Biology 313 Exam 1

Front 1

cohesin

Back 1

protein binding chromatids together
*mitosis: broken by separase
*meiosis: allows for recombination; protected by shugoshin ("guardian spirit") at centromere

Front 2

penetrance

Back 2

percentage of individuals with a particular genotype that express the associated phenotype

Front 3

hemizygous

Back 3

inability to be hetero or homozygous b/c individual possesses only one chromosome
*example: human males only have one x chromosome

Front 4

Prophase 1

Back 4

5 substages:
leptotene
zygotene (crossing over initiates)
pachytene (synaptonemal complex)
diplotene (chiasmata: point @ which crossing over occurs)
diakinesis

Front 5

Synapsis

Back 5

very close pairing association of homologous chromosomes

Front 6

Tetrad

Back 6

pair of synapsed chromosomes

Front 7

Metaphase 1

Back 7

tetrads align on plate; microtubules attach, one to a pair

Front 8

Prophase

Back 8

chromosomes condense and mitotic spindle forms

Front 9

Prometaphase

Back 9

nuclear envelope disintegrates, and spindle microtubules anchor to kinetochores

Front 10

Metaphase

Back 10

chromosomes align on the spindle-assembly checkpoint

Front 11

Anaphase

Back 11

sister chromatids separate, becoming individual chromosomes that migrate towards spindle poles

Front 12

Telophase

Back 12

chromosomes arrive at spindle poles, the nuclear envelop re-forms and the condensed chromosomes relax

Front 13

Cytokinesis

Back 13

cytoplasm divides; cell wall forms in plant cells

Front 14

Monoecious

Back 14

hermaphroditism “one house”

Front 15

Turner syndrome

Back 15

single x chromosome
sterile, short, broad chest, normal IQ

Front 16

Klinefelter syndrome

Back 16

one y, multiple x
male, tall, reduced male characteristic

Front 17

Qualitative traits (Discontinuous)

Back 17

analyzed using Mendelian crosses by placing each individual in a phenotypic class

Front 18

Quantitative traits (continuous)

Back 18

individuals vary in the quantity of the characteristic; no discrete phenotypic classes

Front 19

standard deviation

Back 19

normally distributed populations = describes shape of distribution

Front 20

correllation coefficient (r)

Back 20

measures the strength of the association b/t two traits
*line slope

Front 21

phenotypic variance

Back 21

*genotypic variance
*environmental variance
*interaction variance

Front 22

High heritability

Back 22

Genetic differences cause much of the phenotypic variance
*VG / VP (genotypic variance divided by total phenotypic variance)

Front 23

Incomplete (partial) dominance

Back 23

offspring falls between homozygotes

Front 24

Codominance

Back 24

Heterozygote shows both phenotypes
*common for traits with a molecular / biochemical phenotype
*blood type is an example

Front 25

Overdominance

Back 25

Heterozygote is more extreme than either homozygote

Front 26

Heterogametic sex

Back 26

Produces gametes with two sex chromosome genotypes

Front 27

Homogametic sex

Back 27

Produces gametes with one sex chromosome genotype

Front 28

Chromosome composition

Back 28

controls sex determination gene action.
X:A composition -> X:A ratio measuring genes activated -> Sex-specific genes activated

Front 29

Sex determination genes

Back 29

control an individual’s sex
* Primary signal: one gene on the Y: SRY (sex determining region on the Y) produces TDF (testis determining factor).

Response to the primary signal:
Presence of TDF produces a male gonad.
Absence of TDF produces a female gonad.

Gonads produce sex determining hormones

Front 30

Dosage compensation

Back 30

makes up for the imbalance of sex chromosomal influence (ex. barr bodies)

Front 31

Dihybrid Genotypic Ratio

Back 31

1:2:1:2:4:2:1:2:1

Front 32

dihybrid Phenotypic ratio (normal)

Back 32

9:3:3:1

Front 33

Lethal period

Back 33

time in which lethal alleles kill carrier

Front 34

Penetrance

Back 34

percentage of mutant individuals with mutant phenotypes

Front 35

Expressivity

Back 35

the severity of the phenotype

Front 36

Epistasis

Back 36

expression of one gene masks the expression of another gene
*ex: recessive h in human blood type _ _ hh = O antigen

Front 37

Conditional alleles

Back 37

*Gene expression is affected by the external environment (ex. temperature sensitive)
*Gene expression is affected by other alleles in the “genetic background,” or the internal environment (ex. sex-limited, position effects)

Front 38

Sex-limited

Back 38

The expression of some genes is different in males and females.
(ex. baldness)

Front 39

Cytoplasmic inheritance

Back 39

The phenotype is controlled by genes in the cytoplasmic organelles (mitochondria and chloroplasts)
*test: backcross (should not produce male characteristic)

Front 40

Maternal effect

Back 40

Gene products packaged in the egg by the mother determine offspring phenotype
*the maternal genotype determines the offspring phenotype, regardless of the offspring genotype.
*only affects one generation

Front 41

Infective inheritance

Back 41

The phenotype is controlled by infectious, cytoplasmic agents

Front 42

Genomic imprinting

Back 42

the allele from one parent is inactivated.
*paternal imprint: father's genes are not expressed

Front 43

Viroids

Back 43

Small, circular nucleic acid molecules that do not code for any proteins.