Download Genome DNA (deoxyribonucleic acid) Chromosome Gene Allele

Genome
All of the genetic information or hereditary material possessed by an organism; the
entire genetic complement of an organism.
Includes both nuclear & organelle genetic information.
DNA (deoxyribonucleic acid)
Doubled stranded helix
Sugar-phosphate backbone
Complementary base pairing
Adenine
Thymine
Guanine
Cytosine
Chromosome
Discrete unit of the genome that carries many genes.
Each chromosome consists of a long molecule of
double-stranded DNA and proteins.
Gene
The functional and physical unit of heredity passed from parent
to offspring. A gene is a sequence of DNA (A,C,G,T) that
occupies a specific location on a chromosome. Genes encode
the particular characteristics of individuals.
Allele
One of several alternative forms of a gene that occupies a given locus on a
chromosome. Alleles can differ from one another in their phenotypic effects.
At the molecular level, alleles differ from one another based on their nucleotide
sequences, regardless of their effect on phenotype.
Replicates itself – passes information from cell to cell
Stores information
(A, C, G, T)
Controls the flow of information in organisms
Transcription
mRNA
Translation
protein
Information is transmitted
via the universal (nearly)
genetic code
Sex-linked traits
Genes that are present only on the Xchromosome (no counterpart on the Y)
Expression of trait depends on…
e.g. in autosomes
(not sex chromosomes)
Traits are dominant when 1 copy of the
gene is sufficient to express the trait.
(1) sex of individual
(2) dominant (or recessive) expression of trait
!
"
*
Trait is
expressed
*
* Sex-linked gene found only on the X-chromosome
Traits are recessive when 2 copies of the
gene are necessary to express the trait.
Genes on the X-chromosome in females can
be either homozygous or heterozygous
Almost all genes on the X-chromosome in
males are hemizygous
(red-green color blindness, hemophilia A,
e.g. of X-linked recessive traits)
Trait is
expressed
Trait NOT
expressed
“carrier”
Sex-influenced traits
Genes are on autosomes, but trait expression
varies between males & females
(“male-pattern” baldness)
Genotype
Male
Female
B/B
bald
bald
B/b
bald
not bald
b/b
not bald
not bald
John Adams
(1735-1826)
John Quincy Adams
(1767-1848)
Charles Francis Adams
(1807-1886)
Henry Adams
(1838-1918)
Sex-limited traits
Genes are on autosomes, but trait expression
is limited to either males or females
(beard growth, milk production)
Consequences of having genetic sex determination
(1)! Dosage effects
(2)! Sex-linked traits
(3)! Degeneration of sex chromosomes
Inversions SUPPRESS recombination…
ACCTTG CATCGGTCTGAT AGGATTAG!
“proto” X
ACGTTG CATCGATCTGAT ACGATAAG!
“proto” Y
ACGTTG CATCGATCTGAT ACGATAAG!
Inversion on
“proto” Y
ACGTTG TAGTCTAGCTAC ACGATAAG!
ACGTTG TAGTCTAGCTAC ACGATAAG!
“proto” Y (inversion)
ACCTTG CATCGGTCTGAT AGGATTAG!
“proto” X
No recombination
Why does SUPPRESSED recombination lead to degeneration?