biology module 6 HSC

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what are genetic disorders?

• Condition that is caused by abnormality in individuals DNA

• Can be as small as a single-base mutation in just one gene 

• Can be addition or subtraction

what are mutagens?

• Agent that increases rate of genetic mutation by interfering with function of nucleic acids (DNA or RNA)

• Causes any mutation 

• Can be unpredictable and random

• Most mutations have no effect on organism function

• Some may result in phenotypic change to individual 

• MUTAGENS ARE PUT INTO CATEGORIES - chemical, radiation, and biological

electromagnetic radiation

• Ionising radiation

• UV - causes chemical damage to DNA - breaks hydrogen bonds, sugar-phosphate backbone or nitrogenous base changing it so it no longer pairs with corresponding base (can be carcinogenic)

• Radioactive material emit gamma radiation - electrons pass through cells, free radicals such as hydrogen peroxide which can damage DNA

chemical mutagens

• Mutations can also be caused by chemicals 

• Can be inserted into nucleotides during replication resulting in the production of non-functional proteins

• Reactive oxygen species (ROS) such as free radicals 

• Deaminating agents like nitrous acids (convert Cytosine to Uracil by deleting some atoms i.e. amino group) → change one base into another

examples of chemical mutagens

INGESTED CHEMICALS AND ENVIRONMENTAL	HEAVY METALS
Alcohol  Tobacco  Benezene  Asbestos  Pesticides Nitrosamines - chemicals that form in the stomach from food like processed and smoked meats - need metabolic activation - makes them carcinogenic   EXAMPLE: Sausages, when cooked at high temps, causes nitrates and amines to combine forming carcinogenic nitrosamines	Mercury  Arsenic  Cadmium  Can cause sugar-phosphate back bone of DNA to break and can also inhibit enzymes which repair DNA

what are transopons?

• Sections of DNA that spontaneously fragment 

• Relocate or multiply 

• Insert themselves into chromosomal DNA, disrupt function 

genetic mutations

• Each gene is specific due to the order in which the nucleotide base pair is arranged 

• Mutations can occur randomly/spontaneously or can be induced by mutagens 

• Errors or changes in DNA can occur in a single gene, multiple genes or an entire chromosome 

• Most mutations are detected and can be repaired but some cannot 

what is a point mutation?

• Changes to single base pair of DNA and only affect a single gene 

• They can be SUBSTITUTIONS, INSERTIONS AND DELETIONS 

• Frameshift mutations are a result of a deletion or insertion of a nucleotide pair that ‘shifts’ the entire ‘reading’ frame of the DNA

• This may lead to a change in one amino acid or many - may affect function of protein

• Chromosome mutations are large scale where the structure of a chromosome or the entire number of chromosomes is altered

• The outcome of a mutation can result in being beneficial, harmful or neutral to survival

what is a point (substitution) mutation?

One nucleotide is replaced by another, it can result in missense, nonsense and silent mutations

missense mutation?

• Results in different amino acid incorporated into chain during polypeptide formation 

• Different protein will be formed

• Protein may function differently to correct protein and create enormous problems for individual that inherits faulty gene 

example of a missense mutation + amino acid it changes

Sickle cell anaemia; amino acid glutamine (Glu) is replaced by valine (Val) - causes a distortion of the shape of haemoglobin and therefore the red blood cells are sickle shaped

nonsense mutation? (point)

• When a substitution results in a STOP codon (UAA, UAG, UGA)

• stop/terminate protein synthesis 

• Result in incomplete and non-functional proteins

• Genetic disease such as Duchenne muscular dystrophy (DMD) is caused by a nonsense mutation in a gene responsible for a specific protein called dystrophin

example of a nonsense mutation? (point)

Thalassemia - codon 17 of 147 codons codes for STOP instead of lysine. Blood disorder reduces production of haemoglobin

silent mutation? (point)

• Substitution has no effect and the same amino acid is collected at the ribosome 

• Sometimes four or more anticodons that code for the same amino acids 

• When amino acid is added with no effect on resulting protein = no effect on polypeptide or protein

what is a deletion mutation?

• Nucleotide is deleted from DNA code

• Effect is similar to that caused by insertion of nucleotide

• Results in the significant effects on the polypeptide and therefore results in the loss of the functional protein 

• Also frameshift mutation 

what is an insertion mutation?

• One or more extra nucleotides are added to the DNA sequence

• resulting in a difference in the amino acid sequence and the protein that is formed 

• From mutation onwards, amino acids will be completely different, causing a frameshift mutation 

• Results in non-functioning protein 

what is a chromosomal mutation

involve either a change in number of chromosomes or a rearrangement in the structure of a chromosome

what is a duplication (chromosomal) mutation?

when parts of a chromosome appear twice or more

what is a inversion (chomosomal) mutation?

• Chunk of chromosome gets flipped around 

• Breaks and region in wrong way

what is a deletion (chromosomal) mutation?

• Two types - make sure you specify block deletion 

• When chromosomes get deleted 

EXAMPLE —> ABCDEF-GHIJKL

        ABC-GHIJKL

what is an insertion (chromosomal) mutation?

Segment of DNA is added into a chromosome

what is a translocation (chromosomal) mutation?

• When pieces are removed and inserted into another chromosome 

• Results in swapping bits of a chromosome from one chromosome to another 

how do they detect chromosomal mutations?

Chromosome abnormalities are easily detected by observing the karyotype 

Changes in the chromosome number can also occur. give an example

EXAMPLE —> Down syndrome - trisomy 21, Patau syndrome - trisomy 13

• This results in gametes with the incorrect haploid number and therefore incorrect diploid number 

what are somatic mutations?

• Occur in somatic (body) cells due to replication errors prior to mitosis 

• If not repaired will continue to divide amplifying error 

example of a somatic mutation

MELANOMA: a change in a skin cell can lead to melanoma and other skin cancers 

• If the genes involved in DNA repair undergo mutations, serious cancers can develop 

what is a germline mutation?

• Occur in gametic cells and can be passed onto offspring

• The mutation is replicated in every cell of the developing embryo

example of a germline mutation

HAEMOPHILIA —> : the royal family passed down a recessive mutation causing haemophilia - mutation occured in one of Queen Victoria’s gamete cells, her son, ended up with haemophilia and two of her daughters were carriers

what are non-coding dna?

introns

what are coding dna?

exons

description of non-coding dna (introns)

• Not involved in gene expression 

• It can be the introns that are removed after transcriptions 

• Mutations in this DNA have little effect 

• BUT non-coding DNA segments can control the action of regulatory proteins (proteins that act on genes and regulate their functions) - any change will result in a protein to be expressed in the wrong time or place

description of coding dna (exons)

• Transcribed into mRNA and this code is translated into proteins 

• Involved in gene expression

• If DNA is altered by a mutagen that codes for a protein, then this could alter activity of the cell 

• Any change in an exon is carried over into errors in protein production and can result in a non functional protein 

• In some cases, mutations in coding region are harmless

cause of genetic variation in meiosis

• Events that occur during meiosis result in genetic recombination and therefore variation in the gametes are produced

• Crossing over involved exchange of segments of DNA between homologous chromosomes results in all chromatids being genetically different 

• During meiosis, pairs of homologous chromosomes are divided in half to form haploid cells -  results in alleles for different traits sorted into gametes

• independent assortment results in random separation of each pair of chromosomes (random segregation) into 2 possible gamete/sex cells

mutations in meiosis

EARLY: DNA replication - point and frame mutation 

LATER: during separation (nondisjunction) chromosome mutations 

• Mutations can be caused by either exposure to mutagens or spontaneous 

what is genetic flow?

Gene flow occurs when new alleles are added or removed from the gene pool, due to the movement of fertile individuals

what is genetic drift?

Genetic drift occurs due to random chance events and does not involve natural selection

bottleneck effect (gene drift)?

Occurs when a large population reduces suddenly in size

founder effect (gene drift)?

• Occurs when a few individuals become isolated from a larger population

• They form a new population with a gene pool not quite the same as original population

what is biotechnology?

• Use of biological material (living things) or processes to fulfill human needs 

give examples of past biotechnologies.

• fermentation (use of microorganisms), manipulation of animal and plant breeding to produce desired traits (selective breeding)

• Selective breeding - or artificial selection, humans have breed plants/animals for specific desirable genetic traits, the frequency becomes more common in successive generations 

• Plant hybridisation - selective breeding of plants using artificial pollination for improved yield, nutrient value and resistance (disease, drought etc) EG: wheat 

give an example of a modern biotechnology

transgenic organisms (GMO) for medicine and agriculture (golden rice, Bt cotton)

give an example of a future biotechnology.

CRISPR - it uses a customizable guide RNA to direct an enzyme (usually Cas9) to a specific DNA sequence

what is biodiversity?

• Comes from two words Bio meaning life and diversity meaning variability 

• Biodiversity is the variety of all living things; the different plants, animals and micro organism, the genetic information they contain and the ecosystems they form

overview for present biotechnologies

• Accelerated after discovery of DNA - manipulation of DNA is known as gene technology 

• PCR, dna profiling and DNA sequencing used in genetic research such as study of inheritance 

• Genetic technologies such as engineering and techniques like gene cloning, screen, therapy, recombinant DNA technologies are used to manipulate DNA to make specific proteins and also to regulate cell processes to meet the needs of the medicine industry 

• Most common steps = cutting, copying and pasting 

EG: modified bacteria to produce human insulin 

• GMO - genetically modified organism - have a ‘newly constructed genome to pass onto the next generation = transgenic species 

• A shift from selective breeding to genetic modification of animals and plant food, eg: soy and canola 

• Industrial biotech - such as enzyme engineering, bio-nanotechnology and synthetic biology as well as biochemical and bio-material engineering 

give an example of genetic engineering.

• Using enzymes (restriction enzymes) to cut out (DNA splicing) a human gene and insert it into bacteria (recombining DNA - pasting genes, using DNA ligase enzymes to join pieces of DNA)

• Enabling the bacteria to produce human proteins like insulin and human growth hormone 

• The new DNA is from more than one species (bacterial DNA with a human gene inserted) is known as recombinant DNA (rDNA)

artificial insemination process? (simplified)

• Collecting semen from male (mechanical stimulation) then frozen in liquid nitrogen 

• Placed in sterile insemination ‘gun’ 

• Inserted into the vagina to the cervix where semen is deposited

outcomes of artificial insemination (+ve and -ve)

• Important in modern animal husbandry - offspring can be produced with favourable traits such as more meaty, and disease resistant (+ve)

• Used to inseminate many females (+ve)

• Reduces gene diversity (-ve)

• Lack of diversity could endanger the survival of the species (-ve)

• Frozen semen can be stored and transported (+ve) 

• Increases breeding life of male (+ve)

• Important in zoos for endangered species conservation (+ve)

artificial pollination process? (simplified)

• Remove stamens from the plant 

• Dust pollen onto the stigma 

• Of the same plant (self pollination) 

• Of different plant (cross pollination)

outcomes of artificial pollination (+ve and -ve)

• Important in horticulture - produce offspring with favourable traits (+ve)

EG → plant hybrids for flower colour or disease resistant fruit (+ve)

• Increase gene diversity by creating new varieties - introduces new alleles into the gene pool, can improve survivability of crops (+ve)

• Overuse may lead to a specific pest/disease if all plants are too similar (-ve_

EG → irish potato famine (1845-1851) - fungal disease 

• Conservation of endangered plant species - impact on pollinator species such as bees

in vitro fertilisation (IVF) process? (simplified)

Hormone treatment to stimulate egg production

Removal of multiple eggs from ovaries

Fertilisation (eggs and sperm are combined in the lab)

Incubation (hopefully leading to the production of embryos)

Embryos are implanted into uterus, or frozen

OR

• Fertilisation outside of mothers body 

• Zygote grown to a certain stage before implanting into the mother or are frozen 

• Used when decreased fertility in parents

outcomes of IVF (+ve and -ve)

• Gene diversity is reduced due to production of large numbers of viable embryos from small selection of parents (male sperm banks)

• allows for parents who have trouble conceiving to have their own child