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HUMAN BIOLOGY > Evolution mechanisms > Flashcards

Evolution mechanisms Flashcards

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1
Q

What is evolution

A

The change in characteristics, or phenotype of a species over time

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2
Q

How does antibiotic resistance happen

A
  1. Population with 1 antiobiotic resistant bacterium
  2. Diferent bacterium with antibiotic resistance survive while others die from antibiotics. (selection pressure)
  3. Bacterium with antibiotic resistance reproduce and populate the circle
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3
Q

What is a species

A

a group of similiar organsism that are capable of interbreeding under natural conditions to produce offspring

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4
Q

What are variations

A

variations are the differences in traits, or phenotypes, that occur between individuals of the same species.

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5
Q

Reasons for phenotype variation

A

Environmental interactions with genes, alter gene expression in individuals.
Mutations introduce new alleles.

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6
Q

In sexual reproduction, how does the gamete produ ction mix up parent alleles

A
  • Random assortment
    -Cross over and recombination
    -Random fertilization
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7
Q

What is a
Gene
Allele
Population
Gene pool
Allele frequency

A

Gene: a section of chromosome that codes for a protein
Allele: variations of the same gene
Population: a group of organisms of the same species living together at the same place at the same time
Gene pool: the sum of all alleles in a given population
Allele frequency: how often a particular allele of a gene occurs in the gene pool for that population.

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8
Q

How can changes in allele frequency occur?

A
  • New alleles forming as a result of mutations
  • New individuals introduced into a population through migrations, all called gene flow
    -Alter due to selective pressure in environment, which is called natural selection.
    -Occurs by chance, which is called random genetic drift.
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9
Q

What is a mutation

A

A permanent change in the DNA sequence of a chromosome

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10
Q

What is gene mutation

A

A permanent change in the DNA sequence of an individual gene, that will potenitially affect only thje protein produced by that gene. caused by spontaenous mutations.

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11
Q

Chromosome mutation

A

A permanent change in the DNA sequence of part or all of a chromosome, which will affect many genes and therefore production of protein.

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12
Q

Germline vs somatic cells in terms of mutations

A

Mutations in somatic cells occurs in affected body cells and daughter cells,. Germ line cells affect gametes and have the potential to be inherited or passed on to the next generation, so they are incorporated into every cell in the offspring.

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13
Q

Causes of mutations induced

A

Mutagens: a chemical or physical agent capable of inducing changes in the DNA causing a mutagen. e.g radiation, chemical agents, viruses and antibiotics.

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14
Q

How can mutagens cause mutations in the DNA sequence

A
  1. Radiation can directly damage the DNA structure
  2. Trigger DNA replication errors
  3. Can block DNA replication
  4. Can chemically react with and then modify the DNA structure
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15
Q

Cause of mutaitons - spontaneous

A
  1. DNA replication: random mistakes can happen during the s phase of the cell cycle when producing new strands when DNA is unzipped
  2. Crossing over: non homologous chromosomes can tangle and recombine, the reattachment of chromatids during recombination
  3. Non-disjunction: when during metaphase 1 the chromatids may fail to seperate causing an extra chromosome in some and less in some. - called aneuploidy
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16
Q

A point mutation

A

random mistakes that occur during DNA replication that involve a change in a single nucleotide within the DNA sequence

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17
Q

When does a frameshift occur

A

when there is an insertion of a new nucleotide into the DNA sequence, or there is a deletion of a nucleotide within the DNA sequence

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18
Q

Chromosomal mutations are caused by

A

-Spontaneous mutations during cell division
-Mutagens that can caus damage to DNA

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19
Q

What are the 4 errors during cell division

A

Deletion: a chromosome may undergo double strand breaks at two position causing the section to drop out with the genes with it.
Translocations: Sometimes the chromatid of one chromosome breaks off and reattaches to another chromosome
Duplications: when an extra copy of a section of a chromosome is made and is inserted into the same chromosome - harmful
Inversions: occurs if a chromosome breaks in two places and the segment rotates 180 and rejoins, reversing the normal sequence in genes.

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20
Q

Down syndrome

A

Extra chromosome/trisomy
- Facial expressions, small eyes, small nose
-Intellectual disability, weak muscles

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21
Q

turner’s syndrome

A

Monosomy/Missing 1 chromosome where females are missing an x chromsome
- teeth problems
-Large number of moles
-A broad chest and wide nipples
-arms that turn out slightly at the elbow

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21
Q

Klinefelter’s syndrome

A

Trisomy for males with an extra x chromosome
- Small testes that do not produce sperm
-Breasts are enlarged
-Occasional intellectual disability

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22
Q

What are harmful mutations and examples of it

A

Ones that reduce the survival capacity/lifespan of the organism. This also means that this mutation is less likely to be passed onto offspring. e.g cancer

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23
Q

What are neutral mutations and examples of it

A

have no observable effect on the phenotype of an organism and therefore has no effect on their survival in their environment. e.g heterochromia

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24
What are beneficial mutations and examples of it
Helpful to an organisms survival in their environment. Must affect phenotype. e.g HIV resistance
25
Impacts of mutations on gene pools
A mutation introdcues new alleles into the gene pool. - If the mutation is benefecial, the allele would likely increase in the gene pool over time as individuals are more likely to survive. - If the mutations is harmful the freqency of this new allele would be expected to decrease in the gene pool over time as the individual that have this mutation are less like to survive.
26
Difference between gene mutation and chromosomal mutations?
Gene mutations only occur in genes and affects only the production of protein that that specific gene codes for whereas chromosomal mutations affect the functioning of multiple genes and sometimes the whole chromosome.
27
Silent mutation vs nonsense mutation vs missense mutation vs neutral mutation
Silent mutation: a change in the DNA sequence does not cause a change in amino acids and therefore the protein is produced Nonsense mutation: a change in the nucleotide sequence to the codon to stop, which will result in a shorter peptide chain affecting the function of a protein. Missense mutation: can cause a change in the single amino acid, but the replacement amino acid is having the same properties as the original amino acid. Structure is not affected. neutral mutation: can cause a change in the amino acid, but the repla
28
What is duchenne muscular drsytphy
A condition that causes skeletal and heart muscle weakness inherited on the x linked pattern. Caused by spontaenous or inherited genetic mutation.
29
What is cystic fibrosis
Inherited disease caused by mutations in a gene called CFTR. the CFTR gene provides instructions for the protein linked. It is a progressive, genetic disease that affects the lungs, pancreas and other organs.
30
Darwins 3 inferences
1. Because of the excessive birth rate and limited resources there must be a struggle for existence. 2.As there was a range of variations in a any species, those with charactersitics best suited to their environment are likely to survive and reproduce also known as survival of the fittest.
31
Darwins 3 observations
1. Variation: all members of a species show variations that are inherited onto the next gen 2. Birth rate: darwin realized that all living organisms reproduce at a rate higher than that of which their food supply increases 3. Nature's balance: although the birth rate of organsisms was very high each spcies number remain constant
32
What is natural selection
The process where orgransms that are best suited to the environment seruve and reproduce and pass on their genetic traits to their offspring where populations adapt and evolve.
33
Descent through modification
changes in a species over generations from an ancestral species
34
Evolution is defined as
The change in the characteristics, or phenotypes, of a species over time. 2. A permanent change in allele frequencies of a population over time.
35
Fitness: Selective agent: selection pressure:
Fitness: the capacity of an organism, or species, to survive and reproduce in the environment. Selective agent: environmental factor acting on a population that effects survival and reproductive success Selection pressures: climate, competition, predators, and pathogens
36
Impact of natural selection on gene pools
-The environment selects the phenotype that is best suited to aid an organisms’ ability to survive and reproduce -alleles that produce favorable characteristics gradually increase in frequency in the gene pool over time. -Alleles that do not produce favorable characters gradually decrease in frequency in the gene pool over time.
37
Evolutionary mechanisms
event/process that leads to a change in allele frequency in a gene pool
38
Random Genetic Drift
Changes in allele frequency in a population due to chance events ➔ Affects all populations but is particularly significant in small, isolated populations
39
Founder effect
-the loss of genetic variation due to a migration of a subset of individuals of a larger parent population. -the new founder group no longer represents the genetic variation of the original parent population. ➔ As a result, genetic variation is limited and over subsequent generations gene fixation and loss may occurs -small population can also lead to interbreeding which decrease genetic diversity
40
Bottleneck Effect
an event that severely reduces the size of a population e.g. environmental catastrophe -the smaller group that survives is significantly reduced in terms of genetic variation and it no longer represent the genetic makeup of the original population
41
Gene flow
: the movement of allele from one population to another.
42
Barriers to gene flow
Geographical Barriers: Mountain range, river, ocean 2. Sociocultural Barriers: Religion, language, politics, economic status, educational background.
43
What is Sickle Cell Disease (SCD)
a group of blood disorders that results in abnormality of the beta haemoglobin protein in the red blood cells.
44
Causes of sickle cell
-the HBB gene codes for one of the beta globulin proteins that make up haemoglobin in the red blood cells -SCD is caused by a point mutation in the DNA sequence of the HBB gene found on chromosome 11
45
Symptoms of SCD
fatigue and shortness of breath
46
microevolution
means changed in allele frequencies in a population over time. Involves five mechanisms: Mutations, Natural Selection, RGD, Gene flow (migration), Barriers to gene flow.
47
Isolation in pics
* A geographical barrier, or sociocultural barrier, forms dividing the population into two. * Each population has its own separate gene pool and gene flow is restricted between the two populations.
48
Selection in pics
Because of the excessive birth rate and limited resources, there must be a struggle for existence. * Each population is subjected to different selection pressures. Some variations may provide individuals with a selective advantage in the environment in which they live. * In each population, those individuals with favourable characteristics survive and reproduce,
49
speciation
Over a long period of time the changes in gene frequencies in the gene pools of the two populations may become great enough that eventually the two populations can no longer interbreed to produce fertile offspring.
50
PCR and what it does
PCR: polymerase chain reactions ➔ Used to amplify, or make many copies of, a specific sequence of DNA
51
primer
a short strand of DNA that are complimentary to part of the sequence. important because DNA polymerase can only extend a DNA strand from an existing nucleotide
52
Role of Taq polymerase
catalyze the formation of new DNA molecules from free nucleotides.
53
Denaturation
95 degrees -Heating of DNA to separate the strands, breaking apart hydrogen bonds
54
Annealing
50-60 degrees -a primer binds (anneals) to the complimentary base sequences on opposite ends of each strand -Reduced temperature allows base pairing and the formation of hydrogen bonds
55
extension
72 degrees -Starting from primers, new DNA strands are synthesized in the 5’ to 3’ direction using enzyme and the available nucleotides.
56
Gel electropheresis def
: a technique that separates fragments of DNA according to their size and charge
57
Gel electriphoresis is used for
Forensics ➔ Paternity testing ➔ Establishing evolutionary relationships based of genetic evidence ➔ Identifying whether an individual has a genetic disease or carrier ➔ DNA sequencing
58
Process of gel electropherisis
1 DNA pieces are loaded at one end, the negative terminal, of a bed of agarose gel. 2 An electric current is passed through the gel 3 DNA is negatively charged so it moves through the gel to the positive electrode 4 DNA pieces move through the gel at different speeds, smaller pieces moving faster than larger ones 5 Bands form, called a DNA profile
59
what is DNA sequencing
: the process of determining the precise order of nucleotides within a DNA molecule
60
prcoess of DNA sequencing
Process (SANGER METHOD) 1. Amplify and Denature DNA is amplified using PCR and then denatured usually using heat 2. Set up four separate reactions. 3. Annealing Primer attaches to complementary sequence of the template DNA 4. Extension DNA polymerase uses free nucleotides to build new DNA strands. These strands are various lengths due to the of presence of terminator nucleotides. 5. Separation and analysis Once the four reactions are complete, a gel electrophoresis is run. Each reaction mixture is placed onto a lane to produce a total of 4 lanes
61
similiarities of the two DNA methods
-both methods use dideoxynucleosides to create fragments of variable lengths -both methods require a primer to allow DNA polymerase to begin adding free nucleotide -fragments are separated using the principle of gel electrophoresis with smaller fragments moving faster -Both will result in the identification of the base sequence in an unknown template strand of DNA -Both supplied with free nucleotides to synthesize the new DNA fragments -Both use PCR to amplify the DNA template fragments to be sequenced.
62
differences of the two DNA methods
-Sanger method is a manual process requiring scientists to create and read the DNA profile. Modern sequencers are automated and are run and read by computers -Sanger method uses radioactively labelled primers to make the DNA fragments visible in the gel Modern sequencers have individually fluorescing nucleotides. -Sanger method separates fragments into four separate lanes on the gel. Modern sequencers use a capillary tube to run the gel as a ‘single gene’.
63
comparative genomics
By comparing genomic sequences researchers are able to identify regions of similarity and difference: ➔ Study evolutionary changes among organisms ➔ Identify genes that are preserved among species ➔ Identify genes that give each organism it's unique characteristics
64
ERV AND NON CODING DNA
Non-coding DNA: is DNA that has no apparent function and appears to serve no purpose ERV: an endogenous retrovirus is a viral sequence that has become part of an organism’s genome. -ERVs become part of an organism’s genome when converted viral DNA from a virus becomes inserted into one of the cell’s chromosomes. Only becomes endogenous if the host cell can become inherited by next generation
65
Mitochondrial DNA
Small circular with 37 genes and 16500 base pairs, mitochondrial DNA is maternal inheritance onlyu
66
use of mtDNA for evolutionary relatedness
-lots of mitochondrial DNA, easier to find and extract than nuclear DNA -mtDNA has a higher mutation rate than DNA. Amount of mutations in the mtDNA is roughly proportional to the amount of time that has passed. -Less difference in the mtDNA means species are closely related and maternal ancestor was recent -More difference in the mtDNA means species are distantly related and maternal ancestor was ages ago
67
Ubiquitous proteins
: proteins that appears to be in all species.
68
Cytochrome C
A ubiquitous protein. An enzyme that has a role in cellular respiration
69
Radiocarbon dating is used to date
organic material (contains carbons) -recent fossils -up to 60000 years -artefacts- usually found in association with charcoal from fires -date charcoal then can determine age of artefact
70
Limitations of radiocarbon dating
-material must be organic -Date up to 60000 years old, after this there is usually not enough C-14 left to measure -Need a decent sample size (min 3grams) -Ratio of C14 to C12 in the air is not constant
71
Potassium-Argon Dating
-when igneous rocks are heated to the melting point, any AR-40 (noble gas) contained in them is released into the atmosphere -when the rock recrystallizes it becomes impermeable to gasses again -As K-40 in the rock decays into Ar-40, the gas is trapped in the rock and builds up over time

HUMAN BIOLOGY (1 decks)

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