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Genetics: What is determined in inheritance and what is involved
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Issues of plant and animal breeding
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Early on - how does genetics and inheritance work?
Also involved in genetic analysis
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[e
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have a trait of interest that you want
to study
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Start with a trait or system of interest
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look to see if there are genes
involved in determining wing colour or size etc
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Reverse Genetics- Used more recently since the whole genome can be
sequenced
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Realize that
that’s a gene
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Study is to knock out the gene
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Those are the two ways that genetic analysis can be carried out right
now
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Discovered mechanism of
inheritance
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Mendells work wasn’t appreciated until 1902
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[phenotypes that are easy to
see] Those traits appeared to not be involved or influenced by the
environment at all
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Geneticists picked things that were insensitive
to the environment to avoid genetic determinance
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Some genes may respond differently as well
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Are
there genetic differences involved for an organism to become a male?

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Absence of a single gene or chromosome depicts a female organism
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Genetics can be investigated at the cellular, sub cellular and molecular
levels
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Can have 2 slightly different
versions of the same allele
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Polytene Chromosomes- Oversized chromosomes which have developed
from standard sized chromosomes
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Polytene
chromosomes, have the same DNA
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Use X-rays to determine effect of genes when they’re knocked out
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Chromosome painting- extract DNA, label with fluorescent dye and
hybridize it because DNA can make single stranded on a slide on a slide
and then using fluorescence can figure out where the chromosomes are
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late prophase- 5
chromosomes present
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Find chromosome pairing in 4’s
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Triploid chromosomes are often sterile
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Can probe
for a single gene using a labelled DNA probe
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Load samples
at the anode
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The more toxic the
substance present in the gel; the better it tends to work
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Separate DNA using a known marker
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2 bands in a single stranded conformational polymorphism on a gel
indicate the presence of 1 gene- homozygous
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Another method to visualize genes is using Ethidium bromide stained
agarose gel showing RAPS’s (random amplified polymorphic DNA)- look

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for and study genetic variation
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Run clones
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Can
visualize clones by separating them on the gel
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In addition to nuclear DNA, a small specialized fraction of eukaryotic
genomes is found in mitochondria and chloroplasts
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Reverse transcription is used to maintain the telomeres that form the
chromosome tips when RNA is reverse transcribed into DNA
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Polymorphic dna are dna sequences which are relatively variable
between different individuals or species
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Thus, in diploids, each gene is present as a gene
pair
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DNA and associated nucleosomes are called chromatin
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One extensively used method for detecting specific macromolecules in a
mixture is probing
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The probe is labelled in some way either by a
radioactive atom or by a flourescent compound
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Create mutates and cross link to look for
deviation
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Considering 2 aleles often
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The normal allele is signified by the “+” symbol
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Haploid- Turnera subulata n = 5
Diploid - 2n = 10
Humans - n = 23 and 2n = 46
Diploid- somatic cells have two of every chromosome and are thus
known as homologous pairs or homologs
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The supercoiled form of DNA composed of genes and the
histone proteins [histone octamers] form a nucleosome
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DNA is packaged around
histone proteins and is coiled around itself
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These
regions are often small
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When you have homologous chromosomes - has 2 chromatids [sister
chromatids]
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If you compare 2 of the same homologous
chromosomes [Chromosome 1 and chromosome 1] will mostly always
have the same gene order however the dna sequence of the gene will be
a little different and it may or may not have a phenotypic affect
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Inheritance
1
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15 : 1 ratio]

Goodness to fit tests X2 = 0
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But you won’t get
an exact 3:1 ratio and exact numbers for example
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As the
numbers differ, goodness of fit value get’s larger
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Notes:
• A gene is the basic functional unit of a genome and is a unit of transcription
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• Hereditary change is caused mostly by mutations in DNA, but also by
epigenetic effects
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• Reverse Genetics: Gene (DNA sequence) that has no function —> mutation by
knocking out the gene —> look for effects on the organisms function
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• The genetic approach to understanding a biological property is to discover the
genes that control it
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• Single gene inheritance patterns are produced because genes are parts of
chromosomes, and chromosomes are partitioned vey precisely down
through the generations
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Example round
or wrinkled seeds
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• A hereditary factor called a gene was necessary in producing the desired trait
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A single gamete contains only one
member of the gene pair
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• Sometimes a heterozygote for one gene is called a monohybrid
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• All 1:1, 3:1, and 1:2:1 ratios are diagnostic of single-gene inheritance and
are based on equal segregation in a heterozygote
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The members of a gene pair are segregated as an inevitable
consequence
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It can take
place in diploid or haploid cells
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2 divisions
occur and thus 4 cells are produced
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Thus, in diploids, each gene is present as a
gene pair
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• The number of DNA bands observed after electrophoresis is found to be
equal to the haploid chromosome number, confirming that
each chromosome only contains one DNA molecule

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