Mendel’s Law (ppt 3/3)

Mendelian Law

Each trait in pea plant is controlled by two alleles

-alternate forms of a gene

Dominant allele

Capital letter

• masks expression of the recessive allele (lowercase letter)

Alleles

Occur on a homologous pair of chromosomes at a particular gene locus

Homozygous

Identical alleles

Heterozygous

Different alleles

What do dominant and recessive alleles represent?

Represent DNA sequences that code for proteins

Which proteins dominant alleles code for?

Code for proteins associated with the normal gene function within a cell

What do the recessive alleles represent?

Represents a loss/absence of a function

What happens to the chromosomes and alleles during mitosis I?

• homologous chromosomes separate

• Two alleles separate from each other

Monohybrid cross

Uses true-breeding pants that differ in ONE trait

Dihybrid cross

Uses true-breeding plants that differ in TWO traits

Law of Independent assortment

The pair of factors for one trait segregate independently of the factors for other traits

• all possible combinants of factors can occur in the gametes

Genetic disorders

Medical conditions caused by alleles inherited from parents

Autosome

Any chromosome other than than a sex chromosome (X or Y)

What are causes by genetic disorders by genes on autosomes?

Autosomal disorders

Genetic disorders are autosomal dominant (AA or Aa). If an individual has aa do they have the disorder?

NO

Some autosomal genetic disorders are autosomal recessive (aa only). What letters are autosomal recessive?

Letters aa

What is a pedigree

A pedigree is a family tree

• the interrelationship of parents and children across generations

• Can be used to find inheritance patterns of particular traits and they can be described

What is the child outcome if both parents of the child carry one copy of a recessive gene (autosomal) and both of the parents are unaffected?

The child will have two copies of the gene and will be affected

Two parents have a dominantly inherited disease, will they be affected?

Yes, they will be affected by one copy of the gene

Two parents have a dominantly inherited disease, is it possible for them to have unaffected children?

yes, it is possible for them to have an unaffected child

Multiple allelic traits

Traits that are controlled by multiple alleles

• the gene exists in several allelic forms, but each individual has only two alleles

ABO blood types (the alleles) IA

A antigen on red blood cells=A blood type

ABO blood types (the alleles) IB

B antigen on red blood cells= B blood type

ABO blood types (the alleles) i

Neither A nor B antigen on red blood cells= O type blood