Biol112 Exam I

Front 1

blending inheritance vs. particulate inheritance

Back 1

* Blending Model:
o Offspring are a blend of both parents (i.e. in modern terms, alleles would blend together to form a completely new allele)
o The characteristics of the blended offspring are passed on to the next generation
o Variation is washed out over time[2]

* Particulate Model:
o Offspring are a combination of both parents
o The characteristics of both parents are passed on to the next generation as separate entities
o Variation is maintained over time[3]

Front 2

gene

Back 2

a distinct sequence of nucleotides forming part of a chromosome, the order of which conditions the order of monomers in a polypeptide or nucleic acid molecule which a cell (or virus) may synthesize.

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dominant allele

Back 3

An allele that is fully expressed in the phenotype of a heterozygote.

Front 4

recessive allele

Back 4

An allele whose phenotypic effect is not observed in a heterozygote.

Front 5

Principle of Segregation

Back 5

Mendel’s first principle, stating that the two alleles in a pair segregate (separate) into different gametes during gamete formation.

Front 6

Punnett square

Back 6

A diagram used in the study of inheritance to show the predicted results of random fertilization in genetic crosses.

Front 7

monohybrid cross

Back 7

A monohybrid cross is a cross between parents who are heterozygous at one locus; for example, Bb x Bb (see the Punnett). Example: B = brown. b = blue. BB = Dark Brown. Bb = Brown (not blue). bb = Blue.

Front 8

allele

Back 8

Any of the alternative versions of a gene that produce distinguishable phenotypic effects.

Front 9

locus

Back 9

A specific place along the length of a chromosome where a given gene is located.

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homozygous

Back 10

Having two identical alleles for a given gene.

Front 11

heterozygous

Back 11

Having two different alleles for a given gene.

Front 12

phenotype

Back 12

gene expression

Front 13

genotype

Back 13

The genetic makeup, or set of alleles, of an organism.

Front 14

phenotypic ratio

Back 14

A ratio that shows the varied outcomes that results from a genetic cross and is based on physical appearance alone.

Front 15

genotypic ratio

Back 15

A genotypic ratio is the proportion of genotypes found in individuals after a cross.

Front 16

test cross

Back 16

Breeding an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype. The ratio of phenotypes in the offspring reveals the unknown genotype.

Front 17

Principle of Independent Assortment

Back 17

Mendel’s second principle, stating that each pair of alleles segregates, or assorts, independently of each other pair during gamete formation; applies when genes for two characters are located on different pairs of homologous chromosomes.

Front 18

dihybrid cross

Back 18

An organism that is heterozygous with respect to two genes of interest. All the offspring from a cross between parents doubly homozygous for different alleles are dihybrids. For example, parents of genotypes AABB and aabb produce a dihybrid of genotype AaBb.

Front 19

incomplete dominance

Back 19

The situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele.

Front 20

codominance

Back 20

The situation in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate, distinguishable ways.

Front 21

multiple alleles

Back 21

Any of a set of three or more alleles, or alternative states of a gene, only two of which can be present in a diploid organism.

Front 22

polygenic inheritance

Back 22

An additive effect of two or more genes on a single phenotypic character.

Front 23

pedigree

Back 23

A diagram of a family tree showing the occurrence of heritable characters in parents and offspring over multiple generations.

Front 24

sex chromosomes

Back 24

A chromosome responsible for determining the sex of an individual.

Front 25

autosomes

Back 25

A chromosome that is not directly involved in determining sex; not a sex chromosome.

Front 26

sex linkage

Back 26

A gene Located on A sex chromosome (usually the X chromosome), resulting in A distinctive pattern of inheritance.

Front 27

hemizygous

Back 27

A chromosome in a diploid organism is hemizygous when only one copy is present.[1] The cell or organism is called a hemizygote. Hemizygosity is observed when one copy of a gene is deleted, or in the heterogametic sex when a gene is located on a sex chromosome.

Front 28

linkage

Back 28

Genes located close enough together on a chromosome that they tend to be inherited together.

Front 29

recombination

Back 29

Genetic recombination is a process by which a molecule of nucleic acid (usually DNA, but can also be RNA) is broken and then joined to a different one. Recombination can occur between similar molecules of DNA, as in homologous recombination, or dissimilar molecules, as in non-homologous end joining.

Front 30

crossing over

Back 30

The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.

Front 31

cell cycle

Back 31

An ordered sequence of events in the life of a cell, from its origin in the division of a parent cell until its own division into two; the eukaryotic cell cycle is composed of interphase (including G1, S, and G2 subphases) and M phase (including mitosis and cytokinesis).

Front 32

mitosis (M)

Back 32

A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei.

Front 33

interphase

Back 33

The period in the cell cycle when the cell is not dividing. During interphase, cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase. Interphase accounts for 90% of the cell cycle.

Front 34

prophase

Back 34

The first stage of mitosis, in which the chromatin condenses, the mitotic spindle begins to form, and the nucleolus disappears, but the nucleus remains intact.

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metaphase

Back 35

The third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate.

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anaphase

Back 36

The fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell.

Front 37

telophase

Back 37

The fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun.

Front 38

cytokinesis

Back 38

The division of the cytoplasm to form two separate daughter cells immediately after mitosis, meiosis I, or meiosis II.

Front 39

chromatin vs. chromosome

Back 39

The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.

Front 40

centriole

Back 40

A structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a 9 + 0 pattern. A centrosome has a pair of centrioles.

Front 41

sister chromatids

Back 41

Either of two copies of a duplicated chromosome attached to each other by proteins at the centromere and, sometimes, along the arms. While joined, two sister chromatids make up one chromosome; chromatids are eventually separated during mitosis or meiosis II.

Front 42

centromere

Back 42

The specialized region of the chromosome where two sister chromatids are most closely attached.

Front 43

kinetochore

Back 43

A structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle.

Front 44

asters

Back 44

A radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell undergoing mitosis.

Front 45

meiosis I

Back 45

The first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Front 46

synapsis

Back 46

The pairing and physical connection of replicated homologous chromosomes during prophase I of meiosis.

Front 47

homologous chromosomes/homologs

Back 47

A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism’s father, the other from the mother. Also called homologs, or a homologous pair.

Front 48

meiosis II

Back 48

The second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.

Front 49

chromosome theory of inheritance

Back 49

A basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.