Chapter 10 Lecture

phenotype

phenotype

▪ An individual’s traits

-Result from expression of genes

genotype

• The particular alleles carried by an individual

homozygous

Individuals that carry two identical alleles for a gene

heterozygous

Having two different alleles of a gene (Hybrid)

Monohybrid cross

cross between two organisms with different variations at one genetic locus of interest

Dominant allele

An allele that overrides the effect of a recessive allele

recessive alleles

An allele with an effect that is masked by a dominant allele

Dihybrid cross

Experiment in which individuals with different \n alleles of two genes are crossed (9:3:3:1 ratio)

independent assortment of alleles

the alleles of two (or more) different genes get sorted into gametes independently of one another

codominance vs incomplete dominance

In codominance, both alleles in the genotype are seen in the phenotype. In incomplete dominance, a mixture of the alleles in the genotype is seen in the phenotype

epistasis

a gene that determines whether or not a trait will be expressed

pleiotropy

Genes that affect multiple, apparently unrelated, phenotypes

• What happens when a trait occurs in continuous variation

The more genes and other factors that influence a trait, the more continuous the distribution of phenotype

• Effect of environment on phenotype

Environmental conditions can affect one or more steps in a metabolic pathway

Pedigree

Chart showing the pattern of inheritance of a trait in a family

genetic counseling

gives you information about how genetic conditions might affect you or your family

Genetic abnormality

• an uncommon version of a heritable trait

• does not result in medical problems

Chromosomal abnormalities that give rise to Down syndrome

trisomy 21

Chromosomal abnormalities that give rise to Turner syndrome

one of these chromosomes is missing or abnormal

Chromosomal abnormalities that give rise to Klinefelter’s syndrome

One extra copy of the X chromosome in each cell (XXY)

The risks associated with amniocentesis

Less than 1 in 200 women (less than 1 percent) have a miscarriage after an amnio. Infection in the uterus. Cramping, spotting or leaking amniotic fluid

The risks associated with chorionic villi sampling

pregnancy loss, bleeding, infection, rupture of membranes, and uncertain results

The risks associated with fetoscopy

infection, rupture of amniotic sac, premature labor, and fetal death