ap bio vocab - unit 5 🧑🏿

heredity

the transmission of traits from one generation to the next

variation

differences between members of the same species

genetics

the study of both heredity and inherited variations

locus

a gene’s specific location along the length of a chromosome

asexual reproduction

reproduction where a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes

clone

an individual or group of individuals that are genetically identical to the parent

s-xual reproduction

reproduction where two parents give rise to offspring that have unique combinations of genes inherited from the two parents

life cycle

the generation-to-generation sequence of stages in the reproductive history of an organism, from conception to production of its own offspring

karyotype

a display of the chromosome pairs in a cell arranged by shape and size

homologous chromosomes

the two chromosomes of a pair that have the same length, centromere position, and staining pattern

s-x chromosmes

X and Y chromosomes with a role in s-x determination

autosomes

every other chromosome in the cell other than s-x chromosomes

diploid cell

any cell with two chromosome sets

haploid cells

cells that contain a single set of chromosomes

fertilization

the union of gametes, culminating in fusion of their nuclei

zygote

the resulting fertilized egg from fertilization

meiosis

the type of cell division that reduces the number of sets of chromosomes from two to one in gametes

alternation of generations

a second type of life cycle exhibited by plants and algae where a diploid and haploid organism arise

meiosis I

the first stage of meiosis where homologous chromosomes are separated

meiosis II

the second stage of meiosis where sister chromatids are separated

synaptonemal complex

a zipper-like structure that connects a chromosome to its homolog during prophase I of meiosis

synapsis

the physical connection of a replicated chromosome to its homolog

chiasma

the location where crossing over occurs and where sister chromatid cohesion occurs

character

a heritable feature that varies among individuals

trait

each variant for a character

true-breeding

organisms that produce offspring with only the same variety as the parent through self-pollination

hybridization

the mating of two true-breeding varieties

P generation

the true-breeding parental generation in hybridization

F₁ generation

the first filial generation, the hybrid offspring of the parental generation

F₂ generation

the second filial generation, either from hybridization or self-pollination of first filial generation

alleles

alternative versions of a gene

dominant allele

the allele that determines an organism’s appearance

recessive allele

the allele that has no noticeable effect on an organism’s appearance

law of segregation

the idea that two alleles for a heritable character segregate during gamete formation and end up in different gametes

Punnett square

a diagrammatic device for predicting the allele composition of all offspring resulting from a cross between individuals for known genetic makeup

homozygote

an organism that has a pair of identical alleles for a gene encoding a character

homozygous

the property of having two identical alleles for a character

heterozygote

an organism that has two different alleles for a gene

heterozygous

the property of having two different alleles for a character

phenotype

an organism’s appearance or observable traits

genotype

an organism’s genetic makeup

testcross

the breeding of an organism of unknown genotype with a recessive homozygote

monohybrids

organisms that are heterozygous for one particular character being followed

monohybrid cross

a cross between two monohybrid heterozygotes

dihybrids

organisms heterozygous for two characters being followed

dihybrid cross

a cross between F₁ dihybrids

law of independent assortment

the idea that two or more genes separate independently during gamete fusion

multiplication rule

the rule that determines the probability of one event and another occurring by multiplying the two probabilities of each event together

addition rule

the rule that determines the probability of one event or another occurring by adding their individual probabilities

complete dominance

situations where the phenotypes of heterozygote and the dominant homozygote are indistinguishable

incomplete dominance

the phenomenon where, in some genes, neither allele is completely dominant

codominance

the variation of dominance where two alleles affect the phenotype in separate, distinguishable ways

Tay-Sachs disease

an inherited disorder in humans where brain cells cannot metabolize certain lipids because a crucial enzyme does not work properly

pleiotropy

the property of genes to have multiple phenotypic effects

epistasis

where the phenotypic expression of a gene at one locus alters that of a gene at a second locus

quantitative characters

characters that are not just one of two discrete characters, but vary in a population in gradations along a continuum

polygenic inheritence

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

phenotypic plasticity

the ability of an individual genotype to produce different phenotypes under different environmental conditions

multifactorial

when many factors, both genetic and environmental collectively influence phenotype

pedigree

a family tree describing the traits of parents and children across the generations

carriers

phenotypically normal heterozygotes that may transmit a recessive disorder allele to their offspring

cystic fibrosis

a common lethal genetic disease in the United States where chloride transport channels are defective

Huntington’s disease

a degenerative disease of the nervous system

chromosome theory of inheritance

the idea that Mendelian genes have specific loci along chromosomes and the chromosomes undergo segregation and independent assortment

wild type

the phenotype for a character most commonly observed in natural populations

sex-linked gene

a gene located on either sex chromosome

X-linked genes

the 1,100 genes contained on the X chromosome

Duchenne muscular dystrophy

an X-linked disease characterized by a progressive weakening of the muscles and loss of coordination

hemophilia

an X-linked recessive disorder defined by the absence of one or more of the proteins required for blood clotting

Barr body

a compact object resulting from the condensing of the inactive X chromosome of a female cell

linked genes

genes located near each other on the same chromosome that tend to be inherited together in genetic crosses

genetic recombination

the production of offspring with combinations of traits that differ from those found in either P generation parent

parental types

offspring that inherit a phenotype that matches either one of the P generation originally crossed to produce the F₁ dihybrid cross

recombinant types

the nonparental phenotypes also found among offspring that have new combinations of alleles

crossing over

the process that occasionally breaks the physical connection between specific alleles of genes on the same chromosome

genetic map

an ordered list of the genetic loci along a particular chromosome

linkage map

a genetic map based on recombination frequencies

map unit

the distance between genes equivalent to a 1% recombination frequency

disjunction

a meiotic mishap in which the members of a pair of homologous chromosomes do not move apart properly during meiosis I or sister chromatids fail to separate during meiosis II

aneuploidy

a condition where an aberrant gamete unites with a normal one at fertilization

monosomic

when a cell has only one copy of a chromosome instead of two

trisomic

when a cell has three copies of a chromosome instead of two

polyploidy

a chromosomal alteration where the organism has more than two complete chromosome sets in somatic cells

deletion

a chromosomal change that occurs when a chromosomal fragment is lost

duplication

a chromosomal change where a broken fragment reattaches as an extra segment to a sister or nonsister chromatid

inversion

a chromosomal change where a chromosomal fragment reattaches to the original chromosome but in reverse orientation

translocation

a chromosomal change where a chromosomal fragment joins a nonhomologous chromosome

Down syndrome

an aneuploid condition that is the result of an extra chromosome 21 affecting one out of every 830 children in the U.S.