Autosome
Autosomes are pairs of chromosomes that guide the expression of most traits, excluding those related to genetic sex
Sex Chromosome
The sex chromosomes are the single pair of homologous chromosomes that determine an individual’s genetic sex
Alleles
Alleles are genes that occur at same locus (location) on homologous chromosomes
Homozygous
Homozygous: alleles are same for single trait
Heterozygous
Heterozygous: alleles are different for single trait
Genotype
Genotype: genetic makeup of a person for a trait
Phenotype
Phenotype: physical expression of genotype
Independent assortment
Independent assortment: alleles of two different traits on two different chromosomes are distributed independently of each other
Random fertilization
Single egg is fertilized by a single sperm in a random manner
Dominant-Recessive Inheritance
Dominant alleles are expressed when present, while recessive alleles require two copies to be expressed. Disorders like cystic fibrosis are recessive, while Huntington’s disease is dominant.
Incomplete Dominance
The heterozygote shows an intermediate phenotype. For example, in sickle-cell trait, the heterozygote has a mix of normal and sickle-shaped cells.
Codominance
Both alleles are fully expressed in the heterozygote. An example is the ABO blood group, where both A and B alleles are expressed.
Multiple Alleles
More than two alleles exist in the population, but an individual inherits only two. The ABO blood type system is an example.
Polygenic Inheritance
Multiple genes contribute to a single trait, resulting in a range of phenotypes, such as height or skin color.
Sex-Linked Inheritance
Traits are associated with genes on sex chromosomes. X-linked traits, like hemophilia, are more common in males due to the presence of a single X chromosome.
Punnett square
diagram used to predict possible gene combinations
Small noncoding RNAs
Function to reduce expression of particular genes
Epigenetic marks
Third layer of control of gene expression
Mitochondrial Genes
Not all DNA is located in cell’s nucleus • Errors in mtDNA are linked to rare metabolic disorders associated with oxidative
phosphorylation (cellular respiration)
– possibly Alzheimer’s and Parkinson’s diseases
Pedigree Analysis
This involves constructing a family tree to assess the likelihood of carrying a recessive gene.
Amniocentesis
This fetal testing technique involves extracting amniotic fluid with a needle.
Chorionic Villus Sampling (CVS)
CVS involves taking a sample of the chorion, which is rapidly dividing tissue.
Gene Therapy
This approach is used to correct single-gene disorders by transferring a corrected gene to affected cells.
Huntington’s Disease
This is caused by a dominant allele.
