Patterns and Processes in inheritance (2nd unit 2/2 after Cell cycle)

A quality or characteristic obtained genetically from one’s parent.

Choosing parents with desirable traits (physically, behavioural, mental…) and have them reproduce offspring.

• 1) Many characteristics to observed, peas exhibit many things to look at/examine . More date = more conclusive results.
• 2) Garden peas can self pollinate (clone) and cross pollinate (sex) 
• 3) Garden peas are small and easy to grow. Short generation time.

He hypothesized that there are alternative forms of genes (like the different kinds of pea colour, flower colour and etc, the units that determine heredity

• P generation - Parent 
• - He crossed 2 true breeding plants together (purple and white flower)

• F1 generation - first offspring
• - all flowers are purple Pp (however it still contains genes from the white flower (p)). He then let these flower fertilize

• F2 generation - Second offspring 
• - 75% of the flower were Purple
• - 25% of the flowers were white

The mixing of one trait (eg the mixing of flower colours or the mixing of seed shapes)

If a dominant trait is present in the genes, it overrules the recessive trait. The dominant trait will expressed complete dominance - no intermediate or mix

• Dominant gene - An allele of a gene that when present, will overrule other (recessive) allele
• Recessive gene - An allele of a gene that gets overruled in the presence of a dominant trait.

• Mendel’s First Law if Herodotus is Segregation
• 1) Inherited factors are controlled by paired genes
• - during cross pollination each parent contribute one of its genes or allele
• - Not all copies of a factor(gene) is the same 
• - Homozygous - Same alleles (ex RR or rr)
• - Heterozygous - different alleles (ex Rr)
• 2) Paired genes are separated during formation of sex cells
• - Each gamete, haploid sex cells are from a parent cell
• - Each gamete is genetically unique
• 3) One factor is mask (cover) another (dominance) 
• - Even if a factor is masked, does not mean it is not still there.

• Nomenclature - name system
• Notational Convention - a way of naming genetic factors (/traits) using symbols

• Genotype - genes present 
• eg : PP or Pp
• Phenotype - what you see 
• eg : purple, white

- A cross of one trait/genes between two organism (Eg Ss x SS)

- two alleles per parent trait

- An individual must inherit two recessive allele to express that trait.

Testcross - mixing a known (homorecessive) with an unknown (pair of genes) and looking at the offspring phenotype to find out unknown Genotype.

When genes inherit different traits or inherit 1 of many different combinations of chromosomes (during crossing over) in gamete formation .

- Mendel’s Second law of Heredity is Independent assortment

- Mendel observed that when peas with more than one trait were cross, the offsprings did the always match the parents. He found out that it is because, Genes assort independently (inherit different traits) from each other (during crossing over) in gamete formation.

• Dihybrid Cross - A cross of two separate/different trait between two organism that are identically hybrid for those two traits 
• Eg: BbLl x BBLL 

- 4 Gamete/allele per parent

- 16 boxes

• Genotype - 1:2:1:2:4:2:1:2:1
• Phenotype - 9:3:3:1

Incomplete dominance - Blend of two equally dominant trait (Both traits expressed at the same time)

• Genotype (F2 generation) - 1:2:1
• Phenotype (F2 generation) - 1:2:1

• - One of a group of inherited disorders known as sickle cell disease. It affects the shapes of red blood cells, which carry oxygen to all parts of the body.
• - Red blood cells are usually round and flexible, so they can move easily through blood vessels. In Sickle Cell Anemia red blood cells are shaped like sickles or crescent moons. Red blood cells also become rigid and sticky, which can slow and block blood flow

• • Homozygous gene - HBA HBA = normal
•    - Good O2 transport
•    - Susceptible to Malaria
• • Heterozygous gene - HBA HBS = normal and sickle cell 
•    - Doesn’t have sickle cell anemia/disease but have trouble with O2 transport
• • Homozygous disordered gene - HBS HBS = sickle cell anemia/disease
•    - bad O2 transport
•    - malaria resistant

Both alleles are fully expressed (no blending)

Sex linked traits are characteristics or traits that are influenced by the gene on the sex chromosomes.

• - The Mendelian gene is a basic unit of heredity (the genes that gets passed on) 
• - A sequence of nucleotides forming parts of a chromosome

• - Thomas hunt Morgan is an American Geneticist
• - He studied mutations and recessive in fruit flies to discover sex linked traits
• - Morgan concluded that because X and Y chromosomes are not homologous they must contain different genes (non linked trait/not similar traits)

- The mother gives an X chromosome to the child. The father may contribute an X or Y chromosome. The chromosome from father determine if the baby is male or female.

• - The close location of genes or DNA marker to each other on chromosomes. 
• - The closer the genes are to each other the more likely that they were inherited together from parent/meiosis to offspring

• • Sex linkage is the gene located on the sex chromosomes
• • Y chromosomes are shorter - X chromosomes has genes that Y don’t 
• • X linked traits are more common in men
• • Men get X chromosome from men
• examples: red-green colourblindness, hemophilia, baldness

• Barr body - tightly condensed, inactive X chromosomes in females. 
• Eg Calico cats (Black and organize mix) only in female cats. This is because one of the two chromosomes is active and the other is inactive.

• - Many genes have more than two alleles. (Not just dominant and recessive)
• - Many alleles are alternative form of genes so they can influenced the same trait.

• The Order of dominant traits (which dominant traits is the most dominant) 
• - Wild alleles are usually the most dominant 

Eg: Drosophila (fly) Has 4 different eye colour type

order from most dominant to most recessive 

• 1) Wilde (red)
• 2) honey
• 3) apricot
• 4) white

E>Eh>Ea>e

- The inheritance of trait governed (/determined) by more than one gene/ the inheritance of a trait in which the trait is is produced from the effects of many genes.

• - Group of genes contribute for the same trait
• - Trait for which phenotype vary gradually from one extreme to another (along a scale)
• - Trait are controlled by more than one gene (Eg Height, skin and eye colour)
• - #of dominant traits produces different results.

• Epistatic - when one gene interferes with expression of other genes (eg Dog coat colour)
• Complementary - 2 different genes interact to produce a phenotype that neither is able to produce by itself.
• Pleiotropic - One gene that affects many characteristics

- Gene have blue prints for proteins or part of protein. Gene can be distorted/affected by environment

- Gene functions is influenced by environment 

• Eg: Freckles (sun exposure)
•       Obesity gene (diet)
•       Himalayan rabbit coat (temp.)

The exchanging of genes with homologous pairs, occurs more frequently between genes further apart in a chromosome, than those (genes) closer together.

Map unit - the distance between two genes  on a chromosome that produces 1% recombination 

Chromosome map - summarize the distance between two genes located on the same chromosome. The farther the physical location, the locus of the two genes on a chromosome the higher % recombination chance between these two genes.

The number of recombinants that occurred can be used to determine the distance between (two) genes.

A pedigree chart is a flow chart of mating and offsprings produced, and traits over many generations. Pedigree charts are used for tracing human genes.

Pedigree Symbol - Symbols applied to icons to represent data/information

• Notations:
• • Roman numbers - use to represent generations
• • Numbers - use to represent person (1,2,3)

Dominant (affected), Recessive (unaffected) and X linked traits

• Dominant - if affected individual are in every generations (no skipping)
• Recessive - if skipping occurs 
• X linked - if more males are affected than females