Genes and inheritance

What is a locus?

A part of the genome

What is the blending hypothesis vs particulate hypothesis?

Blending: genes (or parents substance) is uniformly and forever mixed

Particulate: despite mixed appearance there are still individual particles within the person

What is mendel’s first law?

Alternative versions of genes account for variations in inherited characteristics

Words to know: allele, phenotype, genotype

What is mendel’s second law?

For each characteristic, an organism inherits two copies of a gene, one from each parent

Words to know: heterozygotic, homozygotic

What is Mendel’s third law?

If the two alleles at a locus differ, then the dominant allele, determines the organisms appearance

Words to know: dominant, recessive

What is mendel’s fourth law?

Two alleles for a heritable character segregate during gamete formation and end up in different gametes - the law of segregation

The law of independent assortment

Each pair of alleles segregate independently of each other pair of alleles

Dominant, recessive

Each individual characteristic is inherited 3:1 ratio

Degrees of dominance

If a red and a white flower were to be crossed together, it would result in a pink flower. Afterwards the 1st generation pink flower would be crossed with itself and you would get 1 red flower, 1 white flower and 2 pink flowers.

Pleiotropy

1 genetic change that has a large number of phenotypic outcomes; one genotype affects multiple phenotypes

Phenotype

The expression of the trait

Genotype

Pair of alleles

Epistasis

The phenotypic expression of a gene at one locus alters that of a gene at a second locus

Polygenic inheritance

The converse of pleiotropy

Autosomal recessive

^e.g. cystic fibrosis (Cl- ions cannot go through the channel, therefore there is a build up of ions one one side which leads to a build up of mucous, and the person cannot breathe)

Autosomal dominant

^e.g. Huntington’s disease (enlargement of the frontal horns of the lateral vesicles)

X-linked recessive

^ Red-green colour blindness

X-linked dominant

^ X-linked hypophosphatemia

Mitochondrial inheritance

^

Equations

X = population mean

S² = population variance

s² = the sum of (Xk — X)² / (n—1)

S = population standard deviation

s = sqrt (s²)

What percentage of a trait is genetic and what percentage of a trait is environment?

Phenotype (P) = Genotype (G) + Environment (E)

What does Novel mean in genetics?

It means that it is the first occurrence in the family.

Y-linked inheritance

Direct line of paternal inheritance

Y-chromosome likely contains between 70-200 genes (very small amount)

Deletion of these genes cause highly penetrative disorders,