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11 Cards in this Set

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  • Back
Why is a testcross performed with a homozygous recessive parent rather than a homozygous dominant parent?
If the offspring is showing a ressesive trait then we know it is homozygoes but if it is showing a dominant trait than it could be cdominant or resecive
Give the relationships between genes, alleles, and gene loci.
Genes are a codes for a certain trait

Alleles are a variation of that trait

Loci, is the location of the allele. alleles must have the same letter
To what do the terms monohybrid refer? What Law did monohybrid experiments support?
Monohybrid refer to, offspring are hetrozygous for only one pair of alleles. This supports the fact that for a recessive trait to result both alleles must be recessive
To what do the terms dihybrid refer? What Law did Dihybrid experiments support? Explain
Dihybrid means that an offspring is Heteroqygous in two different traits

the law of segregation tells tells us that gametes for a WWSS grandparent have to be WS and gametes for the wwssgrandparent have to be ws so the dihybrid offspring will be WsSs
Allele “X” is codominant with allele “Y” and both are dominant to an allele “z” at the same gene locus. What phenotype would an “Xz” individual have? “XY”? “zz”?
the Xz individual would have the X phenotype

the XY individual would share the traits of X and Y in codominance

The zz individual would show the traits of z
Use a Punnett square to explain a 3:1 ratio in the F2 generation of a monohybrid cross
G g


g G g
Explain how each of these factors influence gene expression: degrees of dominance, 2 or more genes influencing the same trait, pleiotropy, environmental conditions.
The degree of dominance is when dominant alleles have a quanitative effect

2 or more genes influencing the same trait, this is the case of codominance when two alleles are equally expressed like in blood cells

Pleiotorpy is when a single gene codes for multiple phynotipic traits
Why does sex-linked inheritance lead to typically more affected males than females?
because a female must recieve two alleles before she has the condition because most of the conditions are recesive. the male has only to recieve one bad X chromosome because the y chromosome usually does not carry very many alleles.
The law of segregation
1) each individual has two factors for each trait
2)The factors seperate during the formation of gametes
3) Each gamete contains only one factor from each pair of factors
4) Fertilization gives each new individual two factors for each trait
The law of independent assortment states that
1) each pair of factors separates independently without regards the the other factors
2) All possible combination sof factors can occur in gametes
Describe Polygenic alleles
Effects of dominant alleles are additive

Genes effecting the trait may be on multiple chromosomes

Environment influences phenotype