Genetics Continued

Human Karyotype: 23 pairs of chromosomes.

Recap

• Genes are units of DNA located at particular regions of a particular chromosome….usually coding for a particular protein.

• In most cases we inherit one copy of a gene from mom and one from dad.

Gene-Interaction

• Some alleles are dominant or recessive in relationship to other alleles. When you have one copy of a dominant allele, it may cover up the expression of a recessive allele.

• Remember: genotype = the genes you have phenotype = particular trait

• Some alleles dominant are recessive in relationship to other alleles. When you have one copy of a dominant allele, it may cover up the expression of a recessive allele.

• Remember: genotype = the genes you have

phenotype = particular trait

Eye Color: an Exercise

Genotype PhenotypeBB brown eyesBb brown eyesbb blue eyes

Locus of Genes on Chromsomes

Mutations

• Mutations are random changes in genetic material: they are what allow for variation in genes such as alleles.

• Mutations can also result in the duplication or deletion of large portions of a chromosome.

Down’s Syndrome KarotypeTrisomy 21

Sex-Linked Traits

• Females have matched sex chromosomes (XX) and males have UN-matched sex chromosomes (XY).

• This means that males only have one copy of a particular set of genes. Where females have two copies of these same genes.

Sex-Linked Traits

• Genes that are located on the X-Chromosome are inherited differently in males and females.

• For example, if a gene is recessive, a male would only need one copy of that gene to express (show) that trait. Where a female would need TWO copies of the same recessive gene.

Hemophilia Genetics

• There is a particular gene responsible for the clotting mechanism in blood. The gene is located on the X-Chromosome and has two alleles:

• N = Normal blood• h = Blood lacking the clothing Mechanism

Genotype/Phenotype

Genotype Phenotype NN Normal Blood N h Normal Blood (carrier) hh Hemophiliac

Hemophilia

• If a mother was a carrier (Nh) and Dad has Normal Blood (N), daughters would have one of two to genotypes.

• They would either inherit an N from both Mom and Dad (NN: normal blood) or an N or h from mom and a N from Dad (Nh: Normal blood but a carrier.)

Hemophilia

Mom: (Nh) Dad: (N)

• Sons are going to inherit only one copy of this gene beause they inherit the Y –Chromomoe from their father.

• This means that sons are either going to be N, with normal blood or h and be hemophiliacs.

Hemophilia

Sickle Cell

• There is a gene on an autosome (non-sex chromosome) responsible for blood cell shape. It has two alleles: N for normal and S for sickle shaped. N and S are co-dominant: They display incomplete domination.

• NN = Normal Blood• SS = Sickle Cell Anemia• NS = Sickle Cell Trait