internal fertilisation which aids their success in the terrestrial environment.
While a few species lay eggs (monotremes) or give birth to underdeveloped young that further develop in a pouch (marsupials), most mammals are placental mammals.

Where the embryo implants into the uterine wall and gains nutrients from the rich lining until the placenta is formed, providing nutrients, oxygen and protection for the developing young.

Fertilisation refers to the fusion of the nuclei of the sperm and the ovum (egg). Both the sperm and the ovum are haploid, meaning they have a half set of chromosomes, and they fuse to form a diploid zygote which has a full set of chromosomes.

After fertilisation, the zygote divides and continues to do so, eventually forming a cluster of cells called a blastocyst at around day 3-5. The blastocyst travels into the uterus and attaches to the uterine wall - this is known as implantation. Implantation usually occurs 6-12 days after fertilisation. The embryo obtains nutrients from the lining of the uterus until the placenta can be formed

Placenta is an organ that develops in the uterus during pregnancy. This structure provides oxygen and nutrients to a baby while removing watse from its blood. It is usually formed at around 12 weeks

The temporary hormone-secreting structure that develops for early pregnancy only if the ovum has been fertilised and implantation has occured, otherwise it just degenerates prompting menstruation.

1. hCG
2. Progesterone
3. Oestrogen
4. Prolactin
5. Relaxin
6. Oxytocin

Hormone produced by the placenta after implantation to sustain pregnancy by supporting the function of the corpus luteum and stimulating the ovaries to produce estrogen and progesterone

- This is detected by pregnancy tests

A hormone that helps establish the placenta and stimulates the growth of blood vessels that supply the womb and strengthens the pelvic wall muscles for labour

Oestrogen helps the uterus grow, maintains its lining and helps foetal organs develop

A hormone that stimulates milk production and the growth of the mammary gland (where breast milk is made)

A hormone that inhibits uterus contractions to prevent premature birth. It relaxes blood vessels, increasing blood flow to the placenta and kidneys.

a hormone that rises at the beginning of labour by stimulating the contractions of the uterine muscles and increases the production of prostaglandins (help dilate your cervix (make it wider) and cause uterine contractions)

Mitosis is a process where a single cell divides into two genitically identical daughter cells (cell division).

This cell division generates new cells for growth and repair.

Mnemonic - I PMAT

interphase, prophase, metaphase, anaphase, telophase

- The stage where DNA replicates in preperation for cell division - resulting in two identical sets of chromosomes

- Outside of the nucleus are two centrosomes each containing a pair of centrioles (critical for cell division)

Think P for pairing/preparing:

- The chromosomes condense into x shaped structures, each chromosome is composed of two sister chromatids containing identical genetic information

- Each Chromosome pairs up with their respective pair

- At the end of prophase the cell membrane disolves and the centrosomes move to opposite poles

Think M for Middle:

- The chromosomes line up neatly END TO END in the equator of the cell

- The centrosomes are at opposite poles of the cell with the mitotic spindle extending from them

- The mitotic spindle fibres attach to each sister chromatid and their centromere

Think A for Away/Apart:

- Spindle fibres contract pulling the sister chromatids apart to opposite poles of the cell

- Sister chromatids are now regarded as two seperate chromosomes

Think T for Two new cell nuclei:

- At each pole, a full set of chromosomes are gathered together with a nuclear membrane forming around them

- Cytokinesis is occuring concurrently

Division of the cytoplasm:

- The single cell pinches in the middle to form two new genetically identical daughter cells each containing a full set of chromosomes within a nucleus

the cytoplasmic division of a cell at the end of mitosis or meiosis, bringing about the separation into two daughter cells.

The process by which a single cell divides twice to form four haploid, genetically different sex cells (gametes)

Interphase:
- The DNA in the cell is copied resulting in two identical full sets of chromosomes.

- Outside the nucleus are two centrosomes containing a pair of centrioles (critical for cell division)

Prophase I: one cell
- Each Chromosome (composed of two gentically identical sister chromatids) condense into X shaped structures

- The pairs of chromosomes pair up, where they may exchange bits of DNA in a process called crossing over or recombination

- The Membrane around the nucleus in the cell dissolves away

Prophase II: two cells
- In each of the two daughter cells, the chromosomes condense again into X shaped structures

- The membrane dissolves away again, with the centrosomes moving to opposite poles and meoitic spindle forming again

the exchange of genes (DNA) between homologous chromosomes, resulting in a mixture of parental characteristics in offspring.

Metaphase I: one cell
- The chromosome pairs line up NEXT TO eachother along the equator of the cell (Not end to end - mitosis)

- The centrioles are at opposite poles with the meotic spindle extending from them

Metaphase II: two cells)
- Chromosome pairs line up END-TO-END along the cells centre

- Meoitic spindle fibres attach to the centromere of each the chromosomes

Simply where the homologous chromosomes are randomly shuffled into the two daughter cells, causing genetic recombination in Meoisis I (Anaphase & Telophase)

The Law of segregation is simply the equal and random seperation of allele pairs during meosis II so that they can transfer specifically to different gametes
(independant assortment)

Anaphase I: one cell
- The pair of chromosomes are pulled apart by the meotic spindle, with two complete sets of chromsomes at each pole of the cell

- Independant assortment occurs (homologous chromosomes randomly shuffled into daughter cells)

- Note that the sister chromatids stay together (X shape), this is different from Mitosis where they are pulled apart

Anaphase II: two cells
- The sister Chromatids are now pulled apart to opposite poles of the two cells (due to the meoitic spindle)

- The seperated chromatids are now considered individual chromosomes

Telophase I and Cytokinesis: one cell
- The full set of chromsomes at opposite poles of the cell gather together

- The cell pinches and a cell membrane begins to form around each of the chromosome sets creating two new nuclei and daughter cells

Telophase II and Cytokinesis: two cells
- The chromosomes complete their move to the opposite poles of the cell, with each pole containing a full set of chromosomes (Note, Haploid cells have a full set of chromosomes for THE CELL, half of a diploid cell)

- A membrane forms around each set, creating two new nuclei.

- Random segregation

4 haploid daughter cells (gametes):
- In males these are all sperm cells
- In females, one is an egg cell and the rest are polar bodies

deoxyribonucleic acid, a self-replicating material present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.

The process by which DNA makes a copy of itself at cell division. It is a highly controlled process, involving a number of different enzymes

AT2 (2 hydrogen bonds)
GC3 (3 hydrogen bonds)

Antiparallel 5' to 3' (pronounced 5 prime to 3 prime)

1) Helicase
2) DNA Polymerase
3) Primase
4) Ligase

Known as the 'Unzipping enzyme', it is responsbile for the breaking up of hydrogen bonds at the origin and/or the unwinding of DNA strands

Joins individual nucleotides to make complementary strands in a 5' to 3' direction (moves along old template 3' to 5' direction), proofreads the sequence of bases and corrects any errors

Synthesizes an RNA primer which instructs DNA polymerase where to begin

joins Okazaki fragments together

Short lengths of single-stranded DNA produced by the discontinuos replication on the lagging strand.

DNA replication has the possibility of mutation (including subsitution, deletion or insertion of bases and duplication or translocation of chromosomes) giving rise to variations that lead to evolution and speciation.

Prokaryotes:
- Found freely in the cytoplasm and circular in shape

Eukaryotes:
- Contained within a nucleus and linear in shape

1) Transcription
2) Translation

The process by which RNA is synthesised from a DNA template

1) RNA polymerase binds to a section on DNA called the promoter, causing the DNA molecule to unzip

2) The sense strand of DNA acts as a template assembling nucleotides, forming a complementary single stranded mRNA molecule (messenger RNA)

3) The mRNA will have the same bases as the antisense strand except Thymine is replaced with Uracil

4) The mRNA strand then exits the nucleus and makes its way to the cytoplasm where ribosomes are located

The one strand of DNA that is used to make a protein.

The strand of DNA that is not used which carries the complementary sequence of bases, which is transcribed into mRNA.

The process by which RNA is used to produce proteins is called translation.

1) Ribosomes move along mRNA strand and attach tRNA (transcript RNA) molecules to the mRNA. This is done by temporarily pairing the codons of mRNA with the anti-codons of tRNA

2) The amino acids from the tail end of the tRNA are linked together by an enzyme to form a polypeptide

3) The tRNA molecules travel away from the mRNA, back to the cytoplasm where they can be reused.

4) The polypeptide chain is then processed in the cell, joined and folded correctly for it functioning and the forming of its final protein product

a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule.

tRNA = Anticodon
mRNA = Codon

mRNA is broken down into its individual nucleoutides which can then be reused

mRNA carries genetic information (in the form of codons) from the DNA in the nucleus to the ribosomes in the cytoplasm, where it serves as a template for protein synthesis during translation.

tRNA reads the genetic code on the mRNA, pairs with respective base pairs (anti-codons) and ensures the accurate alignment of amino acids in the growing polypeptide chain according to the mRNA template.

an anticodon that is a complement to the mRNA codon at one end and a sepcific amino acid at the other

The genotype is the set of genes in the DNA responsible for a particular phenotypic trait.

The phenotype is the physical expression of that trait, as a protein or physically observable characteristic. eg; hair

the process by which DNA directs protein synthesis which determines the physical and chemical features of each cell type and the overall phenotype of the organism.

genotype and environmental conditions/factors

eg; Blood type = Solely genotype
Height and Weight = Both Genotype and environment (diet)

DIET - Nutritional deficiencies = stunted growth, development abnormalities
TEMPERATURE - Biochemical reactions, enzyme activity and metabolic rates = cellular processes, morphological abnormalities and phenotypic plasticity

the ability of an organism to change its phenotype in response to changes in the environment.

If environmental factors have a strong influence, the phenotypic plasticity is high

Primary Structure: This is the sequence of amino acids in a polypeptide chain, linked by peptide bonds. The primary structure determines the final 3D structure of the protein.

Secondary Structure: This involves the local folding of the polypeptide chain into alpha-helices and beta-pleated sheets, stabilized by hydrogen bonds between the backbone atoms

Tertiary Structure (globs): The three-dimensional shape of a protein created by attraction between folded and pleated polypeptides creating a more complex shape.

Quaternary Structure: This is the arrangement of multiple polypeptide chains into a single functional protein complex. Not all proteins have a quaternary structure; it's only applicable to those made up of more than one polypeptide chain.

SHITS ME:
S - structure (membranes)
H - hormones (insulin)
I - immunity (immunoglobins and other antibodies)
T - Transport (haemoglobin - oxygen transport molecule)
S - sensation (rhodspin - light sensitive receptor)

M - movement (actin in muscle fibres)
E - Enzymes (amaylase)

1) Genetic recombination in Meoisis.
- crossing overandom segregation allowing for independant assortment

2) Fertilisation/fusion of Gametes
- Completely randomised (50% paternal, 50% maternal)

3) Mutations/variations in gene content

Diagrams that are used to show inheritance of a gene in a family over multiple generations. Pedigrees can enable us to determine whether an inherited trait is recessive or dominant, autosomal or sex-linked.

Homozygous: PP or pp. Carries two of the same alleles.

Heterozygous: Pp. Carries two different alleles.

Gene = a section of DNA that holds informtation for a particular trait

Allele = A variation of a gene

Sex linkage occurs when genes on the sex chromosomes (X or Y) code for characteristics other than determining the sex of the individual.

eg: red-green colour blindness, haemophilia, male pattern baldness

Co-Dominance is when both alleles are equally expressed in the phenotype of a heterozygote. eg: Red and white spots on

Incomplete Dominance results in a blend of the two alleles eg: red and white flowered plants = pink heterozygous offspring

The frequency of an allele in a population refers to the proportion of the population that have that given allele

Find the number of times an allele occurs in a gene pool, compared to the total number of alleles in that pool for the same gene
(n. of specific gene/total n. of genes within the population)

Single Nucleotide Polymorphism- a single base pair change (point mutation) in either a coding or non-coding part of the genome, that occurs in atleast 1% of the population

Most commonly in non-coding DNA and thus not observable in the phenotype

A SNP is a point mutation in a segment of DNA that occurs in more than 1% of the population

SNPs provide genetic markers used to distinguish individuals. A genetic marker is defined as a sequence of DNA at a known position (locus) on a chromosome

DNA Sequencing
DNA Profiling

Involves determining the exact order of nucleotides in DNA.
- Biologists isolate fragments of DNA and can study a single gene or determine the sequence of the entire genome.
- It involves a sequence of complex techniques to isolate, amplify (make many copies) and "read" the sequence of nucleotides. Techniques such as the Sanger method and the Maxam-Gilbert method may be used for DNA sequencing.

A technique used to identify or compare individuals by their DNA and more specifically their STRs (short tandem repeats) that are unique to each individual. These STRs are in the non-coding region of DNA and are repeated many times.
- This is useful in areas such as forensic investigations, paternity testing and evolutionary studies.

- Isolating DNA e.g. obtaining nucleated somatic cells, such as saliva, blood, cheek cells, etc.
- PCR (polymerase chain reaction) is used to amplify the amount of DNA being studied.
- The DNA segments are then separated by length, using gel electrophoresis. Smaller fragments have fewer repeats so will move further on the gel.
- Samples can then be used to identify and compare samples.

Non-coding regions in eukaryotic genes that are removed during RNA splicing.

Coding regions in eukaryotic genes that are joined together to form the final mRNA sequence.

Population genetics is the study of genetic variations in a population, including changes in allele frequency.
- Conservation management: Past extinction events
- Inheritance of a disease: the BRCA gene
- Human evolution (Human Genome Project (HGP))

An international effort to decode the entire sequence of the human genome, completed in 2003