Genetics

1
Genetics

• Genetics study of how traits are inherited
  through the interaction of alleles.
• Heredity passing of traits from parent to
  offspring.

2
Basic Laws of Inheritance

• Each organism has 2 factors that are responsible
  for traits (alleles)
• The 2 factors separate when sex cells are formed.
• Each new organism receives 1 factor for a trait
  from each parent.
• Some traits are dominant others are recessive.

3
Vocabulary

• Genotype - the genetic makeup of an organism.
• Phenotype - the external appearance of an
  organism-caused by genotype.
• Traits units of inheritance genetic traits
  (genes)
• give rise to observable traits (phenotype)
• Characteristic of an organism
• Alleles
• Homozygous trait - the genes for that trait are
  the same.(SS)
• Heterozygous trait - the genes for that trait are
  not the same.(Ss)

4
Genotype
5
Phenotype
6
Allelesdifferent forms of a trait one form
of a gene
Example of traits Eye color Skin color Height
Hair texture
Examples of Alleles Brown or blue Albino or
pigmented Tall or short Curly or straight
Most traits (including above) are determined by
multiple genes with multiple alleles
7
Where are genes andhow are they passed along?
Allele alternative versions of a gene
Locus location of a specific gene on a chromosome
8
Female reproductive cell (gamete-egg)
Male reproductive cell (gamete-sperm)
Zygote
9
Male
Female
Interphase duplication of genetic information
Meiosis I and Meiosis II
10
Male gametes
Female gametes
What do the offspring look like?
Light pink dominant dark pink recessive
11
Is there an easier way to figure out what the
offspring look like?

• Dominant the fully expressed gene, has full
  control on the phenotype
• Recessive gene is completely masked in the
  phenotype

12
Dominant alleles are denoted by a capital letter
(A) Recessive alleles lower-case letter (a)
Recessive
Dominant
a
A
13
Male
Female
AA
aA
A
A
a
a
A
A
A
A
14
Is there an easier way to figure out what the
offspring look like?

• Punnett Square

Male (father)
A
a
What are the possible genotypes of the offspring?
A
AA
Aa
Female (mother)
A
Aa
AA
15
Is there an easier way to figure out what the
offspring look like?

• Punnett Square

Male (father)
A
a
If the dominant trait is brown eyes and the
recessive trait is blue eyeswhat are the
phenotype/s of the offspring?
A
AA
Aa
brown
brown
Female (mother)
A
Aa
AA
brown
brown
16
Your turn

• Mother (Aa) x Father (Aa)
• What are the genotypes of the offspring?
• If the dominant gene is attached earlobes and the
  recessive gene is unattached earlobes, what are
  the phenotype/s of the offspring?

17
Male (father)
a
A
A
AA
Aa
attached
attached
Female (mother)
a
aa
Aa
attached
unattached
What is the proportion of offspring with
attached vs. unattached earlobes?
31
18
Dominant recessive alleles (Fig. 10.7)
19
1. Unit Factors (Genes) in Pairs
Each parent carries 2 copies of a trait

• specific allele exists for each gene (trait)
• each individual receives 1 (allele) from each
  parent

20
More Vocabulary

• Gene pool- all of the genes and their alleles
  present in a population.
• Genome- entire genetic material of an organism.
• Hybrid- receive different alleles for a trait
  from each parent

21
Mendelian Genetics
Gregor Mendel -father of modern genetics.
Noticed differences in peas being grown in his
garden. Applied the scientific method to
determine the cause of these differences.
22
Mendelian Genetics
23

• Mendels Experiments
• Began by self-fertilizing 34 different pea
  strains (phenotypes) so that they bred true
  (selfing, the opposite of cross-fertilization).
• Focused on 7 well-defined garden pea traits by
  crossing different phenotypes one at a time
• Flower/seed coat color purple vs. white
  flowers
• grey vs. white seed coats
• (controlled by single gene)
• Seed color yellow vs. green
• Seed shape smooth vs. wrinkled
• Pod color green vs. yellow
• Pod shape inflated vs. pinched
• Stem height tall vs. short
• Flower position axial vs. terminal
• Counted offspring of each phenotype and analyzed
  the results mathematically.

24
Fig. 10.4, Mendels 7 garden pea characters.
25
Appearance of Hybrid
26
Mendelian Genetics
Monohybrid cross
27
(No Transcript)
28
Genetics Since Mendel

• Incomplete Dominance- a dominant and recessive
  allele for a trait show an intermediate phenotype
• Ex.
• 1. cross purebred red and purebred white
  4- oclock flowers
• 2. Result pink flower-neither allele dominant
• 3. Cross pink flowers together
• 4. Red, pink, and white flowers produced
• 5. Not blended- red nor white had dominance-
  produced intermediate phenotype

29
Multiple Alleles

• Def controlled by more than 2 alleles
• Produce gt 3 phenotypes of that trait
• Ex. Blood Type
• Produces only 4 phenotypes A, B, O, AB
• Has only 3 alleles A, B, O (O is recessive)
• What are the 6 different genotypes?
• AA, AO, BB, BO, AB, OO

30
Polygenic Inheritance

• Def Group of gene pairs acts together to produce
  a trait
• Produces wide variety of phenotypes
• Ex. Eye color

31
Human Genes

• Mutations- changes in genes
• Can be helpful or harmful
• Ex. Chromosome disorders-
• Downs Syndrome-extra chromosome
• Short, learning disabilities, heart problems
• Recessive Genetic Disorders
• Caused by recessive genes
• Ex. Cystic Fibrosis
• Produces thick mucous in lungs and intestinal
  tract, instead of thin fluid
• Bacterial respiratory infections, digesting
  problems

32
Human Genes

• Sex-linked Disorders
• Allele inherited on a sex chromosome is a
  sex-linked gene
• MalesXY, Females XX
• Ex. Color Blindness
• Cannot distinguish between certain colors, esp.
  red and green
• Usually occurs in males recessive allele on the
  X chromosome
• Female- must have 2 recessive alleles for this
  trait