Title: Final Concepts for Chapter 11 Mendelian Genetics
1Final Concepts for Chapter 11Mendelian Genetics
- Codominance
- Complete dominance
- Dihybrid cross
- Genotype
- Genotypic ratio
- Heterozygous
- Homozygous
- Incomplete dominance
- Monohybrid cross
- Phenotype
- Phenotypic ratio
- Probability
- Punnett square
- Testcross
- Expected/predicted results
- Actual/observed results
- Karyotype
- Amniocentesis
- Linked genes
- Sex-linked disorders
- Autosomal disorders
- Allele
- Dominant
- Recessive
- P-generation
- F1 generation
- F2 generation
- Law of independent assortment
- Law of segregation
- Chromosomes
- Pure breed
- Trait
2Independent Assortment vs. Linked Genes
- Mendel did not know about chromosomes when he
proposed the Law of Independent Assortment. - The pea traits he studied happened to be located
on different chromosomes so they did assort
independently.
3Independent Assortment vs. Linked Genes
- Question How many traits do you have?
- Question How many chromosomes (per cell) do you
have? - Question Is it possible to have only one trait
per chromosome? - No, lots of genes are carried or linked together
on the same chromosome.
4Independent Assortment vs. Linked Genes
- Do the punnett square for the following cross
assume independent assortment. - Cross two heterozygous tall, heterozygous red
flowered plants - Ttall Rred flower
- t short r white flower
5Independent Assortment vs. Linked Genes
What is the phenotypic ratio?
TR
Tr
tR
tr
TTRR TTRr TtRR TtRr
TTRr TTrr TtRr Ttrr
TtRR TtRr ttRR ttRr
TtRr Ttrr ttRr ttrr
TR
Tr
tR
tr
6Independent Assortment vs. Linked Genes
- 9331 ratio
- 9 tall and red
- 3 tall and white
- 3 short and red
- 1 short and white
- PROBABILITY
- From this cross, 48 offspring were produced.
- How many offspring would you expect to be tall
and red? - How many would expect to be tall and white?
- How many would you expect to be short and white?
7Independent Assortment vs. Linked Genes
- Now, do the following cross BUT the genes for
tallness and red flowers are linked.
Cross two heterozygous tall, heterozygous red
flowered plants Ttall Rred flower t short r
white flower
8Independent Assortment vs. Linked Genes
TtRr X TtRr
Is it possible to produce a Tr gamete?
9Independent Assortment vs. Linked Genes
TtRr X TtRr
What is the phenotypic ratio?
tr
TR
TTRR TtRr
TtRr ttrr
31 3 Tall and Red 1 Short and white
TR
tr
10Independent Assortment vs. Linked Genes
- So out of the 48 offspring, if the genes are
linked, how many would be - 1. tall and red?
- 2. tall and white?
- 3. short and red?
- 4. short and white?
- Answer
- tall and red 36 tall/white 0
- short and white 12 short/red 0
EXPECTED RESULTS!
11Independent Assortment vs. Linked Genes
- Is it possible for our Actual Results to show any
flowers that are tall/white or short/red? - Yes how?
- Crossing over
12Crossing over occurs in meiosis
- Pieces of the chromosomes actual switch places.
13Complete vs Incomplete Dominance
14Codominance the alleles are equally dominant
- Roan Cow Human Blood Type
15Sex-linked Traits
- Traits carried on the X chromosome
Fill in the genotypes on the pedigree.
16Autosomal disorders
- Disorders carried on non-sex chromosomes (first
22 pairs) - Some are autosomal dominant
- Huntingtons disease
- Most are autosomal recessive
- Sickle-cell anemia
- Cystic fibrosis
17- Question How do you know if the pure bred dog
you just paid big bucks for is actually pure?
GG?
Gg?
18Test Cross
- Cross using a homozygous recessive individual
with a dominant individual to determine if the
dominant individual is heterozygous or homozygous
dominant (pure) - Why use a homozygous recessive individual?
19Test Cross
- Do the punnett squares for each case
- GG x gg Gg x gg
20Test Cross
- All offspring produced should show the dominant
characteristics if the dominant parent is pure
(GG) for the trait.