Genetics: Dominant and Recessive Traits

Questions and Answers

What term is used for having two identical alleles?

Homozygous

What term is used for having two different alleles?

Heterozygous

Which genetic disorder results from a recessive gene?

Huntington's Disease

Cystic Fibrosis (correct)

PKU

Down Syndrome

Advancing maternal age decreases the risk of having a child with Down Syndrome.

False Signup and view all the answers

Huntington's Disease is a fatal progressive brain disorder where brain cells die, leading to a loss of control over movements and ___________.

emotions Signup and view all the answers

Match the genetic disorder with its description:

Phenylketonuria = Cannot metabolize phenylalanine, leading to central nervous system impairments Sickle Cell Anemia = Red blood cells take the shape of a sickle, causing clumping and decreased oxygen supply Cystic Fibrosis = Thick buildup of mucus in the lungs, leading to nutrient absorption issues Signup and view all the answers

Study Notes

Traits and Genes

Traits are determined by pairs of genes, each member of a pair is an allele
Homozygous: having two identical alleles
Heterozygous: having two different alleles
Incomplete dominance or codominance: when the effects of both alleles are shown

Dominant and Recessive Traits

People who bear one dominant gene and one recessive gene for a trait are carriers of the recessive gene
Recessive genes can cause diseases such as cystic fibrosis and sickle-cell anemia

Chromosomal Abnormalities

Chromosomal abnormalities can be numerical (e.g. monosomy, trisomy) or structural
Down syndrome is usually caused by an extra chromosome in the 21st pair, resulting in 47 chromosomes
Advancing maternal age increases the risk of having a child with down syndrome
Women between 35 to 39 have the highest percent change at 29%

Sex-Linked Chromosomal Abnormalities

Abnormalities that are transmitted from generation to generation and are carried on the sex chromosome
Examples include infertile, maleness and femaleness differences, and numerous disorders stemming from an abnormal number of sex chromosomes

Genetic Abnormalities

Phenylketonuria (PKU): transmitted by recessive gene, 1 in 12,000 newborns will have PKU
Huntington's disease: fatal progressive brain disorder, genetic miracle discovered
Sickle cell anemia: recessive gene, common among black North Americans, neglected disease due to no precise stats
Cystic fibrosis: recessive gene, most fatal among children and young adults, thick build up of mucus in the lungs, trouble absorbing nutrients
Sex-linked genetic abnormalities: hemophilia, colour blindness, only carried on the X sex chromosomes, females less likely because they have two X chromosomes