BIOL1003 Study Guide - Quiz Guide: Gynoecium, Bad Copy, Turner Syndrome
BIOL1003 Genetics
The Study of Inheritance
Heritability of traits is one of the major premises of natural selection
Very little known about the nature of inheritance intil 1900s
oConception by spirit entering woman
oEntire homonculus present in sperm
oAveraging and blending of parental traits in offspring
Uses of genetics
Disease diagnosis and cure
oHaemophilia- earliest acknowledged genetic disease, Jewish law for mothers
not to circumcise their third boy child if first two die from it, changed rules
due to patterns in inheritance
oCystic fibrosis- replacing faulty gene
oSickle cell anaemia
oRh (blood type) incompatibility
Crop and stock improvement (reproductive technologies)
oWheat: hybridisation to produce tetraploids
oFigs: wide variation in size, colour and sweetness in wild plants, selection for
size and sugar content through asexually cultivating them, consistency
achieved by mass cloning
oSheep: selection for milk, meat and wool, sheep no longer drop their wool
oSince over 11,000 years ago:
Wheat: hybridisation to produce tetraploids
Pea: artificial selection for seed size
Figs: mass cloning for yield
Dogs: selection for low aggression
Sheep: selection for milk, meat and wool
oNow: genetic markers, fingerprinting, genetically modified organisms
oHas been doing this for thousands of years but didn’t know what they were
doing
oWent back through the genome to see where each characteristic came from
to find the genome for the trait you want and selectively breed it
Forensics
oLate to use genetics as need to be completely certain so use old technology
that is definite
oIdentity/ paternity testing
Based on blood types from 1920s
Based on proteins from 1940s
First accepted in court in 1950s
Based on HLA (immunochemistry) from 1960s
Based on cutting DNA from 1970s
Based on amplifying DNA from 1980s
Conservation
oImportance of maintaining genetic diversity
Cheetas lost most of their genetic diversity in the last ice age
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BIOL1003 Genetics
Used to spread across the world
Drying out of the Sahara and migration of humans has dramatically
decreased the amount of individuals, and so their genetic diversity
has been lost
Everything is compatible (organs, tissue)
No flexibility to adapt to change if a disease spreads
oE.g royal families (incest and inbreeding) and domesticated animals
oGet a lot of non-beneficial traits from crossbreeding and inbreeding, side
effect of trying to get one specific trait
Systematics (categorising)
oEarly systematics was based on physical similarity
oYou can add up all different phenotypic qualities but it doesn’t add up- need
to look at genes
oModern systematics based on evolutionary history
Well chosen morphological traits can be good
Genetic features are usually better
oMolecular systematics based on genetic features are more reliable
Making sense of the evolution module
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BIOL1003 Genetics
Chromosomal Basis of Inheritance
To understand the material nature of inheritance, you need to understand where
heritable material can be found
The Chromosome
It was observed under the first microscopes that all organisms were made of cells
It was also observed that all cells have black dots in them- the nucleus
Began to cut up cells to look at them without killing them- when they studied them
for a while they noticed cell division
Dividing cells scramble of all their internal bits, then put them together again,
starting with the nucleus- must be important
The nucleus breaks up to form dark, easily stainable coloured bodies- chromo somes
Only present during cell division
Gene
Mendel hypothesised a factor that conveys traits from parent to offspring (1860s)
Darwin used the phrase “pangenesis”
Mendel’s theory of inheritance and Darwin’s theory of natural selection was
combines by someone who understood both languages
Shortened to “pangen” in 1880
oPangen: the smallest particle (representing) one hereditary characteristic
Gene first used in 1909
oGene: he fundamental physical and functional unit of heredity
Genes and chromosomes
Morgan- used beams of electrons to see bands and stripes on the chromosome- saw
if traits corresponded to the bands of fruit flies, fruit fly chromosomes bloat and
inflate making it easier to study than humans
Through the observation of cell division, chromosomal bands and their correlation to
inherited traits, Thomas Hunt Morgan established in 1920 that genes can be found
on chromosomes
He had no idea what chromosomes were made of
Chromosome
Chromosome: a condensed form of proteins and nucleic acids
carrying genetic information (DNA), visible only during cell division
Chromosome is a unit to make sure that the information is going to
be packaged in an equal way in the daughter cells
When the cell is not dividing it is relaxed, spread out in the nucleus
and is called chromatin, it is still made up of nucleic acids and proteins
but looks different
Image:
oDarker and lighter bits correspond to more active and less active parts of the
genome
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Document Summary
Heritability of traits is one of the major premises of natural selection. Very little known about the nature of inheritance intil 1900s: conception by spirit entering woman, entire homonculus present in sperm, averaging and blending of parental traits in offspring. Forensics: late to use genetics as need to be completely certain so use old technology that is definite, identity/ paternity testing. Cheetas lost most of their genetic diversity in the last ice age. Drying out of the sahara and migration of humans has dramatically decreased the amount of individuals, and so their genetic diversity has been lost. Systematics (categorising: early systematics was based on physical similarity, you can add up all different phenotypic qualities but it doesn"t add up- need to look at genes, modern systematics based on evolutionary history. Well chosen morphological traits can be good. Genetic features are usually better: molecular systematics based on genetic features are more reliable.
