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Bio 156 - Human Biology Chapter 20


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when two copies of each gene in a diploid organism separate from each other during meiosis in germ cells resulting in each gamete containing only one copy of each gene
Parent generation of a cross is designated by a
Offspring of a monohybrid cross are called the
first filial generation (F1)
tool used by genetic counselors to predict the outcome of mating
Punnett square
number between 0 and 1 that expresses the likelihood of a particular event
simple way to determine a genotype of a nonhuman organism working backward from the phonotypes of offspring to help identify the genotype of a parent
monk who hypothesized in the 1850's that factors from each parent were the units of heredity
Gregor Mendel
rule stating that alleles for different traits are sorted into gametes independently of one another
independent assortment
cross in which two traits are studied
dihybrid cross
when there are two contrasting alleles of each gene, one dominant and on recessive (parents have different combinations of alleles)
simple dominance
inheritance principle of independent assortment
either copy of a gene may end up in a particular gamete
A gene is ____ when its instructions are carried out and the cell makes the protein
expression of the gene at just a sinl=gle location on a chromosome may affect two or more traits in positive or negative ways
when both alleles are expressed in a heterozygote
a gene that has three or more alleles
multiple allele system
the probability that someone who inherits an allele will have the phonotype associated with it
condition in which someone has extra fingers or toes
condition caused by the abnormal attachment of muscles to bones of the little finger
when an allele can produce a range of phenotypes its expression is said to be _____
result from the combined expression of several genes
polygenic traits
members show a range of continuous, rather than incremental differences in a trait
continuous variatrion
field of study aimed to pinpoint genetic variatrions that influence how individuals respond to medications
Define difference between gene and allele
genes are the specific units on a specific location on a chromosome and are passed to offspring, alleles are copies of each gene
Define difference between dominant and recessive alleles
an allele is dominant when its effect on a trait masks that of any recessive allele paired with it
Define difference between homozygote and heterozygote
a homozygote is someone who has two identical alleles for a trait and a heterozygote is someone who has 2 different alleles for a trait
Define difference between genotype and phenotype
genotype refers to the particular alleles an individual has, phenotype refers to the actual observable trait an individual has
Does segregation occur during mitosis or meiosis?
Distinguish between monohybrid and dihybrid crosses.
a monohybrid cross is a cross between parents with different versions of a single trait, a dihybrid cross is a cross between parents who show different versions of two traits
why is a testcross useful in genetic analysis?
allows researchers to work backward from the phenotypes of offspring to determine the genotype of a parent
Does independent assortment occur during mitosis or during meiosis?
Alleles are_______
A. alternate forms of a gene
B. different molecular forms of a chromosome
C. always homozygous
D. always heterozygous
A heterozygote has _____
A. only one of the various forms of a gene.
B. a pair of identical alleles
C. a pair of contrasting alleles
D. a haploid condition in genetic terms
The observable traits of an organism are its_____
A phenotype
B. pedigree
C. genotype
D. multiple allele system
Offspring of a monohybrid cross AAxaa are _____.
A. all AA
B. all aa
C. all Aa
D 1.2 AA and 1/2 aa
E. none of the above
Second-generation offspring from a cross between two homozygotes are the ______.
A. F1 generation
B. F2 generation
C. hybrid generation
D. none of the above
Assuming complete dominance, offspring of the cross Az x Aa will show a phenotypic ratio of _____.
A. 1:2:1
B. 1:1:1
C. 9:1
D. 3:1
Which statement best fits the principle of segregation?
A. units of heredity are transmitted to offspring.
B. Two genes of a pair separate from each other during meiosis.
C. Members of a population become segretated.
D. A segregating
Dihybrid crosses of heterozygous individuals (AaBbxAaBb) lead to F2 offspring with phenotypic ratios close to ______.
A. 1:2:1
B. 1:1:1:1
C. 3:1
D. 9:3:3:1

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