GENETICS AND GENETIC - other biologists used Mendel's
ENGINEERING research as basis for own
What is genetics? studies
- branch of biology that studies - Mendelian genetics studied +
heredity + variation in taught throughout world
organisms - died in Brunn on Jan 6, 1884
- tries to explain similarities +
diffs between parents and
offspring
- heredity = passing on of
traits/characteristics from one Genes
gen to next - each chromatid made up of
one, helical DNA molecule
The ‘Father of Genetics’ - each DNA molecule made up
- Gregor Mendel = Austrian of a series of genes
monk - gene = section of DNA (series
- lived at same time as Charles of nucleotides/bases) that
Darwin, but two never met controls hereditary
- Mendel responsible for first characteristics, i.e. is basic
major breakthrough in study unit of heredity in living
of heredity by investigating organisms
transfer of characteristics
from one gen to the next
- realised that something was
passed on from parent to
offspring + that sexual
reproduction combines these
‘somethings’ from each parent
to produce offspring which are
unique, yet still similar
- now know ‘somethings’
passed from parent to
offspring = genes which are
part of DNA molecules in - each chromosome has
chromosomes between several hundred and
- in recent years advances several thousand genes
made in understanding - total number of genes in
structure + functioning of humans thought to be
these genes between 20 000 and 25 000
- in 1866, published work but - nearly all somatic cells have
was not recognised in exact copy of all genes in that
scientific circles until 1900, organism
years after his death - mature red blood cells have
- as Darwin’s theory of no nuclei, therefore no
evolution gradually accepted chromosomes + no genes
so were Mendel’s - because there are two of each
findings/laws kind of chromosome (paternal
and maternal), each cell
contains two of each kind of
1
, gene (before replication) – document what switches genes on or
these versions of gene = off
alleles
- gene pool = set of all genes or Alleles
genetic info in population of - alleles are genes responsible
sexually reproducing for controlling diff versions of
organisms a trait/characteristic found in
- large gene pool indicates high the same locus (position) on
genetic diversity + increased homologous chromosomes
chances of survival - e.g. for the gene determining
- small gene pool indicates low coat colour in cattle, one allele
genetic diversity and could determine a black coat
increased possibility of (B) and another allele a white
extinction coat (b)
- allele = one of two or more
forms of a gene, alternative
How active are genes? version of a gene
- although each cell contains How are alleles represented?
full complement of DNA, only - when describing
genes needed are activated characteristics, alleles are
and others are suppressed represented by means of
- therefore, diff genes are letters
activated in diff cells, creating - often capital letter denotes
specific proteins that give a dominant allele and lower
particular cell type its case the recessive allele
character, e.g. bone cells,
brain cells, skin cells, etc.
- some genes play a role in How are alleles passed from
early development of the parent to offspring?
embryo and are inactive - passed from parents to
thereafter offspring by way of
- some genes are active in chromosomes in gametes that
many types of cells, making are made by process of
proteins needed for basic meiosis in sex organs
functions – called - gamete = a reproductive/sex
‘housekeeping genes’ cell
- other genes are inactive most
of the time to sum up: normal body cells
(somatic cells) = diploid (2n) as they
- high proportion of genes are
have:
non-coding genes, i.e. do not a pair of homologous chromosomes
code for proteins and occur in- two alleles (may be same or diff)
between coding sections – sex cells (gametes) = haploid (n) as
only about 2% of DNA codes they have:
for proteins one of a pair of homologous
chromosomes
one of each pair of alleles.
note: master control genes that
determine way in which body develops
from a single zygote = hox genes What happens to the
the control of genes = epigenetics – gametes?
Human Epigenome Project aims to
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, - during fertilisation male recessive – trait is
gamete, w/ its alleles, fuses w/ suppressed in the
female gamete, w/ its alleles, presence of dominant
to form diploid zygote allele, not expressed in the
- zygote divides by mitosis to offspring
form entire new organism
made up of cells, each w/ to sum up:
same set of chromosomes and genotype
alleles as zygote phenotype
BB (homozygous) black
coat
Genotypes and phenotypes Bb (heterozygous) black
- genotype is made up of all coat
genes an organism carries on bb (homozygous) white
its chromosomes which it has coat
inherited from its parents
- phenotype is physical there are three possible combinations
of alleles or genotypes for determining
appearance of an organism, the coat colour but only two
such as tallness, hair colour – phenotypes, this is because:
is partly programmed by - if one allele is dominant over
genes (genotypes) but also another, a homozygous organism
shaped by external factors (BB) has the same phenotype as a
such as exercise, diet and heterozygous organism (Bb)
environment - the allele b is recessive as its
effect is hidden by dominant B
gene and its characteristic will only
Homozygous and be expressed in the phenotype
heterozygous when there is no dominant allele
- after fertilisation zygote + all present – animals w/ genotype bb
cells that develop from it, will is homozygous recessive, will have
have two alleles for each white coats
gene, one from each parent –
will be in same locus on each Monohybrid crosses
chromosome of homologous - = cross between parents w/
pair diff alleles for a single gene
- if pair of alleles at a locus are - expressed w/ genetic diagram
same, the organism =
homozygous for that particular Genetic diagrams
trait - show how characteristics are
- if the pair of alleles at a locus inherited
are diff, organism = - show genotype + phenotype
heterozygous (hybrid) for that of a cross between two
particular trait parents
- help us understand why the
Dominant and recessive offspring look way they do
alleles - gens shown as follows:
- in heterozygous pairing, one P1 – parent gen
allele of a pair may be: F1 – first filial gen of
dominant – this trait is offspring
expressed in the offspring, F2 – second filial gen of
e.g. black coat offspring
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