Chapter 14 Flashcards
What is the blending hypothesis?
the blending hypothesis is the idea that genetic material from the two parents blends together (like blue and yellow paint blend to make green)
what is the particulate hypothesis?
the particulate hypothesis is the idea that parents pass on discrete heritable units (genes)
what is a character?
a heritable feature that varies among individuals (such as flower color) is called a character
what is a trait?
each variant for a character, such as purple or white color for flowers, is called a trait
what is hybridization?
mating two contrasting, true breeding varieties
how many alleles does each organism inherit?
an organism inherits 2 alleles, one from each parent
what happens if alleles at a locus differ?
the dominant allele determines the organisms appearance and the recessive alelle has no noteiceable affect on appearance
what is the law of segregation?
the two alleles for a heritable character separate (segregate) during gamete formation and end up in different games, thus an egg or sperm gets only one alleles
how does segregation of alleles correspond to meisosi?
this segregation of alleles corresponds to the distribution of homologous chromosomes (metaphes 1) to different gametes in meisosis
what does a punnett square do?
shows possible combinations of sperm and egg can be shown using a Punnett square
what is homozygous?
an organism with two identical alleles for a character is homozygous for the gene controlling that character
what is heterozygous?
an organism that has two different alleles for a gene is heterozygous for the gene controlling that character
are heterozygotes or homozygotes true breeding?
homozygotes are true breeding; heterozygotes are not true breeding
what is phenotype vs genotype?
phenotype is physical appearance and genotype is genetic makeup
what is a testcross?
breeding the mystery individual with a homozygous recessive individual to determine if the mystery parent carries recessive genotype based on if it shows phenotype
what does the law of independent assortment state?
states that each pair of alleles segregates independently of each other pair of alleles during gamete formation
what does the law of independent assortment apply to?
it only applies to genes on different, nonhomologous chromosomes or those far apart on the same chromosome
when are genes linked?
when they are located near eachother on the same chromosome; tend to be inherited together and are linked
True or False: many heritable characters are determined by only one gene with two alleles
False
inheritance of characters by a single gene may deviate from simple Mendelian patterns in the following situations?
- when alleles are not completely dominant or recessive
- when a gene has more than two alleles
- when a gene produces multiple phenotypes
when does complete dominance occur?
complete dominance occurs when phenotypes of the heterozygote and dominant homozygote are identical
what happens in incomplete dominance?
the phenotype of F1 hybrids is somewhere between the pheotypes of the two parental varieties
what happens in codominance?
in codominance, two dominant alleles affect the phenotype in separate, distinguishable ways
what is Tay-Sachs disease?
it is fatal; a dysfunctional enzyme causes an accumulation of lipids in the brain
- at organismal level: allele is recessive
- at biochemical level: phenotype is incompletely dominant
- at molecular level: alleles are codominant
what dominance does blood type AB have?
AB are said to be codominant because they have both A and B alleles present
What is Mendel’s second law of inheritance?
By following two characters at the same time: Crossing 2 true-breeding parents differing in two character produces dihybrids in the F1 generation, heterozygous for both characters
What does a dihybrid cross do?
determines whether two characters are transmitted to offspring as a package or independently
what is the phenotypic ratio?
9:3:3:1
What are the four phenotypes of the ABO blood group in humans determined by?
determined by three alleles for the enzyme (I) that attaches A or B carbohydrates to red blood cells I^a, I^b, and i
What is added for each allele when considering blood groups?
I^a adds A carbohydrate, I^b adds B carbohydrate, i adds neither
what genotypes can blood group A have?
I^a I^a, or I^a i
what genotypes can blood group B have?
I^b I^b, or I^b i
what genotypes can blood group AB have?
I^a I^b
Which blood types are dominant, which are recessive?
A and B are dominant, O is recessive
What is pleiotropy?
When genes have multiple phenotypic effects
- example: pleiotropic alleles are responsible for multiple systems of certain hereditary diseases, such as cystic fibrosis and sickle-cell diseases
What happens in epistasis?
In epistasis, a gene at one locus alters the phenotypic expression of a gene at a second locus
- example: in dogs, coat color depends on 2 genes: one gene determines pigment color and the other determines whether pigment will be deposited
Basically: allele of one gene suppresses another
Polygenic Inheritance?
an additive effect of two or more genes on a single phenotype
- example: skin color in humans is an example
quantitative variation indicate polygenic inheritance
what are examples of polygenic inheritance?
skin color, eye color, height, intelligence
