Download Principles of Genetics Notes

Mendelian Genetics
Gregor Mendel
Father of modern genetics
Objectives
• I can compare and contrast mitosis & meiosis.
• I can properly use the genetic vocabulary
presented.
• I can differentiate and gather data from the
genetic tools of karyotypes, Punnett squares
and pedigrees.
• I can describe and apply Mendel’s Laws.
• I can set up and utilize Punnett squares.
• I can describe different patterns of inheritance.
Cell Division Review
• mitosis produces
two daughter
cells genetically
identical to the
original parent
cell (diploid)
• meiosis produces
four daughter
cells with exactly
half the genetic
material of the
original parent
cell. (haploid)
Gametogenesis-meiosis
Creation of the gametes.
• Male meiosis generally
results in the production
of four sperm that are
capable of producing
offspring.
• Female meiosis
generally results in the
production of ONE viable
oocyte plus 3 polar
bodies.
• allele: different forms of a gene found in the gene pool – ie: A ,
B & O alleles for human blood type.
• phenotype: the physical trait in an organism – ie: hitchhiker’s
thumb
• genotype: the actual genes of an organism – ie: homozygous
recessive (aa)
• dominant allele: if present, determines the phenotype of trait ie: roll tongue
• recessive allele: No dominant allele present, trait will be
expressed – ie: no tongue roll.
• homozygous: the two alleles are the same
(dominant – AA or recessive - aa).
• heterozygous: the two alleles are different
(one big, one small - Aa)
• autosomal trait: a gene located on one of the autosomes (any
chromosome that is not a sex chromosome).
• sex-linked trait: a gene located on one of the sex
chromosomes (either the X (X-linked) or Y (Y-linked)
chromosome).
A karyotype is a picture of an individuals chromosomes
Chromosome
numbers are
arranged by
size.
Pictures
are taken
when the
cell is in
metaphase
Sex chromosomes
are the last pair
Karyotype of normal human male & female. 46 chromosomes (23 pair)
•DNA make up your
chromosomes.
•Chromosomes are
where your genes are
stored.
•Genes determine
your traits (proteins).
•You inherit 1 allele from each
parent for each trait. (total of 2)
•Traits have dominant forms and
recessive forms.
•Your alleles will determine your
genotype and phenotype.
Mendel’s Laws
worked with pea plants to make observations.
• Law of Segregation - The two forms of a gene
(now known as alleles) present in each organism
segregate into different cells during gamete
formation.
• Law of Independent Assortment - The (two)
alleles of the many different genes present in any
given (diploid) organism segregate/assort from one
another in a random fashion.
• Law of Dominance - alleles can be dominant or
recessive. The dominant allele, if present, will always
determine the trait.
Laws of Segregation
& Independent
assortment
Law of Dominance
Karyotype
Tools for Genetics
Pedigrees show how a single
heritable trait runs through
generations.
Pedigree
Punnett Squares
Punnett Squares
The outside of a Punnett Square
represents the possible gametes
that pa parent can give based on
the law of segregation.
gametes
Aa
Aa
gametes
Aa
Aa
The inside of the Punnett Square
represents the possible offspring
if those two gametes fertilized
each other. In this example, all
of the offspring would be yellow
because they each have a
dominant allelle.
Punnett Square Practice!!
T
t
t
Cross a male who is
heterozygous for
tongue rolling (Tt)
with a female that is
homozygous
recessive (tt)
Genotypic ratio:
______________
TT : Tt : tt
t
Phenotypic ratio:
______________
Rolling ; no rolling
Punnett Square Practice!!
F
f
Cross 2 parents
who are
heterozygous for
freckles (Ff)
F
Genotypic ratio:
______________
FF : Ff : ff
f
Phenotypic ratio:
______________
Freckles ; no freckles
Patterns of Human Inheritance
• Dominance – If dominant allele is present, it is
expressed.
• Incomplete dominance - Neither allele fully
expressed in heterozygote -Aa; looks like a
mixture of both (red & white = pink)
• Co-dominance – both alleles equally expressed
in heterozygote -Aa (AB blood type)
• Sex-linked – traits on the sex chromosomes
• Polygenic – many genes control ONE trait
(height)
Pedigrees