2.38 Genetic Variation: Lesson

2.38Genetic Variations

​This lesson also covers:
2.37 Gametogenisis and 2.39 Life Cycle

Allele - a different version or form of a gene.

​​Vocabulary!

Traits - characteristic in an organism.

​​Vocabulary!

Genotype - the LETTERS that make up the genes.

Phenotype - the OBSERVABLE characteristics in an individual.

• Homozygous - genotype that has the SAME alleles.

Vocabulary!

• Heterozygous - genotype that has DIFFERENT alleles.

Hotspot

Which genotypes are considered HOMOZYGOUS?

Hotspot

Which genotypes are considered HETEROZYGOUS?

Vocabulary!

• Dominant- gene that is always expressed when paired with another allele. (EX. BB Bb)

• Recessive - allele that is not expressed if a dominant allele is present. (EX. bb)

Vocabulary Review

A gene is a small section of DNA that codes for a protein.

Chromosomes are long pieces of DNA that have been condensed. They contain many genes.

Mutations are changes in the DNA.

Review: Types of gene mutations

• There are 3 kinds of gene mutations...

• Insertion - Adding bases ( + )

• Deletion - Removing bases ( - )

• Substitution - Changing bases ( = )

• Insertions & deletions are frameshift mutations

Chromosomal Mutations

• There are 4 types of chromosomal mutations

• Duplication

• Inversion

• Deletion

• Translocation

Duplication

Part of the chromosome is "copied & pasted" back into itself.

Inversion

Part of the chromosome is flipped so that the genes are reversed in order.

Deletion

Part of the chromosome is removed and lost.

Translocation

Section of two non-homologous chromosomes are switched.

This is not like crossing over because the pieces are not equivalent!

Crossing Over

Crossing over is not considered to be a mutation.

During crossing over, homologous chromosomes exchange equivalent sections of their genes.

This process naturally occurs in Prophase I.