GENE 310 Exam 1

Alternate forms of a gene are called?

alleles

The point for point pairing of homologous chromosomes is called?_________. It occurs during?______________

synapsis and meiosis I

Two deaf persons have a child with normal hearing. This proves that deafness is dominant, and both parents are heterozygous. (epistasis?)

False

Meiosis in human females actually begins before birth.

True

The diploid chromosome number in cats is 38, in dogs 78 and in turkeys it

is 80. How many chromosomes would be present in the gametes of a

cat?_____, dog?_____, turkey?__________.

19, 39, and 40

How many gametes are expected from each cell that undergoes meiosis in a

human male?______, female?________

4 and 1

Heritability of IQ is rather high. This means that much of the measured

variation is the result of genetic differences.

True

Heritability of IQ is rather high. This means that IQ scores can not be improved by improved environments.

False

A trait that is expressed much earlier in life in some individuals with the gene than others.

variable age of onset; ex. Huntington's

An environmentally induced trait that resembles an inherited trait.

phenocopy; ex. lack of limbs from thalidomide vs phocomelia

Failure of a phenotype to be expressed in an individual in accordance with the genotype.

lack of penetrance; ex. gene for polydactyly but 5 fingers

Masking the expression of one gene by a completely different gene.

epsitasis; color suppressor gene masks gene for pigment

Multiple phenotypic effects caused by a single genetic defect.

pleitrophy ex. galactosemia causes cataracts, low IQ and CNS problems

Heterozygote is intermediate (or a mixture) to the homozygotes.

incomplete dominance - ex. roan is R'R whenRR is red and R'R' white

What is the difference between genetic heterogeneity and variable expressivity? Give a real or made-up example of each.

Genetic heterogeneity more than one gene gives the same phenotype ex. polydactyly Variable expressivity: one genotype results in different phenotypes ex. black spotting in peas

What “apparent exceptions” to Mendel’s laws can be associated with a dominant trait like hereditary detached retina?

Lack of penetrance, variable expressivity, age of onset

Identical twins each get 1/2 their genes from mom 1⁄2 from dad, but the alleles can vary.

False

One twin can be male while the other is female.

False

Tests show that IQ in ID twins reared apert is remarkedly similar.

True

Part of their showing greater similarity than DZ twins likely arises due to being dressed and treated alike in childhood

True

A pure (true) breeding organism, or purebred

an organism that consistently produces offspring with the same phenotype (traits) as the parents when self-fertilized or crossed with another organism of the same lineage

Codominance

is a genetic inheritance pattern where two different alleles for a trait are expressed simultaneously and equally in a heterozygote's phenotype, with neither allele being dominant or recessive. Ex. blood types

Concordance

the presence of the same trait, condition, or genetic marker in both members of a pair of individuals. Ex. Genetic Diseases

Variable expressivity

the same genetic mutation causes different signs and severity of symptoms in different people, ranging from mild to severe, even within the same family, due to other genetic, environmental, and lifestyle factors influencing how the gene is expressed. Ex. marfan syndrome

Quantitative traits

measurable phenotypes that vary continuously across a population, such as height, weight, or intelligence. Ex. Human height

Multiple alleles

The presence of more than two alleles for a single gene locus within a population, allowing for greater genetic diversity and phenotypic expression. Ex. Human ABO Blood Group

Penetrance

the proportion of individuals with a specific genotype who express the associated phenotype (traits or disease symptoms). ex. Huntington’s Disease

heritability

a statistical measure (ranging from 0 to 1) representing the proportion of total variation in a specific trait within a population that is attributable to genetic differences among individuals. ex. High heritability (=0.80) like human height