Human Biology - Gene pools and evolution (Biotech)

Populations can be represented as gene pools that reflect the frequency of alleles of a particular gene; gene pools can be used to compare populations at different times or locations Natural selection occurs when factors in the environment confer a selective advantage on specific phenotypes to enhance survival and reproduction Gene pools are dynamic, with changes in allele frequency caused by: mutations, differing selection pressures,
random genetic drift, including the founder effect, changes in gene flow between adjoining groups The incidence of genetic diseases in particular populations illustrates the effects of different factors on the dynamics of gene pools, for sickle‐cell anaemia The mechanisms underpinning the theory of evolution by natural selection include inherited variation, struggle for existence, isolation and differential selection, producing changes to gene pools to such an extent that speciation occurs Conduct investigations, including the use of virtual or real biotechnological techniques of polymerase chain reaction (PCR, Gel electrophoresis for DNA sequencing, and techniques for relative and absolute dating, safely, competently and methodically for valid and reliable collection of data Developments in the fields of comparative biochemistry (including DNA and protein sequences) and bioinformatics have enabled identification of further evidence for evolutionary relationships, which help refine existing models and theories Developments in biotechnology, for example polymerase chain reaction (PCR), gel electrophoresis and DNA sequencing, have increased access to genetic information of species and provide evidence for evolution (the process of obtaining a DNA sequence is not required)

Evolution

the change in characteristics of a species over time. It is a gradual change that occurs

over a number of generations, rather than the change of a particular individual or generation.

Population

a group of organisms of the same species living together in a particular place at a

particular time.

gene pool

the sum of all the alleles in a given population

allele frequencies

how often each allele of a gene

occurs in the gene pool for that population

example of allele frequencies

an allele for cystic

fibrosis is found on chromosome number 7. If

the frequency of the cystic fibrosis allele in a

given population is 5%, then among population

members, five in every 100 of chromosome

7 will carry that allele. Ninety-five out of 100

chromosome 7s will have the normal form of

the gene.

whats variation due to

new allele being formed (via mutation)

mutation

a change in a gene or chromosome leading to new characteristics in an organism

gene mutation

changes to a single gene so that the traits normally produced by that gene are changed or detroyed

chromosomal mutation

all parts of chromosome affected

whats the cause of mutations

no known cause but many mutagens (UV rays, radiation, mustard gas)

how does a protein become abnormal/missing

There is a change in the 3 bases coding for a particular protein hence changing the protein it codes for; effects entire body

Albinism

an inherited inability to produce pigment in the eyes, hair and skin

induced mutations

mutation caused by mutagenic agent

spontaneous mutation

mutation caused by error in biological processes (mitosis/meiosis)

somatic mutation

a mutation in body cells

cannot pass on mutation

Germline mutations

a mutation in reproductive cells

can be passed on

Missense mutation

cause a change in the amino acid, and therefore the protein produced

Nonsense mutation

change the base sequence to the code to STOP.

synthesis of the protein will stop, a short protein is produced unlikely to fulfill its function

neutral mutation

cause a change in an amino acid

aa is of the same type and doesn’t change structure of the protein enough to change the function

silent mutation

cause no change in the amino acid/protein produced

what does a gene mutation affect

a single gene

what does a chromosomal mutation affect

a number of genes; may change chromosome structure and cause miscarriages

point mutations

a change in one base of a DNA molecule (nucleotide)

what are the 3 ways point mutations occur

insertion, substitution, deletion,

insertion

a new nucleotide is added to the DNA strand

substitution

an existing nucleotide is replaced with another one

deletion

a nucleotide is removed from the DNA strand

frameshift

a mutation involving an insertion or deletion resulting in a change in the way the sequence is read

codon that codes for an animo acid starts at a different base

affect the outcome of all DNA that point on

what are the 5 ways mutations affect a larger section of DNA

duplication, deletion, inversion, translocation, non-disjunction

duplication

a section of chromosome occurs twice

deletion

a piece of DNA is removed

inversion

breaks occur in a chromosome and the broken piece joins back in, the wrong way around

translocation

part of a chromosome breaks off and is rejoined to the wrong chromosome

non-disjunction

during meiosis, a chromosome pair fails to separate so a daughter cell has an extra chromosome

aneuploidy

a change in the chromosome number as a result of non-disjunction

duchenne muscular dystrophy (DMD)

a genetic disease resulting in wasting of leg muscles and then arms, shoulder and chest

how does duchenne muscular dystrophy occur

through gene mutation

sons inherit the mutation from their mother OR occurs in the male zygote

when does duchenne muscular dystrophy become apparent

the age of 3-5 where muscle weakness becomes evident

eventually death occurs due to failed respiratory muscles

life expectancy is no more than 20-25 years

cystic fibrosis

a disorder caused by a mutation resulting in abnormally thick mucus

what is the cause of cystic fibrosis

mutation found on chromosome 7

gene has code for 1480 amino acids which produce a protein that regulates passage of Cl- ions across the CM

recessive allele is inherited from both parents

what are symptoms of cystic fibrosis

salty-tasting skin, persistent coughing, wheezing, digestive problems

what is trisomy a result of

non-disjunction; failure of 1+ chromatids to separate in meiosis II

Egg/sperm formed have one chromosome too many

trisomy 21

down syndrome

a genetic disorder resulting from an extra chromosome 21

what are symptoms of trisomy 21

characteristic facial expression, intellectual disability, weak muscles, small hands, feet, slanted eyes

partial trisomy

part of a chromosome is attachted to another

patau syndrome

a genetic disorder resulting from an extra chromosome 13

symptoms of patau syndrome

intellectual disability, microcephaly, an extra finger, a cleft palate/lip, malformation of eyes/ears

klinefelter syndrome

a genetic disorder resulting from inheritance of 2 X chromosomes and one Y chromosome

symptoms of klinefelter syndrome

small testes that don’t produce sperm, enlarged breasts and sparse body hair

monosomy

an individual has only one copy of a chromosome instead of 2

partial monosomy

part of a pair of chromosomes is missing

cri-du-chat syndrome

a rare genetic disorder caused by a missing part of chromosome 5

symptoms of cri-du-chat syndrome

meowing-like cry of an infant due to problems with the larynx and nervous system

turner syndrome

a genetic disorder resulting from inheritance of one X chromosome and no other sex chromosome

symptoms of turner’s syndrome

short female stature, lack secondary sex characteristics and are infertile

what do most mutations produce

a recessive allele because they prevent the gene from producing a protein that will be able to function in the body

hence why a person could have multiple mutations and not be aware

why are some recessive mutations lethal

if they are not masked by a dominant allele causing the death of the embryo/foetus by miscarriage

lethal recessives

a recessive allele, that inherited in the homozygous condition, results in the death of the embryo

Tay-sachs disease (TSD)

a genetic disorder caused by a missing enzyme that results in fatty substances accumulating in the nervous system

disorder of lipid metabolism inherited in autosomal recessive pattern

cause of tay-sachs disease

lethal recessive caused by mutation in HEXA gene that codes for the enzyme beta-hexosaminidase

enzyme is responsible for breaking down toxic substances in the brain and spinal cord

missing enzyme results in accumulation of GM2 ganglioside in nervous system that destroys neurons

what are changes in allele frequencies from

due to gene flow brought about by migration

gene flow

the movement of genetic material from one population to another

when individuals move between populations, they enable gene flow

migration

the movement of people from one area to another with the intention of settling permanently

whats an example of alteration of allele frequencies

the Chinese population had a past blood group of Rh-positive, when they began trading with Europeans they introduced the Rh-negative allele

How has ABO blood groups been influenced by migration

The inhabitants of East Asia, Mongols, have a proportionately higher frequency of I(b) allele compared to those living to their west. When the Mongols invaded Western Europ they spread their I(b) genes.

what are the barriers of gene flow

Geographical and sociocultural barriers

Geographical barriers

oceans, mountain ranges, lake systems, deserts

EEG Aboriginal Australians were isolated by ocean barriers

Sociocultural barriers

economic status, educational background, social positions, religion, language

EG Australians tend to marry people of similar educational background

Special creation

the belief that God created all species

evolution

the gradual change in the characteristics of a species

charles darwin

put forward the theory of evolution through natural selection in 1858

why was the galapagos islands important

charles darwin was able to observe the differences and similarities between animals separated by geography and time

how was charles darwin able to observe animals separated by geography

those living on the mainland of south america compare to those on the various islands

how was charles darwin able to observe animals separated by time

animals recently extinct compared to species still alive

what influences charles darwin

carolus linnaeus - established basis of classification/naming system

The principles of Geology book

Thomas Malthus (provided idea of his NS theory)

what did thomas malthus’ essay point out

the human population was increasing at a fast rate exceeding food production

demonstrated that natural reproduction rate exceed avaliable resources

what is the natural selection theory based on

variation, birth rate and nature’s balance

variation observation

species members vary, these variations are passed on generations

birth rate observation

all living organisms reproduce at a rate far greater at which food sources increase

nature’s balance observation

though the birth rate is high, each species’ numbers remain at a constant level

darwin’s 1st interpretation

there must be a struggle for existence because of limited resources yet high birth rates

darwin’s 2nd observation

there was a range of variation in any species, the best characteristics were more likely to survive; survival of the fittest

survival of the fittest

a principle whereby organisms with favourable characteristics survive, but organisms with unfavourable characteristics die before they have the chance to reproduce

how is survival of the fittest possible

because there is variation within any species

members of species differ in physical traits, body functioning and behaviour

selective agent

any factor that causes the death of organisms with certain characteristics, but which has no effect on individuals without those characteristics

body stature natural selection example

Africans have short torsos/long limbs: having a larger SA-vol ratio and lose more body heat in hot environments

Inuit people have long torsos/short limbs: having a smaller SA-vol ratio and lose less body heat in cold environments

sickle-cell anaemia

an inherited disease causing early death; results from the inheritance of 2 alleles for sickle cell anaemia

how did malaria increase

Anopheles mosquito needs pools of water to breed, humans began to clear African forests which created more mosquito breeding sites

The human population increased and more bodies for mosquitos to feed from

symptoms of sickle cell anaemia

clogged blood vessels, pneumonia, rheumatism, heart disease, hands/feet inflammation, anaemia

sickle shaped RBCs

how does sickle cell anaemia result

a person is homozygous for a particular recessive allele

a point mutation in the HBB gene that codes for beta-globulin proteins that make up haemoglobin

Valine is then added instead of glutamic acid that creates a different protein and alters the haemoglobin produced and distorts the RBC shape

heterozygous sickle cell anaemia

show no ill effects unless the oxygen is short of supply

RBCs have milk sickling

anaemia

a condition in which there is a reduced amount of haemoglobin in the blood; or a reduce amount of RBCs

why are sickle cell blood cells dangerous

they are inflexible and become stuck in blood vessels causing a blockage

they cause anaemia, fatigue, jaundice, organ damage, high blood pressure and heart failure

why are those with sickle cell anaemia more resistant to malaria

people with SCA have red blood cells that make it hard for the malaria germ to grow

more common in malaria infested areas

having one sickle cell allele gave them a survival advantage (heterozygote advantage)

heterozygote advantage

a situation where a heterozygous genotype has a higher chance of survival than either homozygous genotype

what is haemoglobin made of

four protein chains that fit together, 2 alpha globin chans and 2 beta globin chains

genetic drift

the occurrence of characteristics in a population as a result of chance rather than natural selection; occurs only in small populations

doesn’t have big effect on populations

whats an example of genetic drift

individuals of Mornington island were separated by ocean barriers but still maintained some contact with the Australia mainland

Individuals of Bentinck island did not have contact and have a high proportion of I9b) allele

Mainlanders have a low proportion of I(b) and high proportion of I(a) allele

founder effect

a type of genetic drift where a new population is formed by a small number of individuals; the small sample size can cause marked deviations in allele frequencies from the original population

how does the founder effect occur

a small group of people move way from its homeland to a new area and establish a population that expands