Mcb 104 Midterm #1 Flash Cards

Front 1

Why is Mendel's first law explained by events during the first meiotic division?

Back 1

Because of the fact that homologs pair, align at the metaphase plat, and then separate into two daughter cells. This means that one daughter cell gets the homolog with the "A" allele and the other with the "a" allele. In other words, equal segregation of alleles

Front 2

Why is Mendel's 2nd law explained by events during the first meiotic division?

Back 2

Because of the fact that one pair of homologs align on the metaphase plate without "consulting" any other pair of homologs. The allele from Mom on chromosome 1 can into the top daughter cell and the one from dad into the bottom one or vice versa; they will not "ask" the alleles on chromosome 2 which way they plan to segregate. In other words, independent assortment of alleles.

Front 3

saturation mutagenesis

Back 3

a systematic search for finding all the genes in the genome that can mutate to affect a biological process

Front 4

incomplete dominance

Back 4

the general case in which the phenotype of a heterozygote is intermediate between those of the two homozygotes on some quantitative scale of measurement. (1:2:1 phenotypic ratio); refer to four o'clock flowers

Front 5

codominance

Back 5

the expression of both alleles of a heterozygote (ex. ABO blood system)

Front 6

law of equal segregation

Back 6

the production of equal numbers (50%) of each allele in the meiotic products (e.g. gametes) of a heterozygous meiocyte; the two members of a gene pair segregate from each other in meiosis, each gamete has an equal probability of obtaining either member of the gene pair

Front 7

law of independent assortment

Back 7

unlinked or distantly linked (>50 cM) segregating gene pairs assort independently at meiosis

Front 8

polymorphism

Back 8

coexistence of two or more common phenotypes of a character

Front 9

features of an x-linked recessive disorder in a pedigree

Back 9

1. many more males than female show the rare phenotype under study
2. none of the offspring of an affected male show the phenotype, but all his daughters are carriers who bear the recessive allele masked in the heterozygous condition. In the next generation, half the sons of these carrier daughters show the phenotype
3. none of the sons of an affected male show the phenotype under study, nor will they pass the condition to their descendants.

Front 10

features of an x-linked dominant disorder in a pedigree

Back 10

1. affected males pass the condition to all of their daughters but to none of their sons
2. affected heterozygous females married to unaffected males pass the condition to half their sons and daughters

Front 11

dihybrid

Back 11

a double heterozygote

Front 12

recombination

Back 12

the production of new allele combinations

Front 13

prototrophic

Back 13

able to grow and divide on minimal medium

Front 14

complete dominance

Back 14

simplest type of dominance; a fully dominant allele will be expressed when only one copy is present as in a heterozygote whereas the alternative allele will be fully recessive. In full dominance, the homozygous dominant cannot be distinguished from the heterozygote at the phenotypic level

Front 15

haploinsufficient

Back 15

one of the ways to explain fully dominant mutations. this means that one wild-type dose is no enough to achieve normal levels of function

Front 16

dominant negative

Back 16

another type of dominant mutation; polypeptides with this type of mutation act as "spoilers" or "rogues." In some cases, the gene product is a unit of a homodimeric protein (a protein composed of two units of the same type). In a heterozygote, the spoiler polypeptide binds to the wt polypeptide and distorts it or otherwise interferes with its function.

Front 17

recessive lethal alleles

Back 17

an allele that is capable of causing the death of an organism is called a lethal allele. produces a 2:1 phenotypic ratio because those with the lethal phenotype do not survive to be counted

Front 18

pleiotropic

Back 18

any allele that affects several properties of an organism

Front 19

complementation test

Back 19

cross two homozygous mutant lines to produce a heterozygote; if the heterozygote is wild-type then the two mutations must have been in different genes and are said to have complemented each other

Front 20

recessive epistasis

Back 20

a 9:3:4 ratio in the F2 suggests a type of gene interaction called epistasis. Epistasis is inferred when a mutant allele of one gene masks the expression of a mutant allele of another gene and expresses its own phenotype instead.