Biology Chapter 11A Test

Why are peas a good “model system” for genetics? (1)

a single plant can produce hundreds of offspring

Why are peas a good “model system” for genetics? (2)

short generational time

Why are peas a good “model system” for genetics? (3)

it’s easy to alter the flowers to control pollination

Why are peas a good “model system” for genetics? (4)

they have seven main traits each of which exists in only two distinct forms

Is there any phenotype of which you can always predict the genotype?

recessive phenotype is always homozygous recessive genotype

Why are human genetics difficult to study? (1)

humans mature slowly

Why are human genetics difficult to study? (2)

humans have long generational time

Why are human genetics difficult to study? (3)

humans produce relatively few offspring

What are exceptions to the laws set fourth by Mendel? (1)

not all genes show simple patterns of inheritance

What are exceptions to the laws set fourth by Mendel? (2)

many genes have more than two alleles

What are exceptions to the laws set fourth by Mendel? (3)

many traits are controlled by more than one gene

Genetics

the study of heredity

Heredity

the passing of traits from parents to offspring

Trait

a specific characteristic of an individual

Genes

a portion of DNA that codes for a trait

Alleles

the different forms of a gene

Pure breed

individuals that carry (and therefore pass on) one allele of a gene/trait

Hybrid (1)

the offspring which results from a cross between pure-breed parents each of which carries an opposing allele for a trait

Hybrid (2)

carry both alleles of a gene/trait

Cross (1)

to breed

Cross (2)

to cause fertilization to occur

Fertilization

the union of the egg and sperm

Dominant

alleles are expressed/seed even in the presence of a contrasting allele

Recessive

alleles which are expressed/seen only in the presence of a similar allele

Probability (1)

the likelihood that a particular event will occur

Probability (2)

past outcomes do not affect future outcomes

Punnett Square

uses mathematical probability to help predict the outcomes of a genetic cross

Phenotype

the observable, physical characteristics of an organism

Genotype (1)

the genetic make-up of an organism

Genotype (2)

what alleles it carries for each gene

Homozygous dominant

carries two dominant alleles for that gene

Heterozygous

carries one dominant and one recessive allele for that gene

Homozygous Recessive

carries two recessive alleles for that gene

Letters for homozygous dominant

AA

Letters for homozygous recessive

aa

Letters for heterozygous

Aa

Law of Segregation (1)

homologous chromosomes separate during meiosis

Law of Segregation (2)

each gamete contains one member of each homologous pair

Law of Independent Assortment (1)

traits segregate independently

Law of Independent Assortment (2)

the inheritance of a particular trait is not dependent on the inheritance of any other particular trait

Law of Dominance

some alleles can hide or mask the presence of other alleles for the same trait

Pedigree (1)

a.k.a. family tree of gene/traits

Pedigree (2)

a chart that shows how a trait and the genes that control it are inherited within a family

Carrier

an individual who carries a recessive trait that is not expressed in that individual

Incomplete dominance (1)

when two alleles for a trait do not exhibit a true dominance/recessive relationship

Incomplete dominance (2)

the heterozygote shows a phenotype that is “in between” the phenotype of the two homozygous parents

Incomplete dominance (3)

both alleles are partially expressed in the heterozygote

Codominance

both alleles in the heterozygote express themselves fully

Multiple Alleles

a gene which has three or more alleles that exist in a population

Polygenic Traits (1)

a trait that is controlled by 2 or more genes

Polygenic Traits (2)

show a wide array of phenotypes