NATS 1675 Lecture Notes - Lecture 9: Robert Crippen, Pea, Homologous Chromosome

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6 Feb 2016
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NATS 1675 Lecture #9 Genetics PART 2
Professor: Robert Crippen
Genetics continued…
Species:
It is a population of organisms that retain their individuality in nature because they are
reproductively isolated from other species from them
Reproductive isolation: both include behavior & genetics ; both also include distance and
barrier
Behavioural breakdown in reproductive isolation: A male chicken and female ferret have
an interest in one another
Hybrids:
An organism produced by 2 different species or genotypes
There are cases where different and related species mate and they can reproduce
offspring
One example most people are familiar with is the crossover of the female horse and a
male donkey so their offspring is a mule
Another example is a male horse and female donkey so their offspring is a hinny
You see [above] how just changing the parents , it can make a difference forming a baby
Hybrids are usually incapable of reproduction themselves their chromosomes are
similar enough that they are unable to reproduce
Genotypes:
The genetic makeup of an organism
ex. RR, Rr, rr ; the combination of alleles at a particular locus or all loci
They are “types of genes” that work in pairs
RR: dominant ; Rr: represents a hybrid; it is a genotype because it has a gene that
differs ; rr: recessive
Genotypes incorporates with the environment
Phenotypes:
The appearance of an organism with regards to an inherited characteristic [trait] or all
inherited characteristics
The phenotype is produced by genotype in cooperation with the environment ex. R=
round pea seeds and r= wrinkled pea seeds
[above]: it’s physical appearance
Locus:
It is the location of a gene of a chromosome
It is sometimes used synonymously for gene
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Chromosomes [homologous]
Allele:
It is a pair of gene that occupy corresponding positions on homologous chromosomes
[Remember: it is homologous chromosomes that pair during Prophase 1 synapse]
Alleles are also 1 or 2 more alternate forms of a gene that occupy a particular locus on
homologous chromosomes
ABO blood types is an example: of 3 alternate forms of a gene found at one locus within
the population
Dominant:
It is a trait that appears in phenotype whenever the allele [gene] for it is present in the
genotype ex. RR or Rr =round seeds
Recessive:
It is a trait that appears in phenotype only when 2 alleles for the trait are present in the
genotype
Ex. rr= wrinkled seeds
Homozygous:
Alleles of a gene on a homologous chromosome that are alike [Remember: it is
homologous chromosome that pair during Prophase I
“Homo” = “same” so the genes are alike
Heterozygous:
Alleles of a gene on chromosomes are not alike
“Hetero” = “different” so the genes are different
You don’t need a second word ex. Heterozygous dominant or Heterozygous
recessive ; you just need to write heterozygous
Carrier:
Synonym is heterozygous however the term “carrier” can imply a possibly damaging or
unwanted gene
It is a heterozygous individual [organism] of normal phenotype who has a hidden
recessive allele in its genotype & thus can transmit the recessive allele to offspring
Father of Genetics:
It was theorized by George Mandel, an Austrian monk who presented his research in
1865
Mendel’s paper contained 3 major generalizations…
Homozygous
Heterozygous
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